net/batman-adv/bitarray.c

   1 /*
   2  * Copyright (C) 2006-2012 B.A.T.M.A.N. contributors:
   3  *
   4  * Simon Wunderlich, Marek Lindner
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of version 2 of the GNU General Public
   8  * License as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13  * General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301, USA
  19  *
  20  */
  21
  22 #include "main.h"
  23 #include "bitarray.h"
  24
  25 #include <linux/bitops.h>
  26
  27 /* shift the packet array by n places. */
  28 static void bat_bitmap_shift_left(unsigned long *seq_bits, int32_t n)
  29 {
  30         if (n <= 0 || n >= TQ_LOCAL_WINDOW_SIZE)
  31                 return;
  32
  33         bitmap_shift_left(seq_bits, seq_bits, n, TQ_LOCAL_WINDOW_SIZE);
  34 }
  35
  36
  37 /* receive and process one packet within the sequence number window.
  38  *
  39  * returns:
  40  *  1 if the window was moved (either new or very old)
  41  *  0 if the window was not moved/shifted.
  42  */
  43 int bit_get_packet(void *priv, unsigned long *seq_bits,
  44                     int32_t seq_num_diff, int set_mark)
  45 {
  46         struct bat_priv *bat_priv = priv;
  47
  48         /* sequence number is slightly older. We already got a sequence number
  49          * higher than this one, so we just mark it. */
  50
  51         if ((seq_num_diff <= 0) && (seq_num_diff > -TQ_LOCAL_WINDOW_SIZE)) {
  52                 if (set_mark)
  53                         bat_set_bit(seq_bits, -seq_num_diff);
  54                 return 0;
  55         }
  56
  57         /* sequence number is slightly newer, so we shift the window and
  58          * set the mark if required */
  59
  60         if ((seq_num_diff > 0) && (seq_num_diff < TQ_LOCAL_WINDOW_SIZE)) {
  61                 bat_bitmap_shift_left(seq_bits, seq_num_diff);
  62
  63                 if (set_mark)
  64                         bat_set_bit(seq_bits, 0);
  65                 return 1;
  66         }
  67
  68         /* sequence number is much newer, probably missed a lot of packets */
  69
  70         if ((seq_num_diff >= TQ_LOCAL_WINDOW_SIZE) &&
  71             (seq_num_diff < EXPECTED_SEQNO_RANGE)) {
  72                 bat_dbg(DBG_BATMAN, bat_priv,
  73                         "We missed a lot of packets (%i) !\n",
  74                         seq_num_diff - 1);
  75                 bitmap_zero(seq_bits, TQ_LOCAL_WINDOW_SIZE);
  76                 if (set_mark)
  77                         bat_set_bit(seq_bits, 0);
  78                 return 1;
  79         }
  80
  81         /* received a much older packet. The other host either restarted
  82          * or the old packet got delayed somewhere in the network. The
  83          * packet should be dropped without calling this function if the
  84          * seqno window is protected. */
  85
  86         if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE) ||
  87             (seq_num_diff >= EXPECTED_SEQNO_RANGE)) {
  88
  89                 bat_dbg(DBG_BATMAN, bat_priv,
  90                         "Other host probably restarted!\n");
  91
  92                 bitmap_zero(seq_bits, TQ_LOCAL_WINDOW_SIZE);
  93                 if (set_mark)
  94                         bat_set_bit(seq_bits, 0);
  95
  96                 return 1;
  97         }
  98
  99         /* never reached */
 100         return 0;
 101 }