Merge branch 'merge' of master.kernel.org:/pub/scm/linux/kernel/git/paulus/powerpc
[linux-2.6] / net / ipv4 / tcp_input.c
1 /*
2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
3  *              operating system.  INET is implemented using the  BSD Socket
4  *              interface as the means of communication with the user level.
5  *
6  *              Implementation of the Transmission Control Protocol(TCP).
7  *
8  * Version:     $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
9  *
10  * Authors:     Ross Biro
11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12  *              Mark Evans, <evansmp@uhura.aston.ac.uk>
13  *              Corey Minyard <wf-rch!minyard@relay.EU.net>
14  *              Florian La Roche, <flla@stud.uni-sb.de>
15  *              Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16  *              Linus Torvalds, <torvalds@cs.helsinki.fi>
17  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
18  *              Matthew Dillon, <dillon@apollo.west.oic.com>
19  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20  *              Jorge Cwik, <jorge@laser.satlink.net>
21  */
22
23 /*
24  * Changes:
25  *              Pedro Roque     :       Fast Retransmit/Recovery.
26  *                                      Two receive queues.
27  *                                      Retransmit queue handled by TCP.
28  *                                      Better retransmit timer handling.
29  *                                      New congestion avoidance.
30  *                                      Header prediction.
31  *                                      Variable renaming.
32  *
33  *              Eric            :       Fast Retransmit.
34  *              Randy Scott     :       MSS option defines.
35  *              Eric Schenk     :       Fixes to slow start algorithm.
36  *              Eric Schenk     :       Yet another double ACK bug.
37  *              Eric Schenk     :       Delayed ACK bug fixes.
38  *              Eric Schenk     :       Floyd style fast retrans war avoidance.
39  *              David S. Miller :       Don't allow zero congestion window.
40  *              Eric Schenk     :       Fix retransmitter so that it sends
41  *                                      next packet on ack of previous packet.
42  *              Andi Kleen      :       Moved open_request checking here
43  *                                      and process RSTs for open_requests.
44  *              Andi Kleen      :       Better prune_queue, and other fixes.
45  *              Andrey Savochkin:       Fix RTT measurements in the presence of
46  *                                      timestamps.
47  *              Andrey Savochkin:       Check sequence numbers correctly when
48  *                                      removing SACKs due to in sequence incoming
49  *                                      data segments.
50  *              Andi Kleen:             Make sure we never ack data there is not
51  *                                      enough room for. Also make this condition
52  *                                      a fatal error if it might still happen.
53  *              Andi Kleen:             Add tcp_measure_rcv_mss to make
54  *                                      connections with MSS<min(MTU,ann. MSS)
55  *                                      work without delayed acks.
56  *              Andi Kleen:             Process packets with PSH set in the
57  *                                      fast path.
58  *              J Hadi Salim:           ECN support
59  *              Andrei Gurtov,
60  *              Pasi Sarolahti,
61  *              Panu Kuhlberg:          Experimental audit of TCP (re)transmission
62  *                                      engine. Lots of bugs are found.
63  *              Pasi Sarolahti:         F-RTO for dealing with spurious RTOs
64  */
65
66 #include <linux/mm.h>
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
69 #include <net/tcp.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
74
75 int sysctl_tcp_timestamps __read_mostly = 1;
76 int sysctl_tcp_window_scaling __read_mostly = 1;
77 int sysctl_tcp_sack __read_mostly = 1;
78 int sysctl_tcp_fack __read_mostly = 1;
79 int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
80 int sysctl_tcp_ecn __read_mostly;
81 int sysctl_tcp_dsack __read_mostly = 1;
82 int sysctl_tcp_app_win __read_mostly = 31;
83 int sysctl_tcp_adv_win_scale __read_mostly = 2;
84
85 int sysctl_tcp_stdurg __read_mostly;
86 int sysctl_tcp_rfc1337 __read_mostly;
87 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
88 int sysctl_tcp_frto __read_mostly;
89 int sysctl_tcp_nometrics_save __read_mostly;
90
91 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
92 int sysctl_tcp_abc __read_mostly;
93
94 #define FLAG_DATA               0x01 /* Incoming frame contained data.          */
95 #define FLAG_WIN_UPDATE         0x02 /* Incoming ACK was a window update.       */
96 #define FLAG_DATA_ACKED         0x04 /* This ACK acknowledged new data.         */
97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted.  */
98 #define FLAG_SYN_ACKED          0x10 /* This ACK acknowledged SYN.              */
99 #define FLAG_DATA_SACKED        0x20 /* New SACK.                               */
100 #define FLAG_ECE                0x40 /* ECE in this ACK                         */
101 #define FLAG_DATA_LOST          0x80 /* SACK detected data lossage.             */
102 #define FLAG_SLOWPATH           0x100 /* Do not skip RFC checks for window update.*/
103
104 #define FLAG_ACKED              (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
105 #define FLAG_NOT_DUP            (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
106 #define FLAG_CA_ALERT           (FLAG_DATA_SACKED|FLAG_ECE)
107 #define FLAG_FORWARD_PROGRESS   (FLAG_ACKED|FLAG_DATA_SACKED)
108
109 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
110 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
111 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
112
113 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
114
115 /* Adapt the MSS value used to make delayed ack decision to the
116  * real world.
117  */
118 static void tcp_measure_rcv_mss(struct sock *sk,
119                                 const struct sk_buff *skb)
120 {
121         struct inet_connection_sock *icsk = inet_csk(sk);
122         const unsigned int lss = icsk->icsk_ack.last_seg_size;
123         unsigned int len;
124
125         icsk->icsk_ack.last_seg_size = 0;
126
127         /* skb->len may jitter because of SACKs, even if peer
128          * sends good full-sized frames.
129          */
130         len = skb_shinfo(skb)->gso_size ?: skb->len;
131         if (len >= icsk->icsk_ack.rcv_mss) {
132                 icsk->icsk_ack.rcv_mss = len;
133         } else {
134                 /* Otherwise, we make more careful check taking into account,
135                  * that SACKs block is variable.
136                  *
137                  * "len" is invariant segment length, including TCP header.
138                  */
139                 len += skb->data - skb->h.raw;
140                 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
141                     /* If PSH is not set, packet should be
142                      * full sized, provided peer TCP is not badly broken.
143                      * This observation (if it is correct 8)) allows
144                      * to handle super-low mtu links fairly.
145                      */
146                     (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
147                      !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
148                         /* Subtract also invariant (if peer is RFC compliant),
149                          * tcp header plus fixed timestamp option length.
150                          * Resulting "len" is MSS free of SACK jitter.
151                          */
152                         len -= tcp_sk(sk)->tcp_header_len;
153                         icsk->icsk_ack.last_seg_size = len;
154                         if (len == lss) {
155                                 icsk->icsk_ack.rcv_mss = len;
156                                 return;
157                         }
158                 }
159                 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
160                         icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
161                 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
162         }
163 }
164
165 static void tcp_incr_quickack(struct sock *sk)
166 {
167         struct inet_connection_sock *icsk = inet_csk(sk);
168         unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
169
170         if (quickacks==0)
171                 quickacks=2;
172         if (quickacks > icsk->icsk_ack.quick)
173                 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
174 }
175
176 void tcp_enter_quickack_mode(struct sock *sk)
177 {
178         struct inet_connection_sock *icsk = inet_csk(sk);
179         tcp_incr_quickack(sk);
180         icsk->icsk_ack.pingpong = 0;
181         icsk->icsk_ack.ato = TCP_ATO_MIN;
182 }
183
184 /* Send ACKs quickly, if "quick" count is not exhausted
185  * and the session is not interactive.
186  */
187
188 static inline int tcp_in_quickack_mode(const struct sock *sk)
189 {
190         const struct inet_connection_sock *icsk = inet_csk(sk);
191         return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
192 }
193
194 /* Buffer size and advertised window tuning.
195  *
196  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
197  */
198
199 static void tcp_fixup_sndbuf(struct sock *sk)
200 {
201         int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
202                      sizeof(struct sk_buff);
203
204         if (sk->sk_sndbuf < 3 * sndmem)
205                 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
206 }
207
208 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
209  *
210  * All tcp_full_space() is split to two parts: "network" buffer, allocated
211  * forward and advertised in receiver window (tp->rcv_wnd) and
212  * "application buffer", required to isolate scheduling/application
213  * latencies from network.
214  * window_clamp is maximal advertised window. It can be less than
215  * tcp_full_space(), in this case tcp_full_space() - window_clamp
216  * is reserved for "application" buffer. The less window_clamp is
217  * the smoother our behaviour from viewpoint of network, but the lower
218  * throughput and the higher sensitivity of the connection to losses. 8)
219  *
220  * rcv_ssthresh is more strict window_clamp used at "slow start"
221  * phase to predict further behaviour of this connection.
222  * It is used for two goals:
223  * - to enforce header prediction at sender, even when application
224  *   requires some significant "application buffer". It is check #1.
225  * - to prevent pruning of receive queue because of misprediction
226  *   of receiver window. Check #2.
227  *
228  * The scheme does not work when sender sends good segments opening
229  * window and then starts to feed us spaghetti. But it should work
230  * in common situations. Otherwise, we have to rely on queue collapsing.
231  */
232
233 /* Slow part of check#2. */
234 static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp,
235                              const struct sk_buff *skb)
236 {
237         /* Optimize this! */
238         int truesize = tcp_win_from_space(skb->truesize)/2;
239         int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
240
241         while (tp->rcv_ssthresh <= window) {
242                 if (truesize <= skb->len)
243                         return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
244
245                 truesize >>= 1;
246                 window >>= 1;
247         }
248         return 0;
249 }
250
251 static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
252                             struct sk_buff *skb)
253 {
254         /* Check #1 */
255         if (tp->rcv_ssthresh < tp->window_clamp &&
256             (int)tp->rcv_ssthresh < tcp_space(sk) &&
257             !tcp_memory_pressure) {
258                 int incr;
259
260                 /* Check #2. Increase window, if skb with such overhead
261                  * will fit to rcvbuf in future.
262                  */
263                 if (tcp_win_from_space(skb->truesize) <= skb->len)
264                         incr = 2*tp->advmss;
265                 else
266                         incr = __tcp_grow_window(sk, tp, skb);
267
268                 if (incr) {
269                         tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
270                         inet_csk(sk)->icsk_ack.quick |= 1;
271                 }
272         }
273 }
274
275 /* 3. Tuning rcvbuf, when connection enters established state. */
276
277 static void tcp_fixup_rcvbuf(struct sock *sk)
278 {
279         struct tcp_sock *tp = tcp_sk(sk);
280         int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
281
282         /* Try to select rcvbuf so that 4 mss-sized segments
283          * will fit to window and corresponding skbs will fit to our rcvbuf.
284          * (was 3; 4 is minimum to allow fast retransmit to work.)
285          */
286         while (tcp_win_from_space(rcvmem) < tp->advmss)
287                 rcvmem += 128;
288         if (sk->sk_rcvbuf < 4 * rcvmem)
289                 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
290 }
291
292 /* 4. Try to fixup all. It is made immediately after connection enters
293  *    established state.
294  */
295 static void tcp_init_buffer_space(struct sock *sk)
296 {
297         struct tcp_sock *tp = tcp_sk(sk);
298         int maxwin;
299
300         if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
301                 tcp_fixup_rcvbuf(sk);
302         if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
303                 tcp_fixup_sndbuf(sk);
304
305         tp->rcvq_space.space = tp->rcv_wnd;
306
307         maxwin = tcp_full_space(sk);
308
309         if (tp->window_clamp >= maxwin) {
310                 tp->window_clamp = maxwin;
311
312                 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
313                         tp->window_clamp = max(maxwin -
314                                                (maxwin >> sysctl_tcp_app_win),
315                                                4 * tp->advmss);
316         }
317
318         /* Force reservation of one segment. */
319         if (sysctl_tcp_app_win &&
320             tp->window_clamp > 2 * tp->advmss &&
321             tp->window_clamp + tp->advmss > maxwin)
322                 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
323
324         tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
325         tp->snd_cwnd_stamp = tcp_time_stamp;
326 }
327
328 /* 5. Recalculate window clamp after socket hit its memory bounds. */
329 static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
330 {
331         struct inet_connection_sock *icsk = inet_csk(sk);
332
333         icsk->icsk_ack.quick = 0;
334
335         if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
336             !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
337             !tcp_memory_pressure &&
338             atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
339                 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
340                                     sysctl_tcp_rmem[2]);
341         }
342         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
343                 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
344 }
345
346
347 /* Initialize RCV_MSS value.
348  * RCV_MSS is an our guess about MSS used by the peer.
349  * We haven't any direct information about the MSS.
350  * It's better to underestimate the RCV_MSS rather than overestimate.
351  * Overestimations make us ACKing less frequently than needed.
352  * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
353  */
354 void tcp_initialize_rcv_mss(struct sock *sk)
355 {
356         struct tcp_sock *tp = tcp_sk(sk);
357         unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
358
359         hint = min(hint, tp->rcv_wnd/2);
360         hint = min(hint, TCP_MIN_RCVMSS);
361         hint = max(hint, TCP_MIN_MSS);
362
363         inet_csk(sk)->icsk_ack.rcv_mss = hint;
364 }
365
366 /* Receiver "autotuning" code.
367  *
368  * The algorithm for RTT estimation w/o timestamps is based on
369  * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
370  * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
371  *
372  * More detail on this code can be found at
373  * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
374  * though this reference is out of date.  A new paper
375  * is pending.
376  */
377 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
378 {
379         u32 new_sample = tp->rcv_rtt_est.rtt;
380         long m = sample;
381
382         if (m == 0)
383                 m = 1;
384
385         if (new_sample != 0) {
386                 /* If we sample in larger samples in the non-timestamp
387                  * case, we could grossly overestimate the RTT especially
388                  * with chatty applications or bulk transfer apps which
389                  * are stalled on filesystem I/O.
390                  *
391                  * Also, since we are only going for a minimum in the
392                  * non-timestamp case, we do not smooth things out
393                  * else with timestamps disabled convergence takes too
394                  * long.
395                  */
396                 if (!win_dep) {
397                         m -= (new_sample >> 3);
398                         new_sample += m;
399                 } else if (m < new_sample)
400                         new_sample = m << 3;
401         } else {
402                 /* No previous measure. */
403                 new_sample = m << 3;
404         }
405
406         if (tp->rcv_rtt_est.rtt != new_sample)
407                 tp->rcv_rtt_est.rtt = new_sample;
408 }
409
410 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
411 {
412         if (tp->rcv_rtt_est.time == 0)
413                 goto new_measure;
414         if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
415                 return;
416         tcp_rcv_rtt_update(tp,
417                            jiffies - tp->rcv_rtt_est.time,
418                            1);
419
420 new_measure:
421         tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
422         tp->rcv_rtt_est.time = tcp_time_stamp;
423 }
424
425 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
426 {
427         struct tcp_sock *tp = tcp_sk(sk);
428         if (tp->rx_opt.rcv_tsecr &&
429             (TCP_SKB_CB(skb)->end_seq -
430              TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
431                 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
432 }
433
434 /*
435  * This function should be called every time data is copied to user space.
436  * It calculates the appropriate TCP receive buffer space.
437  */
438 void tcp_rcv_space_adjust(struct sock *sk)
439 {
440         struct tcp_sock *tp = tcp_sk(sk);
441         int time;
442         int space;
443
444         if (tp->rcvq_space.time == 0)
445                 goto new_measure;
446
447         time = tcp_time_stamp - tp->rcvq_space.time;
448         if (time < (tp->rcv_rtt_est.rtt >> 3) ||
449             tp->rcv_rtt_est.rtt == 0)
450                 return;
451
452         space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
453
454         space = max(tp->rcvq_space.space, space);
455
456         if (tp->rcvq_space.space != space) {
457                 int rcvmem;
458
459                 tp->rcvq_space.space = space;
460
461                 if (sysctl_tcp_moderate_rcvbuf &&
462                     !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
463                         int new_clamp = space;
464
465                         /* Receive space grows, normalize in order to
466                          * take into account packet headers and sk_buff
467                          * structure overhead.
468                          */
469                         space /= tp->advmss;
470                         if (!space)
471                                 space = 1;
472                         rcvmem = (tp->advmss + MAX_TCP_HEADER +
473                                   16 + sizeof(struct sk_buff));
474                         while (tcp_win_from_space(rcvmem) < tp->advmss)
475                                 rcvmem += 128;
476                         space *= rcvmem;
477                         space = min(space, sysctl_tcp_rmem[2]);
478                         if (space > sk->sk_rcvbuf) {
479                                 sk->sk_rcvbuf = space;
480
481                                 /* Make the window clamp follow along.  */
482                                 tp->window_clamp = new_clamp;
483                         }
484                 }
485         }
486
487 new_measure:
488         tp->rcvq_space.seq = tp->copied_seq;
489         tp->rcvq_space.time = tcp_time_stamp;
490 }
491
492 /* There is something which you must keep in mind when you analyze the
493  * behavior of the tp->ato delayed ack timeout interval.  When a
494  * connection starts up, we want to ack as quickly as possible.  The
495  * problem is that "good" TCP's do slow start at the beginning of data
496  * transmission.  The means that until we send the first few ACK's the
497  * sender will sit on his end and only queue most of his data, because
498  * he can only send snd_cwnd unacked packets at any given time.  For
499  * each ACK we send, he increments snd_cwnd and transmits more of his
500  * queue.  -DaveM
501  */
502 static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
503 {
504         struct inet_connection_sock *icsk = inet_csk(sk);
505         u32 now;
506
507         inet_csk_schedule_ack(sk);
508
509         tcp_measure_rcv_mss(sk, skb);
510
511         tcp_rcv_rtt_measure(tp);
512
513         now = tcp_time_stamp;
514
515         if (!icsk->icsk_ack.ato) {
516                 /* The _first_ data packet received, initialize
517                  * delayed ACK engine.
518                  */
519                 tcp_incr_quickack(sk);
520                 icsk->icsk_ack.ato = TCP_ATO_MIN;
521         } else {
522                 int m = now - icsk->icsk_ack.lrcvtime;
523
524                 if (m <= TCP_ATO_MIN/2) {
525                         /* The fastest case is the first. */
526                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
527                 } else if (m < icsk->icsk_ack.ato) {
528                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
529                         if (icsk->icsk_ack.ato > icsk->icsk_rto)
530                                 icsk->icsk_ack.ato = icsk->icsk_rto;
531                 } else if (m > icsk->icsk_rto) {
532                         /* Too long gap. Apparently sender failed to
533                          * restart window, so that we send ACKs quickly.
534                          */
535                         tcp_incr_quickack(sk);
536                         sk_stream_mem_reclaim(sk);
537                 }
538         }
539         icsk->icsk_ack.lrcvtime = now;
540
541         TCP_ECN_check_ce(tp, skb);
542
543         if (skb->len >= 128)
544                 tcp_grow_window(sk, tp, skb);
545 }
546
547 /* Called to compute a smoothed rtt estimate. The data fed to this
548  * routine either comes from timestamps, or from segments that were
549  * known _not_ to have been retransmitted [see Karn/Partridge
550  * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
551  * piece by Van Jacobson.
552  * NOTE: the next three routines used to be one big routine.
553  * To save cycles in the RFC 1323 implementation it was better to break
554  * it up into three procedures. -- erics
555  */
556 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
557 {
558         struct tcp_sock *tp = tcp_sk(sk);
559         long m = mrtt; /* RTT */
560
561         /*      The following amusing code comes from Jacobson's
562          *      article in SIGCOMM '88.  Note that rtt and mdev
563          *      are scaled versions of rtt and mean deviation.
564          *      This is designed to be as fast as possible
565          *      m stands for "measurement".
