summaryrefslogtreecommitdiffstats
path: root/net/dccp/ccids/lib/packet_history.c
blob: 2d41bb036271b53ce87b979c5f332ecb9a27f8d6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
 *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
 *
 *  An implementation of the DCCP protocol
 *
 *  This code has been developed by the University of Waikato WAND
 *  research group. For further information please see http://www.wand.net.nz/
 *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
 *
 *  This code also uses code from Lulea University, rereleased as GPL by its
 *  authors:
 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
 *
 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
 *  and to make it work as a loadable module in the DCCP stack written by
 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
 *
 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 */

#include <linux/string.h>
#include <linux/slab.h>
#include "packet_history.h"
#include "../../dccp.h"

/*
 * Transmitter History Routines
 */
static struct kmem_cache *tfrc_tx_hist_slab;

int __init tfrc_tx_packet_history_init(void)
{
	tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
					      sizeof(struct tfrc_tx_hist_entry),
					      0, SLAB_HWCACHE_ALIGN, NULL);
	return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
}

void tfrc_tx_packet_history_exit(void)
{
	if (tfrc_tx_hist_slab != NULL) {
		kmem_cache_destroy(tfrc_tx_hist_slab);
		tfrc_tx_hist_slab = NULL;
	}
}

int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
{
	struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());

	if (entry == NULL)
		return -ENOBUFS;
	entry->seqno = seqno;
	entry->stamp = ktime_get_real();
	entry->next  = *headp;
	*headp	     = entry;
	return 0;
}

void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
{
	struct tfrc_tx_hist_entry *head = *headp;

	while (head != NULL) {
		struct tfrc_tx_hist_entry *next = head->next;

		kmem_cache_free(tfrc_tx_hist_slab, head);
		head = next;
	}

	*headp = NULL;
}

/*
 *	Receiver History Routines
 */
static struct kmem_cache *tfrc_rx_hist_slab;

int __init tfrc_rx_packet_history_init(void)
{
	tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
					      sizeof(struct tfrc_rx_hist_entry),
					      0, SLAB_HWCACHE_ALIGN, NULL);
	return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
}

void tfrc_rx_packet_history_exit(void)
{
	if (tfrc_rx_hist_slab != NULL) {
		kmem_cache_destroy(tfrc_rx_hist_slab);
		tfrc_rx_hist_slab = NULL;
	}
}

static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
					       const struct sk_buff *skb,
					       const u64 ndp)
{
	const struct dccp_hdr *dh = dccp_hdr(skb);

	entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
	entry->tfrchrx_ccval = dh->dccph_ccval;
	entry->tfrchrx_type  = dh->dccph_type;
	entry->tfrchrx_ndp   = ndp;
	entry->tfrchrx_tstamp = ktime_get_real();
}

void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
			     const struct sk_buff *skb,
			     const u64 ndp)
{
	struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);

	tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
}

/* has the packet contained in skb been seen before? */
int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
{
	const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
	int i;

	if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
		return 1;

	for (i = 1; i <= h->loss_count; i++)
		if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
			return 1;

	return 0;
}

static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
{
	const u8 idx_a = tfrc_rx_hist_index(h, a),
		 idx_b = tfrc_rx_hist_index(h, b);

	swap(h->ring[idx_a], h->ring[idx_b]);
}

/*
 * Private helper functions for loss detection.
 *
 * In the descriptions, `Si' refers to the sequence number of entry number i,
 * whose NDP count is `Ni' (lower case is used for variables).
 * Note: All __xxx_loss functions expect that a test against duplicates has been
 *       performed already: the seqno of the skb must not be less than the seqno
 *       of loss_prev; and it must not equal that of any valid history entry.
 */
static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
{
	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
	    s1 = DCCP_SKB_CB(skb)->dccpd_seq;

	if (!dccp_loss_free(s0, s1, n1)) {	/* gap between S0 and S1 */
		h->loss_count = 1;
		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
	}
}

static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
{
	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
	    s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
	    s2 = DCCP_SKB_CB(skb)->dccpd_seq;

	if (likely(dccp_delta_seqno(s1, s2) > 0)) {	/* S1  <  S2 */
		h->loss_count = 2;
		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
		return;
	}

	/* S0  <  S2  <  S1 */

	if (dccp_loss_free(s0, s2, n2)) {
		u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;

		if (dccp_loss_free(s2, s1, n1)) {
			/* hole is filled: S0, S2, and S1 are consecutive */
			h->loss_count = 0;
			h->loss_start = tfrc_rx_hist_index(h, 1);
		} else
			/* gap between S2 and S1: just update loss_prev */
			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);

	} else {	/* gap between S0 and S2 */
		/*
		 * Reorder history to insert S2 between S0 and S1
		 */
		tfrc_rx_hist_swap(h, 0, 3);
		h->loss_start = tfrc_rx_hist_index(h, 3);
		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
		h->loss_count = 2;
	}
}

/* return 1 if a new loss event has been identified */
static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
{
	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
	    s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
	    s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
	    s3 = DCCP_SKB_CB(skb)->dccpd_seq;

	if (likely(dccp_delta_seqno(s2, s3) > 0)) {	/* S2  <  S3 */
		h->loss_count = 3;
		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
		return 1;
	}

	/* S3  <  S2 */

	if (dccp_delta_seqno(s1, s3) > 0) {		/* S1  <  S3  <  S2 */
		/*
		 * Reorder history to insert S3 between S1 and S2
		 */
		tfrc_rx_hist_swap(h, 2, 3);
		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
		h->loss_count = 3;
		return 1;
	}

