Merge branch 'locks' of git://linux-nfs.org/~bfields/linux
[linux-2.6] / net / dccp / ackvec.c
1 /*
2  *  net/dccp/ackvec.c
3  *
4  *  An implementation of the DCCP protocol
5  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
6  *
7  *      This program is free software; you can redistribute it and/or modify it
8  *      under the terms of the GNU General Public License as published by the
9  *      Free Software Foundation; version 2 of the License;
10  */
11
12 #include "ackvec.h"
13 #include "dccp.h"
14
15 #include <linux/dccp.h>
16 #include <linux/init.h>
17 #include <linux/errno.h>
18 #include <linux/kernel.h>
19 #include <linux/skbuff.h>
20 #include <linux/slab.h>
21
22 #include <net/sock.h>
23
24 static struct kmem_cache *dccp_ackvec_slab;
25 static struct kmem_cache *dccp_ackvec_record_slab;
26
27 static struct dccp_ackvec_record *dccp_ackvec_record_new(void)
28 {
29         struct dccp_ackvec_record *avr =
30                         kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
31
32         if (avr != NULL)
33                 INIT_LIST_HEAD(&avr->dccpavr_node);
34
35         return avr;
36 }
37
38 static void dccp_ackvec_record_delete(struct dccp_ackvec_record *avr)
39 {
40         if (unlikely(avr == NULL))
41                 return;
42         /* Check if deleting a linked record */
43         WARN_ON(!list_empty(&avr->dccpavr_node));
44         kmem_cache_free(dccp_ackvec_record_slab, avr);
45 }
46
47 static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
48                                    struct dccp_ackvec_record *avr)
49 {
50         /*
51          * AVRs are sorted by seqno. Since we are sending them in order, we
52          * just add the AVR at the head of the list.
53          * -sorbo.
54          */
55         if (!list_empty(&av->dccpav_records)) {
56                 const struct dccp_ackvec_record *head =
57                                         list_entry(av->dccpav_records.next,
58                                                    struct dccp_ackvec_record,
59                                                    dccpavr_node);
60                 BUG_ON(before48(avr->dccpavr_ack_seqno,
61                                 head->dccpavr_ack_seqno));
62         }
63
64         list_add(&avr->dccpavr_node, &av->dccpav_records);
65 }
66
67 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
68 {
69         struct dccp_sock *dp = dccp_sk(sk);
70         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
71         /* Figure out how many options do we need to represent the ackvec */
72         const u16 nr_opts = DIV_ROUND_UP(av->dccpav_vec_len,
73                                          DCCP_MAX_ACKVEC_OPT_LEN);
74         u16 len = av->dccpav_vec_len + 2 * nr_opts, i;
75         u32 elapsed_time;
76         const unsigned char *tail, *from;
77         unsigned char *to;
78         struct dccp_ackvec_record *avr;
79         suseconds_t delta;
80
81         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
82                 return -1;
83
84         delta = ktime_us_delta(ktime_get_real(), av->dccpav_time);
85         elapsed_time = delta / 10;
86
87         if (elapsed_time != 0 &&
88             dccp_insert_option_elapsed_time(sk, skb, elapsed_time))
89                 return -1;
90
91         avr = dccp_ackvec_record_new();
92         if (avr == NULL)
93                 return -1;
94
95         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
96
97         to   = skb_push(skb, len);
98         len  = av->dccpav_vec_len;
99         from = av->dccpav_buf + av->dccpav_buf_head;
100         tail = av->dccpav_buf + DCCP_MAX_ACKVEC_LEN;
101
102         for (i = 0; i < nr_opts; ++i) {
103                 int copylen = len;
104
105                 if (len > DCCP_MAX_ACKVEC_OPT_LEN)
106                         copylen = DCCP_MAX_ACKVEC_OPT_LEN;
107
108                 *to++ = DCCPO_ACK_VECTOR_0;
109                 *to++ = copylen + 2;
110
111                 /* Check if buf_head wraps */
112                 if (from + copylen > tail) {
113                         const u16 tailsize = tail - from;
114
115                         memcpy(to, from, tailsize);
116                         to      += tailsize;
117                         len     -= tailsize;
118                         copylen -= tailsize;
119                         from    = av->dccpav_buf;
120                 }
121
122                 memcpy(to, from, copylen);
123                 from += copylen;
124                 to   += copylen;
125                 len  -= copylen;
126         }
127
128         /*
129          *      From RFC 4340, A.2:
130          *
131          *      For each acknowledgement it sends, the HC-Receiver will add an
132          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
133          *      sequence number it used for the ack packet; ack_ptr will equal
134          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
135          *      equal buf_nonce.