566          *
567          *      On a 1990 paper the rto value is changed to:
568          *      RTO = rtt + 4 * mdev
569          *
570          * Funny. This algorithm seems to be very broken.
571          * These formulae increase RTO, when it should be decreased, increase
572          * too slowly, when it should be increased quickly, decrease too quickly
573          * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
574          * does not matter how to _calculate_ it. Seems, it was trap
575          * that VJ failed to avoid. 8)
576          */
577         if(m == 0)
578                 m = 1;
579         if (tp->srtt != 0) {
580                 m -= (tp->srtt >> 3);   /* m is now error in rtt est */
581                 tp->srtt += m;          /* rtt = 7/8 rtt + 1/8 new */
582                 if (m < 0) {
583                         m = -m;         /* m is now abs(error) */
584                         m -= (tp->mdev >> 2);   /* similar update on mdev */
585                         /* This is similar to one of Eifel findings.
586                          * Eifel blocks mdev updates when rtt decreases.
587                          * This solution is a bit different: we use finer gain
588                          * for mdev in this case (alpha*beta).
589                          * Like Eifel it also prevents growth of rto,
590                          * but also it limits too fast rto decreases,
591                          * happening in pure Eifel.
592                          */
593                         if (m > 0)
594                                 m >>= 3;
595                 } else {
596                         m -= (tp->mdev >> 2);   /* similar update on mdev */
597                 }
598                 tp->mdev += m;          /* mdev = 3/4 mdev + 1/4 new */
599                 if (tp->mdev > tp->mdev_max) {
600                         tp->mdev_max = tp->mdev;
601                         if (tp->mdev_max > tp->rttvar)
602                                 tp->rttvar = tp->mdev_max;
603                 }
604                 if (after(tp->snd_una, tp->rtt_seq)) {
605                         if (tp->mdev_max < tp->rttvar)
606                                 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
607                         tp->rtt_seq = tp->snd_nxt;
608                         tp->mdev_max = TCP_RTO_MIN;
609                 }
610         } else {
611                 /* no previous measure. */
612                 tp->srtt = m<<3;        /* take the measured time to be rtt */
613                 tp->mdev = m<<1;        /* make sure rto = 3*rtt */
614                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
615                 tp->rtt_seq = tp->snd_nxt;
616         }
617 }
618
619 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
620  * routine referred to above.
621  */
622 static inline void tcp_set_rto(struct sock *sk)
623 {
624         const struct tcp_sock *tp = tcp_sk(sk);
625         /* Old crap is replaced with new one. 8)
626          *
627          * More seriously:
628          * 1. If rtt variance happened to be less 50msec, it is hallucination.
629          *    It cannot be less due to utterly erratic ACK generation made
630          *    at least by solaris and freebsd. "Erratic ACKs" has _nothing_
631          *    to do with delayed acks, because at cwnd>2 true delack timeout
632          *    is invisible. Actually, Linux-2.4 also generates erratic
633          *    ACKs in some circumstances.
634          */
635         inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
636
637         /* 2. Fixups made earlier cannot be right.
638          *    If we do not estimate RTO correctly without them,
639          *    all the algo is pure shit and should be replaced
640          *    with correct one. It is exactly, which we pretend to do.
641          */
642 }
643
644 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
645  * guarantees that rto is higher.
646  */
647 static inline void tcp_bound_rto(struct sock *sk)
648 {
649         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
650                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
651 }
652
653 /* Save metrics learned by this TCP session.
654    This function is called only, when TCP finishes successfully
655    i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
656  */
657 void tcp_update_metrics(struct sock *sk)
658 {
659         struct tcp_sock *tp = tcp_sk(sk);
660         struct dst_entry *dst = __sk_dst_get(sk);
661
662         if (sysctl_tcp_nometrics_save)
663                 return;
664
665         dst_confirm(dst);
666
667         if (dst && (dst->flags&DST_HOST)) {
668                 const struct inet_connection_sock *icsk = inet_csk(sk);
669                 int m;
670
671                 if (icsk->icsk_backoff || !tp->srtt) {
672                         /* This session failed to estimate rtt. Why?
673                          * Probably, no packets returned in time.
674                          * Reset our results.
675                          */
676                         if (!(dst_metric_locked(dst, RTAX_RTT)))
677                                 dst->metrics[RTAX_RTT-1] = 0;
678                         return;
679                 }
680
681                 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
682
683                 /* If newly calculated rtt larger than stored one,
684                  * store new one. Otherwise, use EWMA. Remember,
685                  * rtt overestimation is always better than underestimation.
686                  */
687                 if (!(dst_metric_locked(dst, RTAX_RTT))) {
688                         if (m <= 0)
689                                 dst->metrics[RTAX_RTT-1] = tp->srtt;
690                         else
691                                 dst->metrics[RTAX_RTT-1] -= (m>>3);
692                 }
693
694                 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
695                         if (m < 0)
696                                 m = -m;
697
698                         /* Scale deviation to rttvar fixed point */
699                         m >>= 1;
700                         if (m < tp->mdev)
701                                 m = tp->mdev;
702
703                         if (m >= dst_metric(dst, RTAX_RTTVAR))
704                                 dst->metrics[RTAX_RTTVAR-1] = m;
705                         else
706                                 dst->metrics[RTAX_RTTVAR-1] -=
707                                         (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
708                 }
709
710                 if (tp->snd_ssthresh >= 0xFFFF) {
711                         /* Slow start still did not finish. */
712                         if (dst_metric(dst, RTAX_SSTHRESH) &&
713                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
714                             (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
715                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
716                         if (!dst_metric_locked(dst, RTAX_CWND) &&
717                             tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
718                                 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
719                 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
720                            icsk->icsk_ca_state == TCP_CA_Open) {
721                         /* Cong. avoidance phase, cwnd is reliable. */
722                         if (!dst_metric_locked(dst, RTAX_SSTHRESH))
723                                 dst->metrics[RTAX_SSTHRESH-1] =
724                                         max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
725                         if (!dst_metric_locked(dst, RTAX_CWND))
726                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
727                 } else {
728                         /* Else slow start did not finish, cwnd is non-sense,
729                            ssthresh may be also invalid.
730                          */
731                         if (!dst_metric_locked(dst, RTAX_CWND))
732                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
733                         if (dst->metrics[RTAX_SSTHRESH-1] &&
734                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
735                             tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
736                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
737                 }
738
739                 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
740                         if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
741                             tp->reordering != sysctl_tcp_reordering)
742                                 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
743                 }
744         }
745 }
746
747 /* Numbers are taken from RFC2414.  */
748 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
749 {
750         __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
751
752         if (!cwnd) {
753                 if (tp->mss_cache > 1460)
754                         cwnd = 2;
755                 else
756                         cwnd = (tp->mss_cache > 1095) ? 3 : 4;
757         }
758         return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
759 }
760
761 /* Set slow start threshold and cwnd not falling to slow start */
762 void tcp_enter_cwr(struct sock *sk)
763 {
764         struct tcp_sock *tp = tcp_sk(sk);
765
766         tp->prior_ssthresh = 0;
767         tp->bytes_acked = 0;
768         if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
769                 tp->undo_marker = 0;
770                 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
771                 tp->snd_cwnd = min(tp->snd_cwnd,
772                                    tcp_packets_in_flight(tp) + 1U);
773                 tp->snd_cwnd_cnt = 0;
774                 tp->high_seq = tp->snd_nxt;
775                 tp->snd_cwnd_stamp = tcp_time_stamp;
776                 TCP_ECN_queue_cwr(tp);
777
778                 tcp_set_ca_state(sk, TCP_CA_CWR);
779         }
780 }
781
782 /* Initialize metrics on socket. */
783
784 static void tcp_init_metrics(struct sock *sk)
785 {
786         struct tcp_sock *tp = tcp_sk(sk);
787         struct dst_entry *dst = __sk_dst_get(sk);
788
789         if (dst == NULL)
790                 goto reset;
791
792         dst_confirm(dst);
793
794         if (dst_metric_locked(dst, RTAX_CWND))
795                 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
796         if (dst_metric(dst, RTAX_SSTHRESH)) {
797                 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
798                 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
799                         tp->snd_ssthresh = tp->snd_cwnd_clamp;
800         }
801         if (dst_metric(dst, RTAX_REORDERING) &&
802             tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
803                 tp->rx_opt.sack_ok &= ~2;
804                 tp->reordering = dst_metric(dst, RTAX_REORDERING);
805         }
806
807         if (dst_metric(dst, RTAX_RTT) == 0)
808                 goto reset;
809
810         if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
811                 goto reset;
812
813         /* Initial rtt is determined from SYN,SYN-ACK.
814          * The segment is small and rtt may appear much
815          * less than real one. Use per-dst memory
816          * to make it more realistic.
817          *
818          * A bit of theory. RTT is time passed after "normal" sized packet
819          * is sent until it is ACKed. In normal circumstances sending small
820          * packets force peer to delay ACKs and calculation is correct too.
821          * The algorithm is adaptive and, provided we follow specs, it
822          * NEVER underestimate RTT. BUT! If peer tries to make some clever
823          * tricks sort of "quick acks" for time long enough to decrease RTT
824          * to low value, and then abruptly stops to do it and starts to delay
825          * ACKs, wait for troubles.
826          */
827         if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
828                 tp->srtt = dst_metric(dst, RTAX_RTT);
829                 tp->rtt_seq = tp->snd_nxt;
830         }
831         if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
832                 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
833                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
834         }
835         tcp_set_rto(sk);
836         tcp_bound_rto(sk);
837         if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
838                 goto reset;
839         tp->snd_cwnd = tcp_init_cwnd(tp, dst);
840         tp->snd_cwnd_stamp = tcp_time_stamp;
841         return;
842
843 reset:
844         /* Play conservative. If timestamps are not
845          * supported, TCP will fail to recalculate correct
846          * rtt, if initial rto is too small. FORGET ALL AND RESET!
847          */
848         if (!tp->rx_opt.saw_tstamp && tp->srtt) {
849                 tp->srtt = 0;
850                 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
851                 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
852         }
853 }
854
855 static void tcp_update_reordering(struct sock *sk, const int metric,
856                                   const int ts)
857 {
858         struct tcp_sock *tp = tcp_sk(sk);
859         if (metric > tp->reordering) {
860                 tp->reordering = min(TCP_MAX_REORDERING, metric);
861
862                 /* This exciting event is worth to be remembered. 8) */
863                 if (ts)
864                         NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
865                 else if (IsReno(tp))
866                         NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
867                 else if (IsFack(tp))
868                         NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
869                 else
870                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
871 #if FASTRETRANS_DEBUG > 1
872                 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
873                        tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
874                        tp->reordering,
875                        tp->fackets_out,
876                        tp->sacked_out,
877                        tp->undo_marker ? tp->undo_retrans : 0);
878 #endif
879                 /* Disable FACK yet. */
880                 tp->rx_opt.sack_ok &= ~2;
881         }
882 }
883
884 /* This procedure tags the retransmission queue when SACKs arrive.
885  *
886  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
887  * Packets in queue with these bits set are counted in variables
888  * sacked_out, retrans_out and lost_out, correspondingly.
889  *
890  * Valid combinations are:
891  * Tag  InFlight        Description
892  * 0    1               - orig segment is in flight.
893  * S    0               - nothing flies, orig reached receiver.
894  * L    0               - nothing flies, orig lost by net.
895  * R    2               - both orig and retransmit are in flight.
896  * L|R  1               - orig is lost, retransmit is in flight.
897  * S|R  1               - orig reached receiver, retrans is still in flight.
898  * (L|S|R is logically valid, it could occur when L|R is sacked,
899  *  but it is equivalent to plain S and code short-curcuits it to S.
900  *  L|S is logically invalid, it would mean -1 packet in flight 8))
901  *
902  * These 6 states form finite state machine, controlled by the following events:
903  * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
904  * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
905  * 3. Loss detection event of one of three flavors:
906  *      A. Scoreboard estimator decided the packet is lost.
907  *         A'. Reno "three dupacks" marks head of queue lost.
908  *         A''. Its FACK modfication, head until snd.fack is lost.
909  *      B. SACK arrives sacking data transmitted after never retransmitted
910  *         hole was sent out.
911  *      C. SACK arrives sacking SND.NXT at the moment, when the
912  *         segment was retransmitted.
913  * 4. D-SACK added new rule: D-SACK changes any tag to S.
914  *
915  * It is pleasant to note, that state diagram turns out to be commutative,
916  * so that we are allowed not to be bothered by order of our actions,
917  * when multiple events arrive simultaneously. (see the function below).
918  *
919  * Reordering detection.
920  * --------------------
921  * Reordering metric is maximal distance, which a packet can be displaced
922  * in packet stream. With SACKs we can estimate it:
923  *
924  * 1. SACK fills old hole and the corresponding segment was not
925  *    ever retransmitted -> reordering. Alas, we cannot use it
926  *    when segment was retransmitted.
927  * 2. The last flaw is solved with D-SACK. D-SACK arrives
928  *    for retransmitted and already SACKed segment -> reordering..
929  * Both of these heuristics are not used in Loss state, when we cannot
930  * account for retransmits accurately.
931  */
932 static int
933 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
934 {
935         const struct inet_connection_sock *icsk = inet_csk(sk);
936         struct tcp_sock *tp = tcp_sk(sk);
937         unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
938         struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
939         struct sk_buff *cached_skb;
940         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
941         int reord = tp->packets_out;
942         int prior_fackets;
943         u32 lost_retrans = 0;
944         int flag = 0;
945         int dup_sack = 0;
946         int cached_fack_count;
947         int i;
948         int first_sack_index;
949
950         if (!tp->sacked_out)
951                 tp->fackets_out = 0;
952         prior_fackets = tp->fackets_out;
953
954         /* Check for D-SACK. */
955         if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) {
956                 dup_sack = 1;
957                 tp->rx_opt.sack_ok |= 4;
958                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
959         } else if (num_sacks > 1 &&
960                         !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) &&
961                         !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) {
962                 dup_sack = 1;
963                 tp->rx_opt.sack_ok |= 4;
964                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
965         }
966
967         /* D-SACK for already forgotten data...
968          * Do dumb counting. */
969         if (dup_sack &&
970                         !after(ntohl(sp[0].end_seq), prior_snd_una) &&
971                         after(ntohl(sp[0].end_seq), tp->undo_marker))
972                 tp->undo_retrans--;
973
974         /* Eliminate too old ACKs, but take into
975          * account more or less fresh ones, they can
976          * contain valid SACK info.
977          */
978         if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
979                 return 0;
980
981         /* SACK fastpath:
982          * if the only SACK change is the increase of the end_seq of
983          * the first block then only apply that SACK block
984          * and use retrans queue hinting otherwise slowpath */
985         flag = 1;
986         for (i = 0; i < num_sacks; i++) {
987                 __be32 start_seq = sp[i].start_seq;
988                 __be32 end_seq = sp[i].end_seq;
989
990                 if (i == 0) {
991                         if (tp->recv_sack_cache[i].start_seq != start_seq)
992                                 flag = 0;
993                 } else {
994                         if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
995                             (tp->recv_sack_cache[i].end_seq != end_seq))
996                                 flag = 0;
997                 }
998                 tp->recv_sack_cache[i].start_seq = start_seq;
999                 tp->recv_sack_cache[i].end_seq = end_seq;
1000         }
1001         /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1002         for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) {
1003                 tp->recv_sack_cache[i].start_seq = 0;
1004                 tp->recv_sack_cache[i].end_seq = 0;
1005         }
1006
1007         first_sack_index = 0;
1008         if (flag)
1009                 num_sacks = 1;
1010         else {
1011                 int j;
1012                 tp->fastpath_skb_hint = NULL;
1013
1014                 /* order SACK blocks to allow in order walk of the retrans queue */
1015                 for (i = num_sacks-1; i > 0; i--) {
1016                         for (j = 0; j < i; j++){
1017                                 if (after(ntohl(sp[j].start_seq),
1018                                           ntohl(sp[j+1].start_seq))){
1019                                         struct tcp_sack_block_wire tmp;
1020
1021                                         tmp = sp[j];
1022                                         sp[j] = sp[j+1];
1023                                         sp[j+1] = tmp;
1024
1025                                         /* Track where the first SACK block goes to */
1026                                         if (j == first_sack_index)
1027                                                 first_sack_index = j+1;
1028                                 }
1029
1030                         }
1031                 }
1032         }
1033
1034         /* clear flag as used for different purpose in following code */
1035         flag = 0;
1036
1037         /* Use SACK fastpath hint if valid */
1038         cached_skb = tp->fastpath_skb_hint;
1039         cached_fack_count = tp->fastpath_cnt_hint;
1040         if (!cached_skb) {
1041                 cached_skb = sk->sk_write_queue.next;
1042                 cached_fack_count = 0;
1043         }
1044
1045         for (i=0; i<num_sacks; i++, sp++) {
1046                 struct sk_buff *skb;
1047                 __u32 start_seq = ntohl(sp->start_seq);
1048                 __u32 end_seq = ntohl(sp->end_seq);
1049                 int fack_count;
1050
1051                 skb = cached_skb;
1052                 fack_count = cached_fack_count;
1053
1054                 /* Event "B" in the comment above. */
1055                 if (after(end_seq, tp->high_seq))
1056                         flag |= FLAG_DATA_LOST;
1057
1058                 sk_stream_for_retrans_queue_from(skb, sk) {
1059                         int in_sack, pcount;
1060                         u8 sacked;
1061
1062                         cached_skb = skb;
1063                         cached_fack_count = fack_count;
1064                         if (i == first_sack_index) {
1065                                 tp->fastpath_skb_hint = skb;
1066                                 tp->fastpath_cnt_hint = fack_count;
1067                         }
1068
1069                         /* The retransmission queue is always in order, so
1070                          * we can short-circuit the walk early.
1071                          */
1072                         if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1073                                 break;
1074
1075                         in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1076                                 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1077
1078                         pcount = tcp_skb_pcount(skb);
1079
1080                         if (pcount > 1 && !in_sack &&
1081                             after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1082                                 unsigned int pkt_len;
1083
1084                                 in_sack = !after(start_seq,
1085                                                  TCP_SKB_CB(skb)->seq);
1086
1087                                 if (!in_sack)
1088                                         pkt_len = (start_seq -
1089                                                    TCP_SKB_CB(skb)->seq);
1090                                 else
1091                                         pkt_len = (end_seq -
1092                                                    TCP_SKB_CB(skb)->seq);
1093                                 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size))
1094                                         break;
1095                                 pcount = tcp_skb_pcount(skb);
1096                         }
1097
1098                         fack_count += pcount;
1099
1100                         sacked = TCP_SKB_CB(skb)->sacked;
1101
1102                         /* Account D-SACK for retransmitted packet. */
1103                         if ((dup_sack && in_sack) &&
1104                             (sacked & TCPCB_RETRANS) &&
1105                             after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1106                                 tp->undo_retrans--;
1107
1108                         /* The frame is ACKed. */
1109                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1110                                 if (sacked&TCPCB_RETRANS) {
1111                                         if ((dup_sack && in_sack) &&
1112                                             (sacked&TCPCB_SACKED_ACKED))
1113                                                 reord = min(fack_count, reord);
1114                                 } else {
1115                                         /* If it was in a hole, we detected reordering. */
1116                                         if (fack_count < prior_fackets &&
1117                                             !(sacked&TCPCB_SACKED_ACKED))
1118                                                 reord = min(fack_count, reord);
1119                                 }
1120
1121                                 /* Nothing to do; acked frame is about to be dropped. */
1122                                 continue;
1123                         }
1124
1125                         if ((sacked&TCPCB_SACKED_RETRANS) &&
1126                             after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1127                             (!lost_retrans || after(end_seq, lost_retrans)))
1128                                 lost_retrans = end_seq;
1129
1130                         if (!in_sack)
1131                                 continue;
1132
1133                         if (!(sacked&TCPCB_SACKED_ACKED)) {
1134                                 if (sacked & TCPCB_SACKED_RETRANS) {
1135                                         /* If the segment is not tagged as lost,
1136                                          * we do not clear RETRANS, believing
1137                                          * that retransmission is still in flight.
