/net/dccp/ccids/lib/packet_history.c

  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 http://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 */
 31static struct kmem_cache *tfrc_tx_hist_slab;
 32
 33int __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
 41void 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
 49int 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
 62void 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 */
 79static struct kmem_cache *tfrc_rx_hist_slab;
 80
 81int __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
 89void 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
 97static 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
110void 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? */
120int 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
135static 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 */
152static 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
163static 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 */
200static 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 */
263static 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 */
311int 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
334int 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
347out_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
355void 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 */
369static inline struct tfrc_rx_hist_entry *
370			tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
371{
372	return h->ring[0];
373}
374
375/**
376 * tfrc_rx_hist_rtt_prev_s - previously suitable (wrt rtt_last_s) RTT-sampling entry
377 */
378static inline struct tfrc_rx_hist_entry *
379			tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
380{
381	return h->ring[h->rtt_sample_prev];
382}
383
384/**
385 * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
386 * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
387 * to compute a sample with given data - calling function should check this.
388 */
389u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
390{
391	u32 sample = 0,
392	    delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
393			    tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
394
395	if (delta_v < 1 || delta_v > 4) {	/* unsuitable CCVal delta */
396		if (h->rtt_sample_prev == 2) {	/* previous candidate stored */
397			sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
398				       tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
399			if (sample)
400				sample = 4 / sample *
401				         ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
402							tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
403			else    /*
404				 * FIXME: This condition is in principle not
405				 * possible but occurs when CCID is used for
406				 * two-way data traffic. I have tried to trace
407				 * it, but the cause does not seem to be here.
408				 */
409				DCCP_BUG("please report to dccp@vger.kernel.org"
410					 " => prev = %u, last = %u",
411					 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
412					 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
413		} else if (delta_v < 1) {
414			h->rtt_sample_prev = 1;
415			goto keep_ref_for_next_time;
416		}
417
418	} else if (delta_v == 4) /* optimal match */
419		sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
420	else {			 /* suboptimal match */
421		h->rtt_sample_prev = 2;
422		goto keep_ref_for_next_time;
423	}
424
425	if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
426		DCCP_WARN("RTT sample %u too large, using max\n", sample);
427		sample = DCCP_SANE_RTT_MAX;
428	}
429
430	h->rtt_sample_prev = 0;	       /* use current entry as next reference */
431keep_ref_for_next_time:
432
433	return sample;
434}