net/batman-adv/bitarray.c

   1 /* Copyright (C) 2006-2014 B.A.T.M.A.N. contributors:
   2  *
   3  * Simon Wunderlich, Marek Lindner
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 2 of the GNU General Public
   7  * License as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include "main.h"
  19 #include "bitarray.h"
  20
  21 #include <linux/bitops.h>
  22
  23 /* shift the packet array by n places. */
  24 static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t n)
  25 {
  26         if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
  27                 return;
  28
  29         bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
  30 }
  31
  32 /* receive and process one packet within the sequence number window.
  33  *
  34  * returns:
  35  *  1 if the window was moved (either new or very old)
  36  *  0 if the window was not moved/shifted.
  37  */
  38 int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  39                           int32_t seq_num_diff, int set_mark)
  40 {
  41         struct batadv_priv *bat_priv = priv;
  42
  43         /* sequence number is slightly older. We already got a sequence number
  44          * higher than this one, so we just mark it.
  45          */
  46         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  47                 if (set_mark)
  48                         batadv_set_bit(seq_bits, -seq_num_diff);
  49                 return 0;
  50         }
  51
  52         /* sequence number is slightly newer, so we shift the window and
  53          * set the mark if required
  54          */
  55         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  56                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  57
  58                 if (set_mark)
  59                         batadv_set_bit(seq_bits, 0);
  60                 return 1;
  61         }
  62
  63         /* sequence number is much newer, probably missed a lot of packets */
  64         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  65             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  66                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  67                            "We missed a lot of packets (%i) !\n",
  68                            seq_num_diff - 1);
  69                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  70                 if (set_mark)
  71                         batadv_set_bit(seq_bits, 0);
  72                 return 1;
  73         }
  74
  75         /* received a much older packet. The other host either restarted
  76          * or the old packet got delayed somewhere in the network. The
  77          * packet should be dropped without calling this function if the
  78          * seqno window is protected.
  79          *
  80          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  81          * or
  82          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  83          */
  84         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  85                    "Other host probably restarted!\n");
  86
  87         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  88         if (set_mark)
  89                 batadv_set_bit(seq_bits, 0);
  90
  91         return 1;
  92 }