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ae31c339 ACM |
1 | /* |
2 | * net/dccp/ackvec.c | |
3 | * | |
f17a37c9 GR |
4 | * An implementation of Ack Vectors for the DCCP protocol |
5 | * Copyright (c) 2007 University of Aberdeen, Scotland, UK | |
ae31c339 ACM |
6 | * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net> |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify it | |
9 | * under the terms of the GNU General Public License as published by the | |
10 | * Free Software Foundation; version 2 of the License; | |
11 | */ | |
ae31c339 | 12 | #include "dccp.h" |
9b07ef5d | 13 | #include <linux/kernel.h> |
9b07ef5d | 14 | #include <linux/slab.h> |
ae31c339 | 15 | |
e18b890b CL |
16 | static struct kmem_cache *dccp_ackvec_slab; |
17 | static struct kmem_cache *dccp_ackvec_record_slab; | |
02bcf28c | 18 | |
f17a37c9 | 19 | struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority) |
02bcf28c | 20 | { |
f17a37c9 GR |
21 | struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority); |
22 | ||
23 | if (av != NULL) { | |
b3d14bff | 24 | av->av_buf_head = av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1; |
f17a37c9 GR |
25 | INIT_LIST_HEAD(&av->av_records); |
26 | } | |
27 | return av; | |
28 | } | |
02bcf28c | 29 | |
f17a37c9 GR |
30 | static void dccp_ackvec_purge_records(struct dccp_ackvec *av) |
31 | { | |
32 | struct dccp_ackvec_record *cur, *next; | |
02bcf28c | 33 | |
f17a37c9 GR |
34 | list_for_each_entry_safe(cur, next, &av->av_records, avr_node) |
35 | kmem_cache_free(dccp_ackvec_record_slab, cur); | |
36 | INIT_LIST_HEAD(&av->av_records); | |
02bcf28c AB |
37 | } |
38 | ||
f17a37c9 | 39 | void dccp_ackvec_free(struct dccp_ackvec *av) |
02bcf28c | 40 | { |
f17a37c9 GR |
41 | if (likely(av != NULL)) { |
42 | dccp_ackvec_purge_records(av); | |
43 | kmem_cache_free(dccp_ackvec_slab, av); | |
44 | } | |
02bcf28c AB |
45 | } |
46 | ||
7d870936 GR |
47 | /** |
48 | * dccp_ackvec_update_records - Record information about sent Ack Vectors | |
49 | * @av: Ack Vector records to update | |
50 | * @seqno: Sequence number of the packet carrying the Ack Vector just sent | |
51 | * @nonce_sum: The sum of all buffer nonces contained in the Ack Vector | |
52 | */ | |
53 | int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum) | |
ae31c339 | 54 | { |
02bcf28c AB |
55 | struct dccp_ackvec_record *avr; |
56 | ||
f17a37c9 | 57 | avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC); |
2d0817d1 | 58 | if (avr == NULL) |
7d870936 | 59 | return -ENOBUFS; |
ae31c339 | 60 | |
7d870936 | 61 | avr->avr_ack_seqno = seqno; |
f17a37c9 GR |
62 | avr->avr_ack_ptr = av->av_buf_head; |
63 | avr->avr_ack_ackno = av->av_buf_ackno; | |
7d870936 | 64 | avr->avr_ack_nonce = nonce_sum; |
f17a37c9 | 65 | avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head); |
b3d14bff GR |
66 | /* |
67 | * When the buffer overflows, we keep no more than one record. This is | |
68 | * the simplest way of disambiguating sender-Acks dating from before the | |
69 | * overflow from sender-Acks which refer to after the overflow; a simple | |
70 | * solution is preferable here since we are handling an exception. | |
71 | */ | |
72 | if (av->av_overflow) | |
73 | dccp_ackvec_purge_records(av); | |
7d870936 GR |
74 | /* |
75 | * Since GSS is incremented for each packet, the list is automatically | |
76 | * arranged in descending order of @ack_seqno. | |
77 | */ | |
78 | list_add(&avr->avr_node, &av->av_records); | |
02bcf28c | 79 | |
7d870936 | 80 | dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n", |
a47c5104 | 81 | (unsigned long long)avr->avr_ack_seqno, |
7d870936 GR |
82 | (unsigned long long)avr->avr_ack_ackno, |
83 | avr->avr_ack_runlen); | |
02bcf28c | 84 | return 0; |
ae31c339 ACM |
85 | } |
86 | ||
5753fdfe GR |
87 | static struct dccp_ackvec_record *dccp_ackvec_lookup(struct list_head *av_list, |
88 | const u64 ackno) | |
89 | { | |
90 | struct dccp_ackvec_record *avr; | |
91 | /* | |
92 | * Exploit that records are inserted in descending order of sequence | |
93 | * number, start with the oldest record first. If @ackno is `before' | |
