1/* SCTP kernel reference 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 reference Implementation
8 *
9 * These functions manipulate sctp tsn mapping array.
10 *
11 * The SCTP reference 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 * The SCTP reference 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/types.h>
46#include <net/sctp/sctp.h>
47#include <net/sctp/sm.h>
48
49static void sctp_tsnmap_update(struct sctp_tsnmap *map);
50static void sctp_tsnmap_find_gap_ack(__u8 *map, __u16 off,
51				     __u16 len, __u16 base,
52				     int *started, __u16 *start,
53				     int *ended, __u16 *end);
54
55/* Initialize a block of memory as a tsnmap.  */
56struct sctp_tsnmap *sctp_tsnmap_init(struct sctp_tsnmap *map, __u16 len,
57				     __u32 initial_tsn)
58{
59	map->tsn_map = map->raw_map;
60	map->overflow_map = map->tsn_map + len;
61	map->len = len;
62
63	/* Clear out a TSN ack status.  */
64	memset(map->tsn_map, 0x00, map->len + map->len);
65
66	/* Keep track of TSNs represented by tsn_map.  */
67	map->base_tsn = initial_tsn;
68	map->overflow_tsn = initial_tsn + map->len;
69	map->cumulative_tsn_ack_point = initial_tsn - 1;
70	map->max_tsn_seen = map->cumulative_tsn_ack_point;
71	map->malloced = 0;
72	map->num_dup_tsns = 0;
73
74	return map;
75}
76
77/* Test the tracking state of this TSN.
78 * Returns:
79 *   0 if the TSN has not yet been seen
80 *  >0 if the TSN has been seen (duplicate)
81 *  <0 if the TSN is invalid (too large to track)
82 */
83int sctp_tsnmap_check(const struct sctp_tsnmap *map, __u32 tsn)
84{
85	__s32 gap;
86	int dup;
87
88	/* Calculate the index into the mapping arrays.  */
89	gap = tsn - map->base_tsn;
90
91	/* Verify that we can hold this TSN.  */
92	if (gap >= (/* base */ map->len + /* overflow */ map->len)) {
93		dup = -1;
94		goto out;
95	}
96
97	/* Honk if we've already seen this TSN.
98	 * We have three cases:
99	 *	1. The TSN is ancient or belongs to a previous tsn_map.
100	 *	2. The TSN is already marked in the tsn_map.
101	 *	3. The TSN is already marked in the tsn_map_overflow.
102	 */
103	if (gap < 0 ||
104	    (gap < map->len && map->tsn_map[gap]) ||
105	    (gap >= map->len && map->overflow_map[gap - map->len]))
106		dup = 1;
107	else
108		dup = 0;
109
110out:
111	return dup;
112}
113
114
115/* Mark this TSN as seen.  */
116void sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn)
117{
118	__s32 gap;
119
120	/* Vacuously mark any TSN which precedes the map base or
121	 * exceeds the end of the map.
122	 */
123	if (TSN_lt(tsn, map->base_tsn))
124		return;
125	if (!TSN_lt(tsn, map->base_tsn + map->len + map->len))
126		return;
127
128	/* Bump the max.  */
129	if (TSN_lt(map->max_tsn_seen, tsn))
130		map->max_tsn_seen = tsn;
131
132	/* Assert: TSN is in range.  */
133	gap = tsn - map->base_tsn;
134
135	/* Mark the TSN as received.  */
136	if (gap < map->len)
137		map->tsn_map[gap]++;
138	else
139		map->overflow_map[gap - map->len]++;
140
141	/* Go fixup any internal TSN mapping variables including
142	 * cumulative_tsn_ack_point.
143	 */
144	sctp_tsnmap_update(map);
145}
146
147
148/* Initialize a Gap Ack Block iterator from memory being provided.  */
149SCTP_STATIC void sctp_tsnmap_iter_init(const struct sctp_tsnmap *map,
150				       struct sctp_tsnmap_iter *iter)
151{
152	/* Only start looking one past the Cumulative TSN Ack Point.  */
153	iter->start = map->cumulative_tsn_ack_point + 1;
154}
155
156/* Get the next Gap Ack Blocks. Returns 0 if there was not another block
157 * to get.
