1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
4 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
5 *
6 * An implementation of the DCCP protocol
7 *
8 * This code has been developed by the University of Waikato WAND
9 * research group. For further information please see https://www.wand.net.nz/
10 * or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
11 *
12 * This code also uses code from Lulea University, rereleased as GPL by its
13 * authors:
14 * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
15 *
16 * Changes to meet Linux coding standards, to make it meet latest ccid3 draft
17 * and to make it work as a loadable module in the DCCP stack written by
18 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
19 *
20 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
21 */
22
23 #include <linux/string.h>
24 #include <linux/slab.h>
25 #include "packet_history.h"
26 #include "../../dccp.h"
27
28 /*
29 * Transmitter History Routines
30 */
31 static struct kmem_cache *tfrc_tx_hist_slab;
32
33 int __init tfrc_tx_packet_history_init(void)
34 {
35 tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
36 sizeof(struct tfrc_tx_hist_entry),
37 0, SLAB_HWCACHE_ALIGN, NULL);
38 return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
39 }
40
41 void tfrc_tx_packet_history_exit(void)
42 {
43 if (tfrc_tx_hist_slab != NULL) {
44 kmem_cache_destroy(tfrc_tx_hist_slab);
45 tfrc_tx_hist_slab = NULL;
46 }
47 }
48
49 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
50 {
51 struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
52
53 if (entry == NULL)
54 return -ENOBUFS;
55 entry->seqno = seqno;
56 entry->stamp = ktime_get_real();
57 entry->next = *headp;
58 *headp = entry;
59 return 0;
60 }
61
62 void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
63 {
64 struct tfrc_tx_hist_entry *head = *headp;
65
66 while (head != NULL) {
67 struct tfrc_tx_hist_entry *next = head->next;
68
69 kmem_cache_free(tfrc_tx_hist_slab, head);
70 head = next;
71 }
72
73 *headp = NULL;
74 }
75
76 /*
77 * Receiver History Routines
78 */
79 static struct kmem_cache *tfrc_rx_hist_slab;
80
81 int __init tfrc_rx_packet_history_init(void)
82 {
83 tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
84 sizeof(struct tfrc_rx_hist_entry),
85 0, SLAB_HWCACHE_ALIGN, NULL);
86 return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
87 }
88
89 void tfrc_rx_packet_history_exit(void)
90 {
91 if (tfrc_rx_hist_slab != NULL) {
92 kmem_cache_destroy(tfrc_rx_hist_slab);
93 tfrc_rx_hist_slab = NULL;
94 }
95 }
96
97 static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
98 const struct sk_buff *skb,
99 const u64 ndp)
100 {
101 const struct dccp_hdr *dh = dccp_hdr(skb);
102
103 entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
104 entry->tfrchrx_ccval = dh->dccph_ccval;
105 entry->tfrchrx_type = dh->dccph_type;
106 entry->tfrchrx_ndp = ndp;
107 entry->tfrchrx_tstamp = ktime_get_real();
108 }
109
110 void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
111 const struct sk_buff *skb,
112 const u64 ndp)
113 {
114 struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
115
116 tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
117 }
118
119 /* has the packet contained in skb been seen before? */
120 int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
121 {
122 const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
123 int i;
124
125 if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
126 return 1;
127
128 for (i = 1; i <= h->loss_count; i++)
129 if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
130 return 1;
131
132 return 0;
133 }
134
135 static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
136 {
137 const u8 idx_a = tfrc_rx_hist_index(h, a),
138 idx_b = tfrc_rx_hist_index(h, b);
139
140 swap(h->ring[idx_a], h->ring[idx_b]);
141 }
142
143 /*
144 * Private helper functions for loss detection.
145 *
146 * In the descriptions, `Si' refers to the sequence number of entry number i,
147 * whose NDP count is `Ni' (lower case is used for variables).
148 * Note: All __xxx_loss functions expect that a test against duplicates has been
149 * performed already: the seqno of the skb must not be less than the seqno
150 * of loss_prev; and it must not equal that of any valid history entry.