1138                                          */
1139                                         if (sacked & TCPCB_LOST) {
1140                                                 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1141                                                 tp->lost_out -= tcp_skb_pcount(skb);
1142                                                 tp->retrans_out -= tcp_skb_pcount(skb);
1143
1144                                                 /* clear lost hint */
1145                                                 tp->retransmit_skb_hint = NULL;
1146                                         }
1147                                 } else {
1148                                         /* New sack for not retransmitted frame,
1149                                          * which was in hole. It is reordering.
1150                                          */
1151                                         if (!(sacked & TCPCB_RETRANS) &&
1152                                             fack_count < prior_fackets)
1153                                                 reord = min(fack_count, reord);
1154
1155                                         if (sacked & TCPCB_LOST) {
1156                                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1157                                                 tp->lost_out -= tcp_skb_pcount(skb);
1158
1159                                                 /* clear lost hint */
1160                                                 tp->retransmit_skb_hint = NULL;
1161                                         }
1162                                 }
1163
1164                                 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1165                                 flag |= FLAG_DATA_SACKED;
1166                                 tp->sacked_out += tcp_skb_pcount(skb);
1167
1168                                 if (fack_count > tp->fackets_out)
1169                                         tp->fackets_out = fack_count;
1170                         } else {
1171                                 if (dup_sack && (sacked&TCPCB_RETRANS))
1172                                         reord = min(fack_count, reord);
1173                         }
1174
1175                         /* D-SACK. We can detect redundant retransmission
1176                          * in S|R and plain R frames and clear it.
1177                          * undo_retrans is decreased above, L|R frames
1178                          * are accounted above as well.
1179                          */
1180                         if (dup_sack &&
1181                             (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1182                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1183                                 tp->retrans_out -= tcp_skb_pcount(skb);
1184                                 tp->retransmit_skb_hint = NULL;
1185                         }
1186                 }
1187         }
1188
1189         /* Check for lost retransmit. This superb idea is
1190          * borrowed from "ratehalving". Event "C".
1191          * Later note: FACK people cheated me again 8),
1192          * we have to account for reordering! Ugly,
1193          * but should help.
1194          */
1195         if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
1196                 struct sk_buff *skb;
1197
1198                 sk_stream_for_retrans_queue(skb, sk) {
1199                         if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1200                                 break;
1201                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1202                                 continue;
1203                         if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1204                             after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1205                             (IsFack(tp) ||
1206                              !before(lost_retrans,
1207                                      TCP_SKB_CB(skb)->ack_seq + tp->reordering *
1208                                      tp->mss_cache))) {
1209                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1210                                 tp->retrans_out -= tcp_skb_pcount(skb);
1211
1212                                 /* clear lost hint */
1213                                 tp->retransmit_skb_hint = NULL;
1214
1215                                 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1216                                         tp->lost_out += tcp_skb_pcount(skb);
1217                                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1218                                         flag |= FLAG_DATA_SACKED;
1219                                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1220                                 }
1221                         }
1222                 }
1223         }
1224
1225         tp->left_out = tp->sacked_out + tp->lost_out;
1226
1227         if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1228                 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
1229
1230 #if FASTRETRANS_DEBUG > 0
1231         BUG_TRAP((int)tp->sacked_out >= 0);
1232         BUG_TRAP((int)tp->lost_out >= 0);
1233         BUG_TRAP((int)tp->retrans_out >= 0);
1234         BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1235 #endif
1236         return flag;
1237 }
1238
1239 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1240  * segments to see from the next ACKs whether any data was really missing.
1241  * If the RTO was spurious, new ACKs should arrive.
1242  */
1243 void tcp_enter_frto(struct sock *sk)
1244 {
1245         const struct inet_connection_sock *icsk = inet_csk(sk);
1246         struct tcp_sock *tp = tcp_sk(sk);
1247         struct sk_buff *skb;
1248
1249         tp->frto_counter = 1;
1250
1251         if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1252             tp->snd_una == tp->high_seq ||
1253             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1254                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1255                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1256                 tcp_ca_event(sk, CA_EVENT_FRTO);
1257         }
1258
1259         /* Have to clear retransmission markers here to keep the bookkeeping
1260          * in shape, even though we are not yet in Loss state.
1261          * If something was really lost, it is eventually caught up
1262          * in tcp_enter_frto_loss.
1263          */
1264         tp->retrans_out = 0;
1265         tp->undo_marker = tp->snd_una;
1266         tp->undo_retrans = 0;
1267
1268         sk_stream_for_retrans_queue(skb, sk) {
1269                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1270         }
1271         tcp_sync_left_out(tp);
1272
1273         tcp_set_ca_state(sk, TCP_CA_Open);
1274         tp->frto_highmark = tp->snd_nxt;
1275 }
1276
1277 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1278  * which indicates that we should follow the traditional RTO recovery,
1279  * i.e. mark everything lost and do go-back-N retransmission.
1280  */
1281 static void tcp_enter_frto_loss(struct sock *sk)
1282 {
1283         struct tcp_sock *tp = tcp_sk(sk);
1284         struct sk_buff *skb;
1285         int cnt = 0;
1286
1287         tp->sacked_out = 0;
1288         tp->lost_out = 0;
1289         tp->fackets_out = 0;
1290
1291         sk_stream_for_retrans_queue(skb, sk) {
1292                 cnt += tcp_skb_pcount(skb);
1293                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1294                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1295
1296                         /* Do not mark those segments lost that were
1297                          * forward transmitted after RTO
1298                          */
1299                         if (!after(TCP_SKB_CB(skb)->end_seq,
1300                                    tp->frto_highmark)) {
1301                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1302                                 tp->lost_out += tcp_skb_pcount(skb);
1303                         }
1304                 } else {
1305                         tp->sacked_out += tcp_skb_pcount(skb);
1306                         tp->fackets_out = cnt;
1307                 }
1308         }
1309         tcp_sync_left_out(tp);
1310
1311         tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1312         tp->snd_cwnd_cnt = 0;
1313         tp->snd_cwnd_stamp = tcp_time_stamp;
1314         tp->undo_marker = 0;
1315         tp->frto_counter = 0;
1316
1317         tp->reordering = min_t(unsigned int, tp->reordering,
1318                                              sysctl_tcp_reordering);
1319         tcp_set_ca_state(sk, TCP_CA_Loss);
1320         tp->high_seq = tp->frto_highmark;
1321         TCP_ECN_queue_cwr(tp);
1322
1323         clear_all_retrans_hints(tp);
1324 }
1325
1326 void tcp_clear_retrans(struct tcp_sock *tp)
1327 {
1328         tp->left_out = 0;
1329         tp->retrans_out = 0;
1330
1331         tp->fackets_out = 0;
1332         tp->sacked_out = 0;
1333         tp->lost_out = 0;
1334
1335         tp->undo_marker = 0;
1336         tp->undo_retrans = 0;
1337 }
1338
1339 /* Enter Loss state. If "how" is not zero, forget all SACK information
1340  * and reset tags completely, otherwise preserve SACKs. If receiver
1341  * dropped its ofo queue, we will know this due to reneging detection.
1342  */
1343 void tcp_enter_loss(struct sock *sk, int how)
1344 {
1345         const struct inet_connection_sock *icsk = inet_csk(sk);
1346         struct tcp_sock *tp = tcp_sk(sk);
1347         struct sk_buff *skb;
1348         int cnt = 0;
1349
1350         /* Reduce ssthresh if it has not yet been made inside this window. */
1351         if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1352             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1353                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1354                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1355                 tcp_ca_event(sk, CA_EVENT_LOSS);
1356         }
1357         tp->snd_cwnd       = 1;
1358         tp->snd_cwnd_cnt   = 0;
1359         tp->snd_cwnd_stamp = tcp_time_stamp;
1360
1361         tp->bytes_acked = 0;
1362         tcp_clear_retrans(tp);
1363
1364         /* Push undo marker, if it was plain RTO and nothing
1365          * was retransmitted. */
1366         if (!how)
1367                 tp->undo_marker = tp->snd_una;
1368
1369         sk_stream_for_retrans_queue(skb, sk) {
1370                 cnt += tcp_skb_pcount(skb);
1371                 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1372                         tp->undo_marker = 0;
1373                 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1374                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1375                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1376                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1377                         tp->lost_out += tcp_skb_pcount(skb);
1378                 } else {
1379                         tp->sacked_out += tcp_skb_pcount(skb);
1380                         tp->fackets_out = cnt;
1381                 }
1382         }
1383         tcp_sync_left_out(tp);
1384
1385         tp->reordering = min_t(unsigned int, tp->reordering,
1386                                              sysctl_tcp_reordering);
1387         tcp_set_ca_state(sk, TCP_CA_Loss);
1388         tp->high_seq = tp->snd_nxt;
1389         TCP_ECN_queue_cwr(tp);
1390
1391         clear_all_retrans_hints(tp);
1392 }
1393
1394 static int tcp_check_sack_reneging(struct sock *sk)
1395 {
1396         struct sk_buff *skb;
1397
1398         /* If ACK arrived pointing to a remembered SACK,
1399          * it means that our remembered SACKs do not reflect
1400          * real state of receiver i.e.
1401          * receiver _host_ is heavily congested (or buggy).
1402          * Do processing similar to RTO timeout.
1403          */
1404         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1405             (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
1406                 struct inet_connection_sock *icsk = inet_csk(sk);
1407                 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1408
1409                 tcp_enter_loss(sk, 1);
1410                 icsk->icsk_retransmits++;
1411                 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
1412                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1413                                           icsk->icsk_rto, TCP_RTO_MAX);
1414                 return 1;
1415         }
1416         return 0;
1417 }
1418
1419 static inline int tcp_fackets_out(struct tcp_sock *tp)
1420 {
1421         return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1422 }
1423
1424 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
1425 {
1426         return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
1427 }
1428
1429 static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1430 {
1431         return tp->packets_out &&
1432                tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
1433 }
1434
1435 /* Linux NewReno/SACK/FACK/ECN state machine.
1436  * --------------------------------------
1437  *
1438  * "Open"       Normal state, no dubious events, fast path.
1439  * "Disorder"   In all the respects it is "Open",
1440  *              but requires a bit more attention. It is entered when
1441  *              we see some SACKs or dupacks. It is split of "Open"
1442  *              mainly to move some processing from fast path to slow one.
1443  * "CWR"        CWND was reduced due to some Congestion Notification event.
1444  *              It can be ECN, ICMP source quench, local device congestion.
1445  * "Recovery"   CWND was reduced, we are fast-retransmitting.
1446  * "Loss"       CWND was reduced due to RTO timeout or SACK reneging.
1447  *
1448  * tcp_fastretrans_alert() is entered:
1449  * - each incoming ACK, if state is not "Open"
1450  * - when arrived ACK is unusual, namely:
1451  *      * SACK
1452  *      * Duplicate ACK.
1453  *      * ECN ECE.
1454  *
1455  * Counting packets in flight is pretty simple.
1456  *
1457  *      in_flight = packets_out - left_out + retrans_out
1458  *
1459  *      packets_out is SND.NXT-SND.UNA counted in packets.
1460  *
1461  *      retrans_out is number of retransmitted segments.
1462  *
1463  *      left_out is number of segments left network, but not ACKed yet.
1464  *
1465  *              left_out = sacked_out + lost_out
1466  *
1467  *     sacked_out: Packets, which arrived to receiver out of order
1468  *                 and hence not ACKed. With SACKs this number is simply
1469  *                 amount of SACKed data. Even without SACKs
1470  *                 it is easy to give pretty reliable estimate of this number,
1471  *                 counting duplicate ACKs.
1472  *
1473  *       lost_out: Packets lost by network. TCP has no explicit
1474  *                 "loss notification" feedback from network (for now).
1475  *                 It means that this number can be only _guessed_.
1476  *                 Actually, it is the heuristics to predict lossage that
1477  *                 distinguishes different algorithms.
1478  *
1479  *      F.e. after RTO, when all the queue is considered as lost,
1480  *      lost_out = packets_out and in_flight = retrans_out.
1481  *
1482  *              Essentially, we have now two algorithms counting
1483  *              lost packets.
1484  *
1485  *              FACK: It is the simplest heuristics. As soon as we decided
1486  *              that something is lost, we decide that _all_ not SACKed
1487  *              packets until the most forward SACK are lost. I.e.
1488  *              lost_out = fackets_out - sacked_out and left_out = fackets_out.
1489  *              It is absolutely correct estimate, if network does not reorder
1490  *              packets. And it loses any connection to reality when reordering
1491  *              takes place. We use FACK by default until reordering
1492  *              is suspected on the path to this destination.
1493  *
1494  *              NewReno: when Recovery is entered, we assume that one segment
1495  *              is lost (classic Reno). While we are in Recovery and
1496  *              a partial ACK arrives, we assume that one more packet
1497  *              is lost (NewReno). This heuristics are the same in NewReno
1498  *              and SACK.
1499  *
1500  *  Imagine, that's all! Forget about all this shamanism about CWND inflation
1501  *  deflation etc. CWND is real congestion window, never inflated, changes
1502  *  only according to classic VJ rules.
1503  *
1504  * Really tricky (and requiring careful tuning) part of algorithm
1505  * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1506  * The first determines the moment _when_ we should reduce CWND and,
1507  * hence, slow down forward transmission. In fact, it determines the moment
1508  * when we decide that hole is caused by loss, rather than by a reorder.
1509  *
1510  * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1511  * holes, caused by lost packets.
1512  *
1513  * And the most logically complicated part of algorithm is undo
1514  * heuristics. We detect false retransmits due to both too early
1515  * fast retransmit (reordering) and underestimated RTO, analyzing
1516  * timestamps and D-SACKs. When we detect that some segments were
1517  * retransmitted by mistake and CWND reduction was wrong, we undo
1518  * window reduction and abort recovery phase. This logic is hidden
1519  * inside several functions named tcp_try_undo_<something>.
1520  */
1521
1522 /* This function decides, when we should leave Disordered state
1523  * and enter Recovery phase, reducing congestion window.
1524  *
1525  * Main question: may we further continue forward transmission
1526  * with the same cwnd?
1527  */
1528 static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1529 {
1530         __u32 packets_out;
1531
1532         /* Trick#1: The loss is proven. */
1533         if (tp->lost_out)
1534                 return 1;
1535
1536         /* Not-A-Trick#2 : Classic rule... */
1537         if (tcp_fackets_out(tp) > tp->reordering)
1538                 return 1;
1539
1540         /* Trick#3 : when we use RFC2988 timer restart, fast
1541          * retransmit can be triggered by timeout of queue head.
1542          */
1543         if (tcp_head_timedout(sk, tp))
1544                 return 1;
1545
1546         /* Trick#4: It is still not OK... But will it be useful to delay
1547          * recovery more?
1548          */
1549         packets_out = tp->packets_out;
1550         if (packets_out <= tp->reordering &&
1551             tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1552             !tcp_may_send_now(sk, tp)) {
1553                 /* We have nothing to send. This connection is limited
1554                  * either by receiver window or by application.
1555                  */
1556                 return 1;
1557         }
1558
1559         return 0;
1560 }
1561
1562 /* If we receive more dupacks than we expected counting segments
1563  * in assumption of absent reordering, interpret this as reordering.
1564  * The only another reason could be bug in receiver TCP.
1565  */
1566 static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1567 {
1568         struct tcp_sock *tp = tcp_sk(sk);
1569         u32 holes;
1570
1571         holes = max(tp->lost_out, 1U);
1572         holes = min(holes, tp->packets_out);
1573
1574         if ((tp->sacked_out + holes) > tp->packets_out) {
1575                 tp->sacked_out = tp->packets_out - holes;
1576                 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1577         }
1578 }
1579
1580 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1581
1582 static void tcp_add_reno_sack(struct sock *sk)
1583 {
1584         struct tcp_sock *tp = tcp_sk(sk);
1585         tp->sacked_out++;
1586         tcp_check_reno_reordering(sk, 0);
1587         tcp_sync_left_out(tp);
1588 }
1589
1590 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1591
1592 static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1593 {
1594         if (acked > 0) {
1595                 /* One ACK acked hole. The rest eat duplicate ACKs. */
1596                 if (acked-1 >= tp->sacked_out)
1597                         tp->sacked_out = 0;
1598                 else
1599                         tp->sacked_out -= acked-1;
1600         }
1601         tcp_check_reno_reordering(sk, acked);
1602         tcp_sync_left_out(tp);
1603 }
1604
1605 static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1606 {
1607         tp->sacked_out = 0;
1608         tp->left_out = tp->lost_out;
1609 }
1610
1611 /* Mark head of queue up as lost. */
1612 static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1613                                int packets, u32 high_seq)
1614 {
1615         struct sk_buff *skb;
1616         int cnt;
1617
1618         BUG_TRAP(packets <= tp->packets_out);
1619         if (tp->lost_skb_hint) {
1620                 skb = tp->lost_skb_hint;
1621                 cnt = tp->lost_cnt_hint;
1622         } else {
1623                 skb = sk->sk_write_queue.next;
1624                 cnt = 0;
1625         }
1626
1627         sk_stream_for_retrans_queue_from(skb, sk) {
1628                 /* TODO: do this better */
1629                 /* this is not the most efficient way to do this... */
1630                 tp->lost_skb_hint = skb;
1631                 tp->lost_cnt_hint = cnt;
1632                 cnt += tcp_skb_pcount(skb);
1633                 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
1634                         break;
1635                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1636                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1637                         tp->lost_out += tcp_skb_pcount(skb);
1638
1639                         /* clear xmit_retransmit_queue hints
1640                          *  if this is beyond hint */
1641                         if(tp->retransmit_skb_hint != NULL &&
1642                            before(TCP_SKB_CB(skb)->seq,
1643                                   TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1644
1645                                 tp->retransmit_skb_hint = NULL;
1646                         }
1647                 }
1648         }
1649         tcp_sync_left_out(tp);
1650 }
1651
1652 /* Account newly detected lost packet(s) */
1653
1654 static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1655 {
1656         if (IsFack(tp)) {
1657                 int lost = tp->fackets_out - tp->reordering;
1658                 if (lost <= 0)
1659                         lost = 1;
1660                 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1661         } else {
1662                 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1663         }
1664
1665         /* New heuristics: it is possible only after we switched
1666          * to restart timer each time when something is ACKed.
1667          * Hence, we can detect timed out packets during fast
1668          * retransmit without falling to slow start.
1669          */
1670         if (!IsReno(tp) && tcp_head_timedout(sk, tp)) {
1671                 struct sk_buff *skb;
1672
1673                 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1674                         : sk->sk_write_queue.next;
1675
1676                 sk_stream_for_retrans_queue_from(skb, sk) {
1677                         if (!tcp_skb_timedout(sk, skb))
1678                                 break;
1679
1680                         if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1681                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1682                                 tp->lost_out += tcp_skb_pcount(skb);
1683
1684                                 /* clear xmit_retrans hint */
1685                                 if (tp->retransmit_skb_hint &&
1686                                     before(TCP_SKB_CB(skb)->seq,
1687                                            TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1688
1689                                         tp->retransmit_skb_hint = NULL;
1690                         }
1691                 }
1692
1693                 tp->scoreboard_skb_hint = skb;
1694
1695                 tcp_sync_left_out(tp);
1696         }
1697 }
1698
1699 /* CWND moderation, preventing bursts due to too big ACKs
1700  * in dubious situations.
