linux/net/batman-adv/bitarray.c
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   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. */
  26static 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 */
  41int 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        if (seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE ||
  84            seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE) {
  85
  86                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  87                           "Other host probably restarted!\n");
  88
  89                bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  90                if (set_mark)
  91                        batadv_set_bit(seq_bits, 0);
  92
  93                return 1;
  94        }
  95
  96        /* never reached */
  97        return 0;
  98}
  99
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