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