151 */
152 static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
153 {
154 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
155 s1 = DCCP_SKB_CB(skb)->dccpd_seq;
156
157 if (!dccp_loss_free(s0, s1, n1)) { /* gap between S0 and S1 */
158 h->loss_count = 1;
159 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
160 }
161 }
162
163 static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
164 {
165 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
166 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
167 s2 = DCCP_SKB_CB(skb)->dccpd_seq;
168
169 if (likely(dccp_delta_seqno(s1, s2) > 0)) { /* S1 < S2 */
170 h->loss_count = 2;
171 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
172 return;
173 }
174
175 /* S0 < S2 < S1 */
176
177 if (dccp_loss_free(s0, s2, n2)) {
178 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
179
180 if (dccp_loss_free(s2, s1, n1)) {
181 /* hole is filled: S0, S2, and S1 are consecutive */
182 h->loss_count = 0;
183 h->loss_start = tfrc_rx_hist_index(h, 1);
184 } else
185 /* gap between S2 and S1: just update loss_prev */
186 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
187
188 } else { /* gap between S0 and S2 */
189 /*
190 * Reorder history to insert S2 between S0 and S1
191 */
192 tfrc_rx_hist_swap(h, 0, 3);
193 h->loss_start = tfrc_rx_hist_index(h, 3);
194 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
195 h->loss_count = 2;
196 }
197 }
198
199 /* return 1 if a new loss event has been identified */
200 static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
201 {
202 u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
203 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
204 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
205 s3 = DCCP_SKB_CB(skb)->dccpd_seq;
206
207 if (likely(dccp_delta_seqno(s2, s3) > 0)) { /* S2 < S3 */
208 h->loss_count = 3;
209 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
210 return 1;
211 }
212
213 /* S3 < S2 */
214
215 if (dccp_delta_seqno(s1, s3) > 0) { /* S1 < S3 < S2 */
216 /*
217 * Reorder history to insert S3 between S1 and S2
218 */
219 tfrc_rx_hist_swap(h, 2, 3);
220 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
221 h->loss_count = 3;
222 return 1;
223 }
224
225 /* S0 < S3 < S1 */
226
227 if (dccp_loss_free(s0, s3, n3)) {
228 u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
229
230 if (dccp_loss_free(s3, s1, n1)) {
231 /* hole between S0 and S1 filled by S3 */
232 u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
233
234 if (dccp_loss_free(s1, s2, n2)) {
235 /* entire hole filled by S0, S3, S1, S2 */
236 h->loss_start = tfrc_rx_hist_index(h, 2);
237 h->loss_count = 0;
238 } else {
239 /* gap remains between S1 and S2 */
240 h->loss_start = tfrc_rx_hist_index(h, 1);
241 h->loss_count = 1;
242 }
243
244 } else /* gap exists between S3 and S1, loss_count stays at 2 */
245 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
246
247 return 0;
248 }
249
250 /*
251 * The remaining case: S0 < S3 < S1 < S2; gap between S0 and S3
252 * Reorder history to insert S3 between S0 and S1.
253 */
254 tfrc_rx_hist_swap(h, 0, 3);
255 h->loss_start = tfrc_rx_hist_index(h, 3);
256 tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
257 h->loss_count = 3;
258
259 return 1;
260 }
261
262 /* recycle RX history records to continue loss detection if necessary */
263 static void __three_after_loss(struct tfrc_rx_hist *h)
264 {
265 /*
266 * At this stage we know already that there is a gap between S0 and S1
267 * (since S0 was the highest sequence number received before detecting
268 * the loss). To recycle the loss record, it is thus only necessary to
269 * check for other possible gaps between S1/S2 and between S2/S3.
270 */
271 u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
272 s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
273 s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
274 u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
275 n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
276
277 if (dccp_loss_free(s1, s2, n2)) {
278
279 if (dccp_loss_free(s2, s3, n3)) {
280 /* no gap between S2 and S3: entire hole is filled */
281 h->loss_start = tfrc_rx_hist_index(h, 3);
282 h->loss_count = 0;
283 } else {
284 /* gap between S2 and S3 */
285 h->loss_start = tfrc_rx_hist_index(h, 2);
286 h->loss_count = 1;
287 }
288
289 } else { /* gap between S1 and S2 */
290 h->loss_start = tfrc_rx_hist_index(h, 1);
291 h->loss_count = 2;
292 }
293 }
294
295 /**
296 * tfrc_rx_handle_loss - Loss detection and further processing
297 * @h: The non-empty RX history object
298 * @lh: Loss Intervals database to update
299 * @skb: Currently received packet
300 * @ndp: The NDP count belonging to @skb
301 * @calc_first_li: Caller-dependent computation of first loss interval in @lh
302 * @sk: Used by @calc_first_li (see tfrc_lh_interval_add)
303 *
304 * Chooses action according to pending loss, updates LI database when a new
305 * loss was detected, and does required post-processing. Returns 1 when caller
306 * should send feedback, 0 otherwise.
