Merge with /home/shaggy/git/linus-clean/
[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/config.h>
67 #include <linux/mm.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <net/tcp.h>
71 #include <net/inet_common.h>
72 #include <linux/ipsec.h>
73 #include <asm/unaligned.h>
74
75 int sysctl_tcp_timestamps = 1;
76 int sysctl_tcp_window_scaling = 1;
77 int sysctl_tcp_sack = 1;
78 int sysctl_tcp_fack = 1;
79 int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH;
80 int sysctl_tcp_ecn;
81 int sysctl_tcp_dsack = 1;
82 int sysctl_tcp_app_win = 31;
83 int sysctl_tcp_adv_win_scale = 2;
84
85 int sysctl_tcp_stdurg;
86 int sysctl_tcp_rfc1337;
87 int sysctl_tcp_max_orphans = NR_FILE;
88 int sysctl_tcp_frto;
89 int sysctl_tcp_nometrics_save;
90
91 int sysctl_tcp_moderate_rcvbuf = 1;
92 int sysctl_tcp_abc = 1;
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 inline 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->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                 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
160         }
161 }
162
163 static void tcp_incr_quickack(struct sock *sk)
164 {
165         struct inet_connection_sock *icsk = inet_csk(sk);
166         unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
167
168         if (quickacks==0)
169                 quickacks=2;
170         if (quickacks > icsk->icsk_ack.quick)
171                 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
172 }
173
174 void tcp_enter_quickack_mode(struct sock *sk)
175 {
176         struct inet_connection_sock *icsk = inet_csk(sk);
177         tcp_incr_quickack(sk);
178         icsk->icsk_ack.pingpong = 0;
179         icsk->icsk_ack.ato = TCP_ATO_MIN;
180 }
181
182 /* Send ACKs quickly, if "quick" count is not exhausted
183  * and the session is not interactive.
184  */
185
186 static inline int tcp_in_quickack_mode(const struct sock *sk)
187 {
188         const struct inet_connection_sock *icsk = inet_csk(sk);
189         return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
190 }
191
192 /* Buffer size and advertised window tuning.
193  *
194  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
195  */
196
197 static void tcp_fixup_sndbuf(struct sock *sk)
198 {
199         int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
200                      sizeof(struct sk_buff);
201
202         if (sk->sk_sndbuf < 3 * sndmem)
203                 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
204 }
205
206 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
207  *
208  * All tcp_full_space() is split to two parts: "network" buffer, allocated
209  * forward and advertised in receiver window (tp->rcv_wnd) and
210  * "application buffer", required to isolate scheduling/application
211  * latencies from network.
212  * window_clamp is maximal advertised window. It can be less than
213  * tcp_full_space(), in this case tcp_full_space() - window_clamp
214  * is reserved for "application" buffer. The less window_clamp is
215  * the smoother our behaviour from viewpoint of network, but the lower
216  * throughput and the higher sensitivity of the connection to losses. 8)
217  *
218  * rcv_ssthresh is more strict window_clamp used at "slow start"
219  * phase to predict further behaviour of this connection.
220  * It is used for two goals:
221  * - to enforce header prediction at sender, even when application
222  *   requires some significant "application buffer". It is check #1.
223  * - to prevent pruning of receive queue because of misprediction
224  *   of receiver window. Check #2.
225  *
226  * The scheme does not work when sender sends good segments opening
227  * window and then starts to feed us spaghetti. But it should work
228  * in common situations. Otherwise, we have to rely on queue collapsing.
229  */
230
231 /* Slow part of check#2. */
232 static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp,
233                              const struct sk_buff *skb)
234 {
235         /* Optimize this! */
236         int truesize = tcp_win_from_space(skb->truesize)/2;
237         int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
238
239         while (tp->rcv_ssthresh <= window) {
240                 if (truesize <= skb->len)
241                         return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
242
243                 truesize >>= 1;
244                 window >>= 1;
245         }
246         return 0;
247 }
248
249 static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
250                                    struct sk_buff *skb)
251 {
252         /* Check #1 */
253         if (tp->rcv_ssthresh < tp->window_clamp &&
254             (int)tp->rcv_ssthresh < tcp_space(sk) &&
255             !tcp_memory_pressure) {
256                 int incr;
257
258                 /* Check #2. Increase window, if skb with such overhead
259                  * will fit to rcvbuf in future.
260                  */
261                 if (tcp_win_from_space(skb->truesize) <= skb->len)
262                         incr = 2*tp->advmss;
263                 else
264                         incr = __tcp_grow_window(sk, tp, skb);
265
266                 if (incr) {
267                         tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
268                         inet_csk(sk)->icsk_ack.quick |= 1;
269                 }
270         }
271 }
272
273 /* 3. Tuning rcvbuf, when connection enters established state. */
274
275 static void tcp_fixup_rcvbuf(struct sock *sk)
276 {
277         struct tcp_sock *tp = tcp_sk(sk);
278         int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
279
280         /* Try to select rcvbuf so that 4 mss-sized segments
281          * will fit to window and corresponding skbs will fit to our rcvbuf.
282          * (was 3; 4 is minimum to allow fast retransmit to work.)
283          */
284         while (tcp_win_from_space(rcvmem) < tp->advmss)
285                 rcvmem += 128;
286         if (sk->sk_rcvbuf < 4 * rcvmem)
287                 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
288 }
289
290 /* 4. Try to fixup all. It is made immediately after connection enters
291  *    established state.
292  */
293 static void tcp_init_buffer_space(struct sock *sk)
294 {
295         struct tcp_sock *tp = tcp_sk(sk);
296         int maxwin;
297
298         if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
299                 tcp_fixup_rcvbuf(sk);
300         if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
301                 tcp_fixup_sndbuf(sk);
302
303         tp->rcvq_space.space = tp->rcv_wnd;
304
305         maxwin = tcp_full_space(sk);
306
307         if (tp->window_clamp >= maxwin) {
308                 tp->window_clamp = maxwin;
309
310                 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
311                         tp->window_clamp = max(maxwin -
312                                                (maxwin >> sysctl_tcp_app_win),
313                                                4 * tp->advmss);
314         }
315
316         /* Force reservation of one segment. */
317         if (sysctl_tcp_app_win &&
318             tp->window_clamp > 2 * tp->advmss &&
319             tp->window_clamp + tp->advmss > maxwin)
320                 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
321
322         tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
323         tp->snd_cwnd_stamp = tcp_time_stamp;
324 }
325
326 /* 5. Recalculate window clamp after socket hit its memory bounds. */
327 static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
328 {
329         struct inet_connection_sock *icsk = inet_csk(sk);
330
331         icsk->icsk_ack.quick = 0;
332
333         if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
334             !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
335             !tcp_memory_pressure &&
336             atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
337                 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
338                                     sysctl_tcp_rmem[2]);
339         }
340         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
341                 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
342 }
343
344 /* Receiver "autotuning" code.
345  *
346  * The algorithm for RTT estimation w/o timestamps is based on
347  * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
348  * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
349  *
350  * More detail on this code can be found at
351  * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
352  * though this reference is out of date.  A new paper
353  * is pending.
354  */
355 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
356 {
357         u32 new_sample = tp->rcv_rtt_est.rtt;
358         long m = sample;
359
360         if (m == 0)
361                 m = 1;
362
363         if (new_sample != 0) {
364                 /* If we sample in larger samples in the non-timestamp
365                  * case, we could grossly overestimate the RTT especially
366                  * with chatty applications or bulk transfer apps which
367                  * are stalled on filesystem I/O.
368                  *
369                  * Also, since we are only going for a minimum in the
370                  * non-timestamp case, we do not smoother things out
371                  * else with timestamps disabled convergence takes too
372                  * long.
373                  */
374                 if (!win_dep) {
375                         m -= (new_sample >> 3);
376                         new_sample += m;
377                 } else if (m < new_sample)
378                         new_sample = m << 3;
379         } else {
380                 /* No previous measure. */
381                 new_sample = m << 3;
382         }
383
384         if (tp->rcv_rtt_est.rtt != new_sample)
385                 tp->rcv_rtt_est.rtt = new_sample;
386 }
387
388 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
389 {
390         if (tp->rcv_rtt_est.time == 0)
391                 goto new_measure;
392         if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
393                 return;
394         tcp_rcv_rtt_update(tp,
395                            jiffies - tp->rcv_rtt_est.time,
396                            1);
397
398 new_measure:
399         tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
400         tp->rcv_rtt_est.time = tcp_time_stamp;
401 }
402
403 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
404 {
405         struct tcp_sock *tp = tcp_sk(sk);
406         if (tp->rx_opt.rcv_tsecr &&
407             (TCP_SKB_CB(skb)->end_seq -
408              TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
409                 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
410 }
411
412 /*
413  * This function should be called every time data is copied to user space.
414  * It calculates the appropriate TCP receive buffer space.
415  */
416 void tcp_rcv_space_adjust(struct sock *sk)
417 {
418         struct tcp_sock *tp = tcp_sk(sk);
419         int time;
420         int space;
421         
422         if (tp->rcvq_space.time == 0)
423                 goto new_measure;
424         
425         time = tcp_time_stamp - tp->rcvq_space.time;
426         if (time < (tp->rcv_rtt_est.rtt >> 3) ||
427             tp->rcv_rtt_est.rtt == 0)
428                 return;
429         
430         space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
431
432         space = max(tp->rcvq_space.space, space);
433
434         if (tp->rcvq_space.space != space) {
435                 int rcvmem;
436
437                 tp->rcvq_space.space = space;
438
439                 if (sysctl_tcp_moderate_rcvbuf) {
440                         int new_clamp = space;
441
442                         /* Receive space grows, normalize in order to
443                          * take into account packet headers and sk_buff
444                          * structure overhead.
445                          */
446                         space /= tp->advmss;
447                         if (!space)
448                                 space = 1;
449                         rcvmem = (tp->advmss + MAX_TCP_HEADER +
450                                   16 + sizeof(struct sk_buff));
451                         while (tcp_win_from_space(rcvmem) < tp->advmss)
452                                 rcvmem += 128;
453                         space *= rcvmem;
454                         space = min(space, sysctl_tcp_rmem[2]);
455                         if (space > sk->sk_rcvbuf) {
456                                 sk->sk_rcvbuf = space;
457
458                                 /* Make the window clamp follow along.  */
459                                 tp->window_clamp = new_clamp;
460                         }
461                 }
462         }
463         
464 new_measure:
465         tp->rcvq_space.seq = tp->copied_seq;
466         tp->rcvq_space.time = tcp_time_stamp;
467 }
468
469 /* There is something which you must keep in mind when you analyze the
470  * behavior of the tp->ato delayed ack timeout interval.  When a
471  * connection starts up, we want to ack as quickly as possible.  The
472  * problem is that "good" TCP's do slow start at the beginning of data
473  * transmission.  The means that until we send the first few ACK's the
474  * sender will sit on his end and only queue most of his data, because
475  * he can only send snd_cwnd unacked packets at any given time.  For
476  * each ACK we send, he increments snd_cwnd and transmits more of his
477  * queue.  -DaveM
478  */
479 static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
480 {
481         struct inet_connection_sock *icsk = inet_csk(sk);
482         u32 now;
483
484         inet_csk_schedule_ack(sk);
485
486         tcp_measure_rcv_mss(sk, skb);
487
488         tcp_rcv_rtt_measure(tp);
489         
490         now = tcp_time_stamp;
491
492         if (!icsk->icsk_ack.ato) {
493                 /* The _first_ data packet received, initialize
494                  * delayed ACK engine.
495                  */
496                 tcp_incr_quickack(sk);
497                 icsk->icsk_ack.ato = TCP_ATO_MIN;
498         } else {
499                 int m = now - icsk->icsk_ack.lrcvtime;
500
501                 if (m <= TCP_ATO_MIN/2) {
502                         /* The fastest case is the first. */
503                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
504                 } else if (m < icsk->icsk_ack.ato) {
505                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
506                         if (icsk->icsk_ack.ato > icsk->icsk_rto)
507                                 icsk->icsk_ack.ato = icsk->icsk_rto;
508                 } else if (m > icsk->icsk_rto) {
509                         /* Too long gap. Apparently sender failed to
510                          * restart window, so that we send ACKs quickly.
511                          */
512                         tcp_incr_quickack(sk);
513                         sk_stream_mem_reclaim(sk);
514                 }
515         }
516         icsk->icsk_ack.lrcvtime = now;
517
518         TCP_ECN_check_ce(tp, skb);
519
520         if (skb->len >= 128)
521                 tcp_grow_window(sk, tp, skb);
522 }
523
524 /* Called to compute a smoothed rtt estimate. The data fed to this
525  * routine either comes from timestamps, or from segments that were
526  * known _not_ to have been retransmitted [see Karn/Partridge
527  * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
528  * piece by Van Jacobson.
529  * NOTE: the next three routines used to be one big routine.
530  * To save cycles in the RFC 1323 implementation it was better to break
531  * it up into three procedures. -- erics
532  */
533 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
534 {
535         struct tcp_sock *tp = tcp_sk(sk);
536         long m = mrtt; /* RTT */
537
538         /*      The following amusing code comes from Jacobson's
539          *      article in SIGCOMM '88.  Note that rtt and mdev
540          *      are scaled versions of rtt and mean deviation.
541          *      This is designed to be as fast as possible 
542          *      m stands for "measurement".
543          *
544          *      On a 1990 paper the rto value is changed to:
545          *      RTO = rtt + 4 * mdev
546          *
547          * Funny. This algorithm seems to be very broken.
548          * These formulae increase RTO, when it should be decreased, increase
549          * too slowly, when it should be increased fastly, decrease too fastly
550          * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
551          * does not matter how to _calculate_ it. Seems, it was trap
552          * that VJ failed to avoid. 8)
553          */
554         if(m == 0)
555                 m = 1;
556         if (tp->srtt != 0) {
557                 m -= (tp->srtt >> 3);   /* m is now error in rtt est */
558                 tp->srtt += m;          /* rtt = 7/8 rtt + 1/8 new */
559                 if (m < 0) {
560                         m = -m;         /* m is now abs(error) */
561                         m -= (tp->mdev >> 2);   /* similar update on mdev */
562                         /* This is similar to one of Eifel findings.
563                          * Eifel blocks mdev updates when rtt decreases.
564                          * This solution is a bit different: we use finer gain
565                          * for mdev in this case (alpha*beta).
566                          * Like Eifel it also prevents growth of rto,
567                          * but also it limits too fast rto decreases,
568                          * happening in pure Eifel.
569                          */
570                         if (m > 0)
571                                 m >>= 3;
572                 } else {
573                         m -= (tp->mdev >> 2);   /* similar update on mdev */
574                 }
575                 tp->mdev += m;          /* mdev = 3/4 mdev + 1/4 new */
576                 if (tp->mdev > tp->mdev_max) {
577                         tp->mdev_max = tp->mdev;
578                         if (tp->mdev_max > tp->rttvar)
579                                 tp->rttvar = tp->mdev_max;
580                 }
581                 if (after(tp->snd_una, tp->rtt_seq)) {
582                         if (tp->mdev_max < tp->rttvar)
583                                 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
584                         tp->rtt_seq = tp->snd_nxt;
585                         tp->mdev_max = TCP_RTO_MIN;
586                 }
587         } else {
588                 /* no previous measure. */
589                 tp->srtt = m<<3;        /* take the measured time to be rtt */
590                 tp->mdev = m<<1;        /* make sure rto = 3*rtt */
591                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
592                 tp->rtt_seq = tp->snd_nxt;
593         }
594 }
595
596 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
597  * routine referred to above.
598  */
599 static inline void tcp_set_rto(struct sock *sk)
600 {
601         const struct tcp_sock *tp = tcp_sk(sk);
602         /* Old crap is replaced with new one. 8)
603          *
604          * More seriously:
605          * 1. If rtt variance happened to be less 50msec, it is hallucination.
606          *    It cannot be less due to utterly erratic ACK generation made
607          *    at least by solaris and freebsd. "Erratic ACKs" has _nothing_
608          *    to do with delayed acks, because at cwnd>2 true delack timeout
609          *    is invisible. Actually, Linux-2.4 also generates erratic
610          *    ACKs in some circumstances.
611          */
612         inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
613
614         /* 2. Fixups made earlier cannot be right.
615          *    If we do not estimate RTO correctly without them,
616          *    all the algo is pure shit and should be replaced
617          *    with correct one. It is exactly, which we pretend to do.
618          */
619 }
620
621 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
622  * guarantees that rto is higher.
623  */
624 static inline void tcp_bound_rto(struct sock *sk)
625 {
626         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
627                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
628 }
629
630 /* Save metrics learned by this TCP session.
631    This function is called only, when TCP finishes successfully
632    i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
633  */
634 void tcp_update_metrics(struct sock *sk)
635 {
636         struct tcp_sock *tp = tcp_sk(sk);
637         struct dst_entry *dst = __sk_dst_get(sk);
638
639         if (sysctl_tcp_nometrics_save)
640                 return;
641
642         dst_confirm(dst);
643
644         if (dst && (dst->flags&DST_HOST)) {
645                 const struct inet_connection_sock *icsk = inet_csk(sk);
646                 int m;
647
648                 if (icsk->icsk_backoff || !tp->srtt) {
649                         /* This session failed to estimate rtt. Why?
650                          * Probably, no packets returned in time.
651                          * Reset our results.
652                          */
653                         if (!(dst_metric_locked(dst, RTAX_RTT)))
654                                 dst->metrics[RTAX_RTT-1] = 0;
655                         return;
656                 }
657
658                 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
659
660                 /* If newly calculated rtt larger than stored one,
661                  * store new one. Otherwise, use EWMA. Remember,
662                  * rtt overestimation is always better than underestimation.
