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Linux/net/sctp/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, 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 
 44 static void sctp_tsnmap_update(struct sctp_tsnmap *map);
 45 static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
 46                                      __u16 len, __u16 *start, __u16 *end);
 47 static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 size);
 48 
 49 /* Initialize a block of memory as a tsnmap.  */
 50 struct 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 
 72 void 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  */
 84 int 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.  */
110 int 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.  */
157 static 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  */
167 static 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.  */
205 void 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  */
243 static 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);
277 out:
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  */
287 static 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.  */
315 void 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 
356 static 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 

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