net/batman-adv/bitarray.c

   1 /* Copyright (C) 2006-2012 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, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA
  18  */
  19
  20 #include "main.h"
  21 #include "bitarray.h"
  22
  23 #include <linux/bitops.h>
  24
  25 /* shift the packet array by n places. */
  26 static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t n)
  27 {
  28         if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
  29                 return;
  30
  31         bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
  32 }
  33
  34
  35 /* receive and process one packet within the sequence number window.
  36  *
  37  * returns:
  38  *  1 if the window was moved (either new or very old)
  39  *  0 if the window was not moved/shifted.
  40  */
  41 int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  42                           int32_t seq_num_diff, int set_mark)
  43 {
  44         struct batadv_priv *bat_priv = priv;
  45
  46         /* sequence number is slightly older. We already got a sequence number
  47          * higher than this one, so we just mark it.
  48          */
  49         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  50                 if (set_mark)
  51                         batadv_set_bit(seq_bits, -seq_num_diff);
  52                 return 0;
  53         }
  54
  55         /* sequence number is slightly newer, so we shift the window and
  56          * set the mark if required
  57          */
  58         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  59                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  60
  61                 if (set_mark)
  62                         batadv_set_bit(seq_bits, 0);
  63                 return 1;
  64         }
  65
  66         /* sequence number is much newer, probably missed a lot of packets */
  67         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  68             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  69                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  70                            "We missed a lot of packets (%i) !\n",
  71                            seq_num_diff - 1);
  72                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  73                 if (set_mark)
  74                         batadv_set_bit(seq_bits, 0);
  75                 return 1;
  76         }
  77
  78         /* received a much older packet. The other host either restarted
  79          * or the old packet got delayed somewhere in the network. The
  80          * packet should be dropped without calling this function if the
  81          * seqno window is protected.
  82          *
  83          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  84          * or
  85          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  86          */
  87         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  88                    "Other host probably restarted!\n");
  89
  90         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  91         if (set_mark)
  92                 batadv_set_bit(seq_bits, 0);
  93
  94         return 1;
  95 }