663                  */
664                 if (!(dst_metric_locked(dst, RTAX_RTT))) {
665                         if (m <= 0)
666                                 dst->metrics[RTAX_RTT-1] = tp->srtt;
667                         else
668                                 dst->metrics[RTAX_RTT-1] -= (m>>3);
669                 }
670
671                 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
672                         if (m < 0)
673                                 m = -m;
674
675                         /* Scale deviation to rttvar fixed point */
676                         m >>= 1;
677                         if (m < tp->mdev)
678                                 m = tp->mdev;
679
680                         if (m >= dst_metric(dst, RTAX_RTTVAR))
681                                 dst->metrics[RTAX_RTTVAR-1] = m;
682                         else
683                                 dst->metrics[RTAX_RTTVAR-1] -=
684                                         (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
685                 }
686
687                 if (tp->snd_ssthresh >= 0xFFFF) {
688                         /* Slow start still did not finish. */
689                         if (dst_metric(dst, RTAX_SSTHRESH) &&
690                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
691                             (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
692                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
693                         if (!dst_metric_locked(dst, RTAX_CWND) &&
694                             tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
695                                 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
696                 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
697                            icsk->icsk_ca_state == TCP_CA_Open) {
698                         /* Cong. avoidance phase, cwnd is reliable. */
699                         if (!dst_metric_locked(dst, RTAX_SSTHRESH))
700                                 dst->metrics[RTAX_SSTHRESH-1] =
701                                         max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
702                         if (!dst_metric_locked(dst, RTAX_CWND))
703                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
704                 } else {
705                         /* Else slow start did not finish, cwnd is non-sense,
706                            ssthresh may be also invalid.
707                          */
708                         if (!dst_metric_locked(dst, RTAX_CWND))
709                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
710                         if (dst->metrics[RTAX_SSTHRESH-1] &&
711                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
712                             tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
713                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
714                 }
715
716                 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
717                         if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
718                             tp->reordering != sysctl_tcp_reordering)
719                                 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
720                 }
721         }
722 }
723
724 /* Numbers are taken from RFC2414.  */
725 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
726 {
727         __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
728
729         if (!cwnd) {
730                 if (tp->mss_cache > 1460)
731                         cwnd = 2;
732                 else
733                         cwnd = (tp->mss_cache > 1095) ? 3 : 4;
734         }
735         return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
736 }
737
738 /* Initialize metrics on socket. */
739
740 static void tcp_init_metrics(struct sock *sk)
741 {
742         struct tcp_sock *tp = tcp_sk(sk);
743         struct dst_entry *dst = __sk_dst_get(sk);
744
745         if (dst == NULL)
746                 goto reset;
747
748         dst_confirm(dst);
749
750         if (dst_metric_locked(dst, RTAX_CWND))
751                 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
752         if (dst_metric(dst, RTAX_SSTHRESH)) {
753                 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
754                 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
755                         tp->snd_ssthresh = tp->snd_cwnd_clamp;
756         }
757         if (dst_metric(dst, RTAX_REORDERING) &&
758             tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
759                 tp->rx_opt.sack_ok &= ~2;
760                 tp->reordering = dst_metric(dst, RTAX_REORDERING);
761         }
762
763         if (dst_metric(dst, RTAX_RTT) == 0)
764                 goto reset;
765
766         if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
767                 goto reset;
768
769         /* Initial rtt is determined from SYN,SYN-ACK.
770          * The segment is small and rtt may appear much
771          * less than real one. Use per-dst memory
772          * to make it more realistic.
773          *
774          * A bit of theory. RTT is time passed after "normal" sized packet
775          * is sent until it is ACKed. In normal circumstances sending small
776          * packets force peer to delay ACKs and calculation is correct too.
777          * The algorithm is adaptive and, provided we follow specs, it
778          * NEVER underestimate RTT. BUT! If peer tries to make some clever
779          * tricks sort of "quick acks" for time long enough to decrease RTT
780          * to low value, and then abruptly stops to do it and starts to delay
781          * ACKs, wait for troubles.
782          */
783         if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
784                 tp->srtt = dst_metric(dst, RTAX_RTT);
785                 tp->rtt_seq = tp->snd_nxt;
786         }
787         if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
788                 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
789                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
790         }
791         tcp_set_rto(sk);
792         tcp_bound_rto(sk);
793         if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
794                 goto reset;
795         tp->snd_cwnd = tcp_init_cwnd(tp, dst);
796         tp->snd_cwnd_stamp = tcp_time_stamp;
797         return;
798
799 reset:
800         /* Play conservative. If timestamps are not
801          * supported, TCP will fail to recalculate correct
802          * rtt, if initial rto is too small. FORGET ALL AND RESET!
803          */
804         if (!tp->rx_opt.saw_tstamp && tp->srtt) {
805                 tp->srtt = 0;
806                 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
807                 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
808         }
809 }
810
811 static void tcp_update_reordering(struct sock *sk, const int metric,
812                                   const int ts)
813 {
814         struct tcp_sock *tp = tcp_sk(sk);
815         if (metric > tp->reordering) {
816                 tp->reordering = min(TCP_MAX_REORDERING, metric);
817
818                 /* This exciting event is worth to be remembered. 8) */
819                 if (ts)
820                         NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
821                 else if (IsReno(tp))
822                         NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
823                 else if (IsFack(tp))
824                         NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
825                 else
826                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
827 #if FASTRETRANS_DEBUG > 1
828                 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
829                        tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
830                        tp->reordering,
831                        tp->fackets_out,
832                        tp->sacked_out,
833                        tp->undo_marker ? tp->undo_retrans : 0);
834 #endif
835                 /* Disable FACK yet. */
836                 tp->rx_opt.sack_ok &= ~2;
837         }
838 }
839
840 /* This procedure tags the retransmission queue when SACKs arrive.
841  *
842  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
843  * Packets in queue with these bits set are counted in variables
844  * sacked_out, retrans_out and lost_out, correspondingly.
845  *
846  * Valid combinations are:
847  * Tag  InFlight        Description
848  * 0    1               - orig segment is in flight.
849  * S    0               - nothing flies, orig reached receiver.
850  * L    0               - nothing flies, orig lost by net.
851  * R    2               - both orig and retransmit are in flight.
852  * L|R  1               - orig is lost, retransmit is in flight.
853  * S|R  1               - orig reached receiver, retrans is still in flight.
854  * (L|S|R is logically valid, it could occur when L|R is sacked,
855  *  but it is equivalent to plain S and code short-curcuits it to S.
856  *  L|S is logically invalid, it would mean -1 packet in flight 8))
857  *
858  * These 6 states form finite state machine, controlled by the following events:
859  * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
860  * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
861  * 3. Loss detection event of one of three flavors:
862  *      A. Scoreboard estimator decided the packet is lost.
863  *         A'. Reno "three dupacks" marks head of queue lost.
864  *         A''. Its FACK modfication, head until snd.fack is lost.
865  *      B. SACK arrives sacking data transmitted after never retransmitted
866  *         hole was sent out.
867  *      C. SACK arrives sacking SND.NXT at the moment, when the
868  *         segment was retransmitted.
869  * 4. D-SACK added new rule: D-SACK changes any tag to S.
870  *
871  * It is pleasant to note, that state diagram turns out to be commutative,
872  * so that we are allowed not to be bothered by order of our actions,
873  * when multiple events arrive simultaneously. (see the function below).
874  *
875  * Reordering detection.
876  * --------------------
877  * Reordering metric is maximal distance, which a packet can be displaced
878  * in packet stream. With SACKs we can estimate it:
879  *
880  * 1. SACK fills old hole and the corresponding segment was not
881  *    ever retransmitted -> reordering. Alas, we cannot use it
882  *    when segment was retransmitted.
883  * 2. The last flaw is solved with D-SACK. D-SACK arrives
884  *    for retransmitted and already SACKed segment -> reordering..
885  * Both of these heuristics are not used in Loss state, when we cannot
886  * account for retransmits accurately.
887  */
888 static int
889 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
890 {
891         const struct inet_connection_sock *icsk = inet_csk(sk);
892         struct tcp_sock *tp = tcp_sk(sk);
893         unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
894         struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2);
895         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
896         int reord = tp->packets_out;
897         int prior_fackets;
898         u32 lost_retrans = 0;
899         int flag = 0;
900         int dup_sack = 0;
901         int i;
902
903         if (!tp->sacked_out)
904                 tp->fackets_out = 0;
905         prior_fackets = tp->fackets_out;
906
907         /* SACK fastpath:
908          * if the only SACK change is the increase of the end_seq of
909          * the first block then only apply that SACK block
910          * and use retrans queue hinting otherwise slowpath */
911         flag = 1;
912         for (i = 0; i< num_sacks; i++) {
913                 __u32 start_seq = ntohl(sp[i].start_seq);
914                 __u32 end_seq =  ntohl(sp[i].end_seq);
915
916                 if (i == 0){
917                         if (tp->recv_sack_cache[i].start_seq != start_seq)
918                                 flag = 0;
919                 } else {
920                         if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
921                             (tp->recv_sack_cache[i].end_seq != end_seq))
922                                 flag = 0;
923                 }
924                 tp->recv_sack_cache[i].start_seq = start_seq;
925                 tp->recv_sack_cache[i].end_seq = end_seq;
926
927                 /* Check for D-SACK. */
928                 if (i == 0) {
929                         u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
930
931                         if (before(start_seq, ack)) {
932                                 dup_sack = 1;
933                                 tp->rx_opt.sack_ok |= 4;
934                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
935                         } else if (num_sacks > 1 &&
936                                    !after(end_seq, ntohl(sp[1].end_seq)) &&
937                                    !before(start_seq, ntohl(sp[1].start_seq))) {
938                                 dup_sack = 1;
939                                 tp->rx_opt.sack_ok |= 4;
940                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
941                         }
942
943                         /* D-SACK for already forgotten data...
944                          * Do dumb counting. */
945                         if (dup_sack &&
946                             !after(end_seq, prior_snd_una) &&
947                             after(end_seq, tp->undo_marker))
948                                 tp->undo_retrans--;
949
950                         /* Eliminate too old ACKs, but take into
951                          * account more or less fresh ones, they can
952                          * contain valid SACK info.
953                          */
954                         if (before(ack, prior_snd_una - tp->max_window))
955                                 return 0;
956                 }
957         }
958
959         if (flag)
960                 num_sacks = 1;
961         else {
962                 int j;
963                 tp->fastpath_skb_hint = NULL;
964
965                 /* order SACK blocks to allow in order walk of the retrans queue */
966                 for (i = num_sacks-1; i > 0; i--) {
967                         for (j = 0; j < i; j++){
968                                 if (after(ntohl(sp[j].start_seq),
969                                           ntohl(sp[j+1].start_seq))){
970                                         sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
971                                         sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
972                                         sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
973                                         sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
974                                 }
975
976                         }
977                 }
978         }
979
980         /* clear flag as used for different purpose in following code */
981         flag = 0;
982
983         for (i=0; i<num_sacks; i++, sp++) {
984                 struct sk_buff *skb;
985                 __u32 start_seq = ntohl(sp->start_seq);
986                 __u32 end_seq = ntohl(sp->end_seq);
987                 int fack_count;
988
989                 /* Use SACK fastpath hint if valid */
990                 if (tp->fastpath_skb_hint) {
991                         skb = tp->fastpath_skb_hint;
992                         fack_count = tp->fastpath_cnt_hint;
993                 } else {
994                         skb = sk->sk_write_queue.next;
995                         fack_count = 0;
996                 }
997
998                 /* Event "B" in the comment above. */
999                 if (after(end_seq, tp->high_seq))
1000                         flag |= FLAG_DATA_LOST;
1001
1002                 sk_stream_for_retrans_queue_from(skb, sk) {
1003                         int in_sack, pcount;
1004                         u8 sacked;
1005
1006                         tp->fastpath_skb_hint = skb;
1007                         tp->fastpath_cnt_hint = fack_count;
1008
1009                         /* The retransmission queue is always in order, so
1010                          * we can short-circuit the walk early.
1011                          */
1012                         if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1013                                 break;
1014
1015                         in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1016                                 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1017
1018                         pcount = tcp_skb_pcount(skb);
1019
1020                         if (pcount > 1 && !in_sack &&
1021                             after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1022                                 unsigned int pkt_len;
1023
1024                                 in_sack = !after(start_seq,
1025                                                  TCP_SKB_CB(skb)->seq);
1026
1027                                 if (!in_sack)
1028                                         pkt_len = (start_seq -
1029                                                    TCP_SKB_CB(skb)->seq);
1030                                 else
1031                                         pkt_len = (end_seq -
1032                                                    TCP_SKB_CB(skb)->seq);
1033                                 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->tso_size))
1034                                         break;
1035                                 pcount = tcp_skb_pcount(skb);
1036                         }
1037
1038                         fack_count += pcount;
1039
1040                         sacked = TCP_SKB_CB(skb)->sacked;
1041
1042                         /* Account D-SACK for retransmitted packet. */
1043                         if ((dup_sack && in_sack) &&
1044                             (sacked & TCPCB_RETRANS) &&
1045                             after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1046                                 tp->undo_retrans--;
1047
1048                         /* The frame is ACKed. */
1049                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1050                                 if (sacked&TCPCB_RETRANS) {
1051                                         if ((dup_sack && in_sack) &&
1052                                             (sacked&TCPCB_SACKED_ACKED))
1053                                                 reord = min(fack_count, reord);
1054                                 } else {
1055                                         /* If it was in a hole, we detected reordering. */
1056                                         if (fack_count < prior_fackets &&
1057                                             !(sacked&TCPCB_SACKED_ACKED))
1058                                                 reord = min(fack_count, reord);
1059                                 }
1060
1061                                 /* Nothing to do; acked frame is about to be dropped. */
1062                                 continue;
1063                         }
1064
1065                         if ((sacked&TCPCB_SACKED_RETRANS) &&
1066                             after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1067                             (!lost_retrans || after(end_seq, lost_retrans)))
1068                                 lost_retrans = end_seq;
1069
1070                         if (!in_sack)
1071                                 continue;
1072
1073                         if (!(sacked&TCPCB_SACKED_ACKED)) {
1074                                 if (sacked & TCPCB_SACKED_RETRANS) {
1075                                         /* If the segment is not tagged as lost,
1076                                          * we do not clear RETRANS, believing
1077                                          * that retransmission is still in flight.
1078                                          */
1079                                         if (sacked & TCPCB_LOST) {
1080                                                 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1081                                                 tp->lost_out -= tcp_skb_pcount(skb);
1082                                                 tp->retrans_out -= tcp_skb_pcount(skb);
1083
1084                                                 /* clear lost hint */
1085                                                 tp->retransmit_skb_hint = NULL;
1086                                         }
1087                                 } else {
1088                                         /* New sack for not retransmitted frame,
1089                                          * which was in hole. It is reordering.
1090                                          */
1091                                         if (!(sacked & TCPCB_RETRANS) &&
1092                                             fack_count < prior_fackets)
1093                                                 reord = min(fack_count, reord);
1094
1095                                         if (sacked & TCPCB_LOST) {
1096                                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1097                                                 tp->lost_out -= tcp_skb_pcount(skb);
1098
1099                                                 /* clear lost hint */
1100                                                 tp->retransmit_skb_hint = NULL;
1101                                         }
1102                                 }
1103
1104                                 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1105                                 flag |= FLAG_DATA_SACKED;
1106                                 tp->sacked_out += tcp_skb_pcount(skb);
1107
1108                                 if (fack_count > tp->fackets_out)
1109                                         tp->fackets_out = fack_count;
1110                         } else {
1111                                 if (dup_sack && (sacked&TCPCB_RETRANS))
1112                                         reord = min(fack_count, reord);
1113                         }
1114
1115                         /* D-SACK. We can detect redundant retransmission
1116                          * in S|R and plain R frames and clear it.
1117                          * undo_retrans is decreased above, L|R frames
1118                          * are accounted above as well.
1119                          */
1120                         if (dup_sack &&
1121                             (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1122                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1123                                 tp->retrans_out -= tcp_skb_pcount(skb);
1124                                 tp->retransmit_skb_hint = NULL;
1125                         }
1126                 }
1127         }
1128
1129         /* Check for lost retransmit. This superb idea is
1130          * borrowed from "ratehalving". Event "C".
1131          * Later note: FACK people cheated me again 8),
1132          * we have to account for reordering! Ugly,
1133          * but should help.
1134          */
1135         if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
1136                 struct sk_buff *skb;
1137
1138                 sk_stream_for_retrans_queue(skb, sk) {
1139                         if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1140                                 break;
1141                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1142                                 continue;
1143                         if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1144                             after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1145                             (IsFack(tp) ||
1146                              !before(lost_retrans,
1147                                      TCP_SKB_CB(skb)->ack_seq + tp->reordering *
1148                                      tp->mss_cache))) {
1149                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1150                                 tp->retrans_out -= tcp_skb_pcount(skb);
1151
1152                                 /* clear lost hint */
1153                                 tp->retransmit_skb_hint = NULL;
1154
1155                                 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1156                                         tp->lost_out += tcp_skb_pcount(skb);
1157                                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1158                                         flag |= FLAG_DATA_SACKED;
1159                                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1160                                 }
1161                         }
1162                 }
1163         }
1164
1165         tp->left_out = tp->sacked_out + tp->lost_out;
1166
1167         if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1168                 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
1169
1170 #if FASTRETRANS_DEBUG > 0
1171         BUG_TRAP((int)tp->sacked_out >= 0);
1172         BUG_TRAP((int)tp->lost_out >= 0);
1173         BUG_TRAP((int)tp->retrans_out >= 0);
1174         BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1175 #endif
1176         return flag;
1177 }
1178
1179 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1180  * segments to see from the next ACKs whether any data was really missing.
1181  * If the RTO was spurious, new ACKs should arrive.
1182  */
1183 void tcp_enter_frto(struct sock *sk)
1184 {
1185         const struct inet_connection_sock *icsk = inet_csk(sk);
1186         struct tcp_sock *tp = tcp_sk(sk);
1187         struct sk_buff *skb;
1188
1189         tp->frto_counter = 1;
1190
1191         if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1192             tp->snd_una == tp->high_seq ||
1193             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1194                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1195                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1196                 tcp_ca_event(sk, CA_EVENT_FRTO);
1197         }
1198
1199         /* Have to clear retransmission markers here to keep the bookkeeping
1200          * in shape, even though we are not yet in Loss state.
1201          * If something was really lost, it is eventually caught up
1202          * in tcp_enter_frto_loss.
1203          */
1204         tp->retrans_out = 0;
1205         tp->undo_marker = tp->snd_una;
1206         tp->undo_retrans = 0;
1207
1208         sk_stream_for_retrans_queue(skb, sk) {
1209                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1210         }
1211         tcp_sync_left_out(tp);
1212
1213         tcp_set_ca_state(sk, TCP_CA_Open);
1214         tp->frto_highmark = tp->snd_nxt;
1215 }
1216
1217 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1218  * which indicates that we should follow the traditional RTO recovery,
1219  * i.e. mark everything lost and do go-back-N retransmission.
