1 /*
2 * net/dccp/packet_history.c
3 *
4 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
5 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
6 *
7 * An implementation of the DCCP protocol
8 *
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
12 *
13 * This code also uses code from Lulea University, rereleased as GPL by its
14 * authors:
15 * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
16 *
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>.
20 *
21 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
22 *
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.
27 *
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.
32 *
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.
36 */
37
38 #include <linux/string.h>
39 #include <linux/slab.h>
40 #include "packet_history.h"
41 #include "../../dccp.h"
42
43 /**
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
48 */
49 struct tfrc_tx_hist_entry {
50 struct tfrc_tx_hist_entry *next;
51 u64 seqno;
52 ktime_t stamp;
53 };
54
55 /*
56 * Transmitter History Routines
57 */
58 static struct kmem_cache *tfrc_tx_hist_slab;
59
60 int __init tfrc_tx_packet_history_init(void)
61 {
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;
66 }
67
68 void tfrc_tx_packet_history_exit(void)
69 {
70 if (tfrc_tx_hist_slab != NULL) {
71 kmem_cache_destroy(tfrc_tx_hist_slab);
72 tfrc_tx_hist_slab = NULL;
73 }
74 }
75
76 static struct tfrc_tx_hist_entry *
77 tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
78 {
79 while (head != NULL && head->seqno != seqno)
80 head = head->next;
81
82 return head;
83 }
84
85 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
86 {
87 struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
88
89 if (entry == NULL)
90 return -ENOBUFS;
91 entry->seqno = seqno;
92 entry->stamp = ktime_get_real();
93 entry->next = *headp;
94 *headp = entry;
95 return 0;
96 }
97 EXPORT_SYMBOL_GPL(tfrc_tx_hist_add);
98
99 void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
100 {
101 struct tfrc_tx_hist_entry *head = *headp;
102
103 while (head != NULL) {
104 struct tfrc_tx_hist_entry *next = head->next;
105
106 kmem_cache_free(tfrc_tx_hist_slab, head);
107 head = next;
108 }
109
110 *headp = NULL;
111 }
112 EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
113
114 u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
115 const ktime_t now)
116 {
117 u32 rtt = 0;
118 struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
119
120 if (packet != NULL) {
121 rtt = ktime_us_delta(now, packet->stamp);
122 /*
123 * Garbage-collect older (irrelevant) entries:
124 */
125 tfrc_tx_hist_purge(&packet->next);
126 }
127
128 return rtt;
129 }
130 EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
131
132
133 /*
134 * Receiver History Routines
135 */
136 static struct kmem_cache *tfrc_rx_hist_slab;
137
138 int __init tfrc_rx_packet_history_init(void)
139 {
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;
144 }
145
146 void tfrc_rx_packet_history_exit(void)
147 {
148 if (tfrc_rx_hist_slab != NULL) {
149 kmem_cache_destroy(tfrc_rx_hist_slab);
150 tfrc_rx_hist_slab = NULL;
151 }
152 }
153
154 static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
155 const struct sk_buff *skb,
156 const u32 ndp)
157 {
158 const struct dccp_hdr *dh = dccp_hdr(skb);
159
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();
165 }
166
167 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
168 const struct sk_buff *skb,
169 const u32 ndp)
170 {
171 struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
172
173 tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
174 }
175 EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet);
176
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)
179 {
180 const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
181 int i;
182
183 if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
184 return 1;
185
186 for (i = 1; i <= h->loss_count; i++)
187 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
188 return 1;
189
190 return 0;
191 }
192 EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
193
194 static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
195 {
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];
199
200 h->ring[idx_a] = h->ring[idx_b];
201 h->ring[idx_b] = tmp;
202 }
203
204 /*
205 * Private helper functions for loss detection.
206 *
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.