	/* S0  <  S3  <  S1 */

	if (dccp_loss_free(s0, s3, n3)) {
		u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;

		if (dccp_loss_free(s3, s1, n1)) {
			/* hole between S0 and S1 filled by S3 */
			u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;

			if (dccp_loss_free(s1, s2, n2)) {
				/* entire hole filled by S0, S3, S1, S2 */
				h->loss_start = tfrc_rx_hist_index(h, 2);
				h->loss_count = 0;
			} else {
				/* gap remains between S1 and S2 */
				h->loss_start = tfrc_rx_hist_index(h, 1);
				h->loss_count = 1;
			}

		} else /* gap exists between S3 and S1, loss_count stays at 2 */
			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);

		return 0;
	}

	/*
	 * The remaining case:  S0  <  S3  <  S1  <  S2;  gap between S0 and S3
	 * Reorder history to insert S3 between S0 and S1.
	 */
	tfrc_rx_hist_swap(h, 0, 3);
	h->loss_start = tfrc_rx_hist_index(h, 3);
	tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
	h->loss_count = 3;

	return 1;
}

/* recycle RX history records to continue loss detection if necessary */
static void __three_after_loss(struct tfrc_rx_hist *h)
{
	/*
	 * At this stage we know already that there is a gap between S0 and S1
	 * (since S0 was the highest sequence number received before detecting
	 * the loss). To recycle the loss record, it is	thus only necessary to
	 * check for other possible gaps between S1/S2 and between S2/S3.
	 */
	u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
	    s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
	    s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
	u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
	    n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;

	if (dccp_loss_free(s1, s2, n2)) {

		if (dccp_loss_free(s2, s3, n3)) {
			/* no gap between S2 and S3: entire hole is filled */
			h->loss_start = tfrc_rx_hist_index(h, 3);
			h->loss_count = 0;
		} else {
			/* gap between S2 and S3 */
			h->loss_start = tfrc_rx_hist_index(h, 2);
			h->loss_count = 1;
		}

	} else {	/* gap between S1 and S2 */
		h->loss_start = tfrc_rx_hist_index(h, 1);
		h->loss_count = 2;
	}
}

/**
 *  tfrc_rx_handle_loss  -  Loss detection and further processing
 *  @h:		    The non-empty RX history object
 *  @lh:	    Loss Intervals database to update
 *  @skb:	    Currently received packet
 *  @ndp:	    The NDP count belonging to @skb
 *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
 *  @sk:	    Used by @calc_first_li (see tfrc_lh_interval_add)
 *
 *  Chooses action according to pending loss, updates LI database when a new
 *  loss was detected, and does required post-processing. Returns 1 when caller
 *  should send feedback, 0 otherwise.
 *  Since it also takes care of reordering during loss detection and updates the
 *  records accordingly, the caller should not perform any more RX history
 *  operations when loss_count is greater than 0 after calling this function.
 */
int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
			struct tfrc_loss_hist *lh,
			struct sk_buff *skb, const u64 ndp,
			u32 (*calc_first_li)(struct sock *), struct sock *sk)
{
	int is_new_loss = 0;

	if (h->loss_count == 0) {
		__do_track_loss(h, skb, ndp);
	} else if (h->loss_count == 1) {
		__one_after_loss(h, skb, ndp);
	} else if (h->loss_count != 2) {
		DCCP_BUG("invalid loss_count %d", h->loss_count);
	} else if (__two_after_loss(h, skb, ndp)) {
		/*
		 * Update Loss Interval database and recycle RX records
		 */
		is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
		__three_after_loss(h);
	}
	return is_new_loss;
}

int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
{
	int i;

	for (i = 0; i <= TFRC_NDUPACK; i++) {
		h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
		if (h->ring[i] == NULL)
			goto out_free;
	}

	h->loss_count = h->loss_start = 0;
	return 0;

out_free:
	while (i-- != 0) {
		kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
		h->ring[i] = NULL;
	}
	return -ENOBUFS;
}

void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
{
	int i;

	for (i = 0; i <= TFRC_NDUPACK; ++i)
		if (h->ring[i] != NULL) {
			kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
			h->ring[i] = NULL;
		}
}

/**
 * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
 */
static inline struct tfrc_rx_hist_entry *
			tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
{
	return h->ring[0];
}

/**
 * tfrc_rx_hist_rtt_prev_s - previously suitable (wrt rtt_last_s) RTT-sampling entry
 */
static inline struct tfrc_rx_hist_entry *
			tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
{
	return h->ring[h->rtt_sample_prev];
}

/**
 * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
 * to compute a sample with given data - calling function should check this.
 */
u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
{
	u32 sample = 0,
	    delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
			    tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);

	if (delta_v < 1 || delta_v > 4) {	/* unsuitable CCVal delta */
		if (h->rtt_sample_prev == 2) {	/* previous candidate stored */
			sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
				       tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
			if (sample)
				sample = 4 / sample *
				         ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
							tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
			else    /*
				 * FIXME: This condition is in principle not
				 * possible but occurs when CCID is used for
				 * two-way data traffic. I have tried to trace
				 * it, but the cause does not seem to be here.
				 */
				DCCP_BUG("please report to dccp@vger.kernel.org"
					 " => prev = %u, last = %u",
					 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
					 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
		} else if (delta_v < 1) {
			h->rtt_sample_prev = 1;
			goto keep_ref_for_next_time;
		}

	} else if (delta_v == 4) /* optimal match */
		sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
	else {			 /* suboptimal match */
		h->rtt_sample_prev = 2;
		goto keep_ref_for_next_time;
	}

	if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
		DCCP_WARN("RTT sample %u too large, using max\n", sample);
		sample = DCCP_SANE_RTT_MAX;
	}

	h->rtt_sample_prev = 0;	       /* use current entry as next reference */
keep_ref_for_next_time:

	return sample;
}