1220  */
1221 static void tcp_enter_frto_loss(struct sock *sk)
1222 {
1223         struct tcp_sock *tp = tcp_sk(sk);
1224         struct sk_buff *skb;
1225         int cnt = 0;
1226
1227         tp->sacked_out = 0;
1228         tp->lost_out = 0;
1229         tp->fackets_out = 0;
1230
1231         sk_stream_for_retrans_queue(skb, sk) {
1232                 cnt += tcp_skb_pcount(skb);
1233                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1234                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1235
1236                         /* Do not mark those segments lost that were
1237                          * forward transmitted after RTO
1238                          */
1239                         if (!after(TCP_SKB_CB(skb)->end_seq,
1240                                    tp->frto_highmark)) {
1241                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1242                                 tp->lost_out += tcp_skb_pcount(skb);
1243                         }
1244                 } else {
1245                         tp->sacked_out += tcp_skb_pcount(skb);
1246                         tp->fackets_out = cnt;
1247                 }
1248         }
1249         tcp_sync_left_out(tp);
1250
1251         tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1252         tp->snd_cwnd_cnt = 0;
1253         tp->snd_cwnd_stamp = tcp_time_stamp;
1254         tp->undo_marker = 0;
1255         tp->frto_counter = 0;
1256
1257         tp->reordering = min_t(unsigned int, tp->reordering,
1258                                              sysctl_tcp_reordering);
1259         tcp_set_ca_state(sk, TCP_CA_Loss);
1260         tp->high_seq = tp->frto_highmark;
1261         TCP_ECN_queue_cwr(tp);
1262
1263         clear_all_retrans_hints(tp);
1264 }
1265
1266 void tcp_clear_retrans(struct tcp_sock *tp)
1267 {
1268         tp->left_out = 0;
1269         tp->retrans_out = 0;
1270
1271         tp->fackets_out = 0;
1272         tp->sacked_out = 0;
1273         tp->lost_out = 0;
1274
1275         tp->undo_marker = 0;
1276         tp->undo_retrans = 0;
1277 }
1278
1279 /* Enter Loss state. If "how" is not zero, forget all SACK information
1280  * and reset tags completely, otherwise preserve SACKs. If receiver
1281  * dropped its ofo queue, we will know this due to reneging detection.
1282  */
1283 void tcp_enter_loss(struct sock *sk, int how)
1284 {
1285         const struct inet_connection_sock *icsk = inet_csk(sk);
1286         struct tcp_sock *tp = tcp_sk(sk);
1287         struct sk_buff *skb;
1288         int cnt = 0;
1289
1290         /* Reduce ssthresh if it has not yet been made inside this window. */
1291         if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1292             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1293                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1294                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1295                 tcp_ca_event(sk, CA_EVENT_LOSS);
1296         }
1297         tp->snd_cwnd       = 1;
1298         tp->snd_cwnd_cnt   = 0;
1299         tp->snd_cwnd_stamp = tcp_time_stamp;
1300
1301         tp->bytes_acked = 0;
1302         tcp_clear_retrans(tp);
1303
1304         /* Push undo marker, if it was plain RTO and nothing
1305          * was retransmitted. */
1306         if (!how)
1307                 tp->undo_marker = tp->snd_una;
1308
1309         sk_stream_for_retrans_queue(skb, sk) {
1310                 cnt += tcp_skb_pcount(skb);
1311                 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1312                         tp->undo_marker = 0;
1313                 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1314                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1315                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1316                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1317                         tp->lost_out += tcp_skb_pcount(skb);
1318                 } else {
1319                         tp->sacked_out += tcp_skb_pcount(skb);
1320                         tp->fackets_out = cnt;
1321                 }
1322         }
1323         tcp_sync_left_out(tp);
1324
1325         tp->reordering = min_t(unsigned int, tp->reordering,
1326                                              sysctl_tcp_reordering);
1327         tcp_set_ca_state(sk, TCP_CA_Loss);
1328         tp->high_seq = tp->snd_nxt;
1329         TCP_ECN_queue_cwr(tp);
1330
1331         clear_all_retrans_hints(tp);
1332 }
1333
1334 static int tcp_check_sack_reneging(struct sock *sk)
1335 {
1336         struct sk_buff *skb;
1337
1338         /* If ACK arrived pointing to a remembered SACK,
1339          * it means that our remembered SACKs do not reflect
1340          * real state of receiver i.e.
1341          * receiver _host_ is heavily congested (or buggy).
1342          * Do processing similar to RTO timeout.
1343          */
1344         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1345             (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
1346                 struct inet_connection_sock *icsk = inet_csk(sk);
1347                 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1348
1349                 tcp_enter_loss(sk, 1);
1350                 icsk->icsk_retransmits++;
1351                 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
1352                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1353                                           icsk->icsk_rto, TCP_RTO_MAX);
1354                 return 1;
1355         }
1356         return 0;
1357 }
1358
1359 static inline int tcp_fackets_out(struct tcp_sock *tp)
1360 {
1361         return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1362 }
1363
1364 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
1365 {
1366         return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
1367 }
1368
1369 static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1370 {
1371         return tp->packets_out &&
1372                tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
1373 }
1374
1375 /* Linux NewReno/SACK/FACK/ECN state machine.
1376  * --------------------------------------
1377  *
1378  * "Open"       Normal state, no dubious events, fast path.
1379  * "Disorder"   In all the respects it is "Open",
1380  *              but requires a bit more attention. It is entered when
1381  *              we see some SACKs or dupacks. It is split of "Open"
1382  *              mainly to move some processing from fast path to slow one.
1383  * "CWR"        CWND was reduced due to some Congestion Notification event.
1384  *              It can be ECN, ICMP source quench, local device congestion.
1385  * "Recovery"   CWND was reduced, we are fast-retransmitting.
1386  * "Loss"       CWND was reduced due to RTO timeout or SACK reneging.
1387  *
1388  * tcp_fastretrans_alert() is entered:
1389  * - each incoming ACK, if state is not "Open"
1390  * - when arrived ACK is unusual, namely:
1391  *      * SACK
1392  *      * Duplicate ACK.
1393  *      * ECN ECE.
1394  *
1395  * Counting packets in flight is pretty simple.
1396  *
1397  *      in_flight = packets_out - left_out + retrans_out
1398  *
1399  *      packets_out is SND.NXT-SND.UNA counted in packets.
1400  *
1401  *      retrans_out is number of retransmitted segments.
1402  *
1403  *      left_out is number of segments left network, but not ACKed yet.
1404  *
1405  *              left_out = sacked_out + lost_out
1406  *
1407  *     sacked_out: Packets, which arrived to receiver out of order
1408  *                 and hence not ACKed. With SACKs this number is simply
1409  *                 amount of SACKed data. Even without SACKs
1410  *                 it is easy to give pretty reliable estimate of this number,
1411  *                 counting duplicate ACKs.
1412  *
1413  *       lost_out: Packets lost by network. TCP has no explicit
1414  *                 "loss notification" feedback from network (for now).
1415  *                 It means that this number can be only _guessed_.
1416  *                 Actually, it is the heuristics to predict lossage that
1417  *                 distinguishes different algorithms.
1418  *
1419  *      F.e. after RTO, when all the queue is considered as lost,
1420  *      lost_out = packets_out and in_flight = retrans_out.
1421  *
1422  *              Essentially, we have now two algorithms counting
1423  *              lost packets.
1424  *
1425  *              FACK: It is the simplest heuristics. As soon as we decided
1426  *              that something is lost, we decide that _all_ not SACKed
1427  *              packets until the most forward SACK are lost. I.e.
1428  *              lost_out = fackets_out - sacked_out and left_out = fackets_out.
1429  *              It is absolutely correct estimate, if network does not reorder
1430  *              packets. And it loses any connection to reality when reordering
1431  *              takes place. We use FACK by default until reordering
1432  *              is suspected on the path to this destination.
1433  *
1434  *              NewReno: when Recovery is entered, we assume that one segment
1435  *              is lost (classic Reno). While we are in Recovery and
1436  *              a partial ACK arrives, we assume that one more packet
1437  *              is lost (NewReno). This heuristics are the same in NewReno
1438  *              and SACK.
1439  *
1440  *  Imagine, that's all! Forget about all this shamanism about CWND inflation
1441  *  deflation etc. CWND is real congestion window, never inflated, changes
1442  *  only according to classic VJ rules.
1443  *
1444  * Really tricky (and requiring careful tuning) part of algorithm
1445  * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1446  * The first determines the moment _when_ we should reduce CWND and,
1447  * hence, slow down forward transmission. In fact, it determines the moment
1448  * when we decide that hole is caused by loss, rather than by a reorder.
1449  *
1450  * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1451  * holes, caused by lost packets.
1452  *
1453  * And the most logically complicated part of algorithm is undo
1454  * heuristics. We detect false retransmits due to both too early
1455  * fast retransmit (reordering) and underestimated RTO, analyzing
1456  * timestamps and D-SACKs. When we detect that some segments were
1457  * retransmitted by mistake and CWND reduction was wrong, we undo
1458  * window reduction and abort recovery phase. This logic is hidden
1459  * inside several functions named tcp_try_undo_<something>.
1460  */
1461
1462 /* This function decides, when we should leave Disordered state
1463  * and enter Recovery phase, reducing congestion window.
1464  *
1465  * Main question: may we further continue forward transmission
1466  * with the same cwnd?
1467  */
1468 static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1469 {
1470         __u32 packets_out;
1471
1472         /* Trick#1: The loss is proven. */
1473         if (tp->lost_out)
1474                 return 1;
1475
1476         /* Not-A-Trick#2 : Classic rule... */
1477         if (tcp_fackets_out(tp) > tp->reordering)
1478                 return 1;
1479
1480         /* Trick#3 : when we use RFC2988 timer restart, fast
1481          * retransmit can be triggered by timeout of queue head.
1482          */
1483         if (tcp_head_timedout(sk, tp))
1484                 return 1;
1485
1486         /* Trick#4: It is still not OK... But will it be useful to delay
1487          * recovery more?
1488          */
1489         packets_out = tp->packets_out;
1490         if (packets_out <= tp->reordering &&
1491             tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1492             !tcp_may_send_now(sk, tp)) {
1493                 /* We have nothing to send. This connection is limited
1494                  * either by receiver window or by application.
1495                  */
1496                 return 1;
1497         }
1498
1499         return 0;
1500 }
1501
1502 /* If we receive more dupacks than we expected counting segments
1503  * in assumption of absent reordering, interpret this as reordering.
1504  * The only another reason could be bug in receiver TCP.
1505  */
1506 static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1507 {
1508         struct tcp_sock *tp = tcp_sk(sk);
1509         u32 holes;
1510
1511         holes = max(tp->lost_out, 1U);
1512         holes = min(holes, tp->packets_out);
1513
1514         if ((tp->sacked_out + holes) > tp->packets_out) {
1515                 tp->sacked_out = tp->packets_out - holes;
1516                 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1517         }
1518 }
1519
1520 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1521
1522 static void tcp_add_reno_sack(struct sock *sk)
1523 {
1524         struct tcp_sock *tp = tcp_sk(sk);
1525         tp->sacked_out++;
1526         tcp_check_reno_reordering(sk, 0);
1527         tcp_sync_left_out(tp);
1528 }
1529
1530 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1531
1532 static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1533 {
1534         if (acked > 0) {
1535                 /* One ACK acked hole. The rest eat duplicate ACKs. */
1536                 if (acked-1 >= tp->sacked_out)
1537                         tp->sacked_out = 0;
1538                 else
1539                         tp->sacked_out -= acked-1;
1540         }
1541         tcp_check_reno_reordering(sk, acked);
1542         tcp_sync_left_out(tp);
1543 }
1544
1545 static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1546 {
1547         tp->sacked_out = 0;
1548         tp->left_out = tp->lost_out;
1549 }
1550
1551 /* Mark head of queue up as lost. */
1552 static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1553                                int packets, u32 high_seq)
1554 {
1555         struct sk_buff *skb;
1556         int cnt;
1557
1558         BUG_TRAP(packets <= tp->packets_out);
1559         if (tp->lost_skb_hint) {
1560                 skb = tp->lost_skb_hint;
1561                 cnt = tp->lost_cnt_hint;
1562         } else {
1563                 skb = sk->sk_write_queue.next;
1564                 cnt = 0;
1565         }
1566
1567         sk_stream_for_retrans_queue_from(skb, sk) {
1568                 /* TODO: do this better */
1569                 /* this is not the most efficient way to do this... */
1570                 tp->lost_skb_hint = skb;
1571                 tp->lost_cnt_hint = cnt;
1572                 cnt += tcp_skb_pcount(skb);
1573                 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
1574                         break;
1575                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1576                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1577                         tp->lost_out += tcp_skb_pcount(skb);
1578
1579                         /* clear xmit_retransmit_queue hints
1580                          *  if this is beyond hint */
1581                         if(tp->retransmit_skb_hint != NULL &&
1582                            before(TCP_SKB_CB(skb)->seq,
1583                                   TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1584
1585                                 tp->retransmit_skb_hint = NULL;
1586                         }
1587                 }
1588         }
1589         tcp_sync_left_out(tp);
1590 }
1591
1592 /* Account newly detected lost packet(s) */
1593
1594 static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1595 {
1596         if (IsFack(tp)) {
1597                 int lost = tp->fackets_out - tp->reordering;
1598                 if (lost <= 0)
1599                         lost = 1;
1600                 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1601         } else {
1602                 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1603         }
1604
1605         /* New heuristics: it is possible only after we switched
1606          * to restart timer each time when something is ACKed.
1607          * Hence, we can detect timed out packets during fast
1608          * retransmit without falling to slow start.
1609          */
1610         if (tcp_head_timedout(sk, tp)) {
1611                 struct sk_buff *skb;
1612
1613                 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1614                         : sk->sk_write_queue.next;
1615
1616                 sk_stream_for_retrans_queue_from(skb, sk) {
1617                         if (!tcp_skb_timedout(sk, skb))
1618                                 break;
1619
1620                         if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1621                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1622                                 tp->lost_out += tcp_skb_pcount(skb);
1623
1624                                 /* clear xmit_retrans hint */
1625                                 if (tp->retransmit_skb_hint &&
1626                                     before(TCP_SKB_CB(skb)->seq,
1627                                            TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1628
1629                                         tp->retransmit_skb_hint = NULL;
1630                         }
1631                 }
1632
1633                 tp->scoreboard_skb_hint = skb;
1634
1635                 tcp_sync_left_out(tp);
1636         }
1637 }
1638
1639 /* CWND moderation, preventing bursts due to too big ACKs
1640  * in dubious situations.
1641  */
1642 static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1643 {
1644         tp->snd_cwnd = min(tp->snd_cwnd,
1645                            tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1646         tp->snd_cwnd_stamp = tcp_time_stamp;
1647 }
1648
1649 /* Decrease cwnd each second ack. */
1650 static void tcp_cwnd_down(struct sock *sk)
1651 {
1652         const struct inet_connection_sock *icsk = inet_csk(sk);
1653         struct tcp_sock *tp = tcp_sk(sk);
1654         int decr = tp->snd_cwnd_cnt + 1;
1655
1656         tp->snd_cwnd_cnt = decr&1;
1657         decr >>= 1;
1658
1659         if (decr && tp->snd_cwnd > icsk->icsk_ca_ops->min_cwnd(sk))
1660                 tp->snd_cwnd -= decr;
1661
1662         tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1663         tp->snd_cwnd_stamp = tcp_time_stamp;
1664 }
1665
1666 /* Nothing was retransmitted or returned timestamp is less
1667  * than timestamp of the first retransmission.
1668  */
1669 static inline int tcp_packet_delayed(struct tcp_sock *tp)
1670 {
1671         return !tp->retrans_stamp ||
1672                 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1673                  (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1674 }
1675
1676 /* Undo procedures. */
1677
1678 #if FASTRETRANS_DEBUG > 1
1679 static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1680 {
1681         struct inet_sock *inet = inet_sk(sk);
1682         printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1683                msg,
1684                NIPQUAD(inet->daddr), ntohs(inet->dport),
1685                tp->snd_cwnd, tp->left_out,
1686                tp->snd_ssthresh, tp->prior_ssthresh,
1687                tp->packets_out);
1688 }
1689 #else
1690 #define DBGUNDO(x...) do { } while (0)
1691 #endif
1692
1693 static void tcp_undo_cwr(struct sock *sk, const int undo)
1694 {
1695         struct tcp_sock *tp = tcp_sk(sk);
1696
1697         if (tp->prior_ssthresh) {
1698                 const struct inet_connection_sock *icsk = inet_csk(sk);
1699
1700                 if (icsk->icsk_ca_ops->undo_cwnd)
1701                         tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
1702                 else
1703                         tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1704
1705                 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1706                         tp->snd_ssthresh = tp->prior_ssthresh;
1707                         TCP_ECN_withdraw_cwr(tp);
1708                 }
1709         } else {
1710                 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1711         }
1712         tcp_moderate_cwnd(tp);
1713         tp->snd_cwnd_stamp = tcp_time_stamp;
1714
1715         /* There is something screwy going on with the retrans hints after
1716            an undo */
1717         clear_all_retrans_hints(tp);
1718 }
1719
1720 static inline int tcp_may_undo(struct tcp_sock *tp)
1721 {
1722         return tp->undo_marker &&
1723                 (!tp->undo_retrans || tcp_packet_delayed(tp));
1724 }
1725
1726 /* People celebrate: "We love our President!" */
1727 static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1728 {
1729         if (tcp_may_undo(tp)) {
1730                 /* Happy end! We did not retransmit anything
1731                  * or our original transmission succeeded.
