1/*
2 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
3 *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
4 *
5 *  An implementation of the DCCP protocol
6 *
7 *  This code has been developed by the University of Waikato WAND
8 *  research group. For further information please see http://www.wand.net.nz/
9 *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
10 *
11 *  This code also uses code from Lulea University, rereleased as GPL by its
12 *  authors:
13 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
14 *
15 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
16 *  and to make it work as a loadable module in the DCCP stack written by
17 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
18 *
19 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
20 *
21 *  This program is free software; you can redistribute it and/or modify
22 *  it under the terms of the GNU General Public License as published by
23 *  the Free Software Foundation; either version 2 of the License, or
24 *  (at your option) any later version.
25 *
26 *  This program is distributed in the hope that it will be useful,
27 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
28 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
29 *  GNU General Public License for more details.
30 *
31 *  You should have received a copy of the GNU General Public License
32 *  along with this program; if not, write to the Free Software
33 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
34 */
35
36#include <linux/string.h>
37#include <linux/slab.h>
38#include "packet_history.h"
39#include "../../dccp.h"
40
41/*
42 * Transmitter History Routines
43 */
44static struct kmem_cache *tfrc_tx_hist_slab;
45
46int __init tfrc_tx_packet_history_init(void)
47{
48	tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
49					      sizeof(struct tfrc_tx_hist_entry),
50					      0, SLAB_HWCACHE_ALIGN, NULL);
51	return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
52}
53
54void tfrc_tx_packet_history_exit(void)
55{
56	if (tfrc_tx_hist_slab != NULL) {
57		kmem_cache_destroy(tfrc_tx_hist_slab);
58		tfrc_tx_hist_slab = NULL;
59	}
60}
61
62int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
63{
64	struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
65
66	if (entry == NULL)
67		return -ENOBUFS;
68	entry->seqno = seqno;
69	entry->stamp = ktime_get_real();
70	entry->next  = *headp;
71	*headp	     = entry;
72	return 0;
73}
74
75void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
76{
77	struct tfrc_tx_hist_entry *head = *headp;
78
79	while (head != NULL) {
80		struct tfrc_tx_hist_entry *next = head->next;
81
82		kmem_cache_free(tfrc_tx_hist_slab, head);
83		head = next;
84	}
85
86	*headp = NULL;
87}
88
89/*
90 *	Receiver History Routines
91 */
92static struct kmem_cache *tfrc_rx_hist_slab;
93
94int __init tfrc_rx_packet_history_init(void)
95{
96	tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
97					      sizeof(struct tfrc_rx_hist_entry),
98					      0, SLAB_HWCACHE_ALIGN, NULL);
99	return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
100}
101
102void tfrc_rx_packet_history_exit(void)
103{
104	if (tfrc_rx_hist_slab != NULL) {
105		kmem_cache_destroy(tfrc_rx_hist_slab);
106		tfrc_rx_hist_slab = NULL;
107	}
108}
109
110static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
111					       const struct sk_buff *skb,
112					       const u64 ndp)
113{
114	const struct dccp_hdr *dh = dccp_hdr(skb);
115
116	entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
117	entry->tfrchrx_ccval = dh->dccph_ccval;
118	entry->tfrchrx_type  = dh->dccph_type;
119	entry->tfrchrx_ndp   = ndp;
120	entry->tfrchrx_tstamp = ktime_get_real();
121}
122
123void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
124			     const struct sk_buff *skb,
125			     const u64 ndp)
126{
127	struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
128
129	tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
130}
131
132/* has the packet contained in skb been seen before? */
133int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
134{
135	const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
136	int i;
137
138	if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
139		return 1;
140
141	for (i = 1; i <= h->loss_count; i++)
142		if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
143			return 1;
144
145	return 0;
146}
147
148static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
149{
150	const u8 idx_a = tfrc_rx_hist_index(h, a),
151		 idx_b = tfrc_rx_hist_index(h, b);
152	struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
153
154	h->ring[idx_a] = h->ring[idx_b];
155	h->ring[idx_b] = tmp;
156}
157
158/*
159 * Private helper functions for loss detection.
160 *
161 * In the descriptions, `Si' refers to the sequence number of entry number i,
162 * whose NDP count is `Ni' (lower case is used for variables).