1701  */
1702 static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1703 {
1704         tp->snd_cwnd = min(tp->snd_cwnd,
1705                            tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1706         tp->snd_cwnd_stamp = tcp_time_stamp;
1707 }
1708
1709 /* Lower bound on congestion window is slow start threshold
1710  * unless congestion avoidance choice decides to overide it.
1711  */
1712 static inline u32 tcp_cwnd_min(const struct sock *sk)
1713 {
1714         const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1715
1716         return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
1717 }
1718
1719 /* Decrease cwnd each second ack. */
1720 static void tcp_cwnd_down(struct sock *sk)
1721 {
1722         struct tcp_sock *tp = tcp_sk(sk);
1723         int decr = tp->snd_cwnd_cnt + 1;
1724
1725         tp->snd_cwnd_cnt = decr&1;
1726         decr >>= 1;
1727
1728         if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
1729                 tp->snd_cwnd -= decr;
1730
1731         tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1732         tp->snd_cwnd_stamp = tcp_time_stamp;
1733 }
1734
1735 /* Nothing was retransmitted or returned timestamp is less
1736  * than timestamp of the first retransmission.
1737  */
1738 static inline int tcp_packet_delayed(struct tcp_sock *tp)
1739 {
1740         return !tp->retrans_stamp ||
1741                 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1742                  (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1743 }
1744
1745 /* Undo procedures. */
1746
1747 #if FASTRETRANS_DEBUG > 1
1748 static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1749 {
1750         struct inet_sock *inet = inet_sk(sk);
1751         printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1752                msg,
1753                NIPQUAD(inet->daddr), ntohs(inet->dport),
1754                tp->snd_cwnd, tp->left_out,
1755                tp->snd_ssthresh, tp->prior_ssthresh,
1756                tp->packets_out);
1757 }
1758 #else
1759 #define DBGUNDO(x...) do { } while (0)
1760 #endif
1761
1762 static void tcp_undo_cwr(struct sock *sk, const int undo)
1763 {
1764         struct tcp_sock *tp = tcp_sk(sk);
1765
1766         if (tp->prior_ssthresh) {
1767                 const struct inet_connection_sock *icsk = inet_csk(sk);
1768
1769                 if (icsk->icsk_ca_ops->undo_cwnd)
1770                         tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
1771                 else
1772                         tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1773
1774                 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1775                         tp->snd_ssthresh = tp->prior_ssthresh;
1776                         TCP_ECN_withdraw_cwr(tp);
1777                 }
1778         } else {
1779                 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1780         }
1781         tcp_moderate_cwnd(tp);
1782         tp->snd_cwnd_stamp = tcp_time_stamp;
1783
1784         /* There is something screwy going on with the retrans hints after
1785            an undo */
1786         clear_all_retrans_hints(tp);
1787 }
1788
1789 static inline int tcp_may_undo(struct tcp_sock *tp)
1790 {
1791         return tp->undo_marker &&
1792                 (!tp->undo_retrans || tcp_packet_delayed(tp));
1793 }
1794
1795 /* People celebrate: "We love our President!" */
1796 static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1797 {
1798         if (tcp_may_undo(tp)) {
1799                 /* Happy end! We did not retransmit anything
1800                  * or our original transmission succeeded.
1801                  */
1802                 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1803                 tcp_undo_cwr(sk, 1);
1804                 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
1805                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1806                 else
1807                         NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1808                 tp->undo_marker = 0;
1809         }
1810         if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1811                 /* Hold old state until something *above* high_seq
1812                  * is ACKed. For Reno it is MUST to prevent false
1813                  * fast retransmits (RFC2582). SACK TCP is safe. */
1814                 tcp_moderate_cwnd(tp);
1815                 return 1;
1816         }
1817         tcp_set_ca_state(sk, TCP_CA_Open);
1818         return 0;
1819 }
1820
1821 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1822 static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1823 {
1824         if (tp->undo_marker && !tp->undo_retrans) {
1825                 DBGUNDO(sk, tp, "D-SACK");
1826                 tcp_undo_cwr(sk, 1);
1827                 tp->undo_marker = 0;
1828                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1829         }
1830 }
1831
1832 /* Undo during fast recovery after partial ACK. */
1833
1834 static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1835                                 int acked)
1836 {
1837         /* Partial ACK arrived. Force Hoe's retransmit. */
1838         int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1839
1840         if (tcp_may_undo(tp)) {
1841                 /* Plain luck! Hole if filled with delayed
1842                  * packet, rather than with a retransmit.
1843                  */
1844                 if (tp->retrans_out == 0)
1845                         tp->retrans_stamp = 0;
1846
1847                 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
1848
1849                 DBGUNDO(sk, tp, "Hoe");
1850                 tcp_undo_cwr(sk, 0);
1851                 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1852
1853                 /* So... Do not make Hoe's retransmit yet.
1854                  * If the first packet was delayed, the rest
1855                  * ones are most probably delayed as well.
1856                  */
1857                 failed = 0;
1858         }
1859         return failed;
1860 }
1861
1862 /* Undo during loss recovery after partial ACK. */
1863 static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1864 {
1865         if (tcp_may_undo(tp)) {
1866                 struct sk_buff *skb;
1867                 sk_stream_for_retrans_queue(skb, sk) {
1868                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1869                 }
1870
1871                 clear_all_retrans_hints(tp);
1872
1873                 DBGUNDO(sk, tp, "partial loss");
1874                 tp->lost_out = 0;
1875                 tp->left_out = tp->sacked_out;
1876                 tcp_undo_cwr(sk, 1);
1877                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1878                 inet_csk(sk)->icsk_retransmits = 0;
1879                 tp->undo_marker = 0;
1880                 if (!IsReno(tp))
1881                         tcp_set_ca_state(sk, TCP_CA_Open);
1882                 return 1;
1883         }
1884         return 0;
1885 }
1886
1887 static inline void tcp_complete_cwr(struct sock *sk)
1888 {
1889         struct tcp_sock *tp = tcp_sk(sk);
1890         tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
1891         tp->snd_cwnd_stamp = tcp_time_stamp;
1892         tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
1893 }
1894
1895 static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1896 {
1897         tp->left_out = tp->sacked_out;
1898
1899         if (tp->retrans_out == 0)
1900                 tp->retrans_stamp = 0;
1901
1902         if (flag&FLAG_ECE)
1903                 tcp_enter_cwr(sk);
1904
1905         if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
1906                 int state = TCP_CA_Open;
1907
1908                 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1909                         state = TCP_CA_Disorder;
1910
1911                 if (inet_csk(sk)->icsk_ca_state != state) {
1912                         tcp_set_ca_state(sk, state);
1913                         tp->high_seq = tp->snd_nxt;
1914                 }
1915                 tcp_moderate_cwnd(tp);
1916         } else {
1917                 tcp_cwnd_down(sk);
1918         }
1919 }
1920
1921 static void tcp_mtup_probe_failed(struct sock *sk)
1922 {
1923         struct inet_connection_sock *icsk = inet_csk(sk);
1924
1925         icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
1926         icsk->icsk_mtup.probe_size = 0;
1927 }
1928
1929 static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
1930 {
1931         struct tcp_sock *tp = tcp_sk(sk);
1932         struct inet_connection_sock *icsk = inet_csk(sk);
1933
1934         /* FIXME: breaks with very large cwnd */
1935         tp->prior_ssthresh = tcp_current_ssthresh(sk);
1936         tp->snd_cwnd = tp->snd_cwnd *
1937                        tcp_mss_to_mtu(sk, tp->mss_cache) /
1938                        icsk->icsk_mtup.probe_size;
1939         tp->snd_cwnd_cnt = 0;
1940         tp->snd_cwnd_stamp = tcp_time_stamp;
1941         tp->rcv_ssthresh = tcp_current_ssthresh(sk);
1942
1943         icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
1944         icsk->icsk_mtup.probe_size = 0;
1945         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
1946 }
1947
1948
1949 /* Process an event, which can update packets-in-flight not trivially.
1950  * Main goal of this function is to calculate new estimate for left_out,
1951  * taking into account both packets sitting in receiver's buffer and
1952  * packets lost by network.
1953  *
1954  * Besides that it does CWND reduction, when packet loss is detected
1955  * and changes state of machine.
1956  *
1957  * It does _not_ decide what to send, it is made in function
1958  * tcp_xmit_retransmit_queue().
1959  */
1960 static void
1961 tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1962                       int prior_packets, int flag)
1963 {
1964         struct inet_connection_sock *icsk = inet_csk(sk);
1965         struct tcp_sock *tp = tcp_sk(sk);
1966         int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1967
1968         /* Some technical things:
1969          * 1. Reno does not count dupacks (sacked_out) automatically. */
1970         if (!tp->packets_out)
1971                 tp->sacked_out = 0;
1972         /* 2. SACK counts snd_fack in packets inaccurately. */
1973         if (tp->sacked_out == 0)
1974                 tp->fackets_out = 0;
1975
1976         /* Now state machine starts.
1977          * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1978         if (flag&FLAG_ECE)
1979                 tp->prior_ssthresh = 0;
1980
1981         /* B. In all the states check for reneging SACKs. */
1982         if (tp->sacked_out && tcp_check_sack_reneging(sk))
1983                 return;
1984
1985         /* C. Process data loss notification, provided it is valid. */
1986         if ((flag&FLAG_DATA_LOST) &&
1987             before(tp->snd_una, tp->high_seq) &&
1988             icsk->icsk_ca_state != TCP_CA_Open &&
1989             tp->fackets_out > tp->reordering) {
1990                 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1991                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1992         }
1993
1994         /* D. Synchronize left_out to current state. */
1995         tcp_sync_left_out(tp);
1996
1997         /* E. Check state exit conditions. State can be terminated
1998          *    when high_seq is ACKed. */
1999         if (icsk->icsk_ca_state == TCP_CA_Open) {
2000                 if (!sysctl_tcp_frto)
2001                         BUG_TRAP(tp->retrans_out == 0);
2002                 tp->retrans_stamp = 0;
2003         } else if (!before(tp->snd_una, tp->high_seq)) {
2004                 switch (icsk->icsk_ca_state) {
2005                 case TCP_CA_Loss:
2006                         icsk->icsk_retransmits = 0;
2007                         if (tcp_try_undo_recovery(sk, tp))
2008                                 return;
2009                         break;
2010
2011                 case TCP_CA_CWR:
2012                         /* CWR is to be held something *above* high_seq
2013                          * is ACKed for CWR bit to reach receiver. */
2014                         if (tp->snd_una != tp->high_seq) {
2015                                 tcp_complete_cwr(sk);
2016                                 tcp_set_ca_state(sk, TCP_CA_Open);
2017                         }
2018                         break;
2019
2020                 case TCP_CA_Disorder:
2021                         tcp_try_undo_dsack(sk, tp);
2022                         if (!tp->undo_marker ||
2023                             /* For SACK case do not Open to allow to undo
2024                              * catching for all duplicate ACKs. */
2025                             IsReno(tp) || tp->snd_una != tp->high_seq) {
2026                                 tp->undo_marker = 0;
2027                                 tcp_set_ca_state(sk, TCP_CA_Open);
2028                         }
2029                         break;
2030
2031                 case TCP_CA_Recovery:
2032                         if (IsReno(tp))
2033                                 tcp_reset_reno_sack(tp);
2034                         if (tcp_try_undo_recovery(sk, tp))
2035                                 return;
2036                         tcp_complete_cwr(sk);
2037                         break;
2038                 }
2039         }
2040
2041         /* F. Process state. */
2042         switch (icsk->icsk_ca_state) {
2043         case TCP_CA_Recovery:
2044                 if (prior_snd_una == tp->snd_una) {
2045                         if (IsReno(tp) && is_dupack)
2046                                 tcp_add_reno_sack(sk);
2047                 } else {
2048                         int acked = prior_packets - tp->packets_out;
2049                         if (IsReno(tp))
2050                                 tcp_remove_reno_sacks(sk, tp, acked);
2051                         is_dupack = tcp_try_undo_partial(sk, tp, acked);
2052                 }
2053                 break;
2054         case TCP_CA_Loss:
2055                 if (flag&FLAG_DATA_ACKED)
2056                         icsk->icsk_retransmits = 0;
2057                 if (!tcp_try_undo_loss(sk, tp)) {
2058                         tcp_moderate_cwnd(tp);
2059                         tcp_xmit_retransmit_queue(sk);
2060                         return;
2061                 }
2062                 if (icsk->icsk_ca_state != TCP_CA_Open)
2063                         return;
2064                 /* Loss is undone; fall through to processing in Open state. */
2065         default:
2066                 if (IsReno(tp)) {
2067                         if (tp->snd_una != prior_snd_una)
2068                                 tcp_reset_reno_sack(tp);
2069                         if (is_dupack)
2070                                 tcp_add_reno_sack(sk);
2071                 }
2072
2073                 if (icsk->icsk_ca_state == TCP_CA_Disorder)
2074                         tcp_try_undo_dsack(sk, tp);
2075
2076                 if (!tcp_time_to_recover(sk, tp)) {
2077                         tcp_try_to_open(sk, tp, flag);
2078                         return;
2079                 }
2080
2081                 /* MTU probe failure: don't reduce cwnd */
2082                 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2083                     icsk->icsk_mtup.probe_size &&
2084                     tp->snd_una == tp->mtu_probe.probe_seq_start) {
2085                         tcp_mtup_probe_failed(sk);
2086                         /* Restores the reduction we did in tcp_mtup_probe() */
2087                         tp->snd_cwnd++;
2088                         tcp_simple_retransmit(sk);
2089                         return;
2090                 }
2091
2092                 /* Otherwise enter Recovery state */
2093
2094                 if (IsReno(tp))
2095                         NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
2096                 else
2097                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
2098
2099                 tp->high_seq = tp->snd_nxt;
2100                 tp->prior_ssthresh = 0;
2101                 tp->undo_marker = tp->snd_una;
2102                 tp->undo_retrans = tp->retrans_out;
2103
2104                 if (icsk->icsk_ca_state < TCP_CA_CWR) {
2105                         if (!(flag&FLAG_ECE))
2106                                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2107                         tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2108                         TCP_ECN_queue_cwr(tp);
2109                 }
2110
2111                 tp->bytes_acked = 0;
2112                 tp->snd_cwnd_cnt = 0;
2113                 tcp_set_ca_state(sk, TCP_CA_Recovery);
2114         }
2115
2116         if (is_dupack || tcp_head_timedout(sk, tp))
2117                 tcp_update_scoreboard(sk, tp);
2118         tcp_cwnd_down(sk);
2119         tcp_xmit_retransmit_queue(sk);
2120 }
2121
2122 /* Read draft-ietf-tcplw-high-performance before mucking
2123  * with this code. (Supersedes RFC1323)
2124  */
2125 static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
2126 {
2127         /* RTTM Rule: A TSecr value received in a segment is used to
2128          * update the averaged RTT measurement only if the segment
2129          * acknowledges some new data, i.e., only if it advances the
2130          * left edge of the send window.
2131          *
2132          * See draft-ietf-tcplw-high-performance-00, section 3.3.
2133          * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2134          *
2135          * Changed: reset backoff as soon as we see the first valid sample.
2136          * If we do not, we get strongly overestimated rto. With timestamps
2137          * samples are accepted even from very old segments: f.e., when rtt=1
2138          * increases to 8, we retransmit 5 times and after 8 seconds delayed
2139          * answer arrives rto becomes 120 seconds! If at least one of segments
2140          * in window is lost... Voila.                          --ANK (010210)
2141          */
2142         struct tcp_sock *tp = tcp_sk(sk);
2143         const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
2144         tcp_rtt_estimator(sk, seq_rtt);
2145         tcp_set_rto(sk);
2146         inet_csk(sk)->icsk_backoff = 0;
2147         tcp_bound_rto(sk);
2148 }
2149
2150 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
2151 {
2152         /* We don't have a timestamp. Can only use
2153          * packets that are not retransmitted to determine
2154          * rtt estimates. Also, we must not reset the
2155          * backoff for rto until we get a non-retransmitted
2156          * packet. This allows us to deal with a situation
2157          * where the network delay has increased suddenly.
2158          * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2159          */
2160
2161         if (flag & FLAG_RETRANS_DATA_ACKED)
2162                 return;
2163
2164         tcp_rtt_estimator(sk, seq_rtt);
2165         tcp_set_rto(sk);
2166         inet_csk(sk)->icsk_backoff = 0;
2167         tcp_bound_rto(sk);
2168 }
2169
2170 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
2171                                       const s32 seq_rtt)
2172 {
2173         const struct tcp_sock *tp = tcp_sk(sk);
2174         /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2175         if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
2176                 tcp_ack_saw_tstamp(sk, flag);
2177         else if (seq_rtt >= 0)
2178                 tcp_ack_no_tstamp(sk, seq_rtt, flag);
2179 }
2180
2181 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
2182                            u32 in_flight, int good)
2183 {
2184         const struct inet_connection_sock *icsk = inet_csk(sk);
2185         icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2186         tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
2187 }
2188
2189 /* Restart timer after forward progress on connection.
2190  * RFC2988 recommends to restart timer to now+rto.
2191  */
2192
2193 static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2194 {
2195         if (!tp->packets_out) {
2196                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
2197         } else {
2198                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
2199         }
2200 }
2201
2202 static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2203                          __u32 now, __s32 *seq_rtt)
2204 {
2205         struct tcp_sock *tp = tcp_sk(sk);
2206         struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2207         __u32 seq = tp->snd_una;
2208         __u32 packets_acked;
2209         int acked = 0;
2210
2211         /* If we get here, the whole TSO packet has not been
2212          * acked.
2213          */
2214         BUG_ON(!after(scb->end_seq, seq));
2215
2216         packets_acked = tcp_skb_pcount(skb);
2217         if (tcp_trim_head(sk, skb, seq - scb->seq))
2218                 return 0;
2219         packets_acked -= tcp_skb_pcount(skb);
2220
2221         if (packets_acked) {
2222                 __u8 sacked = scb->sacked;
2223
2224                 acked |= FLAG_DATA_ACKED;
2225                 if (sacked) {
2226                         if (sacked & TCPCB_RETRANS) {
2227                                 if (sacked & TCPCB_SACKED_RETRANS)
2228                                         tp->retrans_out -= packets_acked;
2229                                 acked |= FLAG_RETRANS_DATA_ACKED;
2230                                 *seq_rtt = -1;
2231                         } else if (*seq_rtt < 0)
2232                                 *seq_rtt = now - scb->when;
2233                         if (sacked & TCPCB_SACKED_ACKED)
2234                                 tp->sacked_out -= packets_acked;
2235                         if (sacked & TCPCB_LOST)
2236                                 tp->lost_out -= packets_acked;
2237                         if (sacked & TCPCB_URG) {
2238                                 if (tp->urg_mode &&
2239                                     !before(seq, tp->snd_up))
2240                                         tp->urg_mode = 0;
2241                         }
2242                 } else if (*seq_rtt < 0)
2243                         *seq_rtt = now - scb->when;
2244
2245                 if (tp->fackets_out) {
2246                         __u32 dval = min(tp->fackets_out, packets_acked);
2247                         tp->fackets_out -= dval;
2248                 }
2249                 tp->packets_out -= packets_acked;
2250
2251                 BUG_ON(tcp_skb_pcount(skb) == 0);
2252                 BUG_ON(!before(scb->seq, scb->end_seq));
2253         }
2254
2255         return acked;
2256 }
2257
2258 static u32 tcp_usrtt(struct timeval *tv)
2259 {
2260         struct timeval now;
2261
2262         do_gettimeofday(&now);
2263         return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec);
2264 }
2265
2266 /* Remove acknowledged frames from the retransmission queue. */
2267 static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
2268 {
2269         struct tcp_sock *tp = tcp_sk(sk);
2270         const struct inet_connection_sock *icsk = inet_csk(sk);
2271         struct sk_buff *skb;
2272         __u32 now = tcp_time_stamp;
2273         int acked = 0;
2274         __s32 seq_rtt = -1;
2275         u32 pkts_acked = 0;
2276         void (*rtt_sample)(struct sock *sk, u32 usrtt)
2277                 = icsk->icsk_ca_ops->rtt_sample;
2278         struct timeval tv = { .tv_sec = 0, .tv_usec = 0 };
2279
2280         while ((skb = skb_peek(&sk->sk_write_queue)) &&
2281                skb != sk->sk_send_head) {
2282                 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2283                 __u8 sacked = scb->sacked;
2284
2285                 /* If our packet is before the ack sequence we can
2286                  * discard it as it's confirmed to have arrived at
2287                  * the other end.