212 */
213 static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
214 {
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;
218 int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
219 d12 = dccp_delta_seqno(s1, s2), d2;
220
221 if (d12 > 0) { /* S1 < S2 */
222 h->loss_count = 2;
223 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
224 return;
225 }
226
227 /* S0 < S2 < S1 */
228 d2 = dccp_delta_seqno(s0, s2);
229
230 if (d2 == 1 || n2 >= d2) { /* S2 is direct successor of S0 */
231 int d21 = -d12;
232
233 if (d21 == 1 || n1 >= d21) {
234 /* hole is filled: S0, S2, and S1 are consecutive */
235 h->loss_count = 0;
236 h->loss_start = tfrc_rx_hist_index(h, 1);
237 } else
238 /* gap between S2 and S1: just update loss_prev */
239 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
240
241 } else { /* hole between S0 and S2 */
242 /*
243 * Reorder history to insert S2 between S0 and s1
244 */
245 tfrc_rx_hist_swap(h, 0, 3);
246 h->loss_start = tfrc_rx_hist_index(h, 3);
247 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
248 h->loss_count = 2;
249 }
250 }
251
252 /* return 1 if a new loss event has been identified */
253 static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
254 {
255 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
256 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
257 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
258 s3 = DCCP_SKB_CB(skb)->dccpd_seq;
259 int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp,
260 d23 = dccp_delta_seqno(s2, s3), d13, d3, d31;
261
262 if (d23 > 0) { /* S2 < S3 */
263 h->loss_count = 3;
264 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
265 return 1;
266 }
267
268 /* S3 < S2 */
269 d13 = dccp_delta_seqno(s1, s3);
270
271 if (d13 > 0) {
272 /*
273 * The sequence number order is S1, S3, S2
274 * Reorder history to insert entry between S1 and S2
275 */
276 tfrc_rx_hist_swap(h, 2, 3);
277 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
278 h->loss_count = 3;
279 return 1;
280 }
281
282 /* S0 < S3 < S1 */
283 d31 = -d13;
284 d3 = dccp_delta_seqno(s0, s3);
285
286 if (d3 == 1 || n3 >= d3) { /* S3 is a successor of S0 */
287
288 if (d31 == 1 || n1 >= d31) {
289 /* hole between S0 and S1 filled by S3 */
290 int d2 = dccp_delta_seqno(s1, s2),
291 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
292
293 if (d2 == 1 || n2 >= d2) {
294 /* entire hole filled by S0, S3, S1, S2 */
295 h->loss_start = tfrc_rx_hist_index(h, 2);
296 h->loss_count = 0;
297 } else {
298 /* gap remains between S1 and S2 */
299 h->loss_start = tfrc_rx_hist_index(h, 1);
300 h->loss_count = 1;
301 }
302
303 } else /* gap exists between S3 and S1, loss_count stays at 2 */
304 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
305
306 return 0;
307 }
308
309 /*
310 * The remaining case: S3 is not a successor of S0.
311 * Sequence order is S0, S3, S1, S2; reorder to insert between S0 and S1
312 */
313 tfrc_rx_hist_swap(h, 0, 3);
314 h->loss_start = tfrc_rx_hist_index(h, 3);
315 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
316 h->loss_count = 3;
317
318 return 1;
319 }
320
321 /* return the signed modulo-2^48 sequence number distance from entry e1 to e2 */
322 static s64 tfrc_rx_hist_delta_seqno(struct tfrc_rx_hist *h, u8 e1, u8 e2)
323 {
324 DCCP_BUG_ON(e1 > h->loss_count || e2 > h->loss_count);
325
326 return dccp_delta_seqno(tfrc_rx_hist_entry(h, e1)->tfrchrx_seqno,
327 tfrc_rx_hist_entry(h, e2)->tfrchrx_seqno);
328 }
329
330 /* recycle RX history records to continue loss detection if necessary */
331 static void __three_after_loss(struct tfrc_rx_hist *h)
332 {
333 /*
334 * The distance between S0 and S1 is always greater than 1 and the NDP
335 * count of S1 is smaller than this distance. Otherwise there would
336 * have been no loss. Hence it is only necessary to see whether there
337 * are further missing data packets between S1/S2 and S2/S3.