158 */
159SCTP_STATIC int sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap *map,
160					 struct sctp_tsnmap_iter *iter,
161					 __u16 *start, __u16 *end)
162{
163	int started, ended;
164	__u16 _start, _end, offset;
165
166	/* We haven't found a gap yet.  */
167	started = ended = 0;
168
169	/* If there are no more gap acks possible, get out fast.  */
170	if (TSN_lte(map->max_tsn_seen, iter->start))
171		return 0;
172
173	/* Search the first mapping array.  */
174	if (iter->start - map->base_tsn < map->len) {
175
176		offset = iter->start - map->base_tsn;
177		sctp_tsnmap_find_gap_ack(map->tsn_map, offset, map->len, 0,
178					 &started, &_start, &ended, &_end);
179	}
180
181	/* Do we need to check the overflow map? */
182	if (!ended) {
183		/* Fix up where we'd like to start searching in the
184		 * overflow map.
185		 */
186		if (iter->start - map->base_tsn < map->len)
187			offset = 0;
188		else
189			offset = iter->start - map->base_tsn - map->len;
190
191		/* Search the overflow map.  */
192		sctp_tsnmap_find_gap_ack(map->overflow_map,
193					 offset,
194					 map->len,
195					 map->len,
196					 &started, &_start,
197					 &ended, &_end);
198	}
199
200	/* The Gap Ack Block happens to end at the end of the
201	 * overflow map.
202	 */
203	if (started && !ended) {
204		ended++;
205		_end = map->len + map->len - 1;
206	}
207
208	/* If we found a Gap Ack Block, return the start and end and
209	 * bump the iterator forward.
210	 */
211	if (ended) {
212		/* Fix up the start and end based on the
213		 * Cumulative TSN Ack offset into the map.
214		 */
215		int gap = map->cumulative_tsn_ack_point -
216			map->base_tsn;
217
218		*start = _start - gap;
219		*end = _end - gap;
220
221		/* Move the iterator forward.  */
222		iter->start = map->cumulative_tsn_ack_point + *end + 1;
223	}
224
225	return ended;
226}
227
228/* Mark this and any lower TSN as seen.  */
229void sctp_tsnmap_skip(struct sctp_tsnmap *map, __u32 tsn)
230{
231	__s32 gap;
232
233	/* Vacuously mark any TSN which precedes the map base or
234	 * exceeds the end of the map.
235	 */
236	if (TSN_lt(tsn, map->base_tsn))
237		return;
238	if (!TSN_lt(tsn, map->base_tsn + map->len + map->len))
239		return;
240
241	/* Bump the max.  */
242	if (TSN_lt(map->max_tsn_seen, tsn))
243		map->max_tsn_seen = tsn;
244
245	/* Assert: TSN is in range.  */
246	gap = tsn - map->base_tsn + 1;
247
248	/* Mark the TSNs as received.  */
249	if (gap <= map->len)
250		memset(map->tsn_map, 0x01, gap);
251	else {
252		memset(map->tsn_map, 0x01, map->len);
253		memset(map->overflow_map, 0x01, (gap - map->len));
254	}
255
256	/* Go fixup any internal TSN mapping variables including
257	 * cumulative_tsn_ack_point.
258	 */
259	sctp_tsnmap_update(map);
260}
261
262/********************************************************************
263 * 2nd Level Abstractions
264 ********************************************************************/
265
266/* This private helper function updates the tsnmap buffers and
267 * the Cumulative TSN Ack Point.
268 */
269static void sctp_tsnmap_update(struct sctp_tsnmap *map)
270{
271	__u32 ctsn;
272
273	ctsn = map->cumulative_tsn_ack_point;
274	do {
275		ctsn++;
276		if (ctsn == map->overflow_tsn) {
277			/* Now tsn_map must have been all '1's,
278			 * so we swap the map and check the overflow table
279			 */
280			__u8 *tmp = map->tsn_map;
281			memset(tmp, 0, map->len);
282			map->tsn_map = map->overflow_map;
283			map->overflow_map = tmp;
284
285			/* Update the tsn_map boundaries.  */
286			map->base_tsn += map->len;
287			map->overflow_tsn += map->len;
288		}
289	} while (map->tsn_map[ctsn - map->base_tsn]);
290
291	map->cumulative_tsn_ack_point = ctsn - 1; /* Back up one. */
292}
293
294/* How many data chunks  are we missing from our peer?
