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tsnmap.c
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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 <[email protected]>
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 <[email protected]>
37  * Jon Grimm <[email protected]>
38  * Karl Knutson <[email protected]>
39  * Sridhar Samudrala <[email protected]>
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. */
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;
74  map->num_dup_tsns = 0;
75 
76  return map;
77 }
78 
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  */
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. */
118  struct sctp_transport *trans)
119 {
120  u16 gap;
121 
122  if (TSN_lt(tsn, map->base_tsn))
123  return 0;
124 
125  gap = tsn - map->base_tsn;
126 
127  if (gap >= map->len && !sctp_tsnmap_grow(map, gap))
128  return -ENOMEM;
129 
130  if (!sctp_tsnmap_has_gap(map) && gap == 0) {
131  /* In this case the map has no gaps and the tsn we are
132  * recording is the next expected tsn. We don't touch
133  * the map but simply bump the values.
134  */
135  map->max_tsn_seen++;
137  if (trans)
138  trans->sack_generation =
139  trans->asoc->peer.sack_generation;
140  map->base_tsn++;
141  } else {
142  /* Either we already have a gap, or about to record a gap, so
143  * have work to do.
144  *
145  * Bump the max.
146  */
147  if (TSN_lt(map->max_tsn_seen, tsn))
148  map->max_tsn_seen = tsn;
149 
150  /* Mark the TSN as received. */
151  set_bit(gap, map->tsn_map);
152 
153  /* Go fixup any internal TSN mapping variables including
154  * cumulative_tsn_ack_point.
155  */
156  sctp_tsnmap_update(map);
157  }
158 
159  return 0;
160 }
161 
162 
163 /* Initialize a Gap Ack Block iterator from memory being provided. */
165  struct sctp_tsnmap_iter *iter)
166 {
167  /* Only start looking one past the Cumulative TSN Ack Point. */
168  iter->start = map->cumulative_tsn_ack_point + 1;
169 }
170 
171 /* Get the next Gap Ack Blocks. Returns 0 if there was not another block
172  * to get.
173  */
175  struct sctp_tsnmap_iter *iter,
176  __u16 *start, __u16 *end)
177 {
178  int ended = 0;
179  __u16 start_ = 0, end_ = 0, offset;
180 
181  /* If there are no more gap acks possible, get out fast. */
182  if (TSN_lte(map->max_tsn_seen, iter->start))
183  return 0;
184 
185  offset = iter->start - map->base_tsn;
186  sctp_tsnmap_find_gap_ack(map->tsn_map, offset, map->len,
187  &start_, &end_);
188 
189  /* The Gap Ack Block happens to end at the end of the map. */
190  if (start_ && !end_)
191  end_ = map->len - 1;
192 
193  /* If we found a Gap Ack Block, return the start and end and
194  * bump the iterator forward.
195  */
196  if (end_) {
197  /* Fix up the start and end based on the
198  * Cumulative TSN Ack which is always 1 behind base.
199  */
200  *start = start_ + 1;
201  *end = end_ + 1;
202 
203  /* Move the iterator forward. */
204  iter->start = map->cumulative_tsn_ack_point + *end + 1;
205  ended = 1;
206  }
207 
208  return ended;
209 }
210 
211 /* Mark this and any lower TSN as seen. */
213 {
214  u32 gap;
215 
216  if (TSN_lt(tsn, map->base_tsn))
217  return;
218  if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
219  return;
220 
221  /* Bump the max. */
222  if (TSN_lt(map->max_tsn_seen, tsn))
223  map->max_tsn_seen = tsn;
224 
225  gap = tsn - map->base_tsn + 1;
226 
227  map->base_tsn += gap;
228  map->cumulative_tsn_ack_point += gap;
229  if (gap >= map->len) {
230  /* If our gap is larger then the map size, just
231  * zero out the map.
232  */
233  bitmap_zero(map->tsn_map, map->len);
234  } else {
235  /* If the gap is smaller than the map size,
236  * shift the map by 'gap' bits and update further.
237  */
238  bitmap_shift_right(map->tsn_map, map->tsn_map, gap, map->len);
239  sctp_tsnmap_update(map);
240  }
241 }
242 
243 /********************************************************************
244  * 2nd Level Abstractions
245  ********************************************************************/
246 
247 /* This private helper function updates the tsnmap buffers and
248  * the Cumulative TSN Ack Point.