2288                  */
2289                 if (after(scb->end_seq, tp->snd_una)) {
2290                         if (tcp_skb_pcount(skb) > 1 &&
2291                             after(tp->snd_una, scb->seq))
2292                                 acked |= tcp_tso_acked(sk, skb,
2293                                                        now, &seq_rtt);
2294                         break;
2295                 }
2296
2297                 /* Initial outgoing SYN's get put onto the write_queue
2298                  * just like anything else we transmit.  It is not
2299                  * true data, and if we misinform our callers that
2300                  * this ACK acks real data, we will erroneously exit
2301                  * connection startup slow start one packet too
2302                  * quickly.  This is severely frowned upon behavior.
2303                  */
2304                 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2305                         acked |= FLAG_DATA_ACKED;
2306                         ++pkts_acked;
2307                 } else {
2308                         acked |= FLAG_SYN_ACKED;
2309                         tp->retrans_stamp = 0;
2310                 }
2311
2312                 /* MTU probing checks */
2313                 if (icsk->icsk_mtup.probe_size) {
2314                         if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) {
2315                                 tcp_mtup_probe_success(sk, skb);
2316                         }
2317                 }
2318
2319                 if (sacked) {
2320                         if (sacked & TCPCB_RETRANS) {
2321                                 if(sacked & TCPCB_SACKED_RETRANS)
2322                                         tp->retrans_out -= tcp_skb_pcount(skb);
2323                                 acked |= FLAG_RETRANS_DATA_ACKED;
2324                                 seq_rtt = -1;
2325                         } else if (seq_rtt < 0) {
2326                                 seq_rtt = now - scb->when;
2327                                 skb_get_timestamp(skb, &tv);
2328                         }
2329                         if (sacked & TCPCB_SACKED_ACKED)
2330                                 tp->sacked_out -= tcp_skb_pcount(skb);
2331                         if (sacked & TCPCB_LOST)
2332                                 tp->lost_out -= tcp_skb_pcount(skb);
2333                         if (sacked & TCPCB_URG) {
2334                                 if (tp->urg_mode &&
2335                                     !before(scb->end_seq, tp->snd_up))
2336                                         tp->urg_mode = 0;
2337                         }
2338                 } else if (seq_rtt < 0) {
2339                         seq_rtt = now - scb->when;
2340                         skb_get_timestamp(skb, &tv);
2341                 }
2342                 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2343                 tcp_packets_out_dec(tp, skb);
2344                 __skb_unlink(skb, &sk->sk_write_queue);
2345                 sk_stream_free_skb(sk, skb);
2346                 clear_all_retrans_hints(tp);
2347         }
2348
2349         if (acked&FLAG_ACKED) {
2350                 tcp_ack_update_rtt(sk, acked, seq_rtt);
2351                 tcp_ack_packets_out(sk, tp);
2352                 if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED))
2353                         (*rtt_sample)(sk, tcp_usrtt(&tv));
2354
2355                 if (icsk->icsk_ca_ops->pkts_acked)
2356                         icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
2357         }
2358
2359 #if FASTRETRANS_DEBUG > 0
2360         BUG_TRAP((int)tp->sacked_out >= 0);
2361         BUG_TRAP((int)tp->lost_out >= 0);
2362         BUG_TRAP((int)tp->retrans_out >= 0);
2363         if (!tp->packets_out && tp->rx_opt.sack_ok) {
2364                 const struct inet_connection_sock *icsk = inet_csk(sk);
2365                 if (tp->lost_out) {
2366                         printk(KERN_DEBUG "Leak l=%u %d\n",
2367                                tp->lost_out, icsk->icsk_ca_state);
2368                         tp->lost_out = 0;
2369                 }
2370                 if (tp->sacked_out) {
2371                         printk(KERN_DEBUG "Leak s=%u %d\n",
2372                                tp->sacked_out, icsk->icsk_ca_state);
2373                         tp->sacked_out = 0;
2374                 }
2375                 if (tp->retrans_out) {
2376                         printk(KERN_DEBUG "Leak r=%u %d\n",
2377                                tp->retrans_out, icsk->icsk_ca_state);
2378                         tp->retrans_out = 0;
2379                 }
2380         }
2381 #endif
2382         *seq_rtt_p = seq_rtt;
2383         return acked;
2384 }
2385
2386 static void tcp_ack_probe(struct sock *sk)
2387 {
2388         const struct tcp_sock *tp = tcp_sk(sk);
2389         struct inet_connection_sock *icsk = inet_csk(sk);
2390
2391         /* Was it a usable window open? */
2392
2393         if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2394                    tp->snd_una + tp->snd_wnd)) {
2395                 icsk->icsk_backoff = 0;
2396                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
2397                 /* Socket must be waked up by subsequent tcp_data_snd_check().
2398                  * This function is not for random using!
2399                  */
2400         } else {
2401                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2402                                           min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2403                                           TCP_RTO_MAX);
2404         }
2405 }
2406
2407 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
2408 {
2409         return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
2410                 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
2411 }
2412
2413 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
2414 {
2415         const struct tcp_sock *tp = tcp_sk(sk);
2416         return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
2417                 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
2418 }
2419
2420 /* Check that window update is acceptable.
2421  * The function assumes that snd_una<=ack<=snd_next.
2422  */
2423 static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2424                                         const u32 ack_seq, const u32 nwin)
2425 {
2426         return (after(ack, tp->snd_una) ||
2427                 after(ack_seq, tp->snd_wl1) ||
2428                 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2429 }
2430
2431 /* Update our send window.
2432  *
2433  * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2434  * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2435  */
2436 static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2437                                  struct sk_buff *skb, u32 ack, u32 ack_seq)
2438 {
2439         int flag = 0;
2440         u32 nwin = ntohs(skb->h.th->window);
2441
2442         if (likely(!skb->h.th->syn))
2443                 nwin <<= tp->rx_opt.snd_wscale;
2444
2445         if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2446                 flag |= FLAG_WIN_UPDATE;
2447                 tcp_update_wl(tp, ack, ack_seq);
2448
2449                 if (tp->snd_wnd != nwin) {
2450                         tp->snd_wnd = nwin;
2451
2452                         /* Note, it is the only place, where
2453                          * fast path is recovered for sending TCP.
2454                          */
2455                         tp->pred_flags = 0;
2456                         tcp_fast_path_check(sk, tp);
2457
2458                         if (nwin > tp->max_window) {
2459                                 tp->max_window = nwin;
2460                                 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
2461                         }
2462                 }
2463         }
2464
2465         tp->snd_una = ack;
2466
2467         return flag;
2468 }
2469
2470 static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2471 {
2472         struct tcp_sock *tp = tcp_sk(sk);
2473
2474         tcp_sync_left_out(tp);
2475
2476         if (tp->snd_una == prior_snd_una ||
2477             !before(tp->snd_una, tp->frto_highmark)) {
2478                 /* RTO was caused by loss, start retransmitting in
2479                  * go-back-N slow start
2480                  */
2481                 tcp_enter_frto_loss(sk);
2482                 return;
2483         }
2484
2485         if (tp->frto_counter == 1) {
2486                 /* First ACK after RTO advances the window: allow two new
2487                  * segments out.
2488                  */
2489                 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2490         } else {
2491                 /* Also the second ACK after RTO advances the window.
2492                  * The RTO was likely spurious. Reduce cwnd and continue
2493                  * in congestion avoidance
2494                  */
2495                 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2496                 tcp_moderate_cwnd(tp);
2497         }
2498
2499         /* F-RTO affects on two new ACKs following RTO.
2500          * At latest on third ACK the TCP behavior is back to normal.
2501          */
2502         tp->frto_counter = (tp->frto_counter + 1) % 3;
2503 }
2504
2505 /* This routine deals with incoming acks, but not outgoing ones. */
2506 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2507 {
2508         struct inet_connection_sock *icsk = inet_csk(sk);
2509         struct tcp_sock *tp = tcp_sk(sk);
2510         u32 prior_snd_una = tp->snd_una;
2511         u32 ack_seq = TCP_SKB_CB(skb)->seq;
2512         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2513         u32 prior_in_flight;
2514         s32 seq_rtt;
2515         int prior_packets;
2516
2517         /* If the ack is newer than sent or older than previous acks
2518          * then we can probably ignore it.
2519          */
2520         if (after(ack, tp->snd_nxt))
2521                 goto uninteresting_ack;
2522
2523         if (before(ack, prior_snd_una))
2524                 goto old_ack;
2525
2526         if (sysctl_tcp_abc) {
2527                 if (icsk->icsk_ca_state < TCP_CA_CWR)
2528                         tp->bytes_acked += ack - prior_snd_una;
2529                 else if (icsk->icsk_ca_state == TCP_CA_Loss)
2530                         /* we assume just one segment left network */
2531                         tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache);
2532         }
2533
2534         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2535                 /* Window is constant, pure forward advance.
2536                  * No more checks are required.
2537                  * Note, we use the fact that SND.UNA>=SND.WL2.
2538                  */
2539                 tcp_update_wl(tp, ack, ack_seq);
2540                 tp->snd_una = ack;
2541                 flag |= FLAG_WIN_UPDATE;
2542
2543                 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
2544
2545                 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2546         } else {
2547                 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2548                         flag |= FLAG_DATA;
2549                 else
2550                         NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2551
2552                 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2553
2554                 if (TCP_SKB_CB(skb)->sacked)
2555                         flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2556
2557                 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2558                         flag |= FLAG_ECE;
2559
2560                 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
2561         }
2562
2563         /* We passed data and got it acked, remove any soft error
2564          * log. Something worked...
2565          */
2566         sk->sk_err_soft = 0;
2567         tp->rcv_tstamp = tcp_time_stamp;
2568         prior_packets = tp->packets_out;
2569         if (!prior_packets)
2570                 goto no_queue;
2571
2572         prior_in_flight = tcp_packets_in_flight(tp);
2573
2574         /* See if we can take anything off of the retransmit queue. */
2575         flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
2576
2577         if (tp->frto_counter)
2578                 tcp_process_frto(sk, prior_snd_una);
2579
2580         if (tcp_ack_is_dubious(sk, flag)) {
2581                 /* Advance CWND, if state allows this. */
2582                 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2583                         tcp_cong_avoid(sk, ack,  seq_rtt, prior_in_flight, 0);
2584                 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2585         } else {
2586                 if ((flag & FLAG_DATA_ACKED))
2587                         tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
2588         }
2589
2590         if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2591                 dst_confirm(sk->sk_dst_cache);
2592
2593         return 1;
2594
2595 no_queue:
2596         icsk->icsk_probes_out = 0;
2597
2598         /* If this ack opens up a zero window, clear backoff.  It was
2599          * being used to time the probes, and is probably far higher than
2600          * it needs to be for normal retransmission.
2601          */
2602         if (sk->sk_send_head)
2603                 tcp_ack_probe(sk);
2604         return 1;
2605
2606 old_ack:
2607         if (TCP_SKB_CB(skb)->sacked)
2608                 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2609
2610 uninteresting_ack:
2611         SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2612         return 0;
2613 }
2614
2615
2616 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2617  * But, this can also be called on packets in the established flow when
2618  * the fast version below fails.
2619  */
2620 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2621 {
2622         unsigned char *ptr;
2623         struct tcphdr *th = skb->h.th;
2624         int length=(th->doff*4)-sizeof(struct tcphdr);
2625
2626         ptr = (unsigned char *)(th + 1);
2627         opt_rx->saw_tstamp = 0;
2628
2629         while(length>0) {
2630                 int opcode=*ptr++;
2631                 int opsize;
2632
2633                 switch (opcode) {
2634                         case TCPOPT_EOL:
2635                                 return;
2636                         case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
2637                                 length--;
2638                                 continue;
2639                         default:
2640                                 opsize=*ptr++;
2641                                 if (opsize < 2) /* "silly options" */
2642                                         return;
2643                                 if (opsize > length)
2644                                         return; /* don't parse partial options */
2645                                 switch(opcode) {
2646                                 case TCPOPT_MSS:
2647                                         if(opsize==TCPOLEN_MSS && th->syn && !estab) {
2648                                                 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr));
2649                                                 if (in_mss) {
2650                                                         if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2651                                                                 in_mss = opt_rx->user_mss;
2652                                                         opt_rx->mss_clamp = in_mss;
2653                                                 }
2654                                         }
2655                                         break;
2656                                 case TCPOPT_WINDOW:
2657                                         if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2658                                                 if (sysctl_tcp_window_scaling) {
2659                                                         __u8 snd_wscale = *(__u8 *) ptr;
2660                                                         opt_rx->wscale_ok = 1;
2661                                                         if (snd_wscale > 14) {
2662                                                                 if(net_ratelimit())
2663                                                                         printk(KERN_INFO "tcp_parse_options: Illegal window "
2664                                                                                "scaling value %d >14 received.\n",
2665                                                                                snd_wscale);
2666                                                                 snd_wscale = 14;
2667                                                         }
2668                                                         opt_rx->snd_wscale = snd_wscale;
2669                                                 }
2670                                         break;
2671                                 case TCPOPT_TIMESTAMP:
2672                                         if(opsize==TCPOLEN_TIMESTAMP) {
2673                                                 if ((estab && opt_rx->tstamp_ok) ||
2674                                                     (!estab && sysctl_tcp_timestamps)) {
2675                                                         opt_rx->saw_tstamp = 1;
2676                                                         opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr));
2677                                                         opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4)));
2678                                                 }
2679                                         }
2680                                         break;
2681                                 case TCPOPT_SACK_PERM:
2682                                         if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2683                                                 if (sysctl_tcp_sack) {
2684                                                         opt_rx->sack_ok = 1;
2685                                                         tcp_sack_reset(opt_rx);
2686                                                 }
2687                                         }
2688                                         break;
2689
2690                                 case TCPOPT_SACK:
2691                                         if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2692                                            !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2693                                            opt_rx->sack_ok) {
2694                                                 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2695                                         }
2696 #ifdef CONFIG_TCP_MD5SIG
2697                                 case TCPOPT_MD5SIG:
2698                                         /*
2699                                          * The MD5 Hash has already been
2700                                          * checked (see tcp_v{4,6}_do_rcv()).
2701                                          */
2702                                         break;
2703 #endif
2704                                 };
2705                                 ptr+=opsize-2;
2706                                 length-=opsize;
2707                 };
2708         }
2709 }
2710
2711 /* Fast parse options. This hopes to only see timestamps.
2712  * If it is wrong it falls back on tcp_parse_options().
2713  */
2714 static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2715                                   struct tcp_sock *tp)
2716 {
2717         if (th->doff == sizeof(struct tcphdr)>>2) {
2718                 tp->rx_opt.saw_tstamp = 0;
2719                 return 0;
2720         } else if (tp->rx_opt.tstamp_ok &&
2721                    th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
2722                 __be32 *ptr = (__be32 *)(th + 1);
2723                 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
2724                                   | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2725                         tp->rx_opt.saw_tstamp = 1;
2726                         ++ptr;
2727                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
2728                         ++ptr;
2729                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2730                         return 1;
2731                 }
2732         }
2733         tcp_parse_options(skb, &tp->rx_opt, 1);
2734         return 1;
2735 }
2736
2737 static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2738 {
2739         tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2740         tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2741 }
2742
2743 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2744 {
2745         if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2746                 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2747                  * extra check below makes sure this can only happen
2748                  * for pure ACK frames.  -DaveM
2749                  *
2750                  * Not only, also it occurs for expired timestamps.
2751                  */
2752
2753                 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2754                    xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2755                         tcp_store_ts_recent(tp);
2756         }
2757 }
2758
2759 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2760  *
2761  * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2762  * it can pass through stack. So, the following predicate verifies that
2763  * this segment is not used for anything but congestion avoidance or
2764  * fast retransmit. Moreover, we even are able to eliminate most of such
2765  * second order effects, if we apply some small "replay" window (~RTO)
2766  * to timestamp space.
2767  *
2768  * All these measures still do not guarantee that we reject wrapped ACKs
2769  * on networks with high bandwidth, when sequence space is recycled fastly,
2770  * but it guarantees that such events will be very rare and do not affect
2771  * connection seriously. This doesn't look nice, but alas, PAWS is really
2772  * buggy extension.
2773  *
2774  * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2775  * states that events when retransmit arrives after original data are rare.
2776  * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2777  * the biggest problem on large power networks even with minor reordering.
2778  * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2779  * up to bandwidth of 18Gigabit/sec. 8) ]
2780  */
2781
2782 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
2783 {
2784         struct tcp_sock *tp = tcp_sk(sk);
2785         struct tcphdr *th = skb->h.th;
2786         u32 seq = TCP_SKB_CB(skb)->seq;
2787         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2788
2789         return (/* 1. Pure ACK with correct sequence number. */
2790                 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2791
2792                 /* 2. ... and duplicate ACK. */
2793                 ack == tp->snd_una &&
2794
2795                 /* 3. ... and does not update window. */
2796                 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2797
2798                 /* 4. ... and sits in replay window. */
2799                 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
2800 }
2801
2802 static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
2803 {
2804         const struct tcp_sock *tp = tcp_sk(sk);
2805         return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2806                 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
2807                 !tcp_disordered_ack(sk, skb));
2808 }
2809
2810 /* Check segment sequence number for validity.
2811  *
2812  * Segment controls are considered valid, if the segment
2813  * fits to the window after truncation to the window. Acceptability
2814  * of data (and SYN, FIN, of course) is checked separately.
2815  * See tcp_data_queue(), for example.
2816  *
2817  * Also, controls (RST is main one) are accepted using RCV.WUP instead
2818  * of RCV.NXT. Peer still did not advance his SND.UNA when we
2819  * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2820  * (borrowed from freebsd)
2821  */
2822
2823 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2824 {
2825         return  !before(end_seq, tp->rcv_wup) &&
2826                 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2827 }
2828
2829 /* When we get a reset we do this. */
2830 static void tcp_reset(struct sock *sk)
2831 {
2832         /* We want the right error as BSD sees it (and indeed as we do). */
2833         switch (sk->sk_state) {
2834                 case TCP_SYN_SENT:
2835                         sk->sk_err = ECONNREFUSED;
2836                         break;
2837                 case TCP_CLOSE_WAIT:
2838                         sk->sk_err = EPIPE;
2839                         break;
2840                 case TCP_CLOSE:
2841                         return;
2842                 default:
2843                         sk->sk_err = ECONNRESET;
2844         }
2845
2846         if (!sock_flag(sk, SOCK_DEAD))
2847                 sk->sk_error_report(sk);
2848
2849         tcp_done(sk);
2850 }
2851
2852 /*
2853  *      Process the FIN bit. This now behaves as it is supposed to work
2854  *      and the FIN takes effect when it is validly part of sequence
2855  *      space. Not before when we get holes.
