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, see
25 * <http://www.gnu.org/licenses/>.
26 *
27 * Please send any bug reports or fixes you make to the
28 * email address(es):
29 *    lksctp developers <linux-sctp@vger.kernel.org>
30 *
31 * Written or modified by:
32 *    La Monte H.P. Yarroll <piggy@acm.org>
33 *    Jon Grimm             <jgrimm@us.ibm.com>
34 *    Karl Knutson          <karl@athena.chicago.il.us>
35 *    Sridhar Samudrala     <sri@us.ibm.com>
36 */
37
38#include <linux/slab.h>
39#include <linux/types.h>
40#include <linux/bitmap.h>
41#include <net/sctp/sctp.h>
42#include <net/sctp/sm.h>
43
44static void sctp_tsnmap_update(struct sctp_tsnmap *map);
45static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
46				     __u16 len, __u16 *start, __u16 *end);
47static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 size);
48
49/* Initialize a block of memory as a tsnmap.  */
50struct sctp_tsnmap *sctp_tsnmap_init(struct sctp_tsnmap *map, __u16 len,
51				     __u32 initial_tsn, gfp_t gfp)
52{
53	if (!map->tsn_map) {
54		map->tsn_map = kzalloc(len>>3, gfp);
55		if (map->tsn_map == NULL)
56			return NULL;
57
58		map->len = len;
59	} else {
60		bitmap_zero(map->tsn_map, map->len);
61	}
62
63	/* Keep track of TSNs represented by tsn_map.  */
64	map->base_tsn = initial_tsn;
65	map->cumulative_tsn_ack_point = initial_tsn - 1;
66	map->max_tsn_seen = map->cumulative_tsn_ack_point;
67	map->num_dup_tsns = 0;
68
69	return map;
70}
71
72void sctp_tsnmap_free(struct sctp_tsnmap *map)
73{
74	map->len = 0;
75	kfree(map->tsn_map);
76}
77
78/* Test the tracking state of this TSN.
79 * Returns:
80 *   0 if the TSN has not yet been seen
81 *  >0 if the TSN has been seen (duplicate)
82 *  <0 if the TSN is invalid (too large to track)
83 */
84int sctp_tsnmap_check(const struct sctp_tsnmap *map, __u32 tsn)
85{
86	u32 gap;
87
88	/* Check to see if this is an old TSN */
89	if (TSN_lte(tsn, map->cumulative_tsn_ack_point))
90		return 1;
91
92	/* Verify that we can hold this TSN and that it will not
93	 * overlfow our map
94	 */
95	if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
96		return -1;
97
98	/* Calculate the index into the mapping arrays.  */
99	gap = tsn - map->base_tsn;
100
101	/* Check to see if TSN has already been recorded.  */
102	if (gap < map->len && test_bit(gap, map->tsn_map))
103		return 1;
104	else
105		return 0;
106}
107
108
109/* Mark this TSN as seen.  */
110int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn,
111		     struct sctp_transport *trans)
112{
113	u16 gap;
114
115	if (TSN_lt(tsn, map->base_tsn))
116		return 0;
117
118	gap = tsn - map->base_tsn;
119
120	if (gap >= map->len && !sctp_tsnmap_grow(map, gap + 1))
121		return -ENOMEM;
122
123	if (!sctp_tsnmap_has_gap(map) && gap == 0) {
124		/* In this case the map has no gaps and the tsn we are
125		 * recording is the next expected tsn.  We don't touch
126		 * the map but simply bump the values.
127		 */
128		map->max_tsn_seen++;
129		map->cumulative_tsn_ack_point++;
130		if (trans)
131			trans->sack_generation =
132				trans->asoc->peer.sack_generation;
133		map->base_tsn++;
134	} else {
135		/* Either we already have a gap, or about to record a gap, so
136		 * have work to do.
137		 *
138		 * Bump the max.
139		 */
140		if (TSN_lt(map->max_tsn_seen, tsn))
141			map->max_tsn_seen = tsn;
142
143		/* Mark the TSN as received.  */
144		set_bit(gap, map->tsn_map);
145
146		/* Go fixup any internal TSN mapping variables including
147		 * cumulative_tsn_ack_point.
148		 */
149		sctp_tsnmap_update(map);
150	}
151
152	return 0;
153}
154
155
156/* Initialize a Gap Ack Block iterator from memory being provided.  */
157static void sctp_tsnmap_iter_init(const struct sctp_tsnmap *map,
158				  struct sctp_tsnmap_iter *iter)
159{
160	/* Only start looking one past the Cumulative TSN Ack Point.  */
161	iter->start = map->cumulative_tsn_ack_point + 1;
162}
163
164/* Get the next Gap Ack Blocks. Returns 0 if there was not another block
165 * to get.
166 */
167static int sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap *map,
168				    struct sctp_tsnmap_iter *iter,
169				    __u16 *start, __u16 *end)
170{
171	int ended = 0;
172	__u16 start_ = 0, end_ = 0, offset;
173
174	/* If there are no more gap acks possible, get out fast.  */
175	if (TSN_lte(map->max_tsn_seen, iter->start))
176		return 0;
177
178	offset = iter->start - map->base_tsn;
179	sctp_tsnmap_find_gap_ack(map->tsn_map, offset, map->len,
180				 &start_, &end_);
181
182	/* The Gap Ack Block happens to end at the end of the map. */
183	if (start_ && !end_)
184		end_ = map->len - 1;
185
186	/* If we found a Gap Ack Block, return the start and end and
187	 * bump the iterator forward.
188	 */
189	if (end_) {
190		/* Fix up the start and end based on the
191		 * Cumulative TSN Ack which is always 1 behind base.