163 * Note: All __xxx_loss functions expect that a test against duplicates has been
164 *       performed already: the seqno of the skb must not be less than the seqno
165 *       of loss_prev; and it must not equal that of any valid history entry.
166 */
167static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
168{
169	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
170	    s1 = DCCP_SKB_CB(skb)->dccpd_seq;
171
172	if (!dccp_loss_free(s0, s1, n1)) {	/* gap between S0 and S1 */
173		h->loss_count = 1;
174		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
175	}
176}
177
178static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
179{
180	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
181	    s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
182	    s2 = DCCP_SKB_CB(skb)->dccpd_seq;
183
184	if (likely(dccp_delta_seqno(s1, s2) > 0)) {	/* S1  <  S2 */
185		h->loss_count = 2;
186		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
187		return;
188	}
189
190	/* S0  <  S2  <  S1 */
191
192	if (dccp_loss_free(s0, s2, n2)) {
193		u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
194
195		if (dccp_loss_free(s2, s1, n1)) {
196			/* hole is filled: S0, S2, and S1 are consecutive */
197			h->loss_count = 0;
198			h->loss_start = tfrc_rx_hist_index(h, 1);
199		} else
200			/* gap between S2 and S1: just update loss_prev */
201			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
202
203	} else {	/* gap between S0 and S2 */
204		/*
205		 * Reorder history to insert S2 between S0 and S1
206		 */
207		tfrc_rx_hist_swap(h, 0, 3);
208		h->loss_start = tfrc_rx_hist_index(h, 3);
209		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
210		h->loss_count = 2;
211	}
212}
213
214/* return 1 if a new loss event has been identified */
215static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
216{
217	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
218	    s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
219	    s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
220	    s3 = DCCP_SKB_CB(skb)->dccpd_seq;
221
222	if (likely(dccp_delta_seqno(s2, s3) > 0)) {	/* S2  <  S3 */
223		h->loss_count = 3;
224		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
225		return 1;
226	}
227
228	/* S3  <  S2 */
229
230	if (dccp_delta_seqno(s1, s3) > 0) {		/* S1  <  S3  <  S2 */
231		/*
232		 * Reorder history to insert S3 between S1 and S2
233		 */
234		tfrc_rx_hist_swap(h, 2, 3);
235		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
236		h->loss_count = 3;
237		return 1;
238	}
239
240	/* S0  <  S3  <  S1 */
241
242	if (dccp_loss_free(s0, s3, n3)) {
243		u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
244
245		if (dccp_loss_free(s3, s1, n1)) {
246			/* hole between S0 and S1 filled by S3 */
247			u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
248
249			if (dccp_loss_free(s1, s2, n2)) {
250				/* entire hole filled by S0, S3, S1, S2 */
251				h->loss_start = tfrc_rx_hist_index(h, 2);
252				h->loss_count = 0;
253			} else {
254				/* gap remains between S1 and S2 */
255				h->loss_start = tfrc_rx_hist_index(h, 1);
256				h->loss_count = 1;
257			}
258
259		} else /* gap exists between S3 and S1, loss_count stays at 2 */
260			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
261
262		return 0;
263	}
264
265	/*
266	 * The remaining case:  S0  <  S3  <  S1  <  S2;  gap between S0 and S3
267	 * Reorder history to insert S3 between S0 and S1.
268	 */
269	tfrc_rx_hist_swap(h, 0, 3);
270	h->loss_start = tfrc_rx_hist_index(h, 3);
271	tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
272	h->loss_count = 3;
273
274	return 1;
275}
276
277/* recycle RX history records to continue loss detection if necessary */
278static void __three_after_loss(struct tfrc_rx_hist *h)
279{
280	/*
281	 * At this stage we know already that there is a gap between S0 and S1
282	 * (since S0 was the highest sequence number received before detecting
283	 * the loss). To recycle the loss record, it is	thus only necessary to
284	 * check for other possible gaps between S1/S2 and between S2/S3.
