1// SPDX-License-Identifier: GPL-2.0-or-later
2/* SCTP kernel implementation
3 * (C) Copyright IBM Corp. 2001, 2004
4 * Copyright (c) 1999-2000 Cisco, Inc.
5 * Copyright (c) 1999-2001 Motorola, Inc.
6 * Copyright (c) 2001 Intel Corp.
7 *
8 * This file is part of the SCTP kernel implementation
9 *
10 * These functions manipulate sctp tsn mapping array.
11 *
12 * Please send any bug reports or fixes you make to the
13 * email address(es):
14 *    lksctp developers <linux-sctp@vger.kernel.org>
15 *
16 * Written or modified by:
17 *    La Monte H.P. Yarroll <piggy@acm.org>
18 *    Jon Grimm             <jgrimm@us.ibm.com>
19 *    Karl Knutson          <karl@athena.chicago.il.us>
20 *    Sridhar Samudrala     <sri@us.ibm.com>
21 */
22
23#include <linux/slab.h>
24#include <linux/types.h>
25#include <linux/bitmap.h>
26#include <net/sctp/sctp.h>
27#include <net/sctp/sm.h>
28
29static void sctp_tsnmap_update(struct sctp_tsnmap *map);
30static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
31				     __u16 len, __u16 *start, __u16 *end);
32static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 size);
33
34/* Initialize a block of memory as a tsnmap.  */
35struct sctp_tsnmap *sctp_tsnmap_init(struct sctp_tsnmap *map, __u16 len,
36				     __u32 initial_tsn, gfp_t gfp)
37{
38	if (!map->tsn_map) {
39		map->tsn_map = kzalloc(len>>3, gfp);
40		if (map->tsn_map == NULL)
41			return NULL;
42
43		map->len = len;
44	} else {
45		bitmap_zero(map->tsn_map, map->len);
46	}
47
48	/* Keep track of TSNs represented by tsn_map.  */
49	map->base_tsn = initial_tsn;
50	map->cumulative_tsn_ack_point = initial_tsn - 1;
51	map->max_tsn_seen = map->cumulative_tsn_ack_point;
52	map->num_dup_tsns = 0;
53
54	return map;
55}
56
57void sctp_tsnmap_free(struct sctp_tsnmap *map)
58{
59	map->len = 0;
60	kfree(map->tsn_map);
61}
62
63/* Test the tracking state of this TSN.
64 * Returns:
65 *   0 if the TSN has not yet been seen
66 *  >0 if the TSN has been seen (duplicate)
67 *  <0 if the TSN is invalid (too large to track)
68 */
69int sctp_tsnmap_check(const struct sctp_tsnmap *map, __u32 tsn)
70{
71	u32 gap;
72
73	/* Check to see if this is an old TSN */
74	if (TSN_lte(tsn, map->cumulative_tsn_ack_point))
75		return 1;
76
77	/* Verify that we can hold this TSN and that it will not
78	 * overflow our map
79	 */
80	if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
81		return -1;
82
83	/* Calculate the index into the mapping arrays.  */
84	gap = tsn - map->base_tsn;
85
86	/* Check to see if TSN has already been recorded.  */
87	if (gap < map->len && test_bit(gap, map->tsn_map))
88		return 1;
89	else
90		return 0;
91}
92
93
94/* Mark this TSN as seen.  */
95int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn,
96		     struct sctp_transport *trans)
97{
98	u16 gap;
99
100	if (TSN_lt(tsn, map->base_tsn))
101		return 0;
102
103	gap = tsn - map->base_tsn;
104
105	if (gap >= map->len && !sctp_tsnmap_grow(map, gap + 1))
106		return -ENOMEM;
107
108	if (!sctp_tsnmap_has_gap(map) && gap == 0) {
109		/* In this case the map has no gaps and the tsn we are
110		 * recording is the next expected tsn.  We don't touch
111		 * the map but simply bump the values.