1732                  */
1733                 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1734                 tcp_undo_cwr(sk, 1);
1735                 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
1736                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1737                 else
1738                         NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1739                 tp->undo_marker = 0;
1740         }
1741         if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1742                 /* Hold old state until something *above* high_seq
1743                  * is ACKed. For Reno it is MUST to prevent false
1744                  * fast retransmits (RFC2582). SACK TCP is safe. */
1745                 tcp_moderate_cwnd(tp);
1746                 return 1;
1747         }
1748         tcp_set_ca_state(sk, TCP_CA_Open);
1749         return 0;
1750 }
1751
1752 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1753 static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1754 {
1755         if (tp->undo_marker && !tp->undo_retrans) {
1756                 DBGUNDO(sk, tp, "D-SACK");
1757                 tcp_undo_cwr(sk, 1);
1758                 tp->undo_marker = 0;
1759                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1760         }
1761 }
1762
1763 /* Undo during fast recovery after partial ACK. */
1764
1765 static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1766                                 int acked)
1767 {
1768         /* Partial ACK arrived. Force Hoe's retransmit. */
1769         int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1770
1771         if (tcp_may_undo(tp)) {
1772                 /* Plain luck! Hole if filled with delayed
1773                  * packet, rather than with a retransmit.
1774                  */
1775                 if (tp->retrans_out == 0)
1776                         tp->retrans_stamp = 0;
1777
1778                 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
1779
1780                 DBGUNDO(sk, tp, "Hoe");
1781                 tcp_undo_cwr(sk, 0);
1782                 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1783
1784                 /* So... Do not make Hoe's retransmit yet.
1785                  * If the first packet was delayed, the rest
1786                  * ones are most probably delayed as well.
1787                  */
1788                 failed = 0;
1789         }
1790         return failed;
1791 }
1792
1793 /* Undo during loss recovery after partial ACK. */
1794 static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1795 {
1796         if (tcp_may_undo(tp)) {
1797                 struct sk_buff *skb;
1798                 sk_stream_for_retrans_queue(skb, sk) {
1799                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1800                 }
1801
1802                 clear_all_retrans_hints(tp);
1803
1804                 DBGUNDO(sk, tp, "partial loss");
1805                 tp->lost_out = 0;
1806                 tp->left_out = tp->sacked_out;
1807                 tcp_undo_cwr(sk, 1);
1808                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1809                 inet_csk(sk)->icsk_retransmits = 0;
1810                 tp->undo_marker = 0;
1811                 if (!IsReno(tp))
1812                         tcp_set_ca_state(sk, TCP_CA_Open);
1813                 return 1;
1814         }
1815         return 0;
1816 }
1817
1818 static inline void tcp_complete_cwr(struct sock *sk)
1819 {
1820         struct tcp_sock *tp = tcp_sk(sk);
1821         tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
1822         tp->snd_cwnd_stamp = tcp_time_stamp;
1823         tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
1824 }
1825
1826 static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1827 {
1828         tp->left_out = tp->sacked_out;
1829
1830         if (tp->retrans_out == 0)
1831                 tp->retrans_stamp = 0;
1832
1833         if (flag&FLAG_ECE)
1834                 tcp_enter_cwr(sk);
1835
1836         if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
1837                 int state = TCP_CA_Open;
1838
1839                 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1840                         state = TCP_CA_Disorder;
1841
1842                 if (inet_csk(sk)->icsk_ca_state != state) {
1843                         tcp_set_ca_state(sk, state);
1844                         tp->high_seq = tp->snd_nxt;
1845                 }
1846                 tcp_moderate_cwnd(tp);
1847         } else {
1848                 tcp_cwnd_down(sk);
1849         }
1850 }
1851
1852 /* Process an event, which can update packets-in-flight not trivially.
1853  * Main goal of this function is to calculate new estimate for left_out,
1854  * taking into account both packets sitting in receiver's buffer and
1855  * packets lost by network.
1856  *
1857  * Besides that it does CWND reduction, when packet loss is detected
1858  * and changes state of machine.
1859  *
1860  * It does _not_ decide what to send, it is made in function
1861  * tcp_xmit_retransmit_queue().
1862  */
1863 static void
1864 tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1865                       int prior_packets, int flag)
1866 {
1867         struct inet_connection_sock *icsk = inet_csk(sk);
1868         struct tcp_sock *tp = tcp_sk(sk);
1869         int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1870
1871         /* Some technical things:
1872          * 1. Reno does not count dupacks (sacked_out) automatically. */
1873         if (!tp->packets_out)
1874                 tp->sacked_out = 0;
1875         /* 2. SACK counts snd_fack in packets inaccurately. */
1876         if (tp->sacked_out == 0)
1877                 tp->fackets_out = 0;
1878
1879         /* Now state machine starts.
1880          * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1881         if (flag&FLAG_ECE)
1882                 tp->prior_ssthresh = 0;
1883
1884         /* B. In all the states check for reneging SACKs. */
1885         if (tp->sacked_out && tcp_check_sack_reneging(sk))
1886                 return;
1887
1888         /* C. Process data loss notification, provided it is valid. */
1889         if ((flag&FLAG_DATA_LOST) &&
1890             before(tp->snd_una, tp->high_seq) &&
1891             icsk->icsk_ca_state != TCP_CA_Open &&
1892             tp->fackets_out > tp->reordering) {
1893                 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1894                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1895         }
1896
1897         /* D. Synchronize left_out to current state. */
1898         tcp_sync_left_out(tp);
1899
1900         /* E. Check state exit conditions. State can be terminated
1901          *    when high_seq is ACKed. */
1902         if (icsk->icsk_ca_state == TCP_CA_Open) {
1903                 if (!sysctl_tcp_frto)
1904                         BUG_TRAP(tp->retrans_out == 0);
1905                 tp->retrans_stamp = 0;
1906         } else if (!before(tp->snd_una, tp->high_seq)) {
1907                 switch (icsk->icsk_ca_state) {
1908                 case TCP_CA_Loss:
1909                         icsk->icsk_retransmits = 0;
1910                         if (tcp_try_undo_recovery(sk, tp))
1911                                 return;
1912                         break;
1913
1914                 case TCP_CA_CWR:
1915                         /* CWR is to be held something *above* high_seq
1916                          * is ACKed for CWR bit to reach receiver. */
1917                         if (tp->snd_una != tp->high_seq) {
1918                                 tcp_complete_cwr(sk);
1919                                 tcp_set_ca_state(sk, TCP_CA_Open);
1920                         }
1921                         break;
1922
1923                 case TCP_CA_Disorder:
1924                         tcp_try_undo_dsack(sk, tp);
1925                         if (!tp->undo_marker ||
1926                             /* For SACK case do not Open to allow to undo
1927                              * catching for all duplicate ACKs. */
1928                             IsReno(tp) || tp->snd_una != tp->high_seq) {
1929                                 tp->undo_marker = 0;
1930                                 tcp_set_ca_state(sk, TCP_CA_Open);
1931                         }
1932                         break;
1933
1934                 case TCP_CA_Recovery:
1935                         if (IsReno(tp))
1936                                 tcp_reset_reno_sack(tp);
1937                         if (tcp_try_undo_recovery(sk, tp))
1938                                 return;
1939                         tcp_complete_cwr(sk);
1940                         break;
1941                 }
1942         }
1943
1944         /* F. Process state. */
1945         switch (icsk->icsk_ca_state) {
1946         case TCP_CA_Recovery:
1947                 if (prior_snd_una == tp->snd_una) {
1948                         if (IsReno(tp) && is_dupack)
1949                                 tcp_add_reno_sack(sk);
1950                 } else {
1951                         int acked = prior_packets - tp->packets_out;
1952                         if (IsReno(tp))
1953                                 tcp_remove_reno_sacks(sk, tp, acked);
1954                         is_dupack = tcp_try_undo_partial(sk, tp, acked);
1955                 }
1956                 break;
1957         case TCP_CA_Loss:
1958                 if (flag&FLAG_DATA_ACKED)
1959                         icsk->icsk_retransmits = 0;
1960                 if (!tcp_try_undo_loss(sk, tp)) {
1961                         tcp_moderate_cwnd(tp);
1962                         tcp_xmit_retransmit_queue(sk);
1963                         return;
1964                 }
1965                 if (icsk->icsk_ca_state != TCP_CA_Open)
1966                         return;
1967                 /* Loss is undone; fall through to processing in Open state. */
1968         default:
1969                 if (IsReno(tp)) {
1970                         if (tp->snd_una != prior_snd_una)
1971                                 tcp_reset_reno_sack(tp);
1972                         if (is_dupack)
1973                                 tcp_add_reno_sack(sk);
1974                 }
1975
1976                 if (icsk->icsk_ca_state == TCP_CA_Disorder)
1977                         tcp_try_undo_dsack(sk, tp);
1978
1979                 if (!tcp_time_to_recover(sk, tp)) {
1980                         tcp_try_to_open(sk, tp, flag);
1981                         return;
1982                 }
1983
1984                 /* Otherwise enter Recovery state */
1985
1986                 if (IsReno(tp))
1987                         NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
1988                 else
1989                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
1990
1991                 tp->high_seq = tp->snd_nxt;
1992                 tp->prior_ssthresh = 0;
1993                 tp->undo_marker = tp->snd_una;
1994                 tp->undo_retrans = tp->retrans_out;
1995
1996                 if (icsk->icsk_ca_state < TCP_CA_CWR) {
1997                         if (!(flag&FLAG_ECE))
1998                                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1999                         tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2000                         TCP_ECN_queue_cwr(tp);
2001                 }
2002
2003                 tp->bytes_acked = 0;
2004                 tp->snd_cwnd_cnt = 0;
2005                 tcp_set_ca_state(sk, TCP_CA_Recovery);
2006         }
2007
2008         if (is_dupack || tcp_head_timedout(sk, tp))
2009                 tcp_update_scoreboard(sk, tp);
2010         tcp_cwnd_down(sk);
2011         tcp_xmit_retransmit_queue(sk);
2012 }
2013
2014 /* Read draft-ietf-tcplw-high-performance before mucking
2015  * with this code. (Supersedes RFC1323)
2016  */
2017 static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
2018 {
2019         /* RTTM Rule: A TSecr value received in a segment is used to
2020          * update the averaged RTT measurement only if the segment
2021          * acknowledges some new data, i.e., only if it advances the
2022          * left edge of the send window.
2023          *
2024          * See draft-ietf-tcplw-high-performance-00, section 3.3.
2025          * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2026          *
2027          * Changed: reset backoff as soon as we see the first valid sample.
2028          * If we do not, we get strongly overestimated rto. With timestamps
2029          * samples are accepted even from very old segments: f.e., when rtt=1
2030          * increases to 8, we retransmit 5 times and after 8 seconds delayed
2031          * answer arrives rto becomes 120 seconds! If at least one of segments
2032          * in window is lost... Voila.                          --ANK (010210)
2033          */
2034         struct tcp_sock *tp = tcp_sk(sk);
2035         const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
2036         tcp_rtt_estimator(sk, seq_rtt);
2037         tcp_set_rto(sk);
2038         inet_csk(sk)->icsk_backoff = 0;
2039         tcp_bound_rto(sk);
2040 }
2041
2042 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
2043 {
2044         /* We don't have a timestamp. Can only use
2045          * packets that are not retransmitted to determine
2046          * rtt estimates. Also, we must not reset the
2047          * backoff for rto until we get a non-retransmitted
2048          * packet. This allows us to deal with a situation
2049          * where the network delay has increased suddenly.
2050          * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2051          */
2052
2053         if (flag & FLAG_RETRANS_DATA_ACKED)
2054                 return;
2055
2056         tcp_rtt_estimator(sk, seq_rtt);
2057         tcp_set_rto(sk);
2058         inet_csk(sk)->icsk_backoff = 0;
2059         tcp_bound_rto(sk);
2060 }
2061
2062 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
2063                                       const s32 seq_rtt)
2064 {
2065         const struct tcp_sock *tp = tcp_sk(sk);
2066         /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2067         if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
2068                 tcp_ack_saw_tstamp(sk, flag);
2069         else if (seq_rtt >= 0)
2070                 tcp_ack_no_tstamp(sk, seq_rtt, flag);
2071 }
2072
2073 static inline void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
2074                                   u32 in_flight, int good)
2075 {
2076         const struct inet_connection_sock *icsk = inet_csk(sk);
2077         icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2078         tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
2079 }
2080
2081 /* Restart timer after forward progress on connection.
2082  * RFC2988 recommends to restart timer to now+rto.
2083  */
2084
2085 static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2086 {
2087         if (!tp->packets_out) {
2088                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
2089         } else {
2090                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
2091         }
2092 }
2093
2094 static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2095                          __u32 now, __s32 *seq_rtt)
2096 {
2097         struct tcp_sock *tp = tcp_sk(sk);
2098         struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
2099         __u32 seq = tp->snd_una;
2100         __u32 packets_acked;
2101         int acked = 0;
2102
2103         /* If we get here, the whole TSO packet has not been
2104          * acked.
2105          */
2106         BUG_ON(!after(scb->end_seq, seq));
2107
2108         packets_acked = tcp_skb_pcount(skb);
2109         if (tcp_trim_head(sk, skb, seq - scb->seq))
2110                 return 0;
2111         packets_acked -= tcp_skb_pcount(skb);
2112
2113         if (packets_acked) {
2114                 __u8 sacked = scb->sacked;
2115
2116                 acked |= FLAG_DATA_ACKED;
2117                 if (sacked) {
2118                         if (sacked & TCPCB_RETRANS) {
2119                                 if (sacked & TCPCB_SACKED_RETRANS)
2120                                         tp->retrans_out -= packets_acked;
2121                                 acked |= FLAG_RETRANS_DATA_ACKED;
2122                                 *seq_rtt = -1;
2123                         } else if (*seq_rtt < 0)
2124                                 *seq_rtt = now - scb->when;
2125                         if (sacked & TCPCB_SACKED_ACKED)
2126                                 tp->sacked_out -= packets_acked;
2127                         if (sacked & TCPCB_LOST)
2128                                 tp->lost_out -= packets_acked;
2129                         if (sacked & TCPCB_URG) {
2130                                 if (tp->urg_mode &&
2131                                     !before(seq, tp->snd_up))
2132                                         tp->urg_mode = 0;
2133                         }
2134                 } else if (*seq_rtt < 0)
2135                         *seq_rtt = now - scb->when;
2136
2137                 if (tp->fackets_out) {
2138                         __u32 dval = min(tp->fackets_out, packets_acked);
2139                         tp->fackets_out -= dval;
2140                 }
2141                 tp->packets_out -= packets_acked;
2142
2143                 BUG_ON(tcp_skb_pcount(skb) == 0);
2144                 BUG_ON(!before(scb->seq, scb->end_seq));
2145         }
2146
2147         return acked;
2148 }
2149
2150 static inline u32 tcp_usrtt(const struct sk_buff *skb)
2151 {
2152         struct timeval tv, now;
2153
2154         do_gettimeofday(&now);
2155         skb_get_timestamp(skb, &tv);
2156         return (now.tv_sec - tv.tv_sec) * 1000000 + (now.tv_usec - tv.tv_usec);
2157 }
2158
2159 /* Remove acknowledged frames from the retransmission queue. */
2160 static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
2161 {
2162         struct tcp_sock *tp = tcp_sk(sk);
2163         const struct inet_connection_sock *icsk = inet_csk(sk);
2164         struct sk_buff *skb;
2165         __u32 now = tcp_time_stamp;
2166         int acked = 0;
2167         __s32 seq_rtt = -1;
2168         u32 pkts_acked = 0;
2169         void (*rtt_sample)(struct sock *sk, u32 usrtt)
2170                 = icsk->icsk_ca_ops->rtt_sample;
2171
2172         while ((skb = skb_peek(&sk->sk_write_queue)) &&
2173                skb != sk->sk_send_head) {
2174                 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
2175                 __u8 sacked = scb->sacked;
2176
2177                 /* If our packet is before the ack sequence we can
2178                  * discard it as it's confirmed to have arrived at
2179                  * the other end.
2180                  */
2181                 if (after(scb->end_seq, tp->snd_una)) {
2182                         if (tcp_skb_pcount(skb) > 1 &&
2183                             after(tp->snd_una, scb->seq))
2184                                 acked |= tcp_tso_acked(sk, skb,
2185                                                        now, &seq_rtt);
2186                         break;
2187                 }
2188
2189                 /* Initial outgoing SYN's get put onto the write_queue
2190                  * just like anything else we transmit.  It is not
2191                  * true data, and if we misinform our callers that
2192                  * this ACK acks real data, we will erroneously exit
2193                  * connection startup slow start one packet too
2194                  * quickly.  This is severely frowned upon behavior.
2195                  */
2196                 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2197                         acked |= FLAG_DATA_ACKED;
2198                         ++pkts_acked;
2199                 } else {
2200                         acked |= FLAG_SYN_ACKED;
2201                         tp->retrans_stamp = 0;
2202                 }
2203
2204                 if (sacked) {
2205                         if (sacked & TCPCB_RETRANS) {
2206                                 if(sacked & TCPCB_SACKED_RETRANS)
2207                                         tp->retrans_out -= tcp_skb_pcount(skb);
2208                                 acked |= FLAG_RETRANS_DATA_ACKED;
2209                                 seq_rtt = -1;
2210                         } else if (seq_rtt < 0) {
2211                                 seq_rtt = now - scb->when;
2212                                 if (rtt_sample)
2213                                         (*rtt_sample)(sk, tcp_usrtt(skb));
2214                         }
2215                         if (sacked & TCPCB_SACKED_ACKED)
2216                                 tp->sacked_out -= tcp_skb_pcount(skb);
2217                         if (sacked & TCPCB_LOST)
2218                                 tp->lost_out -= tcp_skb_pcount(skb);
2219                         if (sacked & TCPCB_URG) {
2220                                 if (tp->urg_mode &&
2221                                     !before(scb->end_seq, tp->snd_up))
2222                                         tp->urg_mode = 0;
2223                         }
2224                 } else if (seq_rtt < 0) {
2225                         seq_rtt = now - scb->when;
2226                         if (rtt_sample)
2227                                 (*rtt_sample)(sk, tcp_usrtt(skb));
2228                 }
2229                 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2230                 tcp_packets_out_dec(tp, skb);
2231                 __skb_unlink(skb, &sk->sk_write_queue);
2232                 sk_stream_free_skb(sk, skb);
2233                 clear_all_retrans_hints(tp);
2234         }
2235
2236         if (acked&FLAG_ACKED) {
2237                 tcp_ack_update_rtt(sk, acked, seq_rtt);
2238                 tcp_ack_packets_out(sk, tp);
2239
2240                 if (icsk->icsk_ca_ops->pkts_acked)
2241                         icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
2242         }
2243
2244 #if FASTRETRANS_DEBUG > 0
2245         BUG_TRAP((int)tp->sacked_out >= 0);
2246         BUG_TRAP((int)tp->lost_out >= 0);
2247         BUG_TRAP((int)tp->retrans_out >= 0);
2248         if (!tp->packets_out && tp->rx_opt.sack_ok) {
2249                 const struct inet_connection_sock *icsk = inet_csk(sk);
2250                 if (tp->lost_out) {
2251                         printk(KERN_DEBUG "Leak l=%u %d\n",
2252                                tp->lost_out, icsk->icsk_ca_state);
2253                         tp->lost_out = 0;
2254                 }
2255                 if (tp->sacked_out) {
2256                         printk(KERN_DEBUG "Leak s=%u %d\n",
2257                                tp->sacked_out, icsk->icsk_ca_state);
2258                         tp->sacked_out = 0;
2259                 }
2260                 if (tp->retrans_out) {
2261                         printk(KERN_DEBUG "Leak r=%u %d\n",
2262                                tp->retrans_out, icsk->icsk_ca_state);
2263                         tp->retrans_out = 0;
2264                 }
2265         }
2266 #endif
2267         *seq_rtt_p = seq_rtt;
2268         return acked;
2269 }
2270
2271 static void tcp_ack_probe(struct sock *sk)
2272 {
2273         const struct tcp_sock *tp = tcp_sk(sk);
2274         struct inet_connection_sock *icsk = inet_csk(sk);
2275
2276         /* Was it a usable window open? */
2277
2278         if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2279                    tp->snd_una + tp->snd_wnd)) {
2280                 icsk->icsk_backoff = 0;
2281                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
2282                 /* Socket must be waked up by subsequent tcp_data_snd_check().
