4 * An implementation of Ack Vectors for the DCCP protocol
5 * Copyright (c) 2007 University of Aberdeen, Scotland, UK
6 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
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;
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>
24 static struct kmem_cache *dccp_ackvec_slab;
25 static struct kmem_cache *dccp_ackvec_record_slab;
27 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
29 struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
32 av->av_buf_head = DCCPAV_MAX_ACKVEC_LEN - 1;
33 INIT_LIST_HEAD(&av->av_records);
38 static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
40 struct dccp_ackvec_record *cur, *next;
42 list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
43 kmem_cache_free(dccp_ackvec_record_slab, cur);
44 INIT_LIST_HEAD(&av->av_records);
47 void dccp_ackvec_free(struct dccp_ackvec *av)
49 if (likely(av != NULL)) {
50 dccp_ackvec_purge_records(av);
51 kmem_cache_free(dccp_ackvec_slab, av);
55 static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
56 struct dccp_ackvec_record *avr)
59 * AVRs are sorted by seqno. Since we are sending them in order, we
60 * just add the AVR at the head of the list.
63 if (!list_empty(&av->av_records)) {
64 const struct dccp_ackvec_record *head =
65 list_entry(av->av_records.next,
66 struct dccp_ackvec_record,
68 BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno));
71 list_add(&avr->avr_node, &av->av_records);
74 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
76 struct dccp_sock *dp = dccp_sk(sk);
77 struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
78 /* Figure out how many options do we need to represent the ackvec */
79 const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
80 u16 len = av->av_vec_len + 2 * nr_opts;
82 const unsigned char *tail, *from;
84 struct dccp_ackvec_record *avr;
86 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
89 avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
93 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
95 to = skb_push(skb, len);
97 from = av->av_buf + av->av_buf_head;
98 tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
100 for (i = 0; i < nr_opts; ++i) {
103 if (len > DCCP_SINGLE_OPT_MAXLEN)
104 copylen = DCCP_SINGLE_OPT_MAXLEN;
107 * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
108 * its type; ack_nonce is the sum of all individual buf_nonce's.
110 nonce ^= av->av_buf_nonce[i];
112 *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
115 /* Check if buf_head wraps */
116 if (from + copylen > tail) {
117 const u16 tailsize = tail - from;
119 memcpy(to, from, tailsize);
126 memcpy(to, from, copylen);
133 * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
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 = nonce;
139 avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
141 dccp_ackvec_insert_avr(av, avr);
143 dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
145 dccp_role(sk), avr->avr_ack_runlen,
146 (unsigned long long)avr->avr_ack_seqno,
147 (unsigned long long)avr->avr_ack_ackno);
152 * If several packets are missing, the HC-Receiver may prefer to enter multiple
153 * bytes with run length 0, rather than a single byte with a larger run length;
154 * this simplifies table updates if one of the missing packets arrives.
156 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
157 const unsigned int packets,
158 const unsigned char state)
163 if (av->av_vec_len + packets > DCCPAV_MAX_ACKVEC_LEN)
167 new_head = av->av_buf_head - packets;
171 memset(av->av_buf, DCCPAV_NOT_RECEIVED,
175 new_head += DCCPAV_MAX_ACKVEC_LEN;
178 av->av_buf_head = new_head;
181 memset(av->av_buf + av->av_buf_head + 1,
182 DCCPAV_NOT_RECEIVED, gap);
184 av->av_buf[av->av_buf_head] = state;
185 av->av_vec_len += packets;
190 * Implements the RFC 4340, Appendix A
192 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
193 const u64 ackno, const u8 state)
195 u8 *cur_head = av->av_buf + av->av_buf_head,
196 *buf_end = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
198 * Check at the right places if the buffer is full, if it is, tell the
199 * caller to start dropping packets till the HC-Sender acks our ACK
200 * vectors, when we will free up space in av_buf.
202 * We may well decide to do buffer compression, etc, but for now lets
205 * From Appendix A.1.1 (`New Packets'):
207 * Of course, the circular buffer may overflow, either when the
208 * HC-Sender is sending data at a very high rate, when the
209 * HC-Receiver's acknowledgements are not reaching the HC-Sender,
210 * or when the HC-Sender is forgetting to acknowledge those acks
211 * (so the HC-Receiver is unable to clean up old state). In this
212 * case, the HC-Receiver should either compress the buffer (by
213 * increasing run lengths when possible), transfer its state to
214 * a larger buffer, or, as a last resort, drop all received
215 * packets, without processing them whatsoever, until its buffer
219 /* See if this is the first ackno being inserted */
220 if (av->av_vec_len == 0) {
223 } else if (after48(ackno, av->av_buf_ackno)) {
224 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
227 * Look if the state of this packet is the same as the
228 * previous ackno and if so if we can bump the head len.