338 */
339 int d2 = tfrc_rx_hist_delta_seqno(h, 1, 2),
340 d3 = tfrc_rx_hist_delta_seqno(h, 2, 3),
341 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
342 n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
343
344 if (d2 == 1 || n2 >= d2) { /* S2 is successor to S1 */
345
346 if (d3 == 1 || n3 >= d3) {
347 /* S3 is successor of S2: entire hole is filled */
348 h->loss_start = tfrc_rx_hist_index(h, 3);
349 h->loss_count = 0;
350 } else {
351 /* gap between S2 and S3 */
352 h->loss_start = tfrc_rx_hist_index(h, 2);
353 h->loss_count = 1;
354 }
355
356 } else { /* gap between S1 and S2 */
357 h->loss_start = tfrc_rx_hist_index(h, 1);
358 h->loss_count = 2;
359 }
360 }
361
362 /**
363 * tfrc_rx_handle_loss - Loss detection and further processing
364 * @h: The non-empty RX history object
365 * @lh: Loss Intervals database to update
366 * @skb: Currently received packet
367 * @ndp: The NDP count belonging to @skb
368 * @calc_first_li: Caller-dependent computation of first loss interval in @lh
369 * @sk: Used by @calc_first_li (see tfrc_lh_interval_add)
370 * Chooses action according to pending loss, updates LI database when a new
371 * loss was detected, and does required post-processing. Returns 1 when caller
372 * should send feedback, 0 otherwise.
373 */
374 int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
375 struct tfrc_loss_hist *lh,
376 struct sk_buff *skb, u32 ndp,
377 u32 (*calc_first_li)(struct sock *), struct sock *sk)
378 {
379 int is_new_loss = 0;
380
381 if (h->loss_count == 1) {
382 __one_after_loss(h, skb, ndp);
383 } else if (h->loss_count != 2) {
384 DCCP_BUG("invalid loss_count %d", h->loss_count);
385 } else if (__two_after_loss(h, skb, ndp)) {
386 /*
387 * Update Loss Interval database and recycle RX records
388 */
389 is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
390 __three_after_loss(h);
391 }
392 return is_new_loss;
393 }
394 EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
395
396 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
397 {
398 int i;
399
400 for (i = 0; i <= TFRC_NDUPACK; i++) {
401 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
402 if (h->ring[i] == NULL)
403 goto out_free;
404 }
405
406 h->loss_count = h->loss_start = 0;
407 return 0;
408
409 out_free:
410 while (i-- != 0) {
411 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
412 h->ring[i] = NULL;
413 }
414 return -ENOBUFS;
415 }
416 EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
417
418 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
419 {
420 int i;
421
422 for (i = 0; i <= TFRC_NDUPACK; ++i)
423 if (h->ring[i] != NULL) {
424 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
425 h->ring[i] = NULL;
426 }
427 }
428 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
429
430 /**
431 * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
432 */
433 static inline struct tfrc_rx_hist_entry *
434 tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
435 {
436 return h->ring[0];
437 }
438
439 /**
440 * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
441 */
442 static inline struct tfrc_rx_hist_entry *
443 tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
444 {
445 return h->ring[h->rtt_sample_prev];
446 }
447
448 /**
449 * tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal
450 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
451 * to compute a sample with given data - calling function should check this.
452 */
453 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
454 {
455 u32 sample = 0,
456 delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
457 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
458
459 if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */
460 if (h->rtt_sample_prev == 2) { /* previous candidate stored */
461 sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
462 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
463 if (sample)
464 sample = 4 / sample *
465 ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
466 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
467 else /*
468 * FIXME: This condition is in principle not
469 * possible but occurs when CCID is used for
470 * two-way data traffic. I have tried to trace
471 * it, but the cause does not seem to be here.
472 */
473 DCCP_BUG("please report to dccp@vger.kernel.org"
474 " => prev = %u, last = %u",
475 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
476 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
477 } else if (delta_v < 1) {
478 h->rtt_sample_prev = 1;
479 goto keep_ref_for_next_time;
480 }
481
482 } else if (delta_v == 4) /* optimal match */
483 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
484 else { /* suboptimal match */
485 h->rtt_sample_prev = 2;
486 goto keep_ref_for_next_time;
487 }
488
489 if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
490 DCCP_WARN("RTT sample %u too large, using max\n", sample);
491 sample = DCCP_SANE_RTT_MAX;
492 }
493
494 h->rtt_sample_prev = 0; /* use current entry as next reference */
495 keep_ref_for_next_time:
496
497 return sample;
498 }
499 EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);
500
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