2283                  * This function is not for random using!
2284                  */
2285         } else {
2286                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2287                                           min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2288                                           TCP_RTO_MAX);
2289         }
2290 }
2291
2292 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
2293 {
2294         return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
2295                 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
2296 }
2297
2298 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
2299 {
2300         const struct tcp_sock *tp = tcp_sk(sk);
2301         return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
2302                 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
2303 }
2304
2305 /* Check that window update is acceptable.
2306  * The function assumes that snd_una<=ack<=snd_next.
2307  */
2308 static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2309                                         const u32 ack_seq, const u32 nwin)
2310 {
2311         return (after(ack, tp->snd_una) ||
2312                 after(ack_seq, tp->snd_wl1) ||
2313                 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2314 }
2315
2316 /* Update our send window.
2317  *
2318  * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2319  * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2320  */
2321 static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2322                                  struct sk_buff *skb, u32 ack, u32 ack_seq)
2323 {
2324         int flag = 0;
2325         u32 nwin = ntohs(skb->h.th->window);
2326
2327         if (likely(!skb->h.th->syn))
2328                 nwin <<= tp->rx_opt.snd_wscale;
2329
2330         if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2331                 flag |= FLAG_WIN_UPDATE;
2332                 tcp_update_wl(tp, ack, ack_seq);
2333
2334                 if (tp->snd_wnd != nwin) {
2335                         tp->snd_wnd = nwin;
2336
2337                         /* Note, it is the only place, where
2338                          * fast path is recovered for sending TCP.
2339                          */
2340                         tp->pred_flags = 0;
2341                         tcp_fast_path_check(sk, tp);
2342
2343                         if (nwin > tp->max_window) {
2344                                 tp->max_window = nwin;
2345                                 tcp_sync_mss(sk, tp->pmtu_cookie);
2346                         }
2347                 }
2348         }
2349
2350         tp->snd_una = ack;
2351
2352         return flag;
2353 }
2354
2355 static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2356 {
2357         struct tcp_sock *tp = tcp_sk(sk);
2358         
2359         tcp_sync_left_out(tp);
2360         
2361         if (tp->snd_una == prior_snd_una ||
2362             !before(tp->snd_una, tp->frto_highmark)) {
2363                 /* RTO was caused by loss, start retransmitting in
2364                  * go-back-N slow start
2365                  */
2366                 tcp_enter_frto_loss(sk);
2367                 return;
2368         }
2369
2370         if (tp->frto_counter == 1) {
2371                 /* First ACK after RTO advances the window: allow two new
2372                  * segments out.
2373                  */
2374                 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2375         } else {
2376                 /* Also the second ACK after RTO advances the window.
2377                  * The RTO was likely spurious. Reduce cwnd and continue
2378                  * in congestion avoidance
2379                  */
2380                 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2381                 tcp_moderate_cwnd(tp);
2382         }
2383
2384         /* F-RTO affects on two new ACKs following RTO.
2385          * At latest on third ACK the TCP behavior is back to normal.
2386          */
2387         tp->frto_counter = (tp->frto_counter + 1) % 3;
2388 }
2389
2390 /* This routine deals with incoming acks, but not outgoing ones. */
2391 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2392 {
2393         struct inet_connection_sock *icsk = inet_csk(sk);
2394         struct tcp_sock *tp = tcp_sk(sk);
2395         u32 prior_snd_una = tp->snd_una;
2396         u32 ack_seq = TCP_SKB_CB(skb)->seq;
2397         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2398         u32 prior_in_flight;
2399         s32 seq_rtt;
2400         int prior_packets;
2401
2402         /* If the ack is newer than sent or older than previous acks
2403          * then we can probably ignore it.
2404          */
2405         if (after(ack, tp->snd_nxt))
2406                 goto uninteresting_ack;
2407
2408         if (before(ack, prior_snd_una))
2409                 goto old_ack;
2410
2411         if (sysctl_tcp_abc && icsk->icsk_ca_state < TCP_CA_CWR)
2412                 tp->bytes_acked += ack - prior_snd_una;
2413
2414         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2415                 /* Window is constant, pure forward advance.
2416                  * No more checks are required.
2417                  * Note, we use the fact that SND.UNA>=SND.WL2.
2418                  */
2419                 tcp_update_wl(tp, ack, ack_seq);
2420                 tp->snd_una = ack;
2421                 flag |= FLAG_WIN_UPDATE;
2422
2423                 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
2424
2425                 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2426         } else {
2427                 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2428                         flag |= FLAG_DATA;
2429                 else
2430                         NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2431
2432                 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2433
2434                 if (TCP_SKB_CB(skb)->sacked)
2435                         flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2436
2437                 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2438                         flag |= FLAG_ECE;
2439
2440                 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
2441         }
2442
2443         /* We passed data and got it acked, remove any soft error
2444          * log. Something worked...
2445          */
2446         sk->sk_err_soft = 0;
2447         tp->rcv_tstamp = tcp_time_stamp;
2448         prior_packets = tp->packets_out;
2449         if (!prior_packets)
2450                 goto no_queue;
2451
2452         prior_in_flight = tcp_packets_in_flight(tp);
2453
2454         /* See if we can take anything off of the retransmit queue. */
2455         flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
2456
2457         if (tp->frto_counter)
2458                 tcp_process_frto(sk, prior_snd_una);
2459
2460         if (tcp_ack_is_dubious(sk, flag)) {
2461                 /* Advance CWND, if state allows this. */
2462                 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2463                         tcp_cong_avoid(sk, ack,  seq_rtt, prior_in_flight, 0);
2464                 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2465         } else {
2466                 if ((flag & FLAG_DATA_ACKED))
2467                         tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
2468         }
2469
2470         if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2471                 dst_confirm(sk->sk_dst_cache);
2472
2473         return 1;
2474
2475 no_queue:
2476         icsk->icsk_probes_out = 0;
2477
2478         /* If this ack opens up a zero window, clear backoff.  It was
2479          * being used to time the probes, and is probably far higher than
2480          * it needs to be for normal retransmission.
2481          */
2482         if (sk->sk_send_head)
2483                 tcp_ack_probe(sk);
2484         return 1;
2485
2486 old_ack:
2487         if (TCP_SKB_CB(skb)->sacked)
2488                 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2489
2490 uninteresting_ack:
2491         SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2492         return 0;
2493 }
2494
2495
2496 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2497  * But, this can also be called on packets in the established flow when
2498  * the fast version below fails.
2499  */
2500 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2501 {
2502         unsigned char *ptr;
2503         struct tcphdr *th = skb->h.th;
2504         int length=(th->doff*4)-sizeof(struct tcphdr);
2505
2506         ptr = (unsigned char *)(th + 1);
2507         opt_rx->saw_tstamp = 0;
2508
2509         while(length>0) {
2510                 int opcode=*ptr++;
2511                 int opsize;
2512
2513                 switch (opcode) {
2514                         case TCPOPT_EOL:
2515                                 return;
2516                         case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
2517                                 length--;
2518                                 continue;
2519                         default:
2520                                 opsize=*ptr++;
2521                                 if (opsize < 2) /* "silly options" */
2522                                         return;
2523                                 if (opsize > length)
2524                                         return; /* don't parse partial options */
2525                                 switch(opcode) {
2526                                 case TCPOPT_MSS:
2527                                         if(opsize==TCPOLEN_MSS && th->syn && !estab) {
2528                                                 u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
2529                                                 if (in_mss) {
2530                                                         if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2531                                                                 in_mss = opt_rx->user_mss;
2532                                                         opt_rx->mss_clamp = in_mss;
2533                                                 }
2534                                         }
2535                                         break;
2536                                 case TCPOPT_WINDOW:
2537                                         if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2538                                                 if (sysctl_tcp_window_scaling) {
2539                                                         __u8 snd_wscale = *(__u8 *) ptr;
2540                                                         opt_rx->wscale_ok = 1;
2541                                                         if (snd_wscale > 14) {
2542                                                                 if(net_ratelimit())
2543                                                                         printk(KERN_INFO "tcp_parse_options: Illegal window "
2544                                                                                "scaling value %d >14 received.\n",
2545                                                                                snd_wscale);
2546                                                                 snd_wscale = 14;
2547                                                         }
2548                                                         opt_rx->snd_wscale = snd_wscale;
2549                                                 }
2550                                         break;
2551                                 case TCPOPT_TIMESTAMP:
2552                                         if(opsize==TCPOLEN_TIMESTAMP) {
2553                                                 if ((estab && opt_rx->tstamp_ok) ||
2554                                                     (!estab && sysctl_tcp_timestamps)) {
2555                                                         opt_rx->saw_tstamp = 1;
2556                                                         opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
2557                                                         opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
2558                                                 }
2559                                         }
2560                                         break;
2561                                 case TCPOPT_SACK_PERM:
2562                                         if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2563                                                 if (sysctl_tcp_sack) {
2564                                                         opt_rx->sack_ok = 1;
2565                                                         tcp_sack_reset(opt_rx);
2566                                                 }
2567                                         }
2568                                         break;
2569
2570                                 case TCPOPT_SACK:
2571                                         if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2572                                            !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2573                                            opt_rx->sack_ok) {
2574                                                 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2575                                         }
2576                                 };
2577                                 ptr+=opsize-2;
2578                                 length-=opsize;
2579                 };
2580         }
2581 }
2582
2583 /* Fast parse options. This hopes to only see timestamps.
2584  * If it is wrong it falls back on tcp_parse_options().
2585  */
2586 static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2587                                          struct tcp_sock *tp)
2588 {
2589         if (th->doff == sizeof(struct tcphdr)>>2) {
2590                 tp->rx_opt.saw_tstamp = 0;
2591                 return 0;
2592         } else if (tp->rx_opt.tstamp_ok &&
2593                    th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
2594                 __u32 *ptr = (__u32 *)(th + 1);
2595                 if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
2596                                   | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2597                         tp->rx_opt.saw_tstamp = 1;
2598                         ++ptr;
2599                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
2600                         ++ptr;
2601                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2602                         return 1;
2603                 }
2604         }
2605         tcp_parse_options(skb, &tp->rx_opt, 1);
2606         return 1;
2607 }
2608
2609 static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2610 {
2611         tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2612         tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2613 }
2614
2615 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2616 {
2617         if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2618                 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2619                  * extra check below makes sure this can only happen
2620                  * for pure ACK frames.  -DaveM
2621                  *
2622                  * Not only, also it occurs for expired timestamps.
2623                  */
2624
2625                 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2626                    xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2627                         tcp_store_ts_recent(tp);
2628         }
2629 }
2630
2631 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2632  *
2633  * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2634  * it can pass through stack. So, the following predicate verifies that
2635  * this segment is not used for anything but congestion avoidance or
2636  * fast retransmit. Moreover, we even are able to eliminate most of such
2637  * second order effects, if we apply some small "replay" window (~RTO)
2638  * to timestamp space.
2639  *
2640  * All these measures still do not guarantee that we reject wrapped ACKs
2641  * on networks with high bandwidth, when sequence space is recycled fastly,
2642  * but it guarantees that such events will be very rare and do not affect
2643  * connection seriously. This doesn't look nice, but alas, PAWS is really
2644  * buggy extension.
2645  *
2646  * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2647  * states that events when retransmit arrives after original data are rare.
2648  * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2649  * the biggest problem on large power networks even with minor reordering.
2650  * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2651  * up to bandwidth of 18Gigabit/sec. 8) ]
2652  */
2653
2654 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
2655 {
2656         struct tcp_sock *tp = tcp_sk(sk);
2657         struct tcphdr *th = skb->h.th;
2658         u32 seq = TCP_SKB_CB(skb)->seq;
2659         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2660
2661         return (/* 1. Pure ACK with correct sequence number. */
2662                 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2663
2664                 /* 2. ... and duplicate ACK. */
2665                 ack == tp->snd_una &&
2666
2667                 /* 3. ... and does not update window. */
2668                 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2669
2670                 /* 4. ... and sits in replay window. */
2671                 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
2672 }
2673
2674 static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
2675 {
2676         const struct tcp_sock *tp = tcp_sk(sk);
2677         return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2678                 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
2679                 !tcp_disordered_ack(sk, skb));
2680 }
2681
2682 /* Check segment sequence number for validity.
2683  *
2684  * Segment controls are considered valid, if the segment
2685  * fits to the window after truncation to the window. Acceptability
2686  * of data (and SYN, FIN, of course) is checked separately.
2687  * See tcp_data_queue(), for example.
2688  *
2689  * Also, controls (RST is main one) are accepted using RCV.WUP instead
2690  * of RCV.NXT. Peer still did not advance his SND.UNA when we
2691  * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2692  * (borrowed from freebsd)
2693  */
2694
2695 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2696 {
2697         return  !before(end_seq, tp->rcv_wup) &&
2698                 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2699 }
2700
2701 /* When we get a reset we do this. */
2702 static void tcp_reset(struct sock *sk)
2703 {
2704         /* We want the right error as BSD sees it (and indeed as we do). */
2705         switch (sk->sk_state) {
2706                 case TCP_SYN_SENT:
2707                         sk->sk_err = ECONNREFUSED;
2708                         break;
2709                 case TCP_CLOSE_WAIT:
2710                         sk->sk_err = EPIPE;
2711                         break;
2712                 case TCP_CLOSE:
2713                         return;
2714                 default:
2715                         sk->sk_err = ECONNRESET;
2716         }
2717
2718         if (!sock_flag(sk, SOCK_DEAD))
2719                 sk->sk_error_report(sk);
2720
2721         tcp_done(sk);
2722 }
2723
2724 /*
2725  *      Process the FIN bit. This now behaves as it is supposed to work
2726  *      and the FIN takes effect when it is validly part of sequence
2727  *      space. Not before when we get holes.
2728  *
2729  *      If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2730  *      (and thence onto LAST-ACK and finally, CLOSE, we never enter
2731  *      TIME-WAIT)
2732  *
2733  *      If we are in FINWAIT-1, a received FIN indicates simultaneous
2734  *      close and we go into CLOSING (and later onto TIME-WAIT)
2735  *
2736  *      If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2737  */
2738 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2739 {
2740         struct tcp_sock *tp = tcp_sk(sk);
2741
2742         inet_csk_schedule_ack(sk);
2743
2744         sk->sk_shutdown |= RCV_SHUTDOWN;
2745         sock_set_flag(sk, SOCK_DONE);
2746
2747         switch (sk->sk_state) {
2748                 case TCP_SYN_RECV:
2749                 case TCP_ESTABLISHED:
2750                         /* Move to CLOSE_WAIT */
2751                         tcp_set_state(sk, TCP_CLOSE_WAIT);
2752                         inet_csk(sk)->icsk_ack.pingpong = 1;
2753                         break;
2754
2755                 case TCP_CLOSE_WAIT:
2756                 case TCP_CLOSING:
2757                         /* Received a retransmission of the FIN, do
2758                          * nothing.
2759                          */
2760                         break;
2761                 case TCP_LAST_ACK:
2762                         /* RFC793: Remain in the LAST-ACK state. */
2763                         break;
2764
2765                 case TCP_FIN_WAIT1:
2766                         /* This case occurs when a simultaneous close
2767                          * happens, we must ack the received FIN and
2768                          * enter the CLOSING state.
2769                          */
2770                         tcp_send_ack(sk);
2771                         tcp_set_state(sk, TCP_CLOSING);
2772                         break;
2773                 case TCP_FIN_WAIT2:
2774                         /* Received a FIN -- send ACK and enter TIME_WAIT. */
2775                         tcp_send_ack(sk);
2776                         tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2777                         break;
2778                 default:
2779                         /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2780                          * cases we should never reach this piece of code.
2781                          */
2782                         printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2783                                __FUNCTION__, sk->sk_state);
2784                         break;
2785         };
2786
2787         /* It _is_ possible, that we have something out-of-order _after_ FIN.
2788          * Probably, we should reset in this case. For now drop them.
