2 * net/dccp/packet_history.c
4 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
5 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
7 * An implementation of the DCCP protocol
9 * This code has been developed by the University of Waikato WAND
10 * research group. For further information please see http://www.wand.net.nz/
11 * or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
13 * This code also uses code from Lulea University, rereleased as GPL by its
15 * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
17 * Changes to meet Linux coding standards, to make it meet latest ccid3 draft
18 * and to make it work as a loadable module in the DCCP stack written by
19 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
21 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
23 * This program is free software; you can redistribute it and/or modify
24 * it under the terms of the GNU General Public License as published by
25 * the Free Software Foundation; either version 2 of the License, or
26 * (at your option) any later version.
28 * This program is distributed in the hope that it will be useful,
29 * but WITHOUT ANY WARRANTY; without even the implied warranty of
30 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
31 * GNU General Public License for more details.
33 * You should have received a copy of the GNU General Public License
34 * along with this program; if not, write to the Free Software
35 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
38 #include <linux/string.h>
39 #include <linux/slab.h>
40 #include "packet_history.h"
41 #include "../../dccp.h"
44 * tfrc_tx_hist_entry - Simple singly-linked TX history list
45 * @next: next oldest entry (LIFO order)
46 * @seqno: sequence number of this entry
47 * @stamp: send time of packet with sequence number @seqno
49 struct tfrc_tx_hist_entry {
50 struct tfrc_tx_hist_entry *next;
56 * Transmitter History Routines
58 static struct kmem_cache *tfrc_tx_hist_slab;
60 int __init tfrc_tx_packet_history_init(void)
62 tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
63 sizeof(struct tfrc_tx_hist_entry),
64 0, SLAB_HWCACHE_ALIGN, NULL);
65 return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
68 void tfrc_tx_packet_history_exit(void)
70 if (tfrc_tx_hist_slab != NULL) {
71 kmem_cache_destroy(tfrc_tx_hist_slab);
72 tfrc_tx_hist_slab = NULL;
76 static struct tfrc_tx_hist_entry *
77 tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
79 while (head != NULL && head->seqno != seqno)
85 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
87 struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
92 entry->stamp = ktime_get_real();
97 EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
99 void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
101 struct tfrc_tx_hist_entry *head = *headp;
103 while (head != NULL) {
104 struct tfrc_tx_hist_entry *next = head->next;
106 kmem_cache_free(tfrc_tx_hist_slab, head);
112 EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
114 u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
118 struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
120 if (packet != NULL) {
121 rtt = ktime_us_delta(now, packet->stamp);
123 * Garbage-collect older (irrelevant) entries:
125 tfrc_tx_hist_purge(&packet->next);
130 EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
134 * Receiver History Routines
136 static struct kmem_cache *tfrc_rx_hist_slab;
138 int __init tfrc_rx_packet_history_init(void)
140 tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
141 sizeof(struct tfrc_rx_hist_entry),
142 0, SLAB_HWCACHE_ALIGN, NULL);
143 return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
146 void tfrc_rx_packet_history_exit(void)
148 if (tfrc_rx_hist_slab != NULL) {
149 kmem_cache_destroy(tfrc_rx_hist_slab);
150 tfrc_rx_hist_slab = NULL;
154 static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
155 const struct sk_buff *skb,
158 const struct dccp_hdr *dh = dccp_hdr(skb);
160 entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
161 entry->tfrchrx_ccval = dh->dccph_ccval;
162 entry->tfrchrx_type = dh->dccph_type;
163 entry->tfrchrx_ndp = ndp;
164 entry->tfrchrx_tstamp = ktime_get_real();
167 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
168 const struct sk_buff *skb,
171 struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
173 tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
175 EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
177 /* has the packet contained in skb been seen before? */
178 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
180 const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
183 if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
186 for (i = 1; i <= h->loss_count; i++)
187 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
192 EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
194 static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
196 const u8 idx_a = tfrc_rx_hist_index(h, a),
197 idx_b = tfrc_rx_hist_index(h, b);
198 struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
200 h->ring[idx_a] = h->ring[idx_b];
201 h->ring[idx_b] = tmp;
205 * Private helper functions for loss detection.
207 * In the descriptions, `Si' refers to the sequence number of entry number i,
208 * whose NDP count is `Ni' (lower case is used for variables).
209 * Note: All __after_loss functions expect that a test against duplicates has
210 * been performed already: the seqno of the skb must not be less than the
211 * seqno of loss_prev; and it must not equal that of any valid hist_entry.