112		 */
113		map->max_tsn_seen++;
114		map->cumulative_tsn_ack_point++;
115		if (trans)
116			trans->sack_generation =
117				trans->asoc->peer.sack_generation;
118		map->base_tsn++;
119	} else {
120		/* Either we already have a gap, or about to record a gap, so
121		 * have work to do.
122		 *
123		 * Bump the max.
124		 */
125		if (TSN_lt(map->max_tsn_seen, tsn))
126			map->max_tsn_seen = tsn;
127
128		/* Mark the TSN as received.  */
129		set_bit(gap, map->tsn_map);
130
131		/* Go fixup any internal TSN mapping variables including
132		 * cumulative_tsn_ack_point.
133		 */
134		sctp_tsnmap_update(map);
135	}
136
137	return 0;
138}
139
140
141/* Initialize a Gap Ack Block iterator from memory being provided.  */
142static void sctp_tsnmap_iter_init(const struct sctp_tsnmap *map,
143				  struct sctp_tsnmap_iter *iter)
144{
145	/* Only start looking one past the Cumulative TSN Ack Point.  */
146	iter->start = map->cumulative_tsn_ack_point + 1;
147}
148
149/* Get the next Gap Ack Blocks. Returns 0 if there was not another block
150 * to get.
151 */
152static int sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap *map,
153				    struct sctp_tsnmap_iter *iter,
154				    __u16 *start, __u16 *end)
155{
156	int ended = 0;
157	__u16 start_ = 0, end_ = 0, offset;
158
159	/* If there are no more gap acks possible, get out fast.  */
160	if (TSN_lte(map->max_tsn_seen, iter->start))
161		return 0;
162
163	offset = iter->start - map->base_tsn;
164	sctp_tsnmap_find_gap_ack(map->tsn_map, offset, map->len,
165				 &start_, &end_);
166
167	/* The Gap Ack Block happens to end at the end of the map. */
168	if (start_ && !end_)
169		end_ = map->len - 1;
170
171	/* If we found a Gap Ack Block, return the start and end and
172	 * bump the iterator forward.
173	 */
174	if (end_) {
175		/* Fix up the start and end based on the
176		 * Cumulative TSN Ack which is always 1 behind base.
177		 */
178		*start = start_ + 1;
179		*end = end_ + 1;
180
181		/* Move the iterator forward.  */
182		iter->start = map->cumulative_tsn_ack_point + *end + 1;
183		ended = 1;
184	}
185
186	return ended;
187}
188
189/* Mark this and any lower TSN as seen.  */
190void sctp_tsnmap_skip(struct sctp_tsnmap *map, __u32 tsn)
191{
192	u32 gap;
193
194	if (TSN_lt(tsn, map->base_tsn))
195		return;
196	if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
197		return;
198
199	/* Bump the max.  */
200	if (TSN_lt(map->max_tsn_seen, tsn))
201		map->max_tsn_seen = tsn;
202
203	gap = tsn - map->base_tsn + 1;
204
205	map->base_tsn += gap;
206	map->cumulative_tsn_ack_point += gap;
207	if (gap >= map->len) {
208		/* If our gap is larger then the map size, just
209		 * zero out the map.
210		 */
211		bitmap_zero(map->tsn_map, map->len);
212	} else {
213		/* If the gap is smaller than the map size,
214		 * shift the map by 'gap' bits and update further.
215		 */
216		bitmap_shift_right(map->tsn_map, map->tsn_map, gap, map->len);
217		sctp_tsnmap_update(map);
218	}
219}
220
221/********************************************************************
222 * 2nd Level Abstractions
223 ********************************************************************/
224
225/* This private helper function updates the tsnmap buffers and
226 * the Cumulative TSN Ack Point.
