net/batman-adv/bitarray.c

   1 /* Copyright (C) 2006-2016  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 "bitarray.h"
  19 #include "main.h"
  20
  21 #include <linux/bitmap.h>
  22
  23 /* shift the packet array by n places. */
  24 static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 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  * batadv_bit_get_packet - receive and process one packet within the sequence
  34  *  number window
  35  * @priv: the bat priv with all the soft interface information
  36  * @seq_bits: pointer to the sequence number receive packet
  37  * @seq_num_diff: difference between the current/received sequence number and
  38  *  the last sequence number
  39  * @set_mark: whether this packet should be marked in seq_bits
  40  *
  41  * Return: 1 if the window was moved (either new or very old),
  42  *  0 if the window was not moved/shifted.
  43  */
  44 int batadv_bit_get_packet(void *priv, unsigned long *seq_bits, s32 seq_num_diff,
  45                           int set_mark)
  46 {
  47         struct batadv_priv *bat_priv = priv;
  48
  49         /* sequence number is slightly older. We already got a sequence number
  50          * higher than this one, so we just mark it.
  51          */
  52         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  53                 if (set_mark)
  54                         batadv_set_bit(seq_bits, -seq_num_diff);
  55                 return 0;
  56         }
  57
  58         /* sequence number is slightly newer, so we shift the window and
  59          * set the mark if required
  60          */
  61         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  62                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  63
  64                 if (set_mark)
  65                         batadv_set_bit(seq_bits, 0);
  66                 return 1;
  67         }
  68
  69         /* sequence number is much newer, probably missed a lot of packets */
  70         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  71             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  72                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  73                            "We missed a lot of packets (%i) !\n",
  74                            seq_num_diff - 1);
  75                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  76                 if (set_mark)
  77                         batadv_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          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  87          * or
  88          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  89          */
  90         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  91                    "Other host probably restarted!\n");
  92
  93         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  94         if (set_mark)
  95                 batadv_set_bit(seq_bits, 0);
  96
  97         return 1;
  98 }