94 | * the earliest ack_ackno, the packet is too old to be considered. | |
95 | */ | |
96 | list_for_each_entry_reverse(avr, av_list, avr_node) { | |
97 | if (avr->avr_ack_seqno == ackno) | |
98 | return avr; | |
99 | if (before48(ackno, avr->avr_ack_seqno)) | |
100 | break; | |
101 | } | |
102 | return NULL; | |
103 | } | |
104 | ||
b3d14bff GR |
105 | /* |
106 | * Buffer index and length computation using modulo-buffersize arithmetic. | |
107 | * Note that, as pointers move from right to left, head is `before' tail. | |
108 | */ | |
109 | static inline u16 __ackvec_idx_add(const u16 a, const u16 b) | |
110 | { | |
111 | return (a + b) % DCCPAV_MAX_ACKVEC_LEN; | |
112 | } | |
113 | ||
114 | static inline u16 __ackvec_idx_sub(const u16 a, const u16 b) | |
115 | { | |
116 | return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b); | |
117 | } | |
118 | ||
119 | u16 dccp_ackvec_buflen(const struct dccp_ackvec *av) | |
120 | { | |
121 | if (unlikely(av->av_overflow)) | |
122 | return DCCPAV_MAX_ACKVEC_LEN; | |
123 | return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head); | |
124 | } | |
125 | ||
38024086 GR |
126 | /** |
127 | * dccp_ackvec_update_old - Update previous state as per RFC 4340, 11.4.1 | |
128 | * @av: non-empty buffer to update | |
129 | * @distance: negative or zero distance of @seqno from buf_ackno downward | |
130 | * @seqno: the (old) sequence number whose record is to be updated | |
131 | * @state: state in which packet carrying @seqno was received | |
132 | */ | |
133 | static void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance, | |
134 | u64 seqno, enum dccp_ackvec_states state) | |
135 | { | |
136 | u16 ptr = av->av_buf_head; | |
137 | ||
138 | BUG_ON(distance > 0); | |
139 | if (unlikely(dccp_ackvec_is_empty(av))) | |
140 | return; | |
141 | ||
142 | do { | |
143 | u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr); | |
144 | ||
145 | if (distance + runlen >= 0) { | |
146 | /* | |
147 | * Only update the state if packet has not been received | |
148 | * yet. This is OK as per the second table in RFC 4340, | |
149 | * 11.4.1; i.e. here we are using the following table: | |
150 | * RECEIVED | |
151 | * 0 1 3 | |
152 | * S +---+---+---+ | |
153 | * T 0 | 0 | 0 | 0 | | |
154 | * O +---+---+---+ | |
155 | * R 1 | 1 | 1 | 1 | | |
156 | * E +---+---+---+ | |
157 | * D 3 | 0 | 1 | 3 | | |
158 | * +---+---+---+ | |
159 | * The "Not Received" state was set by reserve_seats(). | |
160 | */ | |
161 | if (av->av_buf[ptr] == DCCPAV_NOT_RECEIVED) | |
162 | av->av_buf[ptr] = state; | |
163 | else | |
164 | dccp_pr_debug("Not changing %llu state to %u\n", | |
165 | (unsigned long long)seqno, state); | |
166 | break; | |
167 | } | |
168 | ||
169 | distance += runlen + 1; | |
170 | ptr = __ackvec_idx_add(ptr, 1); | |
171 | ||
172 | } while (ptr != av->av_buf_tail); | |
173 | } | |
174 | ||
175 | /* Mark @num entries after buf_head as "Not yet received". */ | |
176 | static void dccp_ackvec_reserve_seats(struct dccp_ackvec *av, u16 num) | |
177 | { | |
178 | u16 start = __ackvec_idx_add(av->av_buf_head, 1), | |
179 | len = DCCPAV_MAX_ACKVEC_LEN - start; | |
180 | ||
181 | /* check for buffer wrap-around */ | |
182 | if (num > len) { | |
183 | memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, len); | |
184 | start = 0; | |
185 | num -= len; | |
186 | } | |
187 | if (num) | |
188 | memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, num); | |
189 | } | |
190 | ||
191 | /** | |
192 | * dccp_ackvec_add_new - Record one or more new entries in Ack Vector buffer | |
193 | * @av: container of buffer to update (can be empty or non-empty) | |
194 | * @num_packets: number of packets to register (must be >= 1) | |
195 | * @seqno: sequence number of the first packet in @num_packets | |
196 | * @state: state in which packet carrying @seqno was received | |
197 | */ | |
198 | static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets, | |
199 | u64 seqno, enum dccp_ackvec_states state) | |
200 | { | |
201 | u32 num_cells = num_packets; | |
202 | ||
203 | if (num_packets > DCCPAV_BURST_THRESH) { | |