2789          */
2790         __skb_queue_purge(&tp->out_of_order_queue);
2791         if (tp->rx_opt.sack_ok)
2792                 tcp_sack_reset(&tp->rx_opt);
2793         sk_stream_mem_reclaim(sk);
2794
2795         if (!sock_flag(sk, SOCK_DEAD)) {
2796                 sk->sk_state_change(sk);
2797
2798                 /* Do not send POLL_HUP for half duplex close. */
2799                 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2800                     sk->sk_state == TCP_CLOSE)
2801                         sk_wake_async(sk, 1, POLL_HUP);
2802                 else
2803                         sk_wake_async(sk, 1, POLL_IN);
2804         }
2805 }
2806
2807 static __inline__ int
2808 tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
2809 {
2810         if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2811                 if (before(seq, sp->start_seq))
2812                         sp->start_seq = seq;
2813                 if (after(end_seq, sp->end_seq))
2814                         sp->end_seq = end_seq;
2815                 return 1;
2816         }
2817         return 0;
2818 }
2819
2820 static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
2821 {
2822         if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2823                 if (before(seq, tp->rcv_nxt))
2824                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2825                 else
2826                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2827
2828                 tp->rx_opt.dsack = 1;
2829                 tp->duplicate_sack[0].start_seq = seq;
2830                 tp->duplicate_sack[0].end_seq = end_seq;
2831                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2832         }
2833 }
2834
2835 static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
2836 {
2837         if (!tp->rx_opt.dsack)
2838                 tcp_dsack_set(tp, seq, end_seq);
2839         else
2840                 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2841 }
2842
2843 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2844 {
2845         struct tcp_sock *tp = tcp_sk(sk);
2846
2847         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2848             before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2849                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
2850                 tcp_enter_quickack_mode(sk);
2851
2852                 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2853                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2854
2855                         if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2856                                 end_seq = tp->rcv_nxt;
2857                         tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2858                 }
2859         }
2860
2861         tcp_send_ack(sk);
2862 }
2863
2864 /* These routines update the SACK block as out-of-order packets arrive or
2865  * in-order packets close up the sequence space.
2866  */
2867 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2868 {
2869         int this_sack;
2870         struct tcp_sack_block *sp = &tp->selective_acks[0];
2871         struct tcp_sack_block *swalk = sp+1;
2872
2873         /* See if the recent change to the first SACK eats into
2874          * or hits the sequence space of other SACK blocks, if so coalesce.
2875          */
2876         for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
2877                 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
2878                         int i;
2879
2880                         /* Zap SWALK, by moving every further SACK up by one slot.
2881                          * Decrease num_sacks.
2882                          */
2883                         tp->rx_opt.num_sacks--;
2884                         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2885                         for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
2886                                 sp[i] = sp[i+1];
2887                         continue;
2888                 }
2889                 this_sack++, swalk++;
2890         }
2891 }
2892
2893 static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
2894 {
2895         __u32 tmp;
2896
2897         tmp = sack1->start_seq;
2898         sack1->start_seq = sack2->start_seq;
2899         sack2->start_seq = tmp;
2900
2901         tmp = sack1->end_seq;
2902         sack1->end_seq = sack2->end_seq;
2903         sack2->end_seq = tmp;
2904 }
2905
2906 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
2907 {
2908         struct tcp_sock *tp = tcp_sk(sk);
2909         struct tcp_sack_block *sp = &tp->selective_acks[0];
2910         int cur_sacks = tp->rx_opt.num_sacks;
2911         int this_sack;
2912
2913         if (!cur_sacks)
2914                 goto new_sack;
2915
2916         for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
2917                 if (tcp_sack_extend(sp, seq, end_seq)) {
2918                         /* Rotate this_sack to the first one. */
2919                         for (; this_sack>0; this_sack--, sp--)
2920                                 tcp_sack_swap(sp, sp-1);
2921                         if (cur_sacks > 1)
2922                                 tcp_sack_maybe_coalesce(tp);
2923                         return;
2924                 }
2925         }
2926
2927         /* Could not find an adjacent existing SACK, build a new one,
2928          * put it at the front, and shift everyone else down.  We
2929          * always know there is at least one SACK present already here.
2930          *
2931          * If the sack array is full, forget about the last one.
2932          */
2933         if (this_sack >= 4) {
2934                 this_sack--;
2935                 tp->rx_opt.num_sacks--;
2936                 sp--;
2937         }
2938         for(; this_sack > 0; this_sack--, sp--)
2939                 *sp = *(sp-1);
2940
2941 new_sack:
2942         /* Build the new head SACK, and we're done. */
2943         sp->start_seq = seq;
2944         sp->end_seq = end_seq;
2945         tp->rx_opt.num_sacks++;
2946         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2947 }
2948
2949 /* RCV.NXT advances, some SACKs should be eaten. */
2950
2951 static void tcp_sack_remove(struct tcp_sock *tp)
2952 {
2953         struct tcp_sack_block *sp = &tp->selective_acks[0];
2954         int num_sacks = tp->rx_opt.num_sacks;
2955         int this_sack;
2956
2957         /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
2958         if (skb_queue_empty(&tp->out_of_order_queue)) {
2959                 tp->rx_opt.num_sacks = 0;
2960                 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
2961                 return;
2962         }
2963
2964         for(this_sack = 0; this_sack < num_sacks; ) {
2965                 /* Check if the start of the sack is covered by RCV.NXT. */
2966                 if (!before(tp->rcv_nxt, sp->start_seq)) {
2967                         int i;
2968
2969                         /* RCV.NXT must cover all the block! */
2970                         BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
2971
2972                         /* Zap this SACK, by moving forward any other SACKS. */
2973                         for (i=this_sack+1; i < num_sacks; i++)
2974                                 tp->selective_acks[i-1] = tp->selective_acks[i];
2975                         num_sacks--;
2976                         continue;
2977                 }
2978                 this_sack++;
2979                 sp++;
2980         }
2981         if (num_sacks != tp->rx_opt.num_sacks) {
2982                 tp->rx_opt.num_sacks = num_sacks;
2983                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2984         }
2985 }
2986
2987 /* This one checks to see if we can put data from the
2988  * out_of_order queue into the receive_queue.
2989  */
2990 static void tcp_ofo_queue(struct sock *sk)
2991 {
2992         struct tcp_sock *tp = tcp_sk(sk);
2993         __u32 dsack_high = tp->rcv_nxt;
2994         struct sk_buff *skb;
2995
2996         while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
2997                 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
2998                         break;
2999
3000                 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3001                         __u32 dsack = dsack_high;
3002                         if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3003                                 dsack_high = TCP_SKB_CB(skb)->end_seq;
3004                         tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3005                 }
3006
3007                 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3008                         SOCK_DEBUG(sk, "ofo packet was already received \n");
3009                         __skb_unlink(skb, &tp->out_of_order_queue);
3010                         __kfree_skb(skb);
3011                         continue;
3012                 }
3013                 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3014                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3015                            TCP_SKB_CB(skb)->end_seq);
3016
3017                 __skb_unlink(skb, &tp->out_of_order_queue);
3018                 __skb_queue_tail(&sk->sk_receive_queue, skb);
3019                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3020                 if(skb->h.th->fin)
3021                         tcp_fin(skb, sk, skb->h.th);
3022         }
3023 }
3024
3025 static int tcp_prune_queue(struct sock *sk);
3026
3027 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3028 {
3029         struct tcphdr *th = skb->h.th;
3030         struct tcp_sock *tp = tcp_sk(sk);
3031         int eaten = -1;
3032
3033         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3034                 goto drop;
3035
3036         __skb_pull(skb, th->doff*4);
3037
3038         TCP_ECN_accept_cwr(tp, skb);
3039
3040         if (tp->rx_opt.dsack) {
3041                 tp->rx_opt.dsack = 0;
3042                 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3043                                                     4 - tp->rx_opt.tstamp_ok);
3044         }
3045
3046         /*  Queue data for delivery to the user.
3047          *  Packets in sequence go to the receive queue.
3048          *  Out of sequence packets to the out_of_order_queue.
3049          */
3050         if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3051                 if (tcp_receive_window(tp) == 0)
3052                         goto out_of_window;
3053
3054                 /* Ok. In sequence. In window. */
3055                 if (tp->ucopy.task == current &&
3056                     tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3057                     sock_owned_by_user(sk) && !tp->urg_data) {
3058                         int chunk = min_t(unsigned int, skb->len,
3059                                                         tp->ucopy.len);
3060
3061                         __set_current_state(TASK_RUNNING);
3062
3063                         local_bh_enable();
3064                         if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3065                                 tp->ucopy.len -= chunk;
3066                                 tp->copied_seq += chunk;
3067                                 eaten = (chunk == skb->len && !th->fin);
3068                                 tcp_rcv_space_adjust(sk);
3069                         }
3070                         local_bh_disable();
3071                 }
3072
3073                 if (eaten <= 0) {
3074 queue_and_out:
3075                         if (eaten < 0 &&
3076                             (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3077                              !sk_stream_rmem_schedule(sk, skb))) {
3078                                 if (tcp_prune_queue(sk) < 0 ||
3079                                     !sk_stream_rmem_schedule(sk, skb))
3080                                         goto drop;
3081                         }
3082                         sk_stream_set_owner_r(skb, sk);
3083                         __skb_queue_tail(&sk->sk_receive_queue, skb);
3084                 }
3085                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3086                 if(skb->len)
3087                         tcp_event_data_recv(sk, tp, skb);
3088                 if(th->fin)
3089                         tcp_fin(skb, sk, th);
3090
3091                 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3092                         tcp_ofo_queue(sk);
3093
3094                         /* RFC2581. 4.2. SHOULD send immediate ACK, when
3095                          * gap in queue is filled.
3096                          */
3097                         if (skb_queue_empty(&tp->out_of_order_queue))
3098                                 inet_csk(sk)->icsk_ack.pingpong = 0;
3099                 }
3100
3101                 if (tp->rx_opt.num_sacks)
3102                         tcp_sack_remove(tp);
3103
3104                 tcp_fast_path_check(sk, tp);
3105
3106                 if (eaten > 0)
3107                         __kfree_skb(skb);
3108                 else if (!sock_flag(sk, SOCK_DEAD))
3109                         sk->sk_data_ready(sk, 0);
3110                 return;
3111         }
3112
3113         if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3114                 /* A retransmit, 2nd most common case.  Force an immediate ack. */
3115                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3116                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3117
3118 out_of_window:
3119                 tcp_enter_quickack_mode(sk);
3120                 inet_csk_schedule_ack(sk);
3121 drop:
3122                 __kfree_skb(skb);
3123                 return;
3124         }
3125
3126         /* Out of window. F.e. zero window probe. */
3127         if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3128                 goto out_of_window;
3129
3130         tcp_enter_quickack_mode(sk);
3131
3132         if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3133                 /* Partial packet, seq < rcv_next < end_seq */
3134                 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3135                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3136                            TCP_SKB_CB(skb)->end_seq);
3137
3138                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3139                 
3140                 /* If window is closed, drop tail of packet. But after
3141                  * remembering D-SACK for its head made in previous line.
3142                  */
3143                 if (!tcp_receive_window(tp))
3144                         goto out_of_window;
3145                 goto queue_and_out;
3146         }
3147
3148         TCP_ECN_check_ce(tp, skb);
3149
3150         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3151             !sk_stream_rmem_schedule(sk, skb)) {
3152                 if (tcp_prune_queue(sk) < 0 ||
3153                     !sk_stream_rmem_schedule(sk, skb))
3154                         goto drop;
3155         }
3156
3157         /* Disable header prediction. */
3158         tp->pred_flags = 0;
3159         inet_csk_schedule_ack(sk);
3160
3161         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3162                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3163
3164         sk_stream_set_owner_r(skb, sk);
3165
3166         if (!skb_peek(&tp->out_of_order_queue)) {
3167                 /* Initial out of order segment, build 1 SACK. */
3168                 if (tp->rx_opt.sack_ok) {
3169                         tp->rx_opt.num_sacks = 1;
3170                         tp->rx_opt.dsack     = 0;
3171                         tp->rx_opt.eff_sacks = 1;
3172                         tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3173                         tp->selective_acks[0].end_seq =
3174                                                 TCP_SKB_CB(skb)->end_seq;
3175                 }
3176                 __skb_queue_head(&tp->out_of_order_queue,skb);
3177         } else {
3178                 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3179                 u32 seq = TCP_SKB_CB(skb)->seq;
3180                 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3181
3182                 if (seq == TCP_SKB_CB(skb1)->end_seq) {
3183                         __skb_append(skb1, skb, &tp->out_of_order_queue);
3184
3185                         if (!tp->rx_opt.num_sacks ||
3186                             tp->selective_acks[0].end_seq != seq)
3187                                 goto add_sack;
3188
3189                         /* Common case: data arrive in order after hole. */
3190                         tp->selective_acks[0].end_seq = end_seq;
3191                         return;
3192                 }
3193
3194                 /* Find place to insert this segment. */
3195                 do {
3196                         if (!after(TCP_SKB_CB(skb1)->seq, seq))
3197                                 break;
3198                 } while ((skb1 = skb1->prev) !=
3199                          (struct sk_buff*)&tp->out_of_order_queue);
3200
3201                 /* Do skb overlap to previous one? */
3202                 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3203                     before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3204                         if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3205                                 /* All the bits are present. Drop. */
3206                                 __kfree_skb(skb);
3207                                 tcp_dsack_set(tp, seq, end_seq);
3208                                 goto add_sack;
3209                         }
3210                         if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3211                                 /* Partial overlap. */
3212                                 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3213                         } else {
3214                                 skb1 = skb1->prev;
3215                         }
3216                 }
3217                 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3218                 
3219                 /* And clean segments covered by new one as whole. */
3220                 while ((skb1 = skb->next) !=
3221                        (struct sk_buff*)&tp->out_of_order_queue &&
3222                        after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3223                        if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3224                                tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3225                                break;
3226                        }
3227                        __skb_unlink(skb1, &tp->out_of_order_queue);
3228                        tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3229                        __kfree_skb(skb1);
3230                 }
3231
3232 add_sack:
3233                 if (tp->rx_opt.sack_ok)
3234                         tcp_sack_new_ofo_skb(sk, seq, end_seq);
3235         }
3236 }
3237
3238 /* Collapse contiguous sequence of skbs head..tail with
3239  * sequence numbers start..end.
3240  * Segments with FIN/SYN are not collapsed (only because this
3241  * simplifies code)
3242  */
3243 static void
3244 tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3245              struct sk_buff *head, struct sk_buff *tail,
3246              u32 start, u32 end)
3247 {
3248         struct sk_buff *skb;
3249
3250         /* First, check that queue is collapsible and find
3251          * the point where collapsing can be useful. */
3252         for (skb = head; skb != tail; ) {
3253                 /* No new bits? It is possible on ofo queue. */
3254                 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3255                         struct sk_buff *next = skb->next;
3256                         __skb_unlink(skb, list);
3257                         __kfree_skb(skb);
3258                         NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3259                         skb = next;
3260                         continue;
3261                 }
3262
3263                 /* The first skb to collapse is:
3264                  * - not SYN/FIN and
3265                  * - bloated or contains data before "start" or
3266                  *   overlaps to the next one.
3267                  */
3268                 if (!skb->h.th->syn && !skb->h.th->fin &&
3269                     (tcp_win_from_space(skb->truesize) > skb->len ||
3270                      before(TCP_SKB_CB(skb)->seq, start) ||
3271                      (skb->next != tail &&
3272                       TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3273                         break;
3274
3275                 /* Decided to skip this, advance start seq. */
3276                 start = TCP_SKB_CB(skb)->end_seq;
3277                 skb = skb->next;
3278         }
3279         if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3280                 return;
3281
3282         while (before(start, end)) {
3283                 struct sk_buff *nskb;
3284                 int header = skb_headroom(skb);
3285                 int copy = SKB_MAX_ORDER(header, 0);
3286
3287                 /* Too big header? This can happen with IPv6. */
3288                 if (copy < 0)
3289                         return;
3290                 if (end-start < copy)
3291                         copy = end-start;
3292                 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3293                 if (!nskb)
3294                         return;
3295                 skb_reserve(nskb, header);
3296                 memcpy(nskb->head, skb->head, header);
3297                 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3298                 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3299                 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3300                 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3301                 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
3302                 __skb_insert(nskb, skb->prev, skb, list);
3303                 sk_stream_set_owner_r(nskb, sk);
3304
3305                 /* Copy data, releasing collapsed skbs. */
3306                 while (copy > 0) {
3307                         int offset = start - TCP_SKB_CB(skb)->seq;
3308                         int size = TCP_SKB_CB(skb)->end_seq - start;
3309
3310                         if (offset < 0) BUG();
3311                         if (size > 0) {
3312                                 size = min(copy, size);
3313                                 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3314                                         BUG();
3315                                 TCP_SKB_CB(nskb)->end_seq += size;
3316                                 copy -= size;
3317                                 start += size;
3318                         }
3319                         if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3320                                 struct sk_buff *next = skb->next;
3321                                 __skb_unlink(skb, list);
3322                                 __kfree_skb(skb);
3323                                 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3324                                 skb = next;
3325                                 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3326                                         return;
3327                         }
3328                 }
3329         }
3330 }
3331
3332 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3333  * and tcp_collapse() them until all the queue is collapsed.
3334  */
3335 static void tcp_collapse_ofo_queue(struct sock *sk)
3336 {
3337         struct tcp_sock *tp = tcp_sk(sk);
3338         struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3339         struct sk_buff *head;
3340         u32 start, end;
3341
3342         if (skb == NULL)
3343                 return;
3344
3345         start = TCP_SKB_CB(skb)->seq;
3346         end = TCP_SKB_CB(skb)->end_seq;
3347         head = skb;
3348
3349         for (;;) {
3350                 skb = skb->next;
3351
3352                 /* Segment is terminated when we see gap or when
3353                  * we are at the end of all the queue. */
3354                 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3355                     after(TCP_SKB_CB(skb)->seq, end) ||
3356                     before(TCP_SKB_CB(skb)->end_seq, start)) {
3357                         tcp_collapse(sk, &tp->out_of_order_queue,
3358                                      head, skb, start, end);
3359                         head = skb;
3360                         if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3361                                 break;
3362                         /* Start new segment */
3363                         start = TCP_SKB_CB(skb)->seq;
3364                         end = TCP_SKB_CB(skb)->end_seq;
3365                 } else {
3366                         if (before(TCP_SKB_CB(skb)->seq, start))
3367                                 start = TCP_SKB_CB(skb)->seq;
3368                         if (after(TCP_SKB_CB(skb)->end_seq, end))
3369                                 end = TCP_SKB_CB(skb)->end_seq;
3370                 }
3371         }
3372 }
3373
3374 /* Reduce allocated memory if we can, trying to get
3375  * the socket within its memory limits again.