213 static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
215 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
216 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
217 s2 = DCCP_SKB_CB(skb)->dccpd_seq;
219 if (likely(dccp_delta_seqno(s1, s2) > 0)) { /* S1 < S2 */
221 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
227 if (dccp_loss_free(s0, s2, n2)) {
228 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
230 if (dccp_loss_free(s2, s1, n1)) {
231 /* hole is filled: S0, S2, and S1 are consecutive */
233 h->loss_start = tfrc_rx_hist_index(h, 1);
235 /* gap between S2 and S1: just update loss_prev */
236 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
238 } else { /* gap between S0 and S2 */
240 * Reorder history to insert S2 between S0 and S1
242 tfrc_rx_hist_swap(h, 0, 3);
243 h->loss_start = tfrc_rx_hist_index(h, 3);
244 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
249 /* return 1 if a new loss event has been identified */
250 static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
252 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
253 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
254 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
255 s3 = DCCP_SKB_CB(skb)->dccpd_seq;
257 if (likely(dccp_delta_seqno(s2, s3) > 0)) { /* S2 < S3 */
259 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
265 if (dccp_delta_seqno(s1, s3) > 0) { /* S1 < S3 < S2 */
267 * Reorder history to insert S3 between S1 and S2
269 tfrc_rx_hist_swap(h, 2, 3);
270 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
277 if (dccp_loss_free(s0, s3, n3)) {
278 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
280 if (dccp_loss_free(s3, s1, n1)) {
281 /* hole between S0 and S1 filled by S3 */
282 u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
284 if (dccp_loss_free(s1, s2, n2)) {
285 /* entire hole filled by S0, S3, S1, S2 */
286 h->loss_start = tfrc_rx_hist_index(h, 2);
289 /* gap remains between S1 and S2 */
290 h->loss_start = tfrc_rx_hist_index(h, 1);
294 } else /* gap exists between S3 and S1, loss_count stays at 2 */
295 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
301 * The remaining case: S0 < S3 < S1 < S2; gap between S0 and S3
302 * Reorder history to insert S3 between S0 and S1.
304 tfrc_rx_hist_swap(h, 0, 3);
305 h->loss_start = tfrc_rx_hist_index(h, 3);
306 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
312 /* recycle RX history records to continue loss detection if necessary */
313 static void __three_after_loss(struct tfrc_rx_hist *h)
316 * At this stage we know already that there is a gap between S0 and S1
317 * (since S0 was the highest sequence number received before detecting
318 * the loss). To recycle the loss record, it is thus only necessary to
319 * check for other possible gaps between S1/S2 and between S2/S3.
321 u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
322 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
323 s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
324 u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
325 n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
327 if (dccp_loss_free(s1, s2, n2)) {
329 if (dccp_loss_free(s2, s3, n3)) {
330 /* no gap between S2 and S3: entire hole is filled */
331 h->loss_start = tfrc_rx_hist_index(h, 3);
334 /* gap between S2 and S3 */
335 h->loss_start = tfrc_rx_hist_index(h, 2);
339 } else { /* gap between S1 and S2 */
340 h->loss_start = tfrc_rx_hist_index(h, 1);
346 * tfrc_rx_handle_loss - Loss detection and further processing
347 * @h: The non-empty RX history object
348 * @lh: Loss Intervals database to update
349 * @skb: Currently received packet
350 * @ndp: The NDP count belonging to @skb
351 * @calc_first_li: Caller-dependent computation of first loss interval in @lh
352 * @sk: Used by @calc_first_li (see tfrc_lh_interval_add)
353 * Chooses action according to pending loss, updates LI database when a new
354 * loss was detected, and does required post-processing. Returns 1 when caller
355 * should send feedback, 0 otherwise.
357 int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
358 struct tfrc_loss_hist *lh,
359 struct sk_buff *skb, u32 ndp,
360 u32 (*calc_first_li)(struct sock *), struct sock *sk)
364 if (h->loss_count == 1) {
365 __one_after_loss(h, skb, ndp);
366 } else if (h->loss_count != 2) {
367 DCCP_BUG("invalid loss_count %d", h->loss_count);
368 } else if (__two_after_loss(h, skb, ndp)) {
370 * Update Loss Interval database and recycle RX records
372 is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
373 __three_after_loss(h);
377 EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
379 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
383 for (i = 0; i <= TFRC_NDUPACK; i++) {
384 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
385 if (h->ring[i] == NULL)
389 h->loss_count = h->loss_start = 0;
394 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
399 EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
401 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
405 for (i = 0; i <= TFRC_NDUPACK; ++i)
406 if (h->ring[i] != NULL) {
407 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
411 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
414 * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
416 static inline struct tfrc_rx_hist_entry *
417 tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
423 * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
425 static inline struct tfrc_rx_hist_entry *
426 tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
428 return h->ring[h->rtt_sample_prev];
432 * tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal
433 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
434 * to compute a sample with given data - calling function should check this.
436 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
439 delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
440 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
442 if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */
443 if (h->rtt_sample_prev == 2) { /* previous candidate stored */
444 sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
445 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
447 sample = 4 / sample *
448 ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
449 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
451 * FIXME: This condition is in principle not
452 * possible but occurs when CCID is used for
453 * two-way data traffic. I have tried to trace
454 * it, but the cause does not seem to be here.
456 DCCP_BUG("please report to dccp@vger.kernel.org"
457 " => prev = %u, last = %u",
458 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
459 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
460 } else if (delta_v < 1) {
461 h->rtt_sample_prev = 1;
462 goto keep_ref_for_next_time;
465 } else if (delta_v == 4) /* optimal match */
466 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
467 else { /* suboptimal match */
468 h->rtt_sample_prev = 2;
469 goto keep_ref_for_next_time;
472 if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
473 DCCP_WARN("RTT sample %u too large, using max\n", sample);
474 sample = DCCP_SANE_RTT_MAX;
477 h->rtt_sample_prev = 0; /* use current entry as next reference */
478 keep_ref_for_next_time:
482 EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);