net/sctp/tsnmap.c

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