285	 */
286	u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
287	    s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
288	    s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
289	u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
290	    n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
291
292	if (dccp_loss_free(s1, s2, n2)) {
293
294		if (dccp_loss_free(s2, s3, n3)) {
295			/* no gap between S2 and S3: entire hole is filled */
296			h->loss_start = tfrc_rx_hist_index(h, 3);
297			h->loss_count = 0;
298		} else {
299			/* gap between S2 and S3 */
300			h->loss_start = tfrc_rx_hist_index(h, 2);
301			h->loss_count = 1;
302		}
303
304	} else {	/* gap between S1 and S2 */
305		h->loss_start = tfrc_rx_hist_index(h, 1);
306		h->loss_count = 2;
307	}
308}
309
310/**
311 *  tfrc_rx_handle_loss  -  Loss detection and further processing
312 *  @h:		    The non-empty RX history object
313 *  @lh:	    Loss Intervals database to update
314 *  @skb:	    Currently received packet
315 *  @ndp:	    The NDP count belonging to @skb
316 *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
317 *  @sk:	    Used by @calc_first_li (see tfrc_lh_interval_add)
318 *
319 *  Chooses action according to pending loss, updates LI database when a new
320 *  loss was detected, and does required post-processing. Returns 1 when caller
321 *  should send feedback, 0 otherwise.
322 *  Since it also takes care of reordering during loss detection and updates the
323 *  records accordingly, the caller should not perform any more RX history
324 *  operations when loss_count is greater than 0 after calling this function.
325 */
326int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
327			struct tfrc_loss_hist *lh,
328			struct sk_buff *skb, const u64 ndp,
329			u32 (*calc_first_li)(struct sock *), struct sock *sk)
330{
331	int is_new_loss = 0;
332
333	if (h->loss_count == 0) {
334		__do_track_loss(h, skb, ndp);
335	} else if (h->loss_count == 1) {
336		__one_after_loss(h, skb, ndp);
337	} else if (h->loss_count != 2) {
338		DCCP_BUG("invalid loss_count %d", h->loss_count);
339	} else if (__two_after_loss(h, skb, ndp)) {
340		/*
341		 * Update Loss Interval database and recycle RX records
342		 */
343		is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
344		__three_after_loss(h);
345	}
346	return is_new_loss;
347}
348
349int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
350{
351	int i;
352
353	for (i = 0; i <= TFRC_NDUPACK; i++) {
354		h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
355		if (h->ring[i] == NULL)
356			goto out_free;
357	}
358
359	h->loss_count = h->loss_start = 0;
360	return 0;
361
362out_free:
363	while (i-- != 0) {
364		kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
365		h->ring[i] = NULL;
366	}
367	return -ENOBUFS;
368}
369
370void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
371{
372	int i;
373
374	for (i = 0; i <= TFRC_NDUPACK; ++i)
375		if (h->ring[i] != NULL) {
376			kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
377			h->ring[i] = NULL;
378		}
379}
380
381/**
382 * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
383 */
384static inline struct tfrc_rx_hist_entry *
385			tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
386{
387	return h->ring[0];
388}
389
390/**
391 * tfrc_rx_hist_rtt_prev_s - previously suitable (wrt rtt_last_s) RTT-sampling entry
392 */
393static inline struct tfrc_rx_hist_entry *
394			tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
395{
396	return h->ring[h->rtt_sample_prev];
397}
398
399/**
400 * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
401 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
402 * to compute a sample with given data - calling function should check this.
403 */
404u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
405{
406	u32 sample = 0,
407	    delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
408			    tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
409
410	if (delta_v < 1 || delta_v > 4) {	/* unsuitable CCVal delta */
411		if (h->rtt_sample_prev == 2) {	/* previous candidate stored */
412			sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
413				       tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
414			if (sample)
415				sample = 4 / sample *
416				         ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
417							tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
418			else    /*
419				 * FIXME: This condition is in principle not
420				 * possible but occurs when CCID is used for
421				 * two-way data traffic. I have tried to trace
422				 * it, but the cause does not seem to be here.
423				 */
424				DCCP_BUG("please report to dccp@vger.kernel.org"
425					 " => prev = %u, last = %u",
426					 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
427					 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
428		} else if (delta_v < 1) {
429			h->rtt_sample_prev = 1;
430			goto keep_ref_for_next_time;
431		}
432
433	} else if (delta_v == 4) /* optimal match */
434		sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
435	else {			 /* suboptimal match */
436		h->rtt_sample_prev = 2;
437		goto keep_ref_for_next_time;
438	}
439
440	if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
441		DCCP_WARN("RTT sample %u too large, using max\n", sample);
442		sample = DCCP_SANE_RTT_MAX;
443	}
444
445	h->rtt_sample_prev = 0;	       /* use current entry as next reference */
446keep_ref_for_next_time:
447
448	return sample;
449}
450