2856  *
2857  *      If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2858  *      (and thence onto LAST-ACK and finally, CLOSE, we never enter
2859  *      TIME-WAIT)
2860  *
2861  *      If we are in FINWAIT-1, a received FIN indicates simultaneous
2862  *      close and we go into CLOSING (and later onto TIME-WAIT)
2863  *
2864  *      If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2865  */
2866 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2867 {
2868         struct tcp_sock *tp = tcp_sk(sk);
2869
2870         inet_csk_schedule_ack(sk);
2871
2872         sk->sk_shutdown |= RCV_SHUTDOWN;
2873         sock_set_flag(sk, SOCK_DONE);
2874
2875         switch (sk->sk_state) {
2876                 case TCP_SYN_RECV:
2877                 case TCP_ESTABLISHED:
2878                         /* Move to CLOSE_WAIT */
2879                         tcp_set_state(sk, TCP_CLOSE_WAIT);
2880                         inet_csk(sk)->icsk_ack.pingpong = 1;
2881                         break;
2882
2883                 case TCP_CLOSE_WAIT:
2884                 case TCP_CLOSING:
2885                         /* Received a retransmission of the FIN, do
2886                          * nothing.
2887                          */
2888                         break;
2889                 case TCP_LAST_ACK:
2890                         /* RFC793: Remain in the LAST-ACK state. */
2891                         break;
2892
2893                 case TCP_FIN_WAIT1:
2894                         /* This case occurs when a simultaneous close
2895                          * happens, we must ack the received FIN and
2896                          * enter the CLOSING state.
2897                          */
2898                         tcp_send_ack(sk);
2899                         tcp_set_state(sk, TCP_CLOSING);
2900                         break;
2901                 case TCP_FIN_WAIT2:
2902                         /* Received a FIN -- send ACK and enter TIME_WAIT. */
2903                         tcp_send_ack(sk);
2904                         tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2905                         break;
2906                 default:
2907                         /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2908                          * cases we should never reach this piece of code.
2909                          */
2910                         printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2911                                __FUNCTION__, sk->sk_state);
2912                         break;
2913         };
2914
2915         /* It _is_ possible, that we have something out-of-order _after_ FIN.
2916          * Probably, we should reset in this case. For now drop them.
2917          */
2918         __skb_queue_purge(&tp->out_of_order_queue);
2919         if (tp->rx_opt.sack_ok)
2920                 tcp_sack_reset(&tp->rx_opt);
2921         sk_stream_mem_reclaim(sk);
2922
2923         if (!sock_flag(sk, SOCK_DEAD)) {
2924                 sk->sk_state_change(sk);
2925
2926                 /* Do not send POLL_HUP for half duplex close. */
2927                 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2928                     sk->sk_state == TCP_CLOSE)
2929                         sk_wake_async(sk, 1, POLL_HUP);
2930                 else
2931                         sk_wake_async(sk, 1, POLL_IN);
2932         }
2933 }
2934
2935 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
2936 {
2937         if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2938                 if (before(seq, sp->start_seq))
2939                         sp->start_seq = seq;
2940                 if (after(end_seq, sp->end_seq))
2941                         sp->end_seq = end_seq;
2942                 return 1;
2943         }
2944         return 0;
2945 }
2946
2947 static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
2948 {
2949         if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2950                 if (before(seq, tp->rcv_nxt))
2951                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2952                 else
2953                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2954
2955                 tp->rx_opt.dsack = 1;
2956                 tp->duplicate_sack[0].start_seq = seq;
2957                 tp->duplicate_sack[0].end_seq = end_seq;
2958                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2959         }
2960 }
2961
2962 static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
2963 {
2964         if (!tp->rx_opt.dsack)
2965                 tcp_dsack_set(tp, seq, end_seq);
2966         else
2967                 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2968 }
2969
2970 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2971 {
2972         struct tcp_sock *tp = tcp_sk(sk);
2973
2974         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2975             before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2976                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
2977                 tcp_enter_quickack_mode(sk);
2978
2979                 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2980                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2981
2982                         if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2983                                 end_seq = tp->rcv_nxt;
2984                         tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2985                 }
2986         }
2987
2988         tcp_send_ack(sk);
2989 }
2990
2991 /* These routines update the SACK block as out-of-order packets arrive or
2992  * in-order packets close up the sequence space.
2993  */
2994 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2995 {
2996         int this_sack;
2997         struct tcp_sack_block *sp = &tp->selective_acks[0];
2998         struct tcp_sack_block *swalk = sp+1;
2999
3000         /* See if the recent change to the first SACK eats into
3001          * or hits the sequence space of other SACK blocks, if so coalesce.
3002          */
3003         for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
3004                 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
3005                         int i;
3006
3007                         /* Zap SWALK, by moving every further SACK up by one slot.
3008                          * Decrease num_sacks.
3009                          */
3010                         tp->rx_opt.num_sacks--;
3011                         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3012                         for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
3013                                 sp[i] = sp[i+1];
3014                         continue;
3015                 }
3016                 this_sack++, swalk++;
3017         }
3018 }
3019
3020 static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
3021 {
3022         __u32 tmp;
3023
3024         tmp = sack1->start_seq;
3025         sack1->start_seq = sack2->start_seq;
3026         sack2->start_seq = tmp;
3027
3028         tmp = sack1->end_seq;
3029         sack1->end_seq = sack2->end_seq;
3030         sack2->end_seq = tmp;
3031 }
3032
3033 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3034 {
3035         struct tcp_sock *tp = tcp_sk(sk);
3036         struct tcp_sack_block *sp = &tp->selective_acks[0];
3037         int cur_sacks = tp->rx_opt.num_sacks;
3038         int this_sack;
3039
3040         if (!cur_sacks)
3041                 goto new_sack;
3042
3043         for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3044                 if (tcp_sack_extend(sp, seq, end_seq)) {
3045                         /* Rotate this_sack to the first one. */
3046                         for (; this_sack>0; this_sack--, sp--)
3047                                 tcp_sack_swap(sp, sp-1);
3048                         if (cur_sacks > 1)
3049                                 tcp_sack_maybe_coalesce(tp);
3050                         return;
3051                 }
3052         }
3053
3054         /* Could not find an adjacent existing SACK, build a new one,
3055          * put it at the front, and shift everyone else down.  We
3056          * always know there is at least one SACK present already here.
3057          *
3058          * If the sack array is full, forget about the last one.
3059          */
3060         if (this_sack >= 4) {
3061                 this_sack--;
3062                 tp->rx_opt.num_sacks--;
3063                 sp--;
3064         }
3065         for(; this_sack > 0; this_sack--, sp--)
3066                 *sp = *(sp-1);
3067
3068 new_sack:
3069         /* Build the new head SACK, and we're done. */
3070         sp->start_seq = seq;
3071         sp->end_seq = end_seq;
3072         tp->rx_opt.num_sacks++;
3073         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3074 }
3075
3076 /* RCV.NXT advances, some SACKs should be eaten. */
3077
3078 static void tcp_sack_remove(struct tcp_sock *tp)
3079 {
3080         struct tcp_sack_block *sp = &tp->selective_acks[0];
3081         int num_sacks = tp->rx_opt.num_sacks;
3082         int this_sack;
3083
3084         /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3085         if (skb_queue_empty(&tp->out_of_order_queue)) {
3086                 tp->rx_opt.num_sacks = 0;
3087                 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3088                 return;
3089         }
3090
3091         for(this_sack = 0; this_sack < num_sacks; ) {
3092                 /* Check if the start of the sack is covered by RCV.NXT. */
3093                 if (!before(tp->rcv_nxt, sp->start_seq)) {
3094                         int i;
3095
3096                         /* RCV.NXT must cover all the block! */
3097                         BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3098
3099                         /* Zap this SACK, by moving forward any other SACKS. */
3100                         for (i=this_sack+1; i < num_sacks; i++)
3101                                 tp->selective_acks[i-1] = tp->selective_acks[i];
3102                         num_sacks--;
3103                         continue;
3104                 }
3105                 this_sack++;
3106                 sp++;
3107         }
3108         if (num_sacks != tp->rx_opt.num_sacks) {
3109                 tp->rx_opt.num_sacks = num_sacks;
3110                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3111         }
3112 }
3113
3114 /* This one checks to see if we can put data from the
3115  * out_of_order queue into the receive_queue.
3116  */
3117 static void tcp_ofo_queue(struct sock *sk)
3118 {
3119         struct tcp_sock *tp = tcp_sk(sk);
3120         __u32 dsack_high = tp->rcv_nxt;
3121         struct sk_buff *skb;
3122
3123         while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3124                 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3125                         break;
3126
3127                 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3128                         __u32 dsack = dsack_high;
3129                         if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3130                                 dsack_high = TCP_SKB_CB(skb)->end_seq;
3131                         tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3132                 }
3133
3134                 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3135                         SOCK_DEBUG(sk, "ofo packet was already received \n");
3136                         __skb_unlink(skb, &tp->out_of_order_queue);
3137                         __kfree_skb(skb);
3138                         continue;
3139                 }
3140                 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3141                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3142                            TCP_SKB_CB(skb)->end_seq);
3143
3144                 __skb_unlink(skb, &tp->out_of_order_queue);
3145                 __skb_queue_tail(&sk->sk_receive_queue, skb);
3146                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3147                 if(skb->h.th->fin)
3148                         tcp_fin(skb, sk, skb->h.th);
3149         }
3150 }
3151
3152 static int tcp_prune_queue(struct sock *sk);
3153
3154 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3155 {
3156         struct tcphdr *th = skb->h.th;
3157         struct tcp_sock *tp = tcp_sk(sk);
3158         int eaten = -1;
3159
3160         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3161                 goto drop;
3162
3163         __skb_pull(skb, th->doff*4);
3164
3165         TCP_ECN_accept_cwr(tp, skb);
3166
3167         if (tp->rx_opt.dsack) {
3168                 tp->rx_opt.dsack = 0;
3169                 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3170                                                     4 - tp->rx_opt.tstamp_ok);
3171         }
3172
3173         /*  Queue data for delivery to the user.
3174          *  Packets in sequence go to the receive queue.
3175          *  Out of sequence packets to the out_of_order_queue.
3176          */
3177         if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3178                 if (tcp_receive_window(tp) == 0)
3179                         goto out_of_window;
3180
3181                 /* Ok. In sequence. In window. */
3182                 if (tp->ucopy.task == current &&
3183                     tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3184                     sock_owned_by_user(sk) && !tp->urg_data) {
3185                         int chunk = min_t(unsigned int, skb->len,
3186                                                         tp->ucopy.len);
3187
3188                         __set_current_state(TASK_RUNNING);
3189
3190                         local_bh_enable();
3191                         if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3192                                 tp->ucopy.len -= chunk;
3193                                 tp->copied_seq += chunk;
3194                                 eaten = (chunk == skb->len && !th->fin);
3195                                 tcp_rcv_space_adjust(sk);
3196                         }
3197                         local_bh_disable();
3198                 }
3199
3200                 if (eaten <= 0) {
3201 queue_and_out:
3202                         if (eaten < 0 &&
3203                             (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3204                              !sk_stream_rmem_schedule(sk, skb))) {
3205                                 if (tcp_prune_queue(sk) < 0 ||
3206                                     !sk_stream_rmem_schedule(sk, skb))
3207                                         goto drop;
3208                         }
3209                         sk_stream_set_owner_r(skb, sk);
3210                         __skb_queue_tail(&sk->sk_receive_queue, skb);
3211                 }
3212                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3213                 if(skb->len)
3214                         tcp_event_data_recv(sk, tp, skb);
3215                 if(th->fin)
3216                         tcp_fin(skb, sk, th);
3217
3218                 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3219                         tcp_ofo_queue(sk);
3220
3221                         /* RFC2581. 4.2. SHOULD send immediate ACK, when
3222                          * gap in queue is filled.
3223                          */
3224                         if (skb_queue_empty(&tp->out_of_order_queue))
3225                                 inet_csk(sk)->icsk_ack.pingpong = 0;
3226                 }
3227
3228                 if (tp->rx_opt.num_sacks)
3229                         tcp_sack_remove(tp);
3230
3231                 tcp_fast_path_check(sk, tp);
3232
3233                 if (eaten > 0)
3234                         __kfree_skb(skb);
3235                 else if (!sock_flag(sk, SOCK_DEAD))
3236                         sk->sk_data_ready(sk, 0);
3237                 return;
3238         }
3239
3240         if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3241                 /* A retransmit, 2nd most common case.  Force an immediate ack. */
3242                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3243                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3244
3245 out_of_window:
3246                 tcp_enter_quickack_mode(sk);
3247                 inet_csk_schedule_ack(sk);
3248 drop:
3249                 __kfree_skb(skb);
3250                 return;
3251         }
3252
3253         /* Out of window. F.e. zero window probe. */
3254         if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3255                 goto out_of_window;
3256
3257         tcp_enter_quickack_mode(sk);
3258
3259         if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3260                 /* Partial packet, seq < rcv_next < end_seq */
3261                 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3262                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3263                            TCP_SKB_CB(skb)->end_seq);
3264
3265                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3266
3267                 /* If window is closed, drop tail of packet. But after
3268                  * remembering D-SACK for its head made in previous line.
3269                  */
3270                 if (!tcp_receive_window(tp))
3271                         goto out_of_window;
3272                 goto queue_and_out;
3273         }
3274
3275         TCP_ECN_check_ce(tp, skb);
3276
3277         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3278             !sk_stream_rmem_schedule(sk, skb)) {
3279                 if (tcp_prune_queue(sk) < 0 ||
3280                     !sk_stream_rmem_schedule(sk, skb))
3281                         goto drop;
3282         }
3283
3284         /* Disable header prediction. */
3285         tp->pred_flags = 0;
3286         inet_csk_schedule_ack(sk);
3287
3288         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3289                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3290
3291         sk_stream_set_owner_r(skb, sk);
3292
3293         if (!skb_peek(&tp->out_of_order_queue)) {
3294                 /* Initial out of order segment, build 1 SACK. */
3295                 if (tp->rx_opt.sack_ok) {
3296                         tp->rx_opt.num_sacks = 1;
3297                         tp->rx_opt.dsack     = 0;
3298                         tp->rx_opt.eff_sacks = 1;
3299                         tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3300                         tp->selective_acks[0].end_seq =
3301                                                 TCP_SKB_CB(skb)->end_seq;
3302                 }
3303                 __skb_queue_head(&tp->out_of_order_queue,skb);
3304         } else {
3305                 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3306                 u32 seq = TCP_SKB_CB(skb)->seq;
3307                 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3308
3309                 if (seq == TCP_SKB_CB(skb1)->end_seq) {
3310                         __skb_append(skb1, skb, &tp->out_of_order_queue);
3311
3312                         if (!tp->rx_opt.num_sacks ||
3313                             tp->selective_acks[0].end_seq != seq)
3314                                 goto add_sack;
3315
3316                         /* Common case: data arrive in order after hole. */
3317                         tp->selective_acks[0].end_seq = end_seq;
3318                         return;
3319                 }
3320
3321                 /* Find place to insert this segment. */
3322                 do {
3323                         if (!after(TCP_SKB_CB(skb1)->seq, seq))
3324                                 break;
3325                 } while ((skb1 = skb1->prev) !=
3326                          (struct sk_buff*)&tp->out_of_order_queue);
3327
3328                 /* Do skb overlap to previous one? */
3329                 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3330                     before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3331                         if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3332                                 /* All the bits are present. Drop. */
3333                                 __kfree_skb(skb);
3334                                 tcp_dsack_set(tp, seq, end_seq);
3335                                 goto add_sack;
3336                         }
3337                         if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3338                                 /* Partial overlap. */
3339                                 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3340                         } else {
3341                                 skb1 = skb1->prev;
3342                         }
3343                 }
3344                 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3345
3346                 /* And clean segments covered by new one as whole. */
3347                 while ((skb1 = skb->next) !=
3348                        (struct sk_buff*)&tp->out_of_order_queue &&
3349                        after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3350                        if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3351                                tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3352                                break;
3353                        }
3354                        __skb_unlink(skb1, &tp->out_of_order_queue);
3355                        tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3356                        __kfree_skb(skb1);
3357                 }
3358
3359 add_sack:
3360                 if (tp->rx_opt.sack_ok)
3361                         tcp_sack_new_ofo_skb(sk, seq, end_seq);
3362         }
3363 }
3364
3365 /* Collapse contiguous sequence of skbs head..tail with
3366  * sequence numbers start..end.
3367  * Segments with FIN/SYN are not collapsed (only because this
3368  * simplifies code)
3369  */
3370 static void
3371 tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3372              struct sk_buff *head, struct sk_buff *tail,
3373              u32 start, u32 end)
3374 {
3375         struct sk_buff *skb;
3376
3377         /* First, check that queue is collapsible and find
3378          * the point where collapsing can be useful. */
3379         for (skb = head; skb != tail; ) {
3380                 /* No new bits? It is possible on ofo queue. */
3381                 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3382                         struct sk_buff *next = skb->next;
3383                         __skb_unlink(skb, list);
3384                         __kfree_skb(skb);
3385                         NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3386                         skb = next;
3387                         continue;
3388                 }
3389
3390                 /* The first skb to collapse is:
3391                  * - not SYN/FIN and
3392                  * - bloated or contains data before "start" or
3393                  *   overlaps to the next one.
3394                  */
3395                 if (!skb->h.th->syn && !skb->h.th->fin &&
3396                     (tcp_win_from_space(skb->truesize) > skb->len ||
3397                      before(TCP_SKB_CB(skb)->seq, start) ||
3398                      (skb->next != tail &&
3399                       TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3400                         break;
3401
3402                 /* Decided to skip this, advance start seq. */
3403                 start = TCP_SKB_CB(skb)->end_seq;
3404                 skb = skb->next;
3405         }
3406         if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3407                 return;
3408
3409         while (before(start, end)) {
3410                 struct sk_buff *nskb;
3411                 int header = skb_headroom(skb);
3412                 int copy = SKB_MAX_ORDER(header, 0);
3413
3414                 /* Too big header? This can happen with IPv6. */
3415                 if (copy < 0)
3416                         return;
3417                 if (end-start < copy)
3418                         copy = end-start;
3419                 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3420                 if (!nskb)
3421                         return;
3422                 skb_reserve(nskb, header);
3423                 memcpy(nskb->head, skb->head, header);
3424                 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3425                 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3426                 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3427                 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3428                 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
3429                 __skb_insert(nskb, skb->prev, skb, list);
3430                 sk_stream_set_owner_r(nskb, sk);
3431
3432                 /* Copy data, releasing collapsed skbs. */
3433                 while (copy > 0) {
3434                         int offset = start - TCP_SKB_CB(skb)->seq;
3435                         int size = TCP_SKB_CB(skb)->end_seq - start;
3436
3437                         BUG_ON(offset < 0);
3438                         if (size > 0) {
3439                                 size = min(copy, size);
3440                                 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3441                                         BUG();
3442                                 TCP_SKB_CB(nskb)->end_seq += size;
3443                                 copy -= size;
3444                                 start += size;
3445                         }
3446                         if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3447                                 struct sk_buff *next = skb->next;
3448                                 __skb_unlink(skb, list);
3449                                 __kfree_skb(skb);
3450                                 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3451                                 skb = next;
3452                                 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3453                                         return;
3454                         }
3455                 }
3456         }
3457 }
3458
3459 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3460  * and tcp_collapse() them until all the queue is collapsed.
