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
51static void sctp_tsnmap_update(struct sctp_tsnmap *map);
52static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
53				     __u16 len, __u16 *start, __u16 *end);
54static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 gap);
55
56/* Initialize a block of memory as a tsnmap.  */
57struct 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
79void 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 */
91int 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.  */
117int 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.  */
160SCTP_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 */
170SCTP_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.  */
208void 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 */
246static 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 */
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
284out:
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 */
294static 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.  */
322void 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? */
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, end;
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
363static 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