307 * Since it also takes care of reordering during loss detection and updates the
308 * records accordingly, the caller should not perform any more RX history
309 * operations when loss_count is greater than 0 after calling this function.
310 */
311 int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
312 struct tfrc_loss_hist *lh,
313 struct sk_buff *skb, const u64 ndp,
314 u32 (*calc_first_li)(struct sock *), struct sock *sk)
315 {
316 int is_new_loss = 0;
317
318 if (h->loss_count == 0) {
319 __do_track_loss(h, skb, ndp);
320 } else if (h->loss_count == 1) {
321 __one_after_loss(h, skb, ndp);
322 } else if (h->loss_count != 2) {
323 DCCP_BUG("invalid loss_count %d", h->loss_count);
324 } else if (__two_after_loss(h, skb, ndp)) {
325 /*
326 * Update Loss Interval database and recycle RX records
327 */
328 is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
329 __three_after_loss(h);
330 }
331 return is_new_loss;
332 }
333
334 int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
335 {
336 int i;
337
338 for (i = 0; i <= TFRC_NDUPACK; i++) {
339 h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
340 if (h->ring[i] == NULL)
341 goto out_free;
342 }
343
344 h->loss_count = h->loss_start = 0;
345 return 0;
346
347 out_free:
348 while (i-- != 0) {
349 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
350 h->ring[i] = NULL;
351 }
352 return -ENOBUFS;
353 }
354
355 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
356 {
357 int i;
358
359 for (i = 0; i <= TFRC_NDUPACK; ++i)
360 if (h->ring[i] != NULL) {
361 kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
362 h->ring[i] = NULL;
363 }
364 }
365
366 /**
367 * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
368 * @h: The non-empty RX history object
369 */
370 static inline struct tfrc_rx_hist_entry *
371 tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
372 {
373 return h->ring[0];
374 }
375
376 /**
377 * tfrc_rx_hist_rtt_prev_s - previously suitable (wrt rtt_last_s) RTT-sampling entry
378 * @h: The non-empty RX history object
379 */
380 static inline struct tfrc_rx_hist_entry *
381 tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
382 {
383 return h->ring[h->rtt_sample_prev];
384 }
385
386 /**
387 * tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal
388 * @h: receive histogram
389 * @skb: packet containing timestamp.
390 *
391 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
392 * to compute a sample with given data - calling function should check this.
393 */
394 u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
395 {
396 u32 sample = 0,
397 delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
398 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
399
400 if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */
401 if (h->rtt_sample_prev == 2) { /* previous candidate stored */
402 sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
403 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
404 if (sample)
405 sample = 4 / sample *
406 ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
407 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
408 else /*
409 * FIXME: This condition is in principle not
410 * possible but occurs when CCID is used for
411 * two-way data traffic. I have tried to trace
412 * it, but the cause does not seem to be here.
413 */
414 DCCP_BUG("please report to dccp@vger.kernel.org"
415 " => prev = %u, last = %u",
416 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
417 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
418 } else if (delta_v < 1) {
419 h->rtt_sample_prev = 1;
420 goto keep_ref_for_next_time;
421 }
422
423 } else if (delta_v == 4) /* optimal match */
424 sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
425 else { /* suboptimal match */
426 h->rtt_sample_prev = 2;
427 goto keep_ref_for_next_time;
428 }
429
430 if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
431 DCCP_WARN("RTT sample %u too large, using max\n", sample);
432 sample = DCCP_SANE_RTT_MAX;
433 }
434
435 h->rtt_sample_prev = 0; /* use current entry as next reference */
436 keep_ref_for_next_time:
437
438 return sample;
439 }
440
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