192		 */
193		*start = start_ + 1;
194		*end = end_ + 1;
195
196		/* Move the iterator forward.  */
197		iter->start = map->cumulative_tsn_ack_point + *end + 1;
198		ended = 1;
199	}
200
201	return ended;
202}
203
204/* Mark this and any lower TSN as seen.  */
205void sctp_tsnmap_skip(struct sctp_tsnmap *map, __u32 tsn)
206{
207	u32 gap;
208
209	if (TSN_lt(tsn, map->base_tsn))
210		return;
211	if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
212		return;
213
214	/* Bump the max.  */
215	if (TSN_lt(map->max_tsn_seen, tsn))
216		map->max_tsn_seen = tsn;
217
218	gap = tsn - map->base_tsn + 1;
219
220	map->base_tsn += gap;
221	map->cumulative_tsn_ack_point += gap;
222	if (gap >= map->len) {
223		/* If our gap is larger then the map size, just
224		 * zero out the map.
225		 */
226		bitmap_zero(map->tsn_map, map->len);
227	} else {
228		/* If the gap is smaller than the map size,
229		 * shift the map by 'gap' bits and update further.
230		 */
231		bitmap_shift_right(map->tsn_map, map->tsn_map, gap, map->len);
232		sctp_tsnmap_update(map);
233	}
234}
235
236/********************************************************************
237 * 2nd Level Abstractions
238 ********************************************************************/
239
240/* This private helper function updates the tsnmap buffers and
241 * the Cumulative TSN Ack Point.
242 */
243static void sctp_tsnmap_update(struct sctp_tsnmap *map)
244{
245	u16 len;
246	unsigned long zero_bit;
247
248
249	len = map->max_tsn_seen - map->cumulative_tsn_ack_point;
250	zero_bit = find_first_zero_bit(map->tsn_map, len);
251	if (!zero_bit)
252		return;		/* The first 0-bit is bit 0.  nothing to do */
253
254	map->base_tsn += zero_bit;
255	map->cumulative_tsn_ack_point += zero_bit;
256
257	bitmap_shift_right(map->tsn_map, map->tsn_map, zero_bit, map->len);
258}
259
260/* How many data chunks  are we missing from our peer?
261 */
262__u16 sctp_tsnmap_pending(struct sctp_tsnmap *map)
263{
264	__u32 cum_tsn = map->cumulative_tsn_ack_point;
265	__u32 max_tsn = map->max_tsn_seen;
266	__u32 base_tsn = map->base_tsn;
267	__u16 pending_data;
268	u32 gap;
269
270	pending_data = max_tsn - cum_tsn;
271	gap = max_tsn - base_tsn;
272
273	if (gap == 0 || gap >= map->len)
274		goto out;
275
276	pending_data -= bitmap_weight(map->tsn_map, gap + 1);
277out:
278	return pending_data;
279}
280
281/* This is a private helper for finding Gap Ack Blocks.  It searches a
282 * single array for the start and end of a Gap Ack Block.
283 *
284 * The flags "started" and "ended" tell is if we found the beginning
285 * or (respectively) the end of a Gap Ack Block.
286 */
287static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
288				     __u16 len, __u16 *start, __u16 *end)
289{
290	int i = off;
291
292	/* Look through the entire array, but break out
293	 * early if we have found the end of the Gap Ack Block.
294	 */
295
296	/* Also, stop looking past the maximum TSN seen. */
297
298	/* Look for the start. */
299	i = find_next_bit(map, len, off);
300	if (i < len)
301		*start = i;
302
303	/* Look for the end.  */
304	if (*start) {
305		/* We have found the start, let's find the
306		 * end.  If we find the end, break out.
307		 */
308		i = find_next_zero_bit(map, len, i);
309		if (i < len)
310			*end = i - 1;
311	}
312}
313
314/* Renege that we have seen a TSN.  */
315void sctp_tsnmap_renege(struct sctp_tsnmap *map, __u32 tsn)
316{
317	u32 gap;
318
319	if (TSN_lt(tsn, map->base_tsn))
320		return;
321	/* Assert: TSN is in range.  */
322	if (!TSN_lt(tsn, map->base_tsn + map->len))
323		return;
324
325	gap = tsn - map->base_tsn;
326
327	/* Pretend we never saw the TSN.  */
328	clear_bit(gap, map->tsn_map);
329}
330
331/* How many gap ack blocks do we have recorded? */
332__u16 sctp_tsnmap_num_gabs(struct sctp_tsnmap *map,
333			   struct sctp_gap_ack_block *gabs)
334{
335	struct sctp_tsnmap_iter iter;
336	int ngaps = 0;
337
338	/* Refresh the gap ack information. */
339	if (sctp_tsnmap_has_gap(map)) {
340		__u16 start = 0, end = 0;
341		sctp_tsnmap_iter_init(map, &iter);
342		while (sctp_tsnmap_next_gap_ack(map, &iter,
343						&start,
344						&end)) {
345
346			gabs[ngaps].start = htons(start);
347			gabs[ngaps].end = htons(end);
348			ngaps++;
349			if (ngaps >= SCTP_MAX_GABS)
350				break;
351		}
352	}
353	return ngaps;
354}
355
356static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 size)
357{
358	unsigned long *new;
359	unsigned long inc;
360	u16  len;
361
362	if (size > SCTP_TSN_MAP_SIZE)
363		return 0;
364
365	inc = ALIGN((size - map->len), BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
366	len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
367
368	new = kzalloc(len>>3, GFP_ATOMIC);
369	if (!new)
370		return 0;
371
372	bitmap_copy(new, map->tsn_map,
373		map->max_tsn_seen - map->cumulative_tsn_ack_point);
374	kfree(map->tsn_map);
375	map->tsn_map = new;
376	map->len = len;
377
378	return 1;
379}
380