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 <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
  49 static void sctp_tsnmap_update(struct sctp_tsnmap *map);
  50 static 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.  */
  56 struct 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  */
  83 int 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
 110 out:
 111         return dup;
 112 }
 113
 114
 115 /* Mark this TSN as seen.  */
 116 void 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.  */
 149 SCTP_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  */
 159 SCTP_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.  */
 229 void 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  */
 269 static 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
 327 out:
 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  */
 337 static 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.  */
 377 void 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 }