1 /* SCTP kernel implementation
2  * (C) Copyright IBM Corp. 2001, 2004
3  * Copyright (c) 1999-2000 Cisco, Inc.
4  * Copyright (c) 1999-2001 Motorola, Inc.
5  * Copyright (c) 2001 Intel Corp.
6  *
7  * This file is part of the SCTP kernel implementation
8  *
9  * These functions manipulate sctp tsn mapping array.
10  *
11  * This SCTP implementation is free software;
12  * you can redistribute it and/or modify it under the terms of
13  * the GNU General Public License as published by
14  * the Free Software Foundation; either version 2, or (at your option)
15  * any later version.
16  *
17  * This SCTP implementation is distributed in the hope that it
18  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
19  *                 ************************
20  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
21  * See the GNU General Public License for more details.
22  *
23  * You should have received a copy of the GNU General Public License
24  * along with GNU CC; see the file COPYING.  If not, write to
25  * the Free Software Foundation, 59 Temple Place - Suite 330,
26  * Boston, MA 02111-1307, USA.
27  *
28  * Please send any bug reports or fixes you make to the
29  * email address(es):
30  *    lksctp developers <lksctp-developers@lists.sourceforge.net>
31  *
32  * Or submit a bug report through the following website:
33  *    http://www.sf.net/projects/lksctp
34  *
35  * Written or modified by:
36  *    La Monte H.P. Yarroll <piggy@acm.org>
37  *    Jon Grimm             <jgrimm@us.ibm.com>
38  *    Karl Knutson          <karl@athena.chicago.il.us>
39  *    Sridhar Samudrala     <sri@us.ibm.com>
40  *
41  * Any bugs reported given to us we will try to fix... any fixes shared will
42  * be incorporated into the next SCTP release.
43  */
44 
45 #include <linux/slab.h>
46 #include <linux/types.h>
47 #include <linux/bitmap.h>
48 #include <net/sctp/sctp.h>
49 #include <net/sctp/sm.h>
50 
51 static void sctp_tsnmap_update(struct sctp_tsnmap *map);
52 static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
53 				     __u16 len, __u16 *start, __u16 *end);
54 static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 gap);
55 
56 /* Initialize a block of memory as a tsnmap.  */
sctp_tsnmap_init(struct sctp_tsnmap * map,__u16 len,__u32 initial_tsn,gfp_t gfp)57 struct sctp_tsnmap *sctp_tsnmap_init(struct sctp_tsnmap *map, __u16 len,
58 				     __u32 initial_tsn, gfp_t gfp)
59 {
60 	if (!map->tsn_map) {
61 		map->tsn_map = kzalloc(len>>3, gfp);
62 		if (map->tsn_map == NULL)
63 			return NULL;
64 
65 		map->len = len;
66 	} else {
67 		bitmap_zero(map->tsn_map, map->len);
68 	}
69 
70 	/* Keep track of TSNs represented by tsn_map.  */
71 	map->base_tsn = initial_tsn;
72 	map->cumulative_tsn_ack_point = initial_tsn - 1;
73 	map->max_tsn_seen = map->cumulative_tsn_ack_point;
74 	map->num_dup_tsns = 0;
75 
76 	return map;
77 }
78 
sctp_tsnmap_free(struct sctp_tsnmap * map)79 void sctp_tsnmap_free(struct sctp_tsnmap *map)
80 {
81 	map->len = 0;
82 	kfree(map->tsn_map);
83 }
84 
85 /* Test the tracking state of this TSN.
86  * Returns:
87  *   0 if the TSN has not yet been seen
88  *  >0 if the TSN has been seen (duplicate)
89  *  <0 if the TSN is invalid (too large to track)
90  */
sctp_tsnmap_check(const struct sctp_tsnmap * map,__u32 tsn)91 int sctp_tsnmap_check(const struct sctp_tsnmap *map, __u32 tsn)
92 {
93 	u32 gap;
94 
95 	/* Check to see if this is an old TSN */
96 	if (TSN_lte(tsn, map->cumulative_tsn_ack_point))
97 		return 1;
98 
99 	/* Verify that we can hold this TSN and that it will not
100 	 * overlfow our map
101 	 */
102 	if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
103 		return -1;
104 
105 	/* Calculate the index into the mapping arrays.  */
106 	gap = tsn - map->base_tsn;
107 
108 	/* Check to see if TSN has already been recorded.  */
109 	if (gap < map->len && test_bit(gap, map->tsn_map))
110 		return 1;
111 	else
112 		return 0;
113 }
114 
115 
116 /* Mark this TSN as seen.  */
sctp_tsnmap_mark(struct sctp_tsnmap * map,__u32 tsn)117 int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn)
118 {
119 	u16 gap;
120 
121 	if (TSN_lt(tsn, map->base_tsn))
122 		return 0;
123 
124 	gap = tsn - map->base_tsn;
125 
126 	if (gap >= map->len && !sctp_tsnmap_grow(map, gap))
127 		return -ENOMEM;
128 
129 	if (!sctp_tsnmap_has_gap(map) && gap == 0) {
130 		/* In this case the map has no gaps and the tsn we are
131 		 * recording is the next expected tsn.  We don't touch
132 		 * the map but simply bump the values.