3376  *
3377  * Return less than zero if we should start dropping frames
3378  * until the socket owning process reads some of the data
3379  * to stabilize the situation.
3380  */
3381 static int tcp_prune_queue(struct sock *sk)
3382 {
3383         struct tcp_sock *tp = tcp_sk(sk); 
3384
3385         SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3386
3387         NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3388
3389         if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3390                 tcp_clamp_window(sk, tp);
3391         else if (tcp_memory_pressure)
3392                 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3393
3394         tcp_collapse_ofo_queue(sk);
3395         tcp_collapse(sk, &sk->sk_receive_queue,
3396                      sk->sk_receive_queue.next,
3397                      (struct sk_buff*)&sk->sk_receive_queue,
3398                      tp->copied_seq, tp->rcv_nxt);
3399         sk_stream_mem_reclaim(sk);
3400
3401         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3402                 return 0;
3403
3404         /* Collapsing did not help, destructive actions follow.
3405          * This must not ever occur. */
3406
3407         /* First, purge the out_of_order queue. */
3408         if (!skb_queue_empty(&tp->out_of_order_queue)) {
3409                 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
3410                 __skb_queue_purge(&tp->out_of_order_queue);
3411
3412                 /* Reset SACK state.  A conforming SACK implementation will
3413                  * do the same at a timeout based retransmit.  When a connection
3414                  * is in a sad state like this, we care only about integrity
3415                  * of the connection not performance.
3416                  */
3417                 if (tp->rx_opt.sack_ok)
3418                         tcp_sack_reset(&tp->rx_opt);
3419                 sk_stream_mem_reclaim(sk);
3420         }
3421
3422         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3423                 return 0;
3424
3425         /* If we are really being abused, tell the caller to silently
3426          * drop receive data on the floor.  It will get retransmitted
3427          * and hopefully then we'll have sufficient space.
3428          */
3429         NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3430
3431         /* Massive buffer overcommit. */
3432         tp->pred_flags = 0;
3433         return -1;
3434 }
3435
3436
3437 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3438  * As additional protections, we do not touch cwnd in retransmission phases,
3439  * and if application hit its sndbuf limit recently.
3440  */
3441 void tcp_cwnd_application_limited(struct sock *sk)
3442 {
3443         struct tcp_sock *tp = tcp_sk(sk);
3444
3445         if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
3446             sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3447                 /* Limited by application or receiver window. */
3448                 u32 win_used = max(tp->snd_cwnd_used, 2U);
3449                 if (win_used < tp->snd_cwnd) {
3450                         tp->snd_ssthresh = tcp_current_ssthresh(sk);
3451                         tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3452                 }
3453                 tp->snd_cwnd_used = 0;
3454         }
3455         tp->snd_cwnd_stamp = tcp_time_stamp;
3456 }
3457
3458 static inline int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
3459 {
3460         /* If the user specified a specific send buffer setting, do
3461          * not modify it.
3462          */
3463         if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3464                 return 0;
3465
3466         /* If we are under global TCP memory pressure, do not expand.  */
3467         if (tcp_memory_pressure)
3468                 return 0;
3469
3470         /* If we are under soft global TCP memory pressure, do not expand.  */
3471         if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3472                 return 0;
3473
3474         /* If we filled the congestion window, do not expand.  */
3475         if (tp->packets_out >= tp->snd_cwnd)
3476                 return 0;
3477
3478         return 1;
3479 }
3480
3481 /* When incoming ACK allowed to free some skb from write_queue,
3482  * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3483  * on the exit from tcp input handler.
3484  *
3485  * PROBLEM: sndbuf expansion does not work well with largesend.
3486  */
3487 static void tcp_new_space(struct sock *sk)
3488 {
3489         struct tcp_sock *tp = tcp_sk(sk);
3490
3491         if (tcp_should_expand_sndbuf(sk, tp)) {
3492                 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
3493                         MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3494                     demanded = max_t(unsigned int, tp->snd_cwnd,
3495                                                    tp->reordering + 1);
3496                 sndmem *= 2*demanded;
3497                 if (sndmem > sk->sk_sndbuf)
3498                         sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3499                 tp->snd_cwnd_stamp = tcp_time_stamp;
3500         }
3501
3502         sk->sk_write_space(sk);
3503 }
3504
3505 static inline void tcp_check_space(struct sock *sk)
3506 {
3507         if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3508                 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3509                 if (sk->sk_socket &&
3510                     test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3511                         tcp_new_space(sk);
3512         }
3513 }
3514
3515 static __inline__ void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
3516 {
3517         tcp_push_pending_frames(sk, tp);
3518         tcp_check_space(sk);
3519 }
3520
3521 /*
3522  * Check if sending an ack is needed.
3523  */
3524 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3525 {
3526         struct tcp_sock *tp = tcp_sk(sk);
3527
3528             /* More than one full frame received... */
3529         if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
3530              /* ... and right edge of window advances far enough.
3531               * (tcp_recvmsg() will send ACK otherwise). Or...
3532               */
3533              && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3534             /* We ACK each frame or... */
3535             tcp_in_quickack_mode(sk) ||
3536             /* We have out of order data. */
3537             (ofo_possible &&
3538              skb_peek(&tp->out_of_order_queue))) {
3539                 /* Then ack it now */
3540                 tcp_send_ack(sk);
3541         } else {
3542                 /* Else, send delayed ack. */
3543                 tcp_send_delayed_ack(sk);
3544         }
3545 }
3546
3547 static __inline__ void tcp_ack_snd_check(struct sock *sk)
3548 {
3549         if (!inet_csk_ack_scheduled(sk)) {
3550                 /* We sent a data segment already. */
3551                 return;
3552         }
3553         __tcp_ack_snd_check(sk, 1);
3554 }
3555
3556 /*
3557  *      This routine is only called when we have urgent data
3558  *      signaled. Its the 'slow' part of tcp_urg. It could be
3559  *      moved inline now as tcp_urg is only called from one
3560  *      place. We handle URGent data wrong. We have to - as
3561  *      BSD still doesn't use the correction from RFC961.
3562  *      For 1003.1g we should support a new option TCP_STDURG to permit
3563  *      either form (or just set the sysctl tcp_stdurg).
3564  */
3565  
3566 static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3567 {
3568         struct tcp_sock *tp = tcp_sk(sk);
3569         u32 ptr = ntohs(th->urg_ptr);
3570
3571         if (ptr && !sysctl_tcp_stdurg)
3572                 ptr--;
3573         ptr += ntohl(th->seq);
3574
3575         /* Ignore urgent data that we've already seen and read. */
3576         if (after(tp->copied_seq, ptr))
3577                 return;
3578
3579         /* Do not replay urg ptr.
3580          *
3581          * NOTE: interesting situation not covered by specs.
3582          * Misbehaving sender may send urg ptr, pointing to segment,
3583          * which we already have in ofo queue. We are not able to fetch
3584          * such data and will stay in TCP_URG_NOTYET until will be eaten
3585          * by recvmsg(). Seems, we are not obliged to handle such wicked
3586          * situations. But it is worth to think about possibility of some
3587          * DoSes using some hypothetical application level deadlock.
3588          */
3589         if (before(ptr, tp->rcv_nxt))
3590                 return;
3591
3592         /* Do we already have a newer (or duplicate) urgent pointer? */
3593         if (tp->urg_data && !after(ptr, tp->urg_seq))
3594                 return;
3595
3596         /* Tell the world about our new urgent pointer. */
3597         sk_send_sigurg(sk);
3598
3599         /* We may be adding urgent data when the last byte read was
3600          * urgent. To do this requires some care. We cannot just ignore
3601          * tp->copied_seq since we would read the last urgent byte again
3602          * as data, nor can we alter copied_seq until this data arrives
3603          * or we break the semantics of SIOCATMARK (and thus sockatmark())
3604          *
3605          * NOTE. Double Dutch. Rendering to plain English: author of comment
3606          * above did something sort of  send("A", MSG_OOB); send("B", MSG_OOB);
3607          * and expect that both A and B disappear from stream. This is _wrong_.
3608          * Though this happens in BSD with high probability, this is occasional.
3609          * Any application relying on this is buggy. Note also, that fix "works"
3610          * only in this artificial test. Insert some normal data between A and B and we will
3611          * decline of BSD again. Verdict: it is better to remove to trap
3612          * buggy users.
3613          */
3614         if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3615             !sock_flag(sk, SOCK_URGINLINE) &&
3616             tp->copied_seq != tp->rcv_nxt) {
3617                 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3618                 tp->copied_seq++;
3619                 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
3620                         __skb_unlink(skb, &sk->sk_receive_queue);
3621                         __kfree_skb(skb);
3622                 }
3623         }
3624
3625         tp->urg_data   = TCP_URG_NOTYET;
3626         tp->urg_seq    = ptr;
3627
3628         /* Disable header prediction. */
3629         tp->pred_flags = 0;
3630 }
3631
3632 /* This is the 'fast' part of urgent handling. */
3633 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3634 {
3635         struct tcp_sock *tp = tcp_sk(sk);
3636
3637         /* Check if we get a new urgent pointer - normally not. */
3638         if (th->urg)
3639                 tcp_check_urg(sk,th);
3640
3641         /* Do we wait for any urgent data? - normally not... */
3642         if (tp->urg_data == TCP_URG_NOTYET) {
3643                 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3644                           th->syn;
3645
3646                 /* Is the urgent pointer pointing into this packet? */   
3647                 if (ptr < skb->len) {
3648                         u8 tmp;
3649                         if (skb_copy_bits(skb, ptr, &tmp, 1))
3650                                 BUG();
3651                         tp->urg_data = TCP_URG_VALID | tmp;
3652                         if (!sock_flag(sk, SOCK_DEAD))
3653                                 sk->sk_data_ready(sk, 0);
3654                 }
3655         }
3656 }
3657
3658 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3659 {
3660         struct tcp_sock *tp = tcp_sk(sk);
3661         int chunk = skb->len - hlen;
3662         int err;
3663
3664         local_bh_enable();
3665         if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3666                 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3667         else
3668                 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3669                                                        tp->ucopy.iov);
3670
3671         if (!err) {
3672                 tp->ucopy.len -= chunk;
3673                 tp->copied_seq += chunk;
3674                 tcp_rcv_space_adjust(sk);
3675         }
3676
3677         local_bh_disable();
3678         return err;
3679 }
3680
3681 static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3682 {
3683         int result;
3684
3685         if (sock_owned_by_user(sk)) {
3686                 local_bh_enable();
3687                 result = __tcp_checksum_complete(skb);
3688                 local_bh_disable();
3689         } else {
3690                 result = __tcp_checksum_complete(skb);
3691         }
3692         return result;
3693 }
3694
3695 static __inline__ int
3696 tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3697 {
3698         return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3699                 __tcp_checksum_complete_user(sk, skb);
3700 }
3701
3702 /*
3703  *      TCP receive function for the ESTABLISHED state. 
3704  *
3705  *      It is split into a fast path and a slow path. The fast path is 
3706  *      disabled when:
3707  *      - A zero window was announced from us - zero window probing
3708  *        is only handled properly in the slow path. 
3709  *      - Out of order segments arrived.
3710  *      - Urgent data is expected.
3711  *      - There is no buffer space left
3712  *      - Unexpected TCP flags/window values/header lengths are received
3713  *        (detected by checking the TCP header against pred_flags) 
3714  *      - Data is sent in both directions. Fast path only supports pure senders
3715  *        or pure receivers (this means either the sequence number or the ack
3716  *        value must stay constant)
3717  *      - Unexpected TCP option.
3718  *
3719  *      When these conditions are not satisfied it drops into a standard 
3720  *      receive procedure patterned after RFC793 to handle all cases.
3721  *      The first three cases are guaranteed by proper pred_flags setting,
3722  *      the rest is checked inline. Fast processing is turned on in 
3723  *      tcp_data_queue when everything is OK.
3724  */
3725 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3726                         struct tcphdr *th, unsigned len)
3727 {
3728         struct tcp_sock *tp = tcp_sk(sk);
3729
3730         /*
3731          *      Header prediction.
3732          *      The code loosely follows the one in the famous 
3733          *      "30 instruction TCP receive" Van Jacobson mail.
3734          *      
3735          *      Van's trick is to deposit buffers into socket queue 
3736          *      on a device interrupt, to call tcp_recv function
3737          *      on the receive process context and checksum and copy
3738          *      the buffer to user space. smart...
3739          *
3740          *      Our current scheme is not silly either but we take the 
3741          *      extra cost of the net_bh soft interrupt processing...
3742          *      We do checksum and copy also but from device to kernel.
3743          */
3744
3745         tp->rx_opt.saw_tstamp = 0;
3746
3747         /*      pred_flags is 0xS?10 << 16 + snd_wnd
3748          *      if header_prediction is to be made
3749          *      'S' will always be tp->tcp_header_len >> 2
3750          *      '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3751          *  turn it off (when there are holes in the receive 
3752          *       space for instance)
3753          *      PSH flag is ignored.
3754          */
3755
3756         if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3757                 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3758                 int tcp_header_len = tp->tcp_header_len;
3759
3760                 /* Timestamp header prediction: tcp_header_len
3761                  * is automatically equal to th->doff*4 due to pred_flags
3762                  * match.
3763                  */
3764
3765                 /* Check timestamp */
3766                 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
3767                         __u32 *ptr = (__u32 *)(th + 1);
3768
3769                         /* No? Slow path! */
3770                         if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3771                                           | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3772                                 goto slow_path;
3773
3774                         tp->rx_opt.saw_tstamp = 1;
3775                         ++ptr; 
3776                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
3777                         ++ptr;
3778                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3779
3780                         /* If PAWS failed, check it more carefully in slow path */
3781                         if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3782                                 goto slow_path;
3783
3784                         /* DO NOT update ts_recent here, if checksum fails
3785                          * and timestamp was corrupted part, it will result
3786                          * in a hung connection since we will drop all
3787                          * future packets due to the PAWS test.
3788                          */
3789                 }
3790
3791                 if (len <= tcp_header_len) {
3792                         /* Bulk data transfer: sender */
3793                         if (len == tcp_header_len) {
3794                                 /* Predicted packet is in window by definition.
3795                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3796                                  * Hence, check seq<=rcv_wup reduces to:
3797                                  */
3798                                 if (tcp_header_len ==
3799                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3800                                     tp->rcv_nxt == tp->rcv_wup)
3801                                         tcp_store_ts_recent(tp);
3802
3803                                 tcp_rcv_rtt_measure_ts(sk, skb);
3804
3805                                 /* We know that such packets are checksummed
3806                                  * on entry.
3807                                  */
3808                                 tcp_ack(sk, skb, 0);
3809                                 __kfree_skb(skb); 
3810                                 tcp_data_snd_check(sk, tp);
3811                                 return 0;
3812                         } else { /* Header too small */
3813                                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3814                                 goto discard;
3815                         }
3816                 } else {
3817                         int eaten = 0;
3818
3819                         if (tp->ucopy.task == current &&
3820                             tp->copied_seq == tp->rcv_nxt &&
3821                             len - tcp_header_len <= tp->ucopy.len &&
3822                             sock_owned_by_user(sk)) {
3823                                 __set_current_state(TASK_RUNNING);
3824
3825                                 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
3826                                         /* Predicted packet is in window by definition.
3827                                          * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3828                                          * Hence, check seq<=rcv_wup reduces to:
3829                                          */
3830                                         if (tcp_header_len ==
3831                                             (sizeof(struct tcphdr) +
3832                                              TCPOLEN_TSTAMP_ALIGNED) &&
3833                                             tp->rcv_nxt == tp->rcv_wup)
3834                                                 tcp_store_ts_recent(tp);
3835
3836                                         tcp_rcv_rtt_measure_ts(sk, skb);
3837
3838                                         __skb_pull(skb, tcp_header_len);
3839                                         tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3840                                         NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
3841                                         eaten = 1;
3842                                 }
3843                         }
3844                         if (!eaten) {
3845                                 if (tcp_checksum_complete_user(sk, skb))
3846                                         goto csum_error;
3847
3848                                 /* Predicted packet is in window by definition.
3849                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3850                                  * Hence, check seq<=rcv_wup reduces to:
3851                                  */
3852                                 if (tcp_header_len ==
3853                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3854                                     tp->rcv_nxt == tp->rcv_wup)
3855                                         tcp_store_ts_recent(tp);
3856
3857                                 tcp_rcv_rtt_measure_ts(sk, skb);
3858
3859                                 if ((int)skb->truesize > sk->sk_forward_alloc)
3860                                         goto step5;
3861
3862                                 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
3863
3864                                 /* Bulk data transfer: receiver */
3865                                 __skb_pull(skb,tcp_header_len);
3866                                 __skb_queue_tail(&sk->sk_receive_queue, skb);
3867                                 sk_stream_set_owner_r(skb, sk);
3868                                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3869                         }
3870
3871                         tcp_event_data_recv(sk, tp, skb);
3872
3873                         if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
3874                                 /* Well, only one small jumplet in fast path... */
3875                                 tcp_ack(sk, skb, FLAG_DATA);
3876                                 tcp_data_snd_check(sk, tp);
3877                                 if (!inet_csk_ack_scheduled(sk))
3878                                         goto no_ack;
3879                         }
3880
3881                         __tcp_ack_snd_check(sk, 0);
3882 no_ack:
3883                         if (eaten)
3884                                 __kfree_skb(skb);
3885                         else
3886                                 sk->sk_data_ready(sk, 0);
3887                         return 0;
3888                 }
3889         }
3890
3891 slow_path:
3892         if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
3893                 goto csum_error;
3894
3895         /*
3896          * RFC1323: H1. Apply PAWS check first.
3897          */
3898         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
3899             tcp_paws_discard(sk, skb)) {
3900                 if (!th->rst) {
3901                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
3902                         tcp_send_dupack(sk, skb);
3903                         goto discard;
3904                 }
3905                 /* Resets are accepted even if PAWS failed.
3906
3907                    ts_recent update must be made after we are sure
3908                    that the packet is in window.
3909                  */
3910         }
3911
3912         /*
3913          *      Standard slow path.
3914          */
3915
3916         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
3917                 /* RFC793, page 37: "In all states except SYN-SENT, all reset
3918                  * (RST) segments are validated by checking their SEQ-fields."
