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