136          */
137         avr->dccpavr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
138         avr->dccpavr_ack_ptr   = av->dccpav_buf_head;
139         avr->dccpavr_ack_ackno = av->dccpav_buf_ackno;
140         avr->dccpavr_ack_nonce = av->dccpav_buf_nonce;
141         avr->dccpavr_sent_len  = av->dccpav_vec_len;
142
143         dccp_ackvec_insert_avr(av, avr);
144
145         dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
146                       "ack_ackno=%llu\n",
147                       dccp_role(sk), avr->dccpavr_sent_len,
148                       (unsigned long long)avr->dccpavr_ack_seqno,
149                       (unsigned long long)avr->dccpavr_ack_ackno);
150         return 0;
151 }
152
153 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
154 {
155         struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
156
157         if (av != NULL) {
158                 av->dccpav_buf_head     = DCCP_MAX_ACKVEC_LEN - 1;
159                 av->dccpav_buf_ackno    = UINT48_MAX + 1;
160                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
161                 av->dccpav_time      = ktime_set(0, 0);
162                 av->dccpav_vec_len      = 0;
163                 INIT_LIST_HEAD(&av->dccpav_records);
164         }
165
166         return av;
167 }
168
169 void dccp_ackvec_free(struct dccp_ackvec *av)
170 {
171         if (unlikely(av == NULL))
172                 return;
173
174         if (!list_empty(&av->dccpav_records)) {
175                 struct dccp_ackvec_record *avr, *next;
176
177                 list_for_each_entry_safe(avr, next, &av->dccpav_records,
178                                          dccpavr_node) {
179                         list_del_init(&avr->dccpavr_node);
180                         dccp_ackvec_record_delete(avr);
181                 }
182         }
183
184         kmem_cache_free(dccp_ackvec_slab, av);
185 }
186
187 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
188                                    const u32 index)
189 {
190         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
191 }
192
193 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
194                                  const u32 index)
195 {
196         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
197 }
198
199 /*
200  * If several packets are missing, the HC-Receiver may prefer to enter multiple
201  * bytes with run length 0, rather than a single byte with a larger run length;
202  * this simplifies table updates if one of the missing packets arrives.
203  */
204 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
205                                                  const unsigned int packets,
206                                                  const unsigned char state)
207 {
208         unsigned int gap;
209         long new_head;
210
211         if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
212                 return -ENOBUFS;
213
214         gap      = packets - 1;
215         new_head = av->dccpav_buf_head - packets;
216
217         if (new_head < 0) {
218                 if (gap > 0) {
219                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
220                                gap + new_head + 1);
221                         gap = -new_head;
222                 }
223                 new_head += DCCP_MAX_ACKVEC_LEN;
224         }
225
226         av->dccpav_buf_head = new_head;
227
228         if (gap > 0)
229                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
230                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
231
232         av->dccpav_buf[av->dccpav_buf_head] = state;
233         av->dccpav_vec_len += packets;
234         return 0;
235 }
236
237 /*
238  * Implements the RFC 4340, Appendix A
239  */
240 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
241                     const u64 ackno, const u8 state)
242 {
243         /*
244          * Check at the right places if the buffer is full, if it is, tell the
245          * caller to start dropping packets till the HC-Sender acks our ACK
246          * vectors, when we will free up space in dccpav_buf.
247          *
248          * We may well decide to do buffer compression, etc, but for now lets
249          * just drop.
250          *
251          * From Appendix A.1.1 (`New Packets'):
252          *
253          *      Of course, the circular buffer may overflow, either when the
254          *      HC-Sender is sending data at a very high rate, when the
255          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
256          *      or when the HC-Sender is forgetting to acknowledge those acks
257          *      (so the HC-Receiver is unable to clean up old state). In this
258          *      case, the HC-Receiver should either compress the buffer (by
259          *      increasing run lengths when possible), transfer its state to
260          *      a larger buffer, or, as a last resort, drop all received
261          *      packets, without processing them whatsoever, until its buffer
262          *      shrinks again.