230 if (delta == 1 && dccp_ackvec_state(cur_head) == state &&
231 dccp_ackvec_runlen(cur_head) < DCCPAV_MAX_RUNLEN)
233 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
239 * When a packet with Sequence Number S <= buf_ackno
240 * arrives, the HC-Receiver will scan the table for
241 * the byte corresponding to S. (Indexing structures
242 * could reduce the complexity of this scan.)
244 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
247 const u8 len = dccp_ackvec_runlen(cur_head);
249 * valid packets not yet in av_buf have a reserved
250 * entry, with a len equal to 0.
252 if (*cur_head == DCCPAV_NOT_RECEIVED && delta == 0) {
253 dccp_pr_debug("Found %llu reserved seat!\n",
254 (unsigned long long)ackno);
258 /* len == 0 means one packet */
263 if (++cur_head == buf_end)
264 cur_head = av->av_buf;
268 av->av_buf_ackno = ackno;
273 /* Duplicate packet */
274 dccp_pr_debug("Received a dup or already considered lost "
275 "packet: %llu\n", (unsigned long long)ackno);
279 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
280 struct dccp_ackvec_record *avr)
282 struct dccp_ackvec_record *next;
284 /* sort out vector length */
285 if (av->av_buf_head <= avr->avr_ack_ptr)
286 av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
288 av->av_vec_len = DCCPAV_MAX_ACKVEC_LEN - 1 -
289 av->av_buf_head + avr->avr_ack_ptr;
292 list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
293 list_del(&avr->avr_node);
294 kmem_cache_free(dccp_ackvec_record_slab, avr);
298 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
301 struct dccp_ackvec_record *avr;
304 * If we traverse backwards, it should be faster when we have large
305 * windows. We will be receiving ACKs for stuff we sent a while back
308 list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
309 if (ackno == avr->avr_ack_seqno) {
310 dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
311 "ack_ackno=%llu, ACKED!\n",
312 dccp_role(sk), avr->avr_ack_runlen,
313 (unsigned long long)avr->avr_ack_seqno,
314 (unsigned long long)avr->avr_ack_ackno);
315 dccp_ackvec_throw_record(av, avr);
317 } else if (avr->avr_ack_seqno > ackno)
318 break; /* old news */
322 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
323 struct sock *sk, u64 *ackno,
324 const unsigned char len,
325 const unsigned char *vector)
328 struct dccp_ackvec_record *avr;
330 /* Check if we actually sent an ACK vector */
331 if (list_empty(&av->av_records))
337 * I think it might be more efficient to work backwards. See comment on
340 avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
342 const u8 rl = dccp_ackvec_runlen(vector);
345 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
348 * If our AVR sequence number is greater than the ack, go
349 * forward in the AVR list until it is not so.
351 list_for_each_entry_from(avr, &av->av_records, avr_node) {
352 if (!after48(avr->avr_ack_seqno, *ackno))
355 /* End of the av_records list, not found, exit */
358 if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
359 if (dccp_ackvec_state(vector) != DCCPAV_NOT_RECEIVED) {
360 dccp_pr_debug("%s ACK vector 0, len=%d, "
361 "ack_seqno=%llu, ack_ackno=%llu, "
368 dccp_ackvec_throw_record(av, avr);
372 * If it wasn't received, continue scanning... we might
377 dccp_set_seqno(ackno, ackno_end_rl - 1);
382 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
383 u64 *ackno, const u8 opt, const u8 *value, const u8 len)
385 if (len > DCCP_SINGLE_OPT_MAXLEN)
388 /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
389 dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
394 int __init dccp_ackvec_init(void)
396 dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
397 sizeof(struct dccp_ackvec), 0,
398 SLAB_HWCACHE_ALIGN, NULL);
399 if (dccp_ackvec_slab == NULL)
402 dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
403 sizeof(struct dccp_ackvec_record),
404 0, SLAB_HWCACHE_ALIGN, NULL);
405 if (dccp_ackvec_record_slab == NULL)
406 goto out_destroy_slab;
411 kmem_cache_destroy(dccp_ackvec_slab);
412 dccp_ackvec_slab = NULL;
414 DCCP_CRIT("Unable to create Ack Vector slab cache");
418 void dccp_ackvec_exit(void)
420 if (dccp_ackvec_slab != NULL) {
421 kmem_cache_destroy(dccp_ackvec_slab);
422 dccp_ackvec_slab = NULL;
424 if (dccp_ackvec_record_slab != NULL) {
425 kmem_cache_destroy(dccp_ackvec_record_slab);
426 dccp_ackvec_record_slab = NULL;