3919                  * And page 69: "If an incoming segment is not acceptable,
3920                  * an acknowledgment should be sent in reply (unless the RST bit
3921                  * is set, if so drop the segment and return)".
3922                  */
3923                 if (!th->rst)
3924                         tcp_send_dupack(sk, skb);
3925                 goto discard;
3926         }
3927
3928         if(th->rst) {
3929                 tcp_reset(sk);
3930                 goto discard;
3931         }
3932
3933         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
3934
3935         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3936                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3937                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
3938                 tcp_reset(sk);
3939                 return 1;
3940         }
3941
3942 step5:
3943         if(th->ack)
3944                 tcp_ack(sk, skb, FLAG_SLOWPATH);
3945
3946         tcp_rcv_rtt_measure_ts(sk, skb);
3947
3948         /* Process urgent data. */
3949         tcp_urg(sk, skb, th);
3950
3951         /* step 7: process the segment text */
3952         tcp_data_queue(sk, skb);
3953
3954         tcp_data_snd_check(sk, tp);
3955         tcp_ack_snd_check(sk);
3956         return 0;
3957
3958 csum_error:
3959         TCP_INC_STATS_BH(TCP_MIB_INERRS);
3960
3961 discard:
3962         __kfree_skb(skb);
3963         return 0;
3964 }
3965
3966 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
3967                                          struct tcphdr *th, unsigned len)
3968 {
3969         struct tcp_sock *tp = tcp_sk(sk);
3970         int saved_clamp = tp->rx_opt.mss_clamp;
3971
3972         tcp_parse_options(skb, &tp->rx_opt, 0);
3973
3974         if (th->ack) {
3975                 struct inet_connection_sock *icsk;
3976                 /* rfc793:
3977                  * "If the state is SYN-SENT then
3978                  *    first check the ACK bit
3979                  *      If the ACK bit is set
3980                  *        If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
3981                  *        a reset (unless the RST bit is set, if so drop
3982                  *        the segment and return)"
3983                  *
3984                  *  We do not send data with SYN, so that RFC-correct
3985                  *  test reduces to:
3986                  */
3987                 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
3988                         goto reset_and_undo;
3989
3990                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
3991                     !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
3992                              tcp_time_stamp)) {
3993                         NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
3994                         goto reset_and_undo;
3995                 }
3996
3997                 /* Now ACK is acceptable.
3998                  *
3999                  * "If the RST bit is set
4000                  *    If the ACK was acceptable then signal the user "error:
4001                  *    connection reset", drop the segment, enter CLOSED state,
4002                  *    delete TCB, and return."
4003                  */
4004
4005                 if (th->rst) {
4006                         tcp_reset(sk);
4007                         goto discard;
4008                 }
4009
4010                 /* rfc793:
4011                  *   "fifth, if neither of the SYN or RST bits is set then
4012                  *    drop the segment and return."
4013                  *
4014                  *    See note below!
4015                  *                                        --ANK(990513)
4016                  */
4017                 if (!th->syn)
4018                         goto discard_and_undo;
4019
4020                 /* rfc793:
4021                  *   "If the SYN bit is on ...
4022                  *    are acceptable then ...
4023                  *    (our SYN has been ACKed), change the connection
4024                  *    state to ESTABLISHED..."
4025                  */
4026
4027                 TCP_ECN_rcv_synack(tp, th);
4028                 if (tp->ecn_flags&TCP_ECN_OK)
4029                         sock_set_flag(sk, SOCK_NO_LARGESEND);
4030
4031                 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4032                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4033
4034                 /* Ok.. it's good. Set up sequence numbers and
4035                  * move to established.
4036                  */
4037                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4038                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4039
4040                 /* RFC1323: The window in SYN & SYN/ACK segments is
4041                  * never scaled.
4042                  */
4043                 tp->snd_wnd = ntohs(th->window);
4044                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4045
4046                 if (!tp->rx_opt.wscale_ok) {
4047                         tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4048                         tp->window_clamp = min(tp->window_clamp, 65535U);
4049                 }
4050
4051                 if (tp->rx_opt.saw_tstamp) {
4052                         tp->rx_opt.tstamp_ok       = 1;
4053                         tp->tcp_header_len =
4054                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4055                         tp->advmss          -= TCPOLEN_TSTAMP_ALIGNED;
4056                         tcp_store_ts_recent(tp);
4057                 } else {
4058                         tp->tcp_header_len = sizeof(struct tcphdr);
4059                 }
4060
4061                 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4062                         tp->rx_opt.sack_ok |= 2;
4063
4064                 tcp_sync_mss(sk, tp->pmtu_cookie);
4065                 tcp_initialize_rcv_mss(sk);
4066
4067                 /* Remember, tcp_poll() does not lock socket!
4068                  * Change state from SYN-SENT only after copied_seq
4069                  * is initialized. */
4070                 tp->copied_seq = tp->rcv_nxt;
4071                 mb();
4072                 tcp_set_state(sk, TCP_ESTABLISHED);
4073
4074                 /* Make sure socket is routed, for correct metrics.  */
4075                 tp->af_specific->rebuild_header(sk);
4076
4077                 tcp_init_metrics(sk);
4078
4079                 tcp_init_congestion_control(sk);
4080
4081                 /* Prevent spurious tcp_cwnd_restart() on first data
4082                  * packet.
4083                  */
4084                 tp->lsndtime = tcp_time_stamp;
4085
4086                 tcp_init_buffer_space(sk);
4087
4088                 if (sock_flag(sk, SOCK_KEEPOPEN))
4089                         inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
4090
4091                 if (!tp->rx_opt.snd_wscale)
4092                         __tcp_fast_path_on(tp, tp->snd_wnd);
4093                 else
4094                         tp->pred_flags = 0;
4095
4096                 if (!sock_flag(sk, SOCK_DEAD)) {
4097                         sk->sk_state_change(sk);
4098                         sk_wake_async(sk, 0, POLL_OUT);
4099                 }
4100
4101                 icsk = inet_csk(sk);
4102
4103                 if (sk->sk_write_pending ||
4104                     icsk->icsk_accept_queue.rskq_defer_accept ||
4105                     icsk->icsk_ack.pingpong) {
4106                         /* Save one ACK. Data will be ready after
4107                          * several ticks, if write_pending is set.
4108                          *
4109                          * It may be deleted, but with this feature tcpdumps
4110                          * look so _wonderfully_ clever, that I was not able
4111                          * to stand against the temptation 8)     --ANK
4112                          */
4113                         inet_csk_schedule_ack(sk);
4114                         icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4115                         icsk->icsk_ack.ato       = TCP_ATO_MIN;
4116                         tcp_incr_quickack(sk);
4117                         tcp_enter_quickack_mode(sk);
4118                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4119                                                   TCP_DELACK_MAX, TCP_RTO_MAX);
4120
4121 discard:
4122                         __kfree_skb(skb);
4123                         return 0;
4124                 } else {
4125                         tcp_send_ack(sk);
4126                 }
4127                 return -1;
4128         }
4129
4130         /* No ACK in the segment */
4131
4132         if (th->rst) {
4133                 /* rfc793:
4134                  * "If the RST bit is set
4135                  *
4136                  *      Otherwise (no ACK) drop the segment and return."
4137                  */
4138
4139                 goto discard_and_undo;
4140         }
4141
4142         /* PAWS check. */
4143         if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4144                 goto discard_and_undo;
4145
4146         if (th->syn) {
4147                 /* We see SYN without ACK. It is attempt of
4148                  * simultaneous connect with crossed SYNs.
4149                  * Particularly, it can be connect to self.
4150                  */
4151                 tcp_set_state(sk, TCP_SYN_RECV);
4152
4153                 if (tp->rx_opt.saw_tstamp) {
4154                         tp->rx_opt.tstamp_ok = 1;
4155                         tcp_store_ts_recent(tp);
4156                         tp->tcp_header_len =
4157                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4158                 } else {
4159                         tp->tcp_header_len = sizeof(struct tcphdr);
4160                 }
4161
4162                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4163                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4164
4165                 /* RFC1323: The window in SYN & SYN/ACK segments is
4166                  * never scaled.
4167                  */
4168                 tp->snd_wnd    = ntohs(th->window);
4169                 tp->snd_wl1    = TCP_SKB_CB(skb)->seq;
4170                 tp->max_window = tp->snd_wnd;
4171
4172                 TCP_ECN_rcv_syn(tp, th);
4173                 if (tp->ecn_flags&TCP_ECN_OK)
4174                         sock_set_flag(sk, SOCK_NO_LARGESEND);
4175
4176                 tcp_sync_mss(sk, tp->pmtu_cookie);
4177                 tcp_initialize_rcv_mss(sk);
4178
4179
4180                 tcp_send_synack(sk);
4181 #if 0
4182                 /* Note, we could accept data and URG from this segment.
4183                  * There are no obstacles to make this.
4184                  *
4185                  * However, if we ignore data in ACKless segments sometimes,
4186                  * we have no reasons to accept it sometimes.
4187                  * Also, seems the code doing it in step6 of tcp_rcv_state_process
4188                  * is not flawless. So, discard packet for sanity.
4189                  * Uncomment this return to process the data.
4190                  */
4191                 return -1;
4192 #else
4193                 goto discard;
4194 #endif
4195         }
4196         /* "fifth, if neither of the SYN or RST bits is set then
4197          * drop the segment and return."
4198          */
4199
4200 discard_and_undo:
4201         tcp_clear_options(&tp->rx_opt);
4202         tp->rx_opt.mss_clamp = saved_clamp;
4203         goto discard;
4204
4205 reset_and_undo:
4206         tcp_clear_options(&tp->rx_opt);
4207         tp->rx_opt.mss_clamp = saved_clamp;
4208         return 1;
4209 }
4210
4211
4212 /*
4213  *      This function implements the receiving procedure of RFC 793 for
4214  *      all states except ESTABLISHED and TIME_WAIT. 
4215  *      It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4216  *      address independent.
4217  */
4218         
4219 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4220                           struct tcphdr *th, unsigned len)
4221 {
4222         struct tcp_sock *tp = tcp_sk(sk);
4223         int queued = 0;
4224
4225         tp->rx_opt.saw_tstamp = 0;
4226
4227         switch (sk->sk_state) {
4228         case TCP_CLOSE:
4229                 goto discard;
4230
4231         case TCP_LISTEN:
4232                 if(th->ack)
4233                         return 1;
4234
4235                 if(th->rst)
4236                         goto discard;
4237
4238                 if(th->syn) {
4239                         if(tp->af_specific->conn_request(sk, skb) < 0)
4240                                 return 1;
4241
4242                         /* Now we have several options: In theory there is 
4243                          * nothing else in the frame. KA9Q has an option to 
4244                          * send data with the syn, BSD accepts data with the
4245                          * syn up to the [to be] advertised window and 
4246                          * Solaris 2.1 gives you a protocol error. For now 
4247                          * we just ignore it, that fits the spec precisely 
4248                          * and avoids incompatibilities. It would be nice in
4249                          * future to drop through and process the data.
4250                          *
4251                          * Now that TTCP is starting to be used we ought to 
4252                          * queue this data.
4253                          * But, this leaves one open to an easy denial of
4254                          * service attack, and SYN cookies can't defend
4255                          * against this problem. So, we drop the data
4256                          * in the interest of security over speed.
4257                          */
4258                         goto discard;
4259                 }
4260                 goto discard;
4261
4262         case TCP_SYN_SENT:
4263                 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4264                 if (queued >= 0)
4265                         return queued;
4266
4267                 /* Do step6 onward by hand. */
4268                 tcp_urg(sk, skb, th);
4269                 __kfree_skb(skb);
4270                 tcp_data_snd_check(sk, tp);
4271                 return 0;
4272         }
4273
4274         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4275             tcp_paws_discard(sk, skb)) {
4276                 if (!th->rst) {
4277                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4278                         tcp_send_dupack(sk, skb);
4279                         goto discard;
4280                 }
4281                 /* Reset is accepted even if it did not pass PAWS. */
4282         }
4283
4284         /* step 1: check sequence number */
4285         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4286                 if (!th->rst)
4287                         tcp_send_dupack(sk, skb);
4288                 goto discard;
4289         }
4290
4291         /* step 2: check RST bit */
4292         if(th->rst) {
4293                 tcp_reset(sk);
4294                 goto discard;
4295         }
4296
4297         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4298
4299         /* step 3: check security and precedence [ignored] */
4300
4301         /*      step 4:
4302          *
4303          *      Check for a SYN in window.
4304          */
4305         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4306                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4307                 tcp_reset(sk);
4308                 return 1;
4309         }
4310
4311         /* step 5: check the ACK field */
4312         if (th->ack) {
4313                 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4314
4315                 switch(sk->sk_state) {
4316                 case TCP_SYN_RECV:
4317                         if (acceptable) {
4318                                 tp->copied_seq = tp->rcv_nxt;
4319                                 mb();
4320                                 tcp_set_state(sk, TCP_ESTABLISHED);
4321                                 sk->sk_state_change(sk);
4322
4323                                 /* Note, that this wakeup is only for marginal
4324                                  * crossed SYN case. Passively open sockets
4325                                  * are not waked up, because sk->sk_sleep ==
4326                                  * NULL and sk->sk_socket == NULL.
4327                                  */
4328                                 if (sk->sk_socket) {
4329                                         sk_wake_async(sk,0,POLL_OUT);
4330                                 }
4331
4332                                 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4333                                 tp->snd_wnd = ntohs(th->window) <<
4334                                               tp->rx_opt.snd_wscale;
4335                                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4336                                             TCP_SKB_CB(skb)->seq);
4337
4338                                 /* tcp_ack considers this ACK as duplicate
4339                                  * and does not calculate rtt.
4340                                  * Fix it at least with timestamps.
4341                                  */
4342                                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4343                                     !tp->srtt)
4344                                         tcp_ack_saw_tstamp(sk, 0);
4345
4346                                 if (tp->rx_opt.tstamp_ok)
4347                                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4348
4349                                 /* Make sure socket is routed, for
4350                                  * correct metrics.
4351                                  */
4352                                 tp->af_specific->rebuild_header(sk);
4353
4354                                 tcp_init_metrics(sk);
4355
4356                                 tcp_init_congestion_control(sk);
4357
4358                                 /* Prevent spurious tcp_cwnd_restart() on
4359                                  * first data packet.
4360                                  */
4361                                 tp->lsndtime = tcp_time_stamp;
4362
4363                                 tcp_initialize_rcv_mss(sk);
4364                                 tcp_init_buffer_space(sk);
4365                                 tcp_fast_path_on(tp);
4366                         } else {
4367                                 return 1;
4368                         }
4369                         break;
4370
4371                 case TCP_FIN_WAIT1:
4372                         if (tp->snd_una == tp->write_seq) {
4373                                 tcp_set_state(sk, TCP_FIN_WAIT2);
4374                                 sk->sk_shutdown |= SEND_SHUTDOWN;
4375                                 dst_confirm(sk->sk_dst_cache);
4376
4377                                 if (!sock_flag(sk, SOCK_DEAD))
4378                                         /* Wake up lingering close() */
4379                                         sk->sk_state_change(sk);
4380                                 else {
4381                                         int tmo;
4382
4383                                         if (tp->linger2 < 0 ||
4384                                             (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4385                                              after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4386                                                 tcp_done(sk);
4387                                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4388                                                 return 1;
4389                                         }
4390
4391                                         tmo = tcp_fin_time(sk);
4392                                         if (tmo > TCP_TIMEWAIT_LEN) {
4393                                                 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
4394                                         } else if (th->fin || sock_owned_by_user(sk)) {
4395                                                 /* Bad case. We could lose such FIN otherwise.
4396                                                  * It is not a big problem, but it looks confusing
4397                                                  * and not so rare event. We still can lose it now,
4398                                                  * if it spins in bh_lock_sock(), but it is really
4399                                                  * marginal case.
4400                                                  */
4401                                                 inet_csk_reset_keepalive_timer(sk, tmo);
4402                                         } else {
4403                                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4404                                                 goto discard;
4405                                         }
4406                                 }
4407                         }
4408                         break;
4409
4410                 case TCP_CLOSING:
4411                         if (tp->snd_una == tp->write_seq) {
4412                                 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4413                                 goto discard;
4414                         }
4415                         break;
4416
4417                 case TCP_LAST_ACK:
4418                         if (tp->snd_una == tp->write_seq) {
4419                                 tcp_update_metrics(sk);
4420                                 tcp_done(sk);
4421                                 goto discard;
4422                         }
4423                         break;
4424                 }
4425         } else
4426                 goto discard;
4427
4428         /* step 6: check the URG bit */
4429         tcp_urg(sk, skb, th);
4430
4431         /* step 7: process the segment text */
4432         switch (sk->sk_state) {
4433         case TCP_CLOSE_WAIT:
4434         case TCP_CLOSING:
4435         case TCP_LAST_ACK:
4436                 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4437                         break;
4438         case TCP_FIN_WAIT1:
4439         case TCP_FIN_WAIT2:
4440                 /* RFC 793 says to queue data in these states,
4441                  * RFC 1122 says we MUST send a reset. 
4442                  * BSD 4.4 also does reset.
4443                  */
4444                 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4445                         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4446                             after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4447                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4448                                 tcp_reset(sk);
4449                                 return 1;
4450                         }
4451                 }
4452                 /* Fall through */
4453         case TCP_ESTABLISHED: 
4454                 tcp_data_queue(sk, skb);
4455                 queued = 1;
4456                 break;
4457         }
4458
4459         /* tcp_data could move socket to TIME-WAIT */
4460         if (sk->sk_state != TCP_CLOSE) {
4461                 tcp_data_snd_check(sk, tp);
4462                 tcp_ack_snd_check(sk);
4463         }
4464
4465         if (!queued) { 
4466 discard:
4467                 __kfree_skb(skb);
4468         }
4469         return 0;
4470 }
4471
4472 EXPORT_SYMBOL(sysctl_tcp_ecn);
4473 EXPORT_SYMBOL(sysctl_tcp_reordering);
4474 EXPORT_SYMBOL(sysctl_tcp_abc);
4475 EXPORT_SYMBOL(tcp_parse_options);
4476 EXPORT_SYMBOL(tcp_rcv_established);
4477 EXPORT_SYMBOL(tcp_rcv_state_process);