263          */
264
265         /* See if this is the first ackno being inserted */
266         if (av->dccpav_vec_len == 0) {
267                 av->dccpav_buf[av->dccpav_buf_head] = state;
268                 av->dccpav_vec_len = 1;
269         } else if (after48(ackno, av->dccpav_buf_ackno)) {
270                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
271                                                    ackno);
272
273                 /*
274                  * Look if the state of this packet is the same as the
275                  * previous ackno and if so if we can bump the head len.
276                  */
277                 if (delta == 1 &&
278                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
279                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
280                      DCCP_ACKVEC_LEN_MASK))
281                         av->dccpav_buf[av->dccpav_buf_head]++;
282                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
283                         return -ENOBUFS;
284         } else {
285                 /*
286                  * A.1.2.  Old Packets
287                  *
288                  *      When a packet with Sequence Number S <= buf_ackno
289                  *      arrives, the HC-Receiver will scan the table for
290                  *      the byte corresponding to S. (Indexing structures
291                  *      could reduce the complexity of this scan.)
292                  */
293                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
294                 u32 index = av->dccpav_buf_head;
295
296                 while (1) {
297                         const u8 len = dccp_ackvec_len(av, index);
298                         const u8 state = dccp_ackvec_state(av, index);
299                         /*
300                          * valid packets not yet in dccpav_buf have a reserved
301                          * entry, with a len equal to 0.
302                          */
303                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
304                             len == 0 && delta == 0) { /* Found our
305                                                          reserved seat! */
306                                 dccp_pr_debug("Found %llu reserved seat!\n",
307                                               (unsigned long long)ackno);
308                                 av->dccpav_buf[index] = state;
309                                 goto out;
310                         }
311                         /* len == 0 means one packet */
312                         if (delta < len + 1)
313                                 goto out_duplicate;
314
315                         delta -= len + 1;
316                         if (++index == DCCP_MAX_ACKVEC_LEN)
317                                 index = 0;
318                 }
319         }
320
321         av->dccpav_buf_ackno = ackno;
322         av->dccpav_time = ktime_get_real();
323 out:
324         return 0;
325
326 out_duplicate:
327         /* Duplicate packet */
328         dccp_pr_debug("Received a dup or already considered lost "
329                       "packet: %llu\n", (unsigned long long)ackno);
330         return -EILSEQ;
331 }
332
333 #ifdef CONFIG_IP_DCCP_DEBUG
334 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
335 {
336         dccp_pr_debug_cat("ACK vector len=%d, ackno=%llu |", len,
337                          (unsigned long long)ackno);
338
339         while (len--) {
340                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
341                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
342
343                 dccp_pr_debug_cat("%d,%d|", state, rl);
344                 ++vector;
345         }
346
347         dccp_pr_debug_cat("\n");
348 }
349
350 void dccp_ackvec_print(const struct dccp_ackvec *av)
351 {
352         dccp_ackvector_print(av->dccpav_buf_ackno,
353                              av->dccpav_buf + av->dccpav_buf_head,
354                              av->dccpav_vec_len);
355 }
356 #endif
357
358 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
359                                      struct dccp_ackvec_record *avr)
360 {
361         struct dccp_ackvec_record *next;
362
363         /* sort out vector length */
364         if (av->dccpav_buf_head <= avr->dccpavr_ack_ptr)
365                 av->dccpav_vec_len = avr->dccpavr_ack_ptr - av->dccpav_buf_head;
366         else
367                 av->dccpav_vec_len = DCCP_MAX_ACKVEC_LEN - 1
368                                      - av->dccpav_buf_head
369                                      + avr->dccpavr_ack_ptr;
370
371         /* free records */
372         list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
373                                       dccpavr_node) {
374                 list_del_init(&avr->dccpavr_node);
375                 dccp_ackvec_record_delete(avr);
376         }
377 }
378
379 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
380                                  const u64 ackno)
381 {
382         struct dccp_ackvec_record *avr;
383
384         /*
385          * If we traverse backwards, it should be faster when we have large
386          * windows. We will be receiving ACKs for stuff we sent a while back
387          * -sorbo.