295 */
296__u16 sctp_tsnmap_pending(struct sctp_tsnmap *map)
297{
298	__u32 cum_tsn = map->cumulative_tsn_ack_point;
299	__u32 max_tsn = map->max_tsn_seen;
300	__u32 base_tsn = map->base_tsn;
301	__u16 pending_data;
302	__s32 gap, start, end, i;
303
304	pending_data = max_tsn - cum_tsn;
305	gap = max_tsn - base_tsn;
306
307	if (gap <= 0 || gap >= (map->len + map->len))
308		goto out;
309
310	start = ((cum_tsn >= base_tsn) ? (cum_tsn - base_tsn + 1) : 0);
311	end = ((gap > map->len ) ? map->len : gap + 1);
312
313	for (i = start; i < end; i++) {
314		if (map->tsn_map[i])
315			pending_data--;
316	}
317
318	if (gap >= map->len) {
319		start = 0;
320		end = gap - map->len + 1;
321		for (i = start; i < end; i++) {
322			if (map->overflow_map[i])
323				pending_data--;
324		}
325	}
326
327out:
328	return pending_data;
329}
330
331/* This is a private helper for finding Gap Ack Blocks.  It searches a
332 * single array for the start and end of a Gap Ack Block.
333 *
334 * The flags "started" and "ended" tell is if we found the beginning
335 * or (respectively) the end of a Gap Ack Block.
336 */
337static void sctp_tsnmap_find_gap_ack(__u8 *map, __u16 off,
338				     __u16 len, __u16 base,
339				     int *started, __u16 *start,
340				     int *ended, __u16 *end)
341{
342	int i = off;
343
344	/* Look through the entire array, but break out
345	 * early if we have found the end of the Gap Ack Block.
346	 */
347
348	/* Also, stop looking past the maximum TSN seen. */
349
350	/* Look for the start. */
351	if (!(*started)) {
352		for (; i < len; i++) {
353			if (map[i]) {
354				(*started)++;
355				*start = base + i;
356				break;
357			}
358		}
359	}
360
361	/* Look for the end.  */
362	if (*started) {
363		/* We have found the start, let's find the
364		 * end.  If we find the end, break out.
365		 */
366		for (; i < len; i++) {
367			if (!map[i]) {
368				(*ended)++;
369				*end = base + i - 1;
370				break;
371			}
372		}
373	}
374}
375
376/* Renege that we have seen a TSN.  */
377void sctp_tsnmap_renege(struct sctp_tsnmap *map, __u32 tsn)
378{
379	__s32 gap;
380
381	if (TSN_lt(tsn, map->base_tsn))
382		return;
383	if (!TSN_lt(tsn, map->base_tsn + map->len + map->len))
384		return;
385
386	/* Assert: TSN is in range.  */
387	gap = tsn - map->base_tsn;
388
389	/* Pretend we never saw the TSN.  */
390	if (gap < map->len)
391		map->tsn_map[gap] = 0;
392	else
393		map->overflow_map[gap - map->len] = 0;
394}
395
396/* How many gap ack blocks do we have recorded? */
397__u16 sctp_tsnmap_num_gabs(struct sctp_tsnmap *map)
398{
399	struct sctp_tsnmap_iter iter;
400	int gabs = 0;
401
402	/* Refresh the gap ack information. */
403	if (sctp_tsnmap_has_gap(map)) {
404		__u16 start, end;
405		sctp_tsnmap_iter_init(map, &iter);
406		while (sctp_tsnmap_next_gap_ack(map, &iter,
407						&start,
408						&end)) {
409
410			map->gabs[gabs].start = htons(start);
411			map->gabs[gabs].end = htons(end);
412			gabs++;
413			if (gabs >= SCTP_MAX_GABS)
414				break;
415		}
416	}
417	return gabs;
418}
419