xref: /linux/net/sctp/tsnmap.c (revision c37fe6aff89cb0d842993fe2f69e48bf3ebe0ab0)
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 
29 static void sctp_tsnmap_update(struct sctp_tsnmap *map);
30 static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
31 				     __u16 len, __u16 *start, __u16 *end);
32 static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 size);
33 
34 /* Initialize a block of memory as a tsnmap.  */
sctp_tsnmap_init(struct sctp_tsnmap * map,__u16 len,__u32 initial_tsn,gfp_t gfp)35 struct 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 
sctp_tsnmap_free(struct sctp_tsnmap * map)57 void 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  */
sctp_tsnmap_check(const struct sctp_tsnmap * map,__u32 tsn)69 int 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.  */
sctp_tsnmap_mark(struct sctp_tsnmap * map,__u32 tsn,struct sctp_transport * trans)95 int 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.  */
sctp_tsnmap_iter_init(const struct sctp_tsnmap * map,struct sctp_tsnmap_iter * iter)142 static 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  */
sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap * map,struct sctp_tsnmap_iter * iter,__u16 * start,__u16 * end)152 static 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.  */
sctp_tsnmap_skip(struct sctp_tsnmap * map,__u32 tsn)190 void 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  */
sctp_tsnmap_update(struct sctp_tsnmap * map)228 static 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  */
sctp_tsnmap_pending(struct sctp_tsnmap * map)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);
262 out:
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  */
sctp_tsnmap_find_gap_ack(unsigned long * map,__u16 off,__u16 len,__u16 * start,__u16 * end)272 static 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.  */
sctp_tsnmap_renege(struct sctp_tsnmap * map,__u32 tsn)300 void 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? */
sctp_tsnmap_num_gabs(struct sctp_tsnmap * map,struct sctp_gap_ack_block * gabs)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 
sctp_tsnmap_grow(struct sctp_tsnmap * map,u16 size)341 static 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