388          */
389         list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
390                 if (ackno == avr->dccpavr_ack_seqno) {
391                         dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
392                                       "ack_ackno=%llu, ACKED!\n",
393                                       dccp_role(sk), 1,
394                                       (unsigned long long)avr->dccpavr_ack_seqno,
395                                       (unsigned long long)avr->dccpavr_ack_ackno);
396                         dccp_ackvec_throw_record(av, avr);
397                         break;
398                 } else if (avr->dccpavr_ack_seqno > ackno)
399                         break; /* old news */
400         }
401 }
402
403 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
404                                             struct sock *sk, u64 *ackno,
405                                             const unsigned char len,
406                                             const unsigned char *vector)
407 {
408         unsigned char i;
409         struct dccp_ackvec_record *avr;
410
411         /* Check if we actually sent an ACK vector */
412         if (list_empty(&av->dccpav_records))
413                 return;
414
415         i = len;
416         /*
417          * XXX
418          * I think it might be more efficient to work backwards. See comment on
419          * rcv_ackno. -sorbo.
420          */
421         avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
422                          dccpavr_node);
423         while (i--) {
424                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
425                 u64 ackno_end_rl;
426
427                 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
428
429                 /*
430                  * If our AVR sequence number is greater than the ack, go
431                  * forward in the AVR list until it is not so.
432                  */
433                 list_for_each_entry_from(avr, &av->dccpav_records,
434                                          dccpavr_node) {
435                         if (!after48(avr->dccpavr_ack_seqno, *ackno))
436                                 goto found;
437                 }
438                 /* End of the dccpav_records list, not found, exit */
439                 break;
440 found:
441                 if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, *ackno)) {
442                         const u8 state = *vector & DCCP_ACKVEC_STATE_MASK;
443                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
444                                 dccp_pr_debug("%s ACK vector 0, len=%d, "
445                                               "ack_seqno=%llu, ack_ackno=%llu, "
446                                               "ACKED!\n",
447                                               dccp_role(sk), len,
448                                               (unsigned long long)
449                                               avr->dccpavr_ack_seqno,
450                                               (unsigned long long)
451                                               avr->dccpavr_ack_ackno);
452                                 dccp_ackvec_throw_record(av, avr);
453                                 break;
454                         }
455                         /*
456                          * If it wasn't received, continue scanning... we might
457                          * find another one.
458                          */
459                 }
460
461                 dccp_set_seqno(ackno, ackno_end_rl - 1);
462                 ++vector;
463         }
464 }
465
466 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
467                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
468 {
469         if (len > DCCP_MAX_ACKVEC_OPT_LEN)
470                 return -1;
471
472         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
473         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
474                                         ackno, len, value);
475         return 0;
476 }
477
478 int __init dccp_ackvec_init(void)
479 {
480         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
481                                              sizeof(struct dccp_ackvec), 0,
482                                              SLAB_HWCACHE_ALIGN, NULL);
483         if (dccp_ackvec_slab == NULL)
484                 goto out_err;
485
486         dccp_ackvec_record_slab =
487                         kmem_cache_create("dccp_ackvec_record",
488                                           sizeof(struct dccp_ackvec_record),
489                                           0, SLAB_HWCACHE_ALIGN, NULL);
490         if (dccp_ackvec_record_slab == NULL)
491                 goto out_destroy_slab;
492
493         return 0;
494
495 out_destroy_slab:
496         kmem_cache_destroy(dccp_ackvec_slab);
497         dccp_ackvec_slab = NULL;
498 out_err:
499         DCCP_CRIT("Unable to create Ack Vector slab cache");
500         return -ENOBUFS;
501 }
502
503 void dccp_ackvec_exit(void)
504 {
505         if (dccp_ackvec_slab != NULL) {
506                 kmem_cache_destroy(dccp_ackvec_slab);
507                 dccp_ackvec_slab = NULL;
508         }
509         if (dccp_ackvec_record_slab != NULL) {
510                 kmem_cache_destroy(dccp_ackvec_record_slab);
511                 dccp_ackvec_record_slab = NULL;
512         }
513 }