[TFRC]: CCID3 (and CCID4) needs to access these inlines
[linux-2.6] / net / dccp / ccids / lib / packet_history.c
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);