3461  */
3462 static void tcp_collapse_ofo_queue(struct sock *sk)
3463 {
3464         struct tcp_sock *tp = tcp_sk(sk);
3465         struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3466         struct sk_buff *head;
3467         u32 start, end;
3468
3469         if (skb == NULL)
3470                 return;
3471
3472         start = TCP_SKB_CB(skb)->seq;
3473         end = TCP_SKB_CB(skb)->end_seq;
3474         head = skb;
3475
3476         for (;;) {
3477                 skb = skb->next;
3478
3479                 /* Segment is terminated when we see gap or when
3480                  * we are at the end of all the queue. */
3481                 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3482                     after(TCP_SKB_CB(skb)->seq, end) ||
3483                     before(TCP_SKB_CB(skb)->end_seq, start)) {
3484                         tcp_collapse(sk, &tp->out_of_order_queue,
3485                                      head, skb, start, end);
3486                         head = skb;
3487                         if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3488                                 break;
3489                         /* Start new segment */
3490                         start = TCP_SKB_CB(skb)->seq;
3491                         end = TCP_SKB_CB(skb)->end_seq;
3492                 } else {
3493                         if (before(TCP_SKB_CB(skb)->seq, start))
3494                                 start = TCP_SKB_CB(skb)->seq;
3495                         if (after(TCP_SKB_CB(skb)->end_seq, end))
3496                                 end = TCP_SKB_CB(skb)->end_seq;
3497                 }
3498         }
3499 }
3500
3501 /* Reduce allocated memory if we can, trying to get
3502  * the socket within its memory limits again.
3503  *
3504  * Return less than zero if we should start dropping frames
3505  * until the socket owning process reads some of the data
3506  * to stabilize the situation.
3507  */
3508 static int tcp_prune_queue(struct sock *sk)
3509 {
3510         struct tcp_sock *tp = tcp_sk(sk);
3511
3512         SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3513
3514         NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3515
3516         if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3517                 tcp_clamp_window(sk, tp);
3518         else if (tcp_memory_pressure)
3519                 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3520
3521         tcp_collapse_ofo_queue(sk);
3522         tcp_collapse(sk, &sk->sk_receive_queue,
3523                      sk->sk_receive_queue.next,
3524                      (struct sk_buff*)&sk->sk_receive_queue,
3525                      tp->copied_seq, tp->rcv_nxt);
3526         sk_stream_mem_reclaim(sk);
3527
3528         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3529                 return 0;
3530
3531         /* Collapsing did not help, destructive actions follow.
3532          * This must not ever occur. */
3533
3534         /* First, purge the out_of_order queue. */
3535         if (!skb_queue_empty(&tp->out_of_order_queue)) {
3536                 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
3537                 __skb_queue_purge(&tp->out_of_order_queue);
3538
3539                 /* Reset SACK state.  A conforming SACK implementation will
3540                  * do the same at a timeout based retransmit.  When a connection
3541                  * is in a sad state like this, we care only about integrity
3542                  * of the connection not performance.
3543                  */
3544                 if (tp->rx_opt.sack_ok)
3545                         tcp_sack_reset(&tp->rx_opt);
3546                 sk_stream_mem_reclaim(sk);
3547         }
3548
3549         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3550                 return 0;
3551
3552         /* If we are really being abused, tell the caller to silently
3553          * drop receive data on the floor.  It will get retransmitted
3554          * and hopefully then we'll have sufficient space.
3555          */
3556         NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3557
3558         /* Massive buffer overcommit. */
3559         tp->pred_flags = 0;
3560         return -1;
3561 }
3562
3563
3564 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3565  * As additional protections, we do not touch cwnd in retransmission phases,
3566  * and if application hit its sndbuf limit recently.
3567  */
3568 void tcp_cwnd_application_limited(struct sock *sk)
3569 {
3570         struct tcp_sock *tp = tcp_sk(sk);
3571
3572         if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
3573             sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3574                 /* Limited by application or receiver window. */
3575                 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
3576                 u32 win_used = max(tp->snd_cwnd_used, init_win);
3577                 if (win_used < tp->snd_cwnd) {
3578                         tp->snd_ssthresh = tcp_current_ssthresh(sk);
3579                         tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3580                 }
3581                 tp->snd_cwnd_used = 0;
3582         }
3583         tp->snd_cwnd_stamp = tcp_time_stamp;
3584 }
3585
3586 static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
3587 {
3588         /* If the user specified a specific send buffer setting, do
3589          * not modify it.
3590          */
3591         if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3592                 return 0;
3593
3594         /* If we are under global TCP memory pressure, do not expand.  */
3595         if (tcp_memory_pressure)
3596                 return 0;
3597
3598         /* If we are under soft global TCP memory pressure, do not expand.  */
3599         if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3600                 return 0;
3601
3602         /* If we filled the congestion window, do not expand.  */
3603         if (tp->packets_out >= tp->snd_cwnd)
3604                 return 0;
3605
3606         return 1;
3607 }
3608
3609 /* When incoming ACK allowed to free some skb from write_queue,
3610  * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3611  * on the exit from tcp input handler.
3612  *
3613  * PROBLEM: sndbuf expansion does not work well with largesend.
3614  */
3615 static void tcp_new_space(struct sock *sk)
3616 {
3617         struct tcp_sock *tp = tcp_sk(sk);
3618
3619         if (tcp_should_expand_sndbuf(sk, tp)) {
3620                 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
3621                         MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3622                     demanded = max_t(unsigned int, tp->snd_cwnd,
3623                                                    tp->reordering + 1);
3624                 sndmem *= 2*demanded;
3625                 if (sndmem > sk->sk_sndbuf)
3626                         sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3627                 tp->snd_cwnd_stamp = tcp_time_stamp;
3628         }
3629
3630         sk->sk_write_space(sk);
3631 }
3632
3633 static void tcp_check_space(struct sock *sk)
3634 {
3635         if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3636                 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3637                 if (sk->sk_socket &&
3638                     test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3639                         tcp_new_space(sk);
3640         }
3641 }
3642
3643 static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
3644 {
3645         tcp_push_pending_frames(sk, tp);
3646         tcp_check_space(sk);
3647 }
3648
3649 /*
3650  * Check if sending an ack is needed.
3651  */
3652 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3653 {
3654         struct tcp_sock *tp = tcp_sk(sk);
3655
3656             /* More than one full frame received... */
3657         if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
3658              /* ... and right edge of window advances far enough.
3659               * (tcp_recvmsg() will send ACK otherwise). Or...
3660               */
3661              && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3662             /* We ACK each frame or... */
3663             tcp_in_quickack_mode(sk) ||
3664             /* We have out of order data. */
3665             (ofo_possible &&
3666              skb_peek(&tp->out_of_order_queue))) {
3667                 /* Then ack it now */
3668                 tcp_send_ack(sk);
3669         } else {
3670                 /* Else, send delayed ack. */
3671                 tcp_send_delayed_ack(sk);
3672         }
3673 }
3674
3675 static inline void tcp_ack_snd_check(struct sock *sk)
3676 {
3677         if (!inet_csk_ack_scheduled(sk)) {
3678                 /* We sent a data segment already. */
3679                 return;
3680         }
3681         __tcp_ack_snd_check(sk, 1);
3682 }
3683
3684 /*
3685  *      This routine is only called when we have urgent data
3686  *      signaled. Its the 'slow' part of tcp_urg. It could be
3687  *      moved inline now as tcp_urg is only called from one
3688  *      place. We handle URGent data wrong. We have to - as
3689  *      BSD still doesn't use the correction from RFC961.
3690  *      For 1003.1g we should support a new option TCP_STDURG to permit
3691  *      either form (or just set the sysctl tcp_stdurg).
3692  */
3693
3694 static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3695 {
3696         struct tcp_sock *tp = tcp_sk(sk);
3697         u32 ptr = ntohs(th->urg_ptr);
3698
3699         if (ptr && !sysctl_tcp_stdurg)
3700                 ptr--;
3701         ptr += ntohl(th->seq);
3702
3703         /* Ignore urgent data that we've already seen and read. */
3704         if (after(tp->copied_seq, ptr))
3705                 return;
3706
3707         /* Do not replay urg ptr.
3708          *
3709          * NOTE: interesting situation not covered by specs.
3710          * Misbehaving sender may send urg ptr, pointing to segment,
3711          * which we already have in ofo queue. We are not able to fetch
3712          * such data and will stay in TCP_URG_NOTYET until will be eaten
3713          * by recvmsg(). Seems, we are not obliged to handle such wicked
3714          * situations. But it is worth to think about possibility of some
3715          * DoSes using some hypothetical application level deadlock.
3716          */
3717         if (before(ptr, tp->rcv_nxt))
3718                 return;
3719
3720         /* Do we already have a newer (or duplicate) urgent pointer? */
3721         if (tp->urg_data && !after(ptr, tp->urg_seq))
3722                 return;
3723
3724         /* Tell the world about our new urgent pointer. */
3725         sk_send_sigurg(sk);
3726
3727         /* We may be adding urgent data when the last byte read was
3728          * urgent. To do this requires some care. We cannot just ignore
3729          * tp->copied_seq since we would read the last urgent byte again
3730          * as data, nor can we alter copied_seq until this data arrives
3731          * or we break the semantics of SIOCATMARK (and thus sockatmark())
3732          *
3733          * NOTE. Double Dutch. Rendering to plain English: author of comment
3734          * above did something sort of  send("A", MSG_OOB); send("B", MSG_OOB);
3735          * and expect that both A and B disappear from stream. This is _wrong_.
3736          * Though this happens in BSD with high probability, this is occasional.
3737          * Any application relying on this is buggy. Note also, that fix "works"
3738          * only in this artificial test. Insert some normal data between A and B and we will
3739          * decline of BSD again. Verdict: it is better to remove to trap
3740          * buggy users.
3741          */
3742         if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3743             !sock_flag(sk, SOCK_URGINLINE) &&
3744             tp->copied_seq != tp->rcv_nxt) {
3745                 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3746                 tp->copied_seq++;
3747                 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
3748                         __skb_unlink(skb, &sk->sk_receive_queue);
3749                         __kfree_skb(skb);
3750                 }
3751         }
3752
3753         tp->urg_data   = TCP_URG_NOTYET;
3754         tp->urg_seq    = ptr;
3755
3756         /* Disable header prediction. */
3757         tp->pred_flags = 0;
3758 }
3759
3760 /* This is the 'fast' part of urgent handling. */
3761 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3762 {
3763         struct tcp_sock *tp = tcp_sk(sk);
3764
3765         /* Check if we get a new urgent pointer - normally not. */
3766         if (th->urg)
3767                 tcp_check_urg(sk,th);
3768
3769         /* Do we wait for any urgent data? - normally not... */
3770         if (tp->urg_data == TCP_URG_NOTYET) {
3771                 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3772                           th->syn;
3773
3774                 /* Is the urgent pointer pointing into this packet? */
3775                 if (ptr < skb->len) {
3776                         u8 tmp;
3777                         if (skb_copy_bits(skb, ptr, &tmp, 1))
3778                                 BUG();
3779                         tp->urg_data = TCP_URG_VALID | tmp;
3780                         if (!sock_flag(sk, SOCK_DEAD))
3781                                 sk->sk_data_ready(sk, 0);
3782                 }
3783         }
3784 }
3785
3786 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3787 {
3788         struct tcp_sock *tp = tcp_sk(sk);
3789         int chunk = skb->len - hlen;
3790         int err;
3791
3792         local_bh_enable();
3793         if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3794                 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3795         else
3796                 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3797                                                        tp->ucopy.iov);
3798
3799         if (!err) {
3800                 tp->ucopy.len -= chunk;
3801                 tp->copied_seq += chunk;
3802                 tcp_rcv_space_adjust(sk);
3803         }
3804
3805         local_bh_disable();
3806         return err;
3807 }
3808
3809 static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3810 {
3811         __sum16 result;
3812
3813         if (sock_owned_by_user(sk)) {
3814                 local_bh_enable();
3815                 result = __tcp_checksum_complete(skb);
3816                 local_bh_disable();
3817         } else {
3818                 result = __tcp_checksum_complete(skb);
3819         }
3820         return result;
3821 }
3822
3823 static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3824 {
3825         return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3826                 __tcp_checksum_complete_user(sk, skb);
3827 }
3828
3829 #ifdef CONFIG_NET_DMA
3830 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen)
3831 {
3832         struct tcp_sock *tp = tcp_sk(sk);
3833         int chunk = skb->len - hlen;
3834         int dma_cookie;
3835         int copied_early = 0;
3836
3837         if (tp->ucopy.wakeup)
3838                 return 0;
3839
3840         if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
3841                 tp->ucopy.dma_chan = get_softnet_dma();
3842
3843         if (tp->ucopy.dma_chan && skb->ip_summed == CHECKSUM_UNNECESSARY) {
3844
3845                 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
3846                         skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list);
3847
3848                 if (dma_cookie < 0)
3849                         goto out;
3850
3851                 tp->ucopy.dma_cookie = dma_cookie;
3852                 copied_early = 1;
3853
3854                 tp->ucopy.len -= chunk;
3855                 tp->copied_seq += chunk;
3856                 tcp_rcv_space_adjust(sk);
3857
3858                 if ((tp->ucopy.len == 0) ||
3859                     (tcp_flag_word(skb->h.th) & TCP_FLAG_PSH) ||
3860                     (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
3861                         tp->ucopy.wakeup = 1;
3862                         sk->sk_data_ready(sk, 0);
3863                 }
3864         } else if (chunk > 0) {
3865                 tp->ucopy.wakeup = 1;
3866                 sk->sk_data_ready(sk, 0);
3867         }
3868 out:
3869         return copied_early;
3870 }
3871 #endif /* CONFIG_NET_DMA */
3872
3873 /*
3874  *      TCP receive function for the ESTABLISHED state.
3875  *
3876  *      It is split into a fast path and a slow path. The fast path is
3877  *      disabled when:
3878  *      - A zero window was announced from us - zero window probing
3879  *        is only handled properly in the slow path.
3880  *      - Out of order segments arrived.
3881  *      - Urgent data is expected.
3882  *      - There is no buffer space left
3883  *      - Unexpected TCP flags/window values/header lengths are received
3884  *        (detected by checking the TCP header against pred_flags)
3885  *      - Data is sent in both directions. Fast path only supports pure senders
3886  *        or pure receivers (this means either the sequence number or the ack
3887  *        value must stay constant)
3888  *      - Unexpected TCP option.
3889  *
3890  *      When these conditions are not satisfied it drops into a standard
3891  *      receive procedure patterned after RFC793 to handle all cases.
3892  *      The first three cases are guaranteed by proper pred_flags setting,
3893  *      the rest is checked inline. Fast processing is turned on in
3894  *      tcp_data_queue when everything is OK.
3895  */
3896 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3897                         struct tcphdr *th, unsigned len)
3898 {
3899         struct tcp_sock *tp = tcp_sk(sk);
3900
3901         /*
3902          *      Header prediction.
3903          *      The code loosely follows the one in the famous
3904          *      "30 instruction TCP receive" Van Jacobson mail.
3905          *
3906          *      Van's trick is to deposit buffers into socket queue
3907          *      on a device interrupt, to call tcp_recv function
3908          *      on the receive process context and checksum and copy
3909          *      the buffer to user space. smart...
3910          *
3911          *      Our current scheme is not silly either but we take the
3912          *      extra cost of the net_bh soft interrupt processing...
3913          *      We do checksum and copy also but from device to kernel.
3914          */
3915
3916         tp->rx_opt.saw_tstamp = 0;
3917
3918         /*      pred_flags is 0xS?10 << 16 + snd_wnd
3919          *      if header_prediction is to be made
3920          *      'S' will always be tp->tcp_header_len >> 2
3921          *      '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3922          *  turn it off (when there are holes in the receive
3923          *       space for instance)
3924          *      PSH flag is ignored.
3925          */
3926
3927         if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3928                 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3929                 int tcp_header_len = tp->tcp_header_len;
3930
3931                 /* Timestamp header prediction: tcp_header_len
3932                  * is automatically equal to th->doff*4 due to pred_flags
3933                  * match.
3934                  */
3935
3936                 /* Check timestamp */
3937                 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
3938                         __be32 *ptr = (__be32 *)(th + 1);
3939
3940                         /* No? Slow path! */
3941                         if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3942                                           | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3943                                 goto slow_path;
3944
3945                         tp->rx_opt.saw_tstamp = 1;
3946                         ++ptr;
3947                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
3948                         ++ptr;
3949                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3950
3951                         /* If PAWS failed, check it more carefully in slow path */
3952                         if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3953                                 goto slow_path;
3954
3955                         /* DO NOT update ts_recent here, if checksum fails
3956                          * and timestamp was corrupted part, it will result
3957                          * in a hung connection since we will drop all
3958                          * future packets due to the PAWS test.
3959                          */
3960                 }
3961
3962                 if (len <= tcp_header_len) {
3963                         /* Bulk data transfer: sender */
3964                         if (len == tcp_header_len) {
3965                                 /* Predicted packet is in window by definition.
3966                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3967                                  * Hence, check seq<=rcv_wup reduces to:
3968                                  */
3969                                 if (tcp_header_len ==
3970                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3971                                     tp->rcv_nxt == tp->rcv_wup)
3972                                         tcp_store_ts_recent(tp);
3973
3974                                 /* We know that such packets are checksummed
3975                                  * on entry.
3976                                  */
3977                                 tcp_ack(sk, skb, 0);
3978                                 __kfree_skb(skb);
3979                                 tcp_data_snd_check(sk, tp);
3980                                 return 0;
3981                         } else { /* Header too small */
3982                                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3983                                 goto discard;
3984                         }
3985                 } else {
3986                         int eaten = 0;
3987                         int copied_early = 0;
3988
3989                         if (tp->copied_seq == tp->rcv_nxt &&
3990                             len - tcp_header_len <= tp->ucopy.len) {
3991 #ifdef CONFIG_NET_DMA
3992                                 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
3993                                         copied_early = 1;
3994                                         eaten = 1;
3995                                 }
3996 #endif
3997                                 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) {
3998                                         __set_current_state(TASK_RUNNING);
3999
4000                                         if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
4001                                                 eaten = 1;
4002                                 }
4003                                 if (eaten) {
4004                                         /* Predicted packet is in window by definition.
4005                                          * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4006                                          * Hence, check seq<=rcv_wup reduces to:
4007                                          */
4008                                         if (tcp_header_len ==
4009                                             (sizeof(struct tcphdr) +
4010                                              TCPOLEN_TSTAMP_ALIGNED) &&
4011                                             tp->rcv_nxt == tp->rcv_wup)
4012                                                 tcp_store_ts_recent(tp);
4013
4014                                         tcp_rcv_rtt_measure_ts(sk, skb);
4015
4016                                         __skb_pull(skb, tcp_header_len);
4017                                         tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4018                                         NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
4019                                 }
4020                                 if (copied_early)
4021                                         tcp_cleanup_rbuf(sk, skb->len);
4022                         }
4023                         if (!eaten) {
4024                                 if (tcp_checksum_complete_user(sk, skb))
4025                                         goto csum_error;
4026
4027                                 /* Predicted packet is in window by definition.