227 */
228static void sctp_tsnmap_update(struct sctp_tsnmap *map)
229{
230	u16 len;
231	unsigned long zero_bit;
232
233
234	len = map->max_tsn_seen - map->cumulative_tsn_ack_point;
235	zero_bit = find_first_zero_bit(map->tsn_map, len);
236	if (!zero_bit)
237		return;		/* The first 0-bit is bit 0.  nothing to do */
238
239	map->base_tsn += zero_bit;
240	map->cumulative_tsn_ack_point += zero_bit;
241
242	bitmap_shift_right(map->tsn_map, map->tsn_map, zero_bit, map->len);
243}
244
245/* How many data chunks  are we missing from our peer?
246 */
247__u16 sctp_tsnmap_pending(struct sctp_tsnmap *map)
248{
249	__u32 cum_tsn = map->cumulative_tsn_ack_point;
250	__u32 max_tsn = map->max_tsn_seen;
251	__u32 base_tsn = map->base_tsn;
252	__u16 pending_data;
253	u32 gap;
254
255	pending_data = max_tsn - cum_tsn;
256	gap = max_tsn - base_tsn;
257
258	if (gap == 0 || gap >= map->len)
259		goto out;
260
261	pending_data -= bitmap_weight(map->tsn_map, gap + 1);
262out:
263	return pending_data;
264}
265
266/* This is a private helper for finding Gap Ack Blocks.  It searches a
267 * single array for the start and end of a Gap Ack Block.
268 *
269 * The flags "started" and "ended" tell is if we found the beginning
270 * or (respectively) the end of a Gap Ack Block.
271 */
272static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
273				     __u16 len, __u16 *start, __u16 *end)
274{
275	int i = off;
276
277	/* Look through the entire array, but break out
278	 * early if we have found the end of the Gap Ack Block.
279	 */
280
281	/* Also, stop looking past the maximum TSN seen. */
282
283	/* Look for the start. */
284	i = find_next_bit(map, len, off);
285	if (i < len)
286		*start = i;
287
288	/* Look for the end.  */
289	if (*start) {
290		/* We have found the start, let's find the
291		 * end.  If we find the end, break out.
292		 */
293		i = find_next_zero_bit(map, len, i);
294		if (i < len)
295			*end = i - 1;
296	}
297}
298
299/* Renege that we have seen a TSN.  */
300void sctp_tsnmap_renege(struct sctp_tsnmap *map, __u32 tsn)
301{
302	u32 gap;
303
304	if (TSN_lt(tsn, map->base_tsn))
305		return;
306	/* Assert: TSN is in range.  */
307	if (!TSN_lt(tsn, map->base_tsn + map->len))
308		return;
309
310	gap = tsn - map->base_tsn;
311
312	/* Pretend we never saw the TSN.  */
313	clear_bit(gap, map->tsn_map);
314}
315
316/* How many gap ack blocks do we have recorded? */
317__u16 sctp_tsnmap_num_gabs(struct sctp_tsnmap *map,
318			   struct sctp_gap_ack_block *gabs)
319{
320	struct sctp_tsnmap_iter iter;
321	int ngaps = 0;
322
323	/* Refresh the gap ack information. */
324	if (sctp_tsnmap_has_gap(map)) {
325		__u16 start = 0, end = 0;
326		sctp_tsnmap_iter_init(map, &iter);
327		while (sctp_tsnmap_next_gap_ack(map, &iter,
328						&start,
329						&end)) {
330
331			gabs[ngaps].start = htons(start);
332			gabs[ngaps].end = htons(end);
333			ngaps++;
334			if (ngaps >= SCTP_MAX_GABS)
335				break;
336		}
337	}
338	return ngaps;
339}
340
341static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 size)
342{
343	unsigned long *new;
344	unsigned long inc;
345	u16  len;
346
347	if (size > SCTP_TSN_MAP_SIZE)
348		return 0;
349
350	inc = ALIGN((size - map->len), BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
351	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
352
353	new = kzalloc(len>>3, GFP_ATOMIC);
354	if (!new)
355		return 0;
356
357	bitmap_copy(new, map->tsn_map,
358		map->max_tsn_seen - map->cumulative_tsn_ack_point);
359	kfree(map->tsn_map);
360	map->tsn_map = new;
361	map->len = len;
362
363	return 1;
364}
365