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, 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 }