4028                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4029                                  * Hence, check seq<=rcv_wup reduces to:
4030                                  */
4031                                 if (tcp_header_len ==
4032                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4033                                     tp->rcv_nxt == tp->rcv_wup)
4034                                         tcp_store_ts_recent(tp);
4035
4036                                 tcp_rcv_rtt_measure_ts(sk, skb);
4037
4038                                 if ((int)skb->truesize > sk->sk_forward_alloc)
4039                                         goto step5;
4040
4041                                 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4042
4043                                 /* Bulk data transfer: receiver */
4044                                 __skb_pull(skb,tcp_header_len);
4045                                 __skb_queue_tail(&sk->sk_receive_queue, skb);
4046                                 sk_stream_set_owner_r(skb, sk);
4047                                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4048                         }
4049
4050                         tcp_event_data_recv(sk, tp, skb);
4051
4052                         if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4053                                 /* Well, only one small jumplet in fast path... */
4054                                 tcp_ack(sk, skb, FLAG_DATA);
4055                                 tcp_data_snd_check(sk, tp);
4056                                 if (!inet_csk_ack_scheduled(sk))
4057                                         goto no_ack;
4058                         }
4059
4060                         __tcp_ack_snd_check(sk, 0);
4061 no_ack:
4062 #ifdef CONFIG_NET_DMA
4063                         if (copied_early)
4064                                 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
4065                         else
4066 #endif
4067                         if (eaten)
4068                                 __kfree_skb(skb);
4069                         else
4070                                 sk->sk_data_ready(sk, 0);
4071                         return 0;
4072                 }
4073         }
4074
4075 slow_path:
4076         if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4077                 goto csum_error;
4078
4079         /*
4080          * RFC1323: H1. Apply PAWS check first.
4081          */
4082         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4083             tcp_paws_discard(sk, skb)) {
4084                 if (!th->rst) {
4085                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4086                         tcp_send_dupack(sk, skb);
4087                         goto discard;
4088                 }
4089                 /* Resets are accepted even if PAWS failed.
4090
4091                    ts_recent update must be made after we are sure
4092                    that the packet is in window.
4093                  */
4094         }
4095
4096         /*
4097          *      Standard slow path.
4098          */
4099
4100         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4101                 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4102                  * (RST) segments are validated by checking their SEQ-fields."
4103                  * And page 69: "If an incoming segment is not acceptable,
4104                  * an acknowledgment should be sent in reply (unless the RST bit
4105                  * is set, if so drop the segment and return)".
4106                  */
4107                 if (!th->rst)
4108                         tcp_send_dupack(sk, skb);
4109                 goto discard;
4110         }
4111
4112         if(th->rst) {
4113                 tcp_reset(sk);
4114                 goto discard;
4115         }
4116
4117         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4118
4119         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4120                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4121                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4122                 tcp_reset(sk);
4123                 return 1;
4124         }
4125
4126 step5:
4127         if(th->ack)
4128                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4129
4130         tcp_rcv_rtt_measure_ts(sk, skb);
4131
4132         /* Process urgent data. */
4133         tcp_urg(sk, skb, th);
4134
4135         /* step 7: process the segment text */
4136         tcp_data_queue(sk, skb);
4137
4138         tcp_data_snd_check(sk, tp);
4139         tcp_ack_snd_check(sk);
4140         return 0;
4141
4142 csum_error:
4143         TCP_INC_STATS_BH(TCP_MIB_INERRS);
4144
4145 discard:
4146         __kfree_skb(skb);
4147         return 0;
4148 }
4149
4150 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4151                                          struct tcphdr *th, unsigned len)
4152 {
4153         struct tcp_sock *tp = tcp_sk(sk);
4154         struct inet_connection_sock *icsk = inet_csk(sk);
4155         int saved_clamp = tp->rx_opt.mss_clamp;
4156
4157         tcp_parse_options(skb, &tp->rx_opt, 0);
4158
4159         if (th->ack) {
4160                 /* rfc793:
4161                  * "If the state is SYN-SENT then
4162                  *    first check the ACK bit
4163                  *      If the ACK bit is set
4164                  *        If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4165                  *        a reset (unless the RST bit is set, if so drop
4166                  *        the segment and return)"
4167                  *
4168                  *  We do not send data with SYN, so that RFC-correct
4169                  *  test reduces to:
4170                  */
4171                 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4172                         goto reset_and_undo;
4173
4174                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4175                     !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4176                              tcp_time_stamp)) {
4177                         NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4178                         goto reset_and_undo;
4179                 }
4180
4181                 /* Now ACK is acceptable.
4182                  *
4183                  * "If the RST bit is set
4184                  *    If the ACK was acceptable then signal the user "error:
4185                  *    connection reset", drop the segment, enter CLOSED state,
4186                  *    delete TCB, and return."
4187                  */
4188
4189                 if (th->rst) {
4190                         tcp_reset(sk);
4191                         goto discard;
4192                 }
4193
4194                 /* rfc793:
4195                  *   "fifth, if neither of the SYN or RST bits is set then
4196                  *    drop the segment and return."
4197                  *
4198                  *    See note below!
4199                  *                                        --ANK(990513)
4200                  */
4201                 if (!th->syn)
4202                         goto discard_and_undo;
4203
4204                 /* rfc793:
4205                  *   "If the SYN bit is on ...
4206                  *    are acceptable then ...
4207                  *    (our SYN has been ACKed), change the connection
4208                  *    state to ESTABLISHED..."
4209                  */
4210
4211                 TCP_ECN_rcv_synack(tp, th);
4212
4213                 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4214                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4215
4216                 /* Ok.. it's good. Set up sequence numbers and
4217                  * move to established.
4218                  */
4219                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4220                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4221
4222                 /* RFC1323: The window in SYN & SYN/ACK segments is
4223                  * never scaled.
4224                  */
4225                 tp->snd_wnd = ntohs(th->window);
4226                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4227
4228                 if (!tp->rx_opt.wscale_ok) {
4229                         tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4230                         tp->window_clamp = min(tp->window_clamp, 65535U);
4231                 }
4232
4233                 if (tp->rx_opt.saw_tstamp) {
4234                         tp->rx_opt.tstamp_ok       = 1;
4235                         tp->tcp_header_len =
4236                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4237                         tp->advmss          -= TCPOLEN_TSTAMP_ALIGNED;
4238                         tcp_store_ts_recent(tp);
4239                 } else {
4240                         tp->tcp_header_len = sizeof(struct tcphdr);
4241                 }
4242
4243                 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4244                         tp->rx_opt.sack_ok |= 2;
4245
4246                 tcp_mtup_init(sk);
4247                 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4248                 tcp_initialize_rcv_mss(sk);
4249
4250                 /* Remember, tcp_poll() does not lock socket!
4251                  * Change state from SYN-SENT only after copied_seq
4252                  * is initialized. */
4253                 tp->copied_seq = tp->rcv_nxt;
4254                 smp_mb();
4255                 tcp_set_state(sk, TCP_ESTABLISHED);
4256
4257                 security_inet_conn_established(sk, skb);
4258
4259                 /* Make sure socket is routed, for correct metrics.  */
4260                 icsk->icsk_af_ops->rebuild_header(sk);
4261
4262                 tcp_init_metrics(sk);
4263
4264                 tcp_init_congestion_control(sk);
4265
4266                 /* Prevent spurious tcp_cwnd_restart() on first data
4267                  * packet.
4268                  */
4269                 tp->lsndtime = tcp_time_stamp;
4270
4271                 tcp_init_buffer_space(sk);
4272
4273                 if (sock_flag(sk, SOCK_KEEPOPEN))
4274                         inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
4275
4276                 if (!tp->rx_opt.snd_wscale)
4277                         __tcp_fast_path_on(tp, tp->snd_wnd);
4278                 else
4279                         tp->pred_flags = 0;
4280
4281                 if (!sock_flag(sk, SOCK_DEAD)) {
4282                         sk->sk_state_change(sk);
4283                         sk_wake_async(sk, 0, POLL_OUT);
4284                 }
4285
4286                 if (sk->sk_write_pending ||
4287                     icsk->icsk_accept_queue.rskq_defer_accept ||
4288                     icsk->icsk_ack.pingpong) {
4289                         /* Save one ACK. Data will be ready after
4290                          * several ticks, if write_pending is set.
4291                          *
4292                          * It may be deleted, but with this feature tcpdumps
4293                          * look so _wonderfully_ clever, that I was not able
4294                          * to stand against the temptation 8)     --ANK
4295                          */
4296                         inet_csk_schedule_ack(sk);
4297                         icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4298                         icsk->icsk_ack.ato       = TCP_ATO_MIN;
4299                         tcp_incr_quickack(sk);
4300                         tcp_enter_quickack_mode(sk);
4301                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4302                                                   TCP_DELACK_MAX, TCP_RTO_MAX);
4303
4304 discard:
4305                         __kfree_skb(skb);
4306                         return 0;
4307                 } else {
4308                         tcp_send_ack(sk);
4309                 }
4310                 return -1;
4311         }
4312
4313         /* No ACK in the segment */
4314
4315         if (th->rst) {
4316                 /* rfc793:
4317                  * "If the RST bit is set
4318                  *
4319                  *      Otherwise (no ACK) drop the segment and return."
4320                  */
4321
4322                 goto discard_and_undo;
4323         }
4324
4325         /* PAWS check. */
4326         if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4327                 goto discard_and_undo;
4328
4329         if (th->syn) {
4330                 /* We see SYN without ACK. It is attempt of
4331                  * simultaneous connect with crossed SYNs.
4332                  * Particularly, it can be connect to self.
4333                  */
4334                 tcp_set_state(sk, TCP_SYN_RECV);
4335
4336                 if (tp->rx_opt.saw_tstamp) {
4337                         tp->rx_opt.tstamp_ok = 1;
4338                         tcp_store_ts_recent(tp);
4339                         tp->tcp_header_len =
4340                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4341                 } else {
4342                         tp->tcp_header_len = sizeof(struct tcphdr);
4343                 }
4344
4345                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4346                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4347
4348                 /* RFC1323: The window in SYN & SYN/ACK segments is
4349                  * never scaled.
4350                  */
4351                 tp->snd_wnd    = ntohs(th->window);
4352                 tp->snd_wl1    = TCP_SKB_CB(skb)->seq;
4353                 tp->max_window = tp->snd_wnd;
4354
4355                 TCP_ECN_rcv_syn(tp, th);
4356
4357                 tcp_mtup_init(sk);
4358                 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4359                 tcp_initialize_rcv_mss(sk);
4360
4361
4362                 tcp_send_synack(sk);
4363 #if 0
4364                 /* Note, we could accept data and URG from this segment.
4365                  * There are no obstacles to make this.
4366                  *
4367                  * However, if we ignore data in ACKless segments sometimes,
4368                  * we have no reasons to accept it sometimes.
4369                  * Also, seems the code doing it in step6 of tcp_rcv_state_process
4370                  * is not flawless. So, discard packet for sanity.
4371                  * Uncomment this return to process the data.
4372                  */
4373                 return -1;
4374 #else
4375                 goto discard;
4376 #endif
4377         }
4378         /* "fifth, if neither of the SYN or RST bits is set then
4379          * drop the segment and return."
4380          */
4381
4382 discard_and_undo:
4383         tcp_clear_options(&tp->rx_opt);
4384         tp->rx_opt.mss_clamp = saved_clamp;
4385         goto discard;
4386
4387 reset_and_undo:
4388         tcp_clear_options(&tp->rx_opt);
4389         tp->rx_opt.mss_clamp = saved_clamp;
4390         return 1;
4391 }
4392
4393
4394 /*
4395  *      This function implements the receiving procedure of RFC 793 for
4396  *      all states except ESTABLISHED and TIME_WAIT.
4397  *      It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4398  *      address independent.
4399  */
4400
4401 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4402                           struct tcphdr *th, unsigned len)
4403 {
4404         struct tcp_sock *tp = tcp_sk(sk);
4405         struct inet_connection_sock *icsk = inet_csk(sk);
4406         int queued = 0;
4407
4408         tp->rx_opt.saw_tstamp = 0;
4409
4410         switch (sk->sk_state) {
4411         case TCP_CLOSE:
4412                 goto discard;
4413
4414         case TCP_LISTEN:
4415                 if(th->ack)
4416                         return 1;
4417
4418                 if(th->rst)
4419                         goto discard;
4420
4421                 if(th->syn) {
4422                         if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
4423                                 return 1;
4424
4425                         /* Now we have several options: In theory there is
4426                          * nothing else in the frame. KA9Q has an option to
4427                          * send data with the syn, BSD accepts data with the
4428                          * syn up to the [to be] advertised window and
4429                          * Solaris 2.1 gives you a protocol error. For now
4430                          * we just ignore it, that fits the spec precisely
4431                          * and avoids incompatibilities. It would be nice in
4432                          * future to drop through and process the data.
4433                          *
4434                          * Now that TTCP is starting to be used we ought to
4435                          * queue this data.
4436                          * But, this leaves one open to an easy denial of
4437                          * service attack, and SYN cookies can't defend
4438                          * against this problem. So, we drop the data
4439                          * in the interest of security over speed unless
4440                          * it's still in use.
4441                          */
4442                         kfree_skb(skb);
4443                         return 0;
4444                 }
4445                 goto discard;
4446
4447         case TCP_SYN_SENT:
4448                 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4449                 if (queued >= 0)
4450                         return queued;
4451
4452                 /* Do step6 onward by hand. */
4453                 tcp_urg(sk, skb, th);
4454                 __kfree_skb(skb);
4455                 tcp_data_snd_check(sk, tp);
4456                 return 0;
4457         }
4458
4459         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4460             tcp_paws_discard(sk, skb)) {
4461                 if (!th->rst) {
4462                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4463                         tcp_send_dupack(sk, skb);
4464                         goto discard;
4465                 }
4466                 /* Reset is accepted even if it did not pass PAWS. */
4467         }
4468
4469         /* step 1: check sequence number */
4470         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4471                 if (!th->rst)
4472                         tcp_send_dupack(sk, skb);
4473                 goto discard;
4474         }
4475
4476         /* step 2: check RST bit */
4477         if(th->rst) {
4478                 tcp_reset(sk);
4479                 goto discard;
4480         }
4481
4482         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4483
4484         /* step 3: check security and precedence [ignored] */
4485
4486         /*      step 4:
4487          *
4488          *      Check for a SYN in window.
4489          */
4490         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4491                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4492                 tcp_reset(sk);
4493                 return 1;
4494         }
4495
4496         /* step 5: check the ACK field */
4497         if (th->ack) {
4498                 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4499
4500                 switch(sk->sk_state) {
4501                 case TCP_SYN_RECV:
4502                         if (acceptable) {
4503                                 tp->copied_seq = tp->rcv_nxt;
4504                                 smp_mb();
4505                                 tcp_set_state(sk, TCP_ESTABLISHED);
4506                                 sk->sk_state_change(sk);
4507
4508                                 /* Note, that this wakeup is only for marginal
4509                                  * crossed SYN case. Passively open sockets
4510                                  * are not waked up, because sk->sk_sleep ==
4511                                  * NULL and sk->sk_socket == NULL.
4512                                  */
4513                                 if (sk->sk_socket) {
4514                                         sk_wake_async(sk,0,POLL_OUT);
4515                                 }
4516
4517                                 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4518                                 tp->snd_wnd = ntohs(th->window) <<
4519                                               tp->rx_opt.snd_wscale;
4520                                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4521                                             TCP_SKB_CB(skb)->seq);
4522
4523                                 /* tcp_ack considers this ACK as duplicate
4524                                  * and does not calculate rtt.
4525                                  * Fix it at least with timestamps.
4526                                  */
4527                                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4528                                     !tp->srtt)
4529                                         tcp_ack_saw_tstamp(sk, 0);
4530
4531                                 if (tp->rx_opt.tstamp_ok)
4532                                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4533
4534                                 /* Make sure socket is routed, for
4535                                  * correct metrics.
4536                                  */
4537                                 icsk->icsk_af_ops->rebuild_header(sk);
4538
4539                                 tcp_init_metrics(sk);
4540
4541                                 tcp_init_congestion_control(sk);
4542
4543                                 /* Prevent spurious tcp_cwnd_restart() on
4544                                  * first data packet.
4545                                  */
4546                                 tp->lsndtime = tcp_time_stamp;
4547
4548                                 tcp_mtup_init(sk);
4549                                 tcp_initialize_rcv_mss(sk);
4550                                 tcp_init_buffer_space(sk);
4551                                 tcp_fast_path_on(tp);
4552                         } else {
4553                                 return 1;
4554                         }
4555                         break;
4556
4557                 case TCP_FIN_WAIT1:
4558                         if (tp->snd_una == tp->write_seq) {
4559                                 tcp_set_state(sk, TCP_FIN_WAIT2);
4560                                 sk->sk_shutdown |= SEND_SHUTDOWN;
4561                                 dst_confirm(sk->sk_dst_cache);
4562
4563                                 if (!sock_flag(sk, SOCK_DEAD))
4564                                         /* Wake up lingering close() */
4565                                         sk->sk_state_change(sk);
4566                                 else {
4567                                         int tmo;
4568
4569                                         if (tp->linger2 < 0 ||
4570                                             (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4571                                              after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4572                                                 tcp_done(sk);
4573                                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4574                                                 return 1;
4575                                         }
4576
4577                                         tmo = tcp_fin_time(sk);
4578                                         if (tmo > TCP_TIMEWAIT_LEN) {
4579                                                 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
4580                                         } else if (th->fin || sock_owned_by_user(sk)) {
4581                                                 /* Bad case. We could lose such FIN otherwise.
4582                                                  * It is not a big problem, but it looks confusing
4583                                                  * and not so rare event. We still can lose it now,
4584                                                  * if it spins in bh_lock_sock(), but it is really
4585                                                  * marginal case.
4586                                                  */
4587                                                 inet_csk_reset_keepalive_timer(sk, tmo);
4588                                         } else {
4589                                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4590                                                 goto discard;
4591                                         }
4592                                 }
4593                         }
4594                         break;
4595
4596                 case TCP_CLOSING:
4597                         if (tp->snd_una == tp->write_seq) {
4598                                 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4599                                 goto discard;
4600                         }
4601                         break;
4602
4603                 case TCP_LAST_ACK:
4604                         if (tp->snd_una == tp->write_seq) {
4605                                 tcp_update_metrics(sk);
4606                                 tcp_done(sk);
4607                                 goto discard;
4608                         }
4609                         break;
4610                 }
4611         } else
4612                 goto discard;
4613
4614         /* step 6: check the URG bit */
4615         tcp_urg(sk, skb, th);
4616
4617         /* step 7: process the segment text */
4618         switch (sk->sk_state) {
4619         case TCP_CLOSE_WAIT:
4620         case TCP_CLOSING:
4621         case TCP_LAST_ACK:
4622                 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4623                         break;
4624         case TCP_FIN_WAIT1:
4625         case TCP_FIN_WAIT2:
4626                 /* RFC 793 says to queue data in these states,
4627                  * RFC 1122 says we MUST send a reset.
4628                  * BSD 4.4 also does reset.
4629                  */
4630                 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4631                         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4632                             after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4633                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4634                                 tcp_reset(sk);
4635                                 return 1;
4636                         }
4637                 }
4638                 /* Fall through */
4639         case TCP_ESTABLISHED:
4640                 tcp_data_queue(sk, skb);
4641                 queued = 1;
4642                 break;
4643         }
4644
4645         /* tcp_data could move socket to TIME-WAIT */
4646         if (sk->sk_state != TCP_CLOSE) {
4647                 tcp_data_snd_check(sk, tp);
4648                 tcp_ack_snd_check(sk);
4649         }
4650
4651         if (!queued) {
4652 discard:
4653                 __kfree_skb(skb);
4654         }
4655         return 0;
4656 }
4657
4658 EXPORT_SYMBOL(sysctl_tcp_ecn);
4659 EXPORT_SYMBOL(sysctl_tcp_reordering);
4660 EXPORT_SYMBOL(tcp_parse_options);
4661 EXPORT_SYMBOL(tcp_rcv_established);
4662 EXPORT_SYMBOL(tcp_rcv_state_process);
4663 EXPORT_SYMBOL(tcp_initialize_rcv_mss);