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
  33 /* receive and process one packet within the sequence number window.
  34  *
  35  * returns:
  36  *  1 if the window was moved (either new or very old)
  37  *  0 if the window was not moved/shifted.
  38  */
  39 int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  40                           int32_t seq_num_diff, int set_mark)
  41 {
  42         struct batadv_priv *bat_priv = priv;
  43
  44         /* sequence number is slightly older. We already got a sequence number
  45          * higher than this one, so we just mark it.
  46          */
  47         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  48                 if (set_mark)
  49                         batadv_set_bit(seq_bits, -seq_num_diff);
  50                 return 0;
  51         }
  52
  53         /* sequence number is slightly newer, so we shift the window and
  54          * set the mark if required
  55          */
  56         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  57                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  58
  59                 if (set_mark)
  60                         batadv_set_bit(seq_bits, 0);
  61                 return 1;
  62         }
  63
  64         /* sequence number is much newer, probably missed a lot of packets */
  65         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  66             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  67                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  68                            "We missed a lot of packets (%i) !\n",
  69                            seq_num_diff - 1);
  70                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  71                 if (set_mark)
  72                         batadv_set_bit(seq_bits, 0);
  73                 return 1;
  74         }
  75
  76         /* received a much older packet. The other host either restarted
  77          * or the old packet got delayed somewhere in the network. The
  78          * packet should be dropped without calling this function if the
  79          * seqno window is protected.
  80          *
  81          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  82          * or
  83          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  84          */
  85         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  86                    "Other host probably restarted!\n");
  87
  88         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  89         if (set_mark)
  90                 batadv_set_bit(seq_bits, 0);
  91
  92         return 1;
  93 }