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 #include "log.h"
  24
  25 /* shift the packet array by n places. */
  26 static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 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  * batadv_bit_get_packet - receive and process one packet within the sequence
  36  *  number window
  37  * @priv: the bat priv with all the soft interface information
  38  * @seq_bits: pointer to the sequence number receive packet
  39  * @seq_num_diff: difference between the current/received sequence number and
  40  *  the last sequence number
  41  * @set_mark: whether this packet should be marked in seq_bits
  42  *
  43  * Return: true if the window was moved (either new or very old),
  44  *  false if the window was not moved/shifted.
  45  */
  46 bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  47                            s32 seq_num_diff, int set_mark)
  48 {
  49         struct batadv_priv *bat_priv = priv;
  50
  51         /* sequence number is slightly older. We already got a sequence number
  52          * higher than this one, so we just mark it.
  53          */
  54         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  55                 if (set_mark)
  56                         batadv_set_bit(seq_bits, -seq_num_diff);
  57                 return false;
  58         }
  59
  60         /* sequence number is slightly newer, so we shift the window and
  61          * set the mark if required
  62          */
  63         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  64                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  65
  66                 if (set_mark)
  67                         batadv_set_bit(seq_bits, 0);
  68                 return true;
  69         }
  70
  71         /* sequence number is much newer, probably missed a lot of packets */
  72         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  73             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  74                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  75                            "We missed a lot of packets (%i) !\n",
  76                            seq_num_diff - 1);
  77                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  78                 if (set_mark)
  79                         batadv_set_bit(seq_bits, 0);
  80                 return true;
  81         }
  82
  83         /* received a much older packet. The other host either restarted
  84          * or the old packet got delayed somewhere in the network. The
  85          * packet should be dropped without calling this function if the
  86          * seqno window is protected.
  87          *
  88          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  89          * or
  90          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  91          */
  92         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  93                    "Other host probably restarted!\n");
  94
  95         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  96         if (set_mark)
  97                 batadv_set_bit(seq_bits, 0);
  98
  99         return true;
 100 }