133 		 */
134 		map->max_tsn_seen++;
135 		map->cumulative_tsn_ack_point++;
136 		map->base_tsn++;
137 	} else {
138 		/* Either we already have a gap, or about to record a gap, so
139 		 * have work to do.
140 		 *
141 		 * Bump the max.
142 		 */
143 		if (TSN_lt(map->max_tsn_seen, tsn))
144 			map->max_tsn_seen = tsn;
145 
146 		/* Mark the TSN as received.  */
147 		set_bit(gap, map->tsn_map);
148 
149 		/* Go fixup any internal TSN mapping variables including
150 		 * cumulative_tsn_ack_point.
151 		 */
152 		sctp_tsnmap_update(map);
153 	}
154 
155 	return 0;
156 }
157 
158 
159 /* Initialize a Gap Ack Block iterator from memory being provided.  */
sctp_tsnmap_iter_init(const struct sctp_tsnmap * map,struct sctp_tsnmap_iter * iter)160 SCTP_STATIC void sctp_tsnmap_iter_init(const struct sctp_tsnmap *map,
161 				       struct sctp_tsnmap_iter *iter)
162 {
163 	/* Only start looking one past the Cumulative TSN Ack Point.  */
164 	iter->start = map->cumulative_tsn_ack_point + 1;
165 }
166 
167 /* Get the next Gap Ack Blocks. Returns 0 if there was not another block
168  * to get.
169  */
sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap * map,struct sctp_tsnmap_iter * iter,__u16 * start,__u16 * end)170 SCTP_STATIC int sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap *map,
171 					 struct sctp_tsnmap_iter *iter,
172 					 __u16 *start, __u16 *end)
173 {
174 	int ended = 0;
175 	__u16 start_ = 0, end_ = 0, offset;
176 
177 	/* If there are no more gap acks possible, get out fast.  */
178 	if (TSN_lte(map->max_tsn_seen, iter->start))
179 		return 0;
180 
181 	offset = iter->start - map->base_tsn;
182 	sctp_tsnmap_find_gap_ack(map->tsn_map, offset, map->len,
183 				 &start_, &end_);
184 
185 	/* The Gap Ack Block happens to end at the end of the map. */
186 	if (start_ && !end_)
187 		end_ = map->len - 1;
188 
189 	/* If we found a Gap Ack Block, return the start and end and
190 	 * bump the iterator forward.
191 	 */
192 	if (end_) {
193 		/* Fix up the start and end based on the
194 		 * Cumulative TSN Ack which is always 1 behind base.
195 		 */
196 		*start = start_ + 1;
197 		*end = end_ + 1;
198 
199 		/* Move the iterator forward.  */
200 		iter->start = map->cumulative_tsn_ack_point + *end + 1;
201 		ended = 1;
202 	}
203 
204 	return ended;
205 }
206 
207 /* Mark this and any lower TSN as seen.  */
sctp_tsnmap_skip(struct sctp_tsnmap * map,__u32 tsn)208 void sctp_tsnmap_skip(struct sctp_tsnmap *map, __u32 tsn)
209 {
210 	u32 gap;
211 
212 	if (TSN_lt(tsn, map->base_tsn))
213 		return;
214 	if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
215 		return;
216 
217 	/* Bump the max.  */
218 	if (TSN_lt(map->max_tsn_seen, tsn))
219 		map->max_tsn_seen = tsn;
220 
221 	gap = tsn - map->base_tsn + 1;
222 
223 	map->base_tsn += gap;
224 	map->cumulative_tsn_ack_point += gap;
225 	if (gap >= map->len) {
226 		/* If our gap is larger then the map size, just
227 		 * zero out the map.
228 		 */
229 		bitmap_zero(map->tsn_map, map->len);
230 	} else {
231 		/* If the gap is smaller than the map size,
232 		 * shift the map by 'gap' bits and update further.
233 		 */
234 		bitmap_shift_right(map->tsn_map, map->tsn_map, gap, map->len);
235 		sctp_tsnmap_update(map);
236 	}
237 }
238 
239 /********************************************************************
240  * 2nd Level Abstractions
241  ********************************************************************/
242 
243 /* This private helper function updates the tsnmap buffers and
244  * the Cumulative TSN Ack Point.