249  */
250 static void sctp_tsnmap_update(struct sctp_tsnmap *map)
251 {
252  u16 len;
253  unsigned long zero_bit;
254 
255 
256  len = map->max_tsn_seen - map->cumulative_tsn_ack_point;
257  zero_bit = find_first_zero_bit(map->tsn_map, len);
258  if (!zero_bit)
259  return; /* The first 0-bit is bit 0. nothing to do */
260 
261  map->base_tsn += zero_bit;
262  map->cumulative_tsn_ack_point += zero_bit;
263 
264  bitmap_shift_right(map->tsn_map, map->tsn_map, zero_bit, map->len);
265 }
266 
267 /* How many data chunks are we missing from our peer?
268  */
270 {
271  __u32 cum_tsn = map->cumulative_tsn_ack_point;
272  __u32 max_tsn = map->max_tsn_seen;
273  __u32 base_tsn = map->base_tsn;
275  u32 gap, i;
276 
277  pending_data = max_tsn - cum_tsn;
278  gap = max_tsn - base_tsn;
279 
280  if (gap == 0 || gap >= map->len)
281  goto out;
282 
283  for (i = 0; i < gap+1; i++) {
284  if (test_bit(i, map->tsn_map))
285  pending_data--;
286  }
287 
288 out:
289  return pending_data;
290 }
291 
292 /* This is a private helper for finding Gap Ack Blocks. It searches a
293  * single array for the start and end of a Gap Ack Block.
294  *
295  * The flags "started" and "ended" tell is if we found the beginning
296  * or (respectively) the end of a Gap Ack Block.
297  */
298 static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
299  __u16 len, __u16 *start, __u16 *end)
300 {
301  int i = off;
302 
303  /* Look through the entire array, but break out
304  * early if we have found the end of the Gap Ack Block.
305  */
306 
307  /* Also, stop looking past the maximum TSN seen. */
308 
309  /* Look for the start. */
310  i = find_next_bit(map, len, off);
311  if (i < len)
312  *start = i;
313 
314  /* Look for the end. */
315  if (*start) {
316  /* We have found the start, let's find the
317  * end. If we find the end, break out.
318  */
319  i = find_next_zero_bit(map, len, i);
320  if (i < len)
321  *end = i - 1;
322  }
323 }
324 
325 /* Renege that we have seen a TSN. */
326 void sctp_tsnmap_renege(struct sctp_tsnmap *map, __u32 tsn)
327 {
328  u32 gap;
329 
330  if (TSN_lt(tsn, map->base_tsn))
331  return;
332  /* Assert: TSN is in range. */
333  if (!TSN_lt(tsn, map->base_tsn + map->len))
334  return;
335 
336  gap = tsn - map->base_tsn;
337 
338  /* Pretend we never saw the TSN. */
339  clear_bit(gap, map->tsn_map);
340 }
341 
342 /* How many gap ack blocks do we have recorded? */
344  struct sctp_gap_ack_block *gabs)
345 {
346  struct sctp_tsnmap_iter iter;
347  int ngaps = 0;
348 
349  /* Refresh the gap ack information. */
350  if (sctp_tsnmap_has_gap(map)) {
351  __u16 start = 0, end = 0;
352  sctp_tsnmap_iter_init(map, &iter);
353  while (sctp_tsnmap_next_gap_ack(map, &iter,
354  &start,
355  &end)) {
356 
357  gabs[ngaps].start = htons(start);
358  gabs[ngaps].end = htons(end);
359  ngaps++;
360  if (ngaps >= SCTP_MAX_GABS)
361  break;
362  }
363  }
364  return ngaps;
365 }
366 
367 static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 gap)
368 {
369  unsigned long *new;
370  unsigned long inc;
371  u16 len;
372 
373  if (gap >= SCTP_TSN_MAP_SIZE)
374  return 0;
375 
376  inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
377  len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);
378 
379  new = kzalloc(len>>3, GFP_ATOMIC);
380  if (!new)
381  return 0;
382 
383  bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
384  kfree(map->tsn_map);
385  map->tsn_map = new;
386  map->len = len;
387 
388  return 1;
389 }