204 | u32 lost_packets = num_packets - 1; | |
205 | ||
206 | DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets); | |
207 | /* | |
208 | * We received 1 packet and have a loss of size "num_packets-1" | |
209 | * which we squeeze into num_cells-1 rather than reserving an | |
210 | * entire byte for each lost packet. | |
211 | * The reason is that the vector grows in O(burst_length); when | |
212 | * it grows too large there will no room left for the payload. | |
213 | * This is a trade-off: if a few packets out of the burst show | |
214 | * up later, their state will not be changed; it is simply too | |
215 | * costly to reshuffle/reallocate/copy the buffer each time. | |
216 | * Should such problems persist, we will need to switch to a | |
217 | * different underlying data structure. | |
218 | */ | |
219 | for (num_packets = num_cells = 1; lost_packets; ++num_cells) { | |
220 | u8 len = min(lost_packets, (u32)DCCPAV_MAX_RUNLEN); | |
221 | ||
222 | av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1); | |
223 | av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED | len; | |
224 | ||
225 | lost_packets -= len; | |
226 | } | |
227 | } | |
228 | ||
229 | if (num_cells + dccp_ackvec_buflen(av) >= DCCPAV_MAX_ACKVEC_LEN) { | |
230 | DCCP_CRIT("Ack Vector buffer overflow: dropping old entries\n"); | |
231 | av->av_overflow = true; | |
232 | } | |
233 | ||
234 | av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, num_packets); | |
235 | if (av->av_overflow) | |
236 | av->av_buf_tail = av->av_buf_head; | |
237 | ||
238 | av->av_buf[av->av_buf_head] = state; | |
239 | av->av_buf_ackno = seqno; | |
240 | ||
241 | if (num_packets > 1) | |
242 | dccp_ackvec_reserve_seats(av, num_packets - 1); | |
243 | } | |
244 | ||
245 | /** | |
246 | * dccp_ackvec_input - Register incoming packet in the buffer | |
247 | */ | |
248 | void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb) | |
249 | { | |
250 | u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq; | |
251 | enum dccp_ackvec_states state = DCCPAV_RECEIVED; | |
252 | ||
253 | if (dccp_ackvec_is_empty(av)) { | |
254 | dccp_ackvec_add_new(av, 1, seqno, state); | |
255 | av->av_tail_ackno = seqno; | |
256 | ||
257 | } else { | |
258 | s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno); | |
259 | u8 *current_head = av->av_buf + av->av_buf_head; | |
260 | ||
261 | if (num_packets == 1 && | |
262 | dccp_ackvec_state(current_head) == state && | |
263 | dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) { | |
264 | ||
265 | *current_head += 1; | |
266 | av->av_buf_ackno = seqno; | |
267 | ||
268 | } else if (num_packets > 0) { | |
269 | dccp_ackvec_add_new(av, num_packets, seqno, state); | |
270 | } else { | |
271 | dccp_ackvec_update_old(av, num_packets, seqno, state); | |
272 | } | |
273 | } | |
274 | } | |
275 | ||
5753fdfe GR |
276 | /** |
277 | * dccp_ackvec_clear_state - Perform house-keeping / garbage-collection | |
278 | * This routine is called when the peer acknowledges the receipt of Ack Vectors | |
279 | * up to and including @ackno. While based on on section A.3 of RFC 4340, here | |
280 | * are additional precautions to prevent corrupted buffer state. In particular, | |
281 | * we use tail_ackno to identify outdated records; it always marks the earliest | |
282 | * packet of group (2) in 11.4.2. | |
283 | */ | |
284 | void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno) | |
285 | { | |
286 | struct dccp_ackvec_record *avr, *next; | |
287 | u8 runlen_now, eff_runlen; | |
288 | s64 delta; | |
289 | ||
290 | avr = dccp_ackvec_lookup(&av->av_records, ackno); | |
291 | if (avr == NULL) | |
292 | return; | |
293 | /* | |
294 | * Deal with outdated acknowledgments: this arises when e.g. there are | |
295 | * several old records and the acks from the peer come in slowly. In | |
296 | * that case we may still have records that pre-date tail_ackno. | |
297 | */ | |
298 | delta = dccp_delta_seqno(av->av_tail_ackno, avr->avr_ack_ackno); | |
299 | if (delta < 0) | |
300 | goto free_records; | |
301 | /* | |