245  */
sctp_tsnmap_update(struct sctp_tsnmap * map)246 static void sctp_tsnmap_update(struct sctp_tsnmap *map)
247 {
248 	u16 len;
249 	unsigned long zero_bit;
250 
251 
252 	len = map->max_tsn_seen - map->cumulative_tsn_ack_point;
253 	zero_bit = find_first_zero_bit(map->tsn_map, len);
254 	if (!zero_bit)
255 		return;		/* The first 0-bit is bit 0.  nothing to do */
256 
257 	map->base_tsn += zero_bit;
258 	map->cumulative_tsn_ack_point += zero_bit;
259 
260 	bitmap_shift_right(map->tsn_map, map->tsn_map, zero_bit, map->len);
261 }
262 
263 /* How many data chunks  are we missing from our peer?
264  */
sctp_tsnmap_pending(struct sctp_tsnmap * map)265 __u16 sctp_tsnmap_pending(struct sctp_tsnmap *map)
266 {
267 	__u32 cum_tsn = map->cumulative_tsn_ack_point;
268 	__u32 max_tsn = map->max_tsn_seen;
269 	__u32 base_tsn = map->base_tsn;
270 	__u16 pending_data;
271 	u32 gap, i;
272 
273 	pending_data = max_tsn - cum_tsn;
274 	gap = max_tsn - base_tsn;
275 
276 	if (gap == 0 || gap >= map->len)
277 		goto out;
278 
279 	for (i = 0; i < gap+1; i++) {
280 		if (test_bit(i, map->tsn_map))
281 			pending_data--;
282 	}
283 
284 out:
285 	return pending_data;
286 }
287 
288 /* This is a private helper for finding Gap Ack Blocks.  It searches a
289  * single array for the start and end of a Gap Ack Block.
290  *
291  * The flags "started" and "ended" tell is if we found the beginning
292  * or (respectively) the end of a Gap Ack Block.
293  */
sctp_tsnmap_find_gap_ack(unsigned long * map,__u16 off,__u16 len,__u16 * start,__u16 * end)294 static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
295 				     __u16 len, __u16 *start, __u16 *end)
296 {
297 	int i = off;
298 
299 	/* Look through the entire array, but break out
300 	 * early if we have found the end of the Gap Ack Block.
301 	 */
302 
303 	/* Also, stop looking past the maximum TSN seen. */
304 
305 	/* Look for the start. */
306 	i = find_next_bit(map, len, off);
307 	if (i < len)
308 		*start = i;
309 
310 	/* Look for the end.  */
311 	if (*start) {
312 		/* We have found the start, let's find the
313 		 * end.  If we find the end, break out.
314 		 */
315 		i = find_next_zero_bit(map, len, i);
316 		if (i < len)
317 			*end = i - 1;
318 	}
319 }
320 
321 /* Renege that we have seen a TSN.  */
sctp_tsnmap_renege(struct sctp_tsnmap * map,__u32 tsn)322 void sctp_tsnmap_renege(struct sctp_tsnmap *map, __u32 tsn)
323 {
324 	u32 gap;
325 
326 	if (TSN_lt(tsn, map->base_tsn))
327 		return;
328 	/* Assert: TSN is in range.  */
329 	if (!TSN_lt(tsn, map->base_tsn + map->len))
330 		return;
331 
332 	gap = tsn - map->base_tsn;
333 
334 	/* Pretend we never saw the TSN.  */
335 	clear_bit(gap, map->tsn_map);
336 }
337 
338 /* How many gap ack blocks do we have recorded? */
sctp_tsnmap_num_gabs(struct sctp_tsnmap * map,struct sctp_gap_ack_block * gabs)339 __u16 sctp_tsnmap_num_gabs(struct sctp_tsnmap *map,
340 			   struct sctp_gap_ack_block *gabs)
341 {
342 	struct sctp_tsnmap_iter iter;
343 	int ngaps = 0;
344 
345 	/* Refresh the gap ack information. */
346 	if (sctp_tsnmap_has_gap(map)) {
347 		__u16 start = 0, end = 0;
348 		sctp_tsnmap_iter_init(map, &iter);
349 		while (sctp_tsnmap_next_gap_ack(map, &iter,
350 						&start,
351 						&end)) {
352 
353 			gabs[ngaps].start = htons(start);
354 			gabs[ngaps].end = htons(end);
355 			ngaps++;
356 			if (ngaps >= SCTP_MAX_GABS)
357 				break;
358 		}
359 	}
360 	return ngaps;
361 }
362 
sctp_tsnmap_grow(struct sctp_tsnmap * map,u16 gap)363 static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 gap)
364 {
365 	unsigned long *new;
366 	unsigned long inc;
367 	u16  len;
368 
369 	if (gap >= SCTP_TSN_MAP_SIZE)
370 		return 0;
371 
372 	inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
373 	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
374 
375 	new = kzalloc(len>>3, GFP_ATOMIC);
376 	if (!new)
377 		return 0;
378 
379 	bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
380 	kfree(map->tsn_map);
381 	map->tsn_map = new;
382 	map->len = len;
383 
384 	return 1;
385 }
386