4 * An implementation of the DCCP protocol
5 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
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;
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>
23 static struct kmem_cache *dccp_ackvec_slab;
24 static struct kmem_cache *dccp_ackvec_record_slab;
26 static struct dccp_ackvec_record *dccp_ackvec_record_new(void)
28 struct dccp_ackvec_record *avr =
29 kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
32 INIT_LIST_HEAD(&avr->avr_node);
37 static void dccp_ackvec_record_delete(struct dccp_ackvec_record *avr)
39 if (unlikely(avr == NULL))
41 /* Check if deleting a linked record */
42 WARN_ON(!list_empty(&avr->avr_node));
43 kmem_cache_free(dccp_ackvec_record_slab, avr);
46 static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
47 struct dccp_ackvec_record *avr)
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.
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,
59 BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno));
62 list_add(&avr->avr_node, &av->av_records);
65 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
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;
73 const unsigned char *tail, *from;
75 struct dccp_ackvec_record *avr;
78 if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
81 delta = ktime_us_delta(ktime_get_real(), av->av_time);
82 elapsed_time = delta / 10;
84 if (elapsed_time != 0 &&
85 dccp_insert_option_elapsed_time(sk, skb, elapsed_time))
88 avr = dccp_ackvec_record_new();
92 DCCP_SKB_CB(skb)->dccpd_opt_len += len;
94 to = skb_push(skb, len);
96 from = av->av_buf + av->av_buf_head;
97 tail = av->av_buf + DCCP_MAX_ACKVEC_LEN;
99 for (i = 0; i < nr_opts; ++i) {
102 if (len > DCCP_SINGLE_OPT_MAXLEN)
103 copylen = DCCP_SINGLE_OPT_MAXLEN;
105 *to++ = DCCPO_ACK_VECTOR_0;
108 /* Check if buf_head wraps */
109 if (from + copylen > tail) {
110 const u16 tailsize = tail - from;
112 memcpy(to, from, tailsize);
119 memcpy(to, from, copylen);
126 * From RFC 4340, A.2:
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
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;
140 dccp_ackvec_insert_avr(av, avr);
142 dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
144 dccp_role(sk), avr->avr_sent_len,
145 (unsigned long long)avr->avr_ack_seqno,
146 (unsigned long long)avr->avr_ack_ackno);
150 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
152 struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, priority);
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);
160 INIT_LIST_HEAD(&av->av_records);
166 void dccp_ackvec_free(struct dccp_ackvec *av)
168 if (unlikely(av == NULL))
171 if (!list_empty(&av->av_records)) {
172 struct dccp_ackvec_record *avr, *next;
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);
180 kmem_cache_free(dccp_ackvec_slab, av);
183 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
186 return av->av_buf[index] & DCCP_ACKVEC_STATE_MASK;
189 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
192 return av->av_buf[index] & DCCP_ACKVEC_LEN_MASK;
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.
200 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
201 const unsigned int packets,
202 const unsigned char state)
207 if (av->av_vec_len + packets > DCCP_MAX_ACKVEC_LEN)
211 new_head = av->av_buf_head - packets;
215 memset(av->av_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
219 new_head += DCCP_MAX_ACKVEC_LEN;
222 av->av_buf_head = new_head;
225 memset(av->av_buf + av->av_buf_head + 1,
226 DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
228 av->av_buf[av->av_buf_head] = state;
229 av->av_vec_len += packets;
234 * Implements the RFC 4340, Appendix A
236 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
237 const u64 ackno, const u8 state)
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.
244 * We may well decide to do buffer compression, etc, but for now lets
247 * From Appendix A.1.1 (`New Packets'):
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
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;
265 } else if (after48(ackno, av->av_buf_ackno)) {
266 const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
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.
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))
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.)
287 u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
288 u32 index = av->av_buf_head;
291 const u8 len = dccp_ackvec_len(av, index);
292 const u8 av_state = dccp_ackvec_state(av, index);
294 * valid packets not yet in av_buf have a reserved
295 * entry, with a len equal to 0.
297 if (av_state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
298 len == 0 && delta == 0) { /* Found our
300 dccp_pr_debug("Found %llu reserved seat!\n",
301 (unsigned long long)ackno);
302 av->av_buf[index] = state;
305 /* len == 0 means one packet */
310 if (++index == DCCP_MAX_ACKVEC_LEN)
315 av->av_buf_ackno = ackno;
316 av->av_time = ktime_get_real();
321 /* Duplicate packet */
322 dccp_pr_debug("Received a dup or already considered lost "
323 "packet: %llu\n", (unsigned long long)ackno);
327 static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
328 struct dccp_ackvec_record *avr)
330 struct dccp_ackvec_record *next;
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;
336 av->av_vec_len = DCCP_MAX_ACKVEC_LEN - 1 -
337 av->av_buf_head + avr->avr_ack_ptr;
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);
346 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
349 struct dccp_ackvec_record *avr;
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
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",
361 (unsigned long long)avr->avr_ack_seqno,
362 (unsigned long long)avr->avr_ack_ackno);
363 dccp_ackvec_throw_record(av, avr);
365 } else if (avr->avr_ack_seqno > ackno)
366 break; /* old news */
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)
376 struct dccp_ackvec_record *avr;
378 /* Check if we actually sent an ACK vector */
379 if (list_empty(&av->av_records))
385 * I think it might be more efficient to work backwards. See comment on
388 avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
390 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
393 dccp_set_seqno(&ackno_end_rl, *ackno - rl);
396 * If our AVR sequence number is greater than the ack, go
397 * forward in the AVR list until it is not so.
399 list_for_each_entry_from(avr, &av->av_records, avr_node) {
400 if (!after48(avr->avr_ack_seqno, *ackno))
403 /* End of the av_records list, not found, exit */
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, "
417 dccp_ackvec_throw_record(av, avr);
421 * If it wasn't received, continue scanning... we might
426 dccp_set_seqno(ackno, ackno_end_rl - 1);
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)
434 if (len > DCCP_SINGLE_OPT_MAXLEN)
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,
443 int __init dccp_ackvec_init(void)
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)
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;
461 kmem_cache_destroy(dccp_ackvec_slab);
462 dccp_ackvec_slab = NULL;
464 DCCP_CRIT("Unable to create Ack Vector slab cache");
468 void dccp_ackvec_exit(void)
470 if (dccp_ackvec_slab != NULL) {
471 kmem_cache_destroy(dccp_ackvec_slab);
472 dccp_ackvec_slab = NULL;
474 if (dccp_ackvec_record_slab != NULL) {
475 kmem_cache_destroy(dccp_ackvec_record_slab);
476 dccp_ackvec_record_slab = NULL;