302 | * Deal with overlapping Ack Vectors: don't subtract more than the | |
303 | * number of packets between tail_ackno and ack_ackno. | |
304 | */ | |
305 | eff_runlen = delta < avr->avr_ack_runlen ? delta : avr->avr_ack_runlen; | |
306 | ||
307 | runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr); | |
308 | /* | |
309 | * The run length of Ack Vector cells does not decrease over time. If | |
310 | * the run length is the same as at the time the Ack Vector was sent, we | |
311 | * free the ack_ptr cell. That cell can however not be freed if the run | |
312 | * length has increased: in this case we need to move the tail pointer | |
313 | * backwards (towards higher indices), to its next-oldest neighbour. | |
314 | */ | |
315 | if (runlen_now > eff_runlen) { | |
316 | ||
317 | av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1; | |
318 | av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1); | |
319 | ||
320 | /* This move may not have cleared the overflow flag. */ | |
321 | if (av->av_overflow) | |
322 | av->av_overflow = (av->av_buf_head == av->av_buf_tail); | |
323 | } else { | |
324 | av->av_buf_tail = avr->avr_ack_ptr; | |
325 | /* | |
326 | * We have made sure that avr points to a valid cell within the | |
327 | * buffer. This cell is either older than head, or equals head | |
328 | * (empty buffer): in both cases we no longer have any overflow. | |
329 | */ | |
330 | av->av_overflow = 0; | |
331 | } | |
332 | ||
333 | /* | |
334 | * The peer has acknowledged up to and including ack_ackno. Hence the | |
335 | * first packet in group (2) of 11.4.2 is the successor of ack_ackno. | |
336 | */ | |
337 | av->av_tail_ackno = ADD48(avr->avr_ack_ackno, 1); | |
338 | ||
339 | free_records: | |
340 | list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) { | |
341 | list_del(&avr->avr_node); | |
342 | kmem_cache_free(dccp_ackvec_record_slab, avr); | |
343 | } | |
344 | } | |
345 | ||
7e87fe84 GR |
346 | /* |
347 | * Routines to keep track of Ack Vectors received in an skb | |
348 | */ | |
349 | int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce) | |
350 | { | |
351 | struct dccp_ackvec_parsed *new = kmalloc(sizeof(*new), GFP_ATOMIC); | |
352 | ||
353 | if (new == NULL) | |
354 | return -ENOBUFS; | |
355 | new->vec = vec; | |
356 | new->len = len; | |
357 | new->nonce = nonce; | |
358 | ||
359 | list_add_tail(&new->node, head); | |
360 | return 0; | |
361 | } | |
362 | EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_add); | |
363 | ||
364 | void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks) | |
365 | { | |
366 | struct dccp_ackvec_parsed *cur, *next; | |
367 | ||
368 | list_for_each_entry_safe(cur, next, parsed_chunks, node) | |
369 | kfree(cur); | |
370 | INIT_LIST_HEAD(parsed_chunks); | |
371 | } | |
372 | EXPORT_SYMBOL_GPL(dccp_ackvec_parsed_cleanup); | |
373 | ||
9b07ef5d ACM |
374 | int __init dccp_ackvec_init(void) |
375 | { | |
376 | dccp_ackvec_slab = kmem_cache_create("dccp_ackvec", | |
377 | sizeof(struct dccp_ackvec), 0, | |
20c2df83 | 378 | SLAB_HWCACHE_ALIGN, NULL); |
02bcf28c AB |
379 | if (dccp_ackvec_slab == NULL) |
380 | goto out_err; | |
381 | ||
f17a37c9 GR |
382 | dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record", |
383 | sizeof(struct dccp_ackvec_record), | |
384 | 0, SLAB_HWCACHE_ALIGN, NULL); | |
02bcf28c AB |
385 | if (dccp_ackvec_record_slab == NULL) |
386 | goto out_destroy_slab; | |
9b07ef5d ACM |
387 | |
388 | return 0; | |
02bcf28c AB |
389 | |
390 | out_destroy_slab: | |
391 | kmem_cache_destroy(dccp_ackvec_slab); | |
392 | dccp_ackvec_slab = NULL; | |
393 | out_err: | |
59348b19 | 394 | DCCP_CRIT("Unable to create Ack Vector slab cache"); |
02bcf28c | 395 | return -ENOBUFS; |
9b07ef5d ACM |
396 | } |
397 | ||
398 | void dccp_ackvec_exit(void) | |
399 | { | |
400 | if (dccp_ackvec_slab != NULL) { | |
401 | kmem_cache_destroy(dccp_ackvec_slab); | |
402 | dccp_ackvec_slab = NULL; | |
403 | } | |
02bcf28c AB |
404 | if (dccp_ackvec_record_slab != NULL) { |
405 | kmem_cache_destroy(dccp_ackvec_record_slab); | |
406 | dccp_ackvec_record_slab = NULL; | |
407 | } | |
9b07ef5d | 408 | } |