LXR linux/net/batman-adv/bitarray.c

   1// SPDX-License-Identifier: GPL-2.0
   2/* Copyright (C) B.A.T.M.A.N. contributors:
   3 *
   4 * Simon Wunderlich, Marek Lindner
   5 */
   6
   7#include "bitarray.h"
   8#include "main.h"
   9
  10#include <linux/bitmap.h>
  11
  12#include "log.h"
  13
  14/* shift the packet array by n places. */
  15static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)
  16{
  17        if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
  18                return;
  19
  20        bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
  21}
  22
  23/**
  24 * batadv_bit_get_packet() - receive and process one packet within the sequence
  25 *  number window
  26 * @priv: the bat priv with all the soft interface information
  27 * @seq_bits: pointer to the sequence number receive packet
  28 * @seq_num_diff: difference between the current/received sequence number and
  29 *  the last sequence number
  30 * @set_mark: whether this packet should be marked in seq_bits
  31 *
  32 * Return: true if the window was moved (either new or very old),
  33 *  false if the window was not moved/shifted.
  34 */
  35bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  36                           s32 seq_num_diff, int set_mark)
  37{
  38        struct batadv_priv *bat_priv = priv;
  39
  40        /* sequence number is slightly older. We already got a sequence number
  41         * higher than this one, so we just mark it.
  42         */
  43        if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
  44                if (set_mark)
  45                        batadv_set_bit(seq_bits, -seq_num_diff);
  46                return false;
  47        }
  48
  49        /* sequence number is slightly newer, so we shift the window and
  50         * set the mark if required
  51         */
  52        if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
  53                batadv_bitmap_shift_left(seq_bits, seq_num_diff);
  54
  55                if (set_mark)
  56                        batadv_set_bit(seq_bits, 0);
  57                return true;
  58        }
  59
  60        /* sequence number is much newer, probably missed a lot of packets */
  61        if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
  62            seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
  63                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  64                           "We missed a lot of packets (%i) !\n",
  65                           seq_num_diff - 1);
  66                bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  67                if (set_mark)
  68                        batadv_set_bit(seq_bits, 0);
  69                return true;
  70        }
  71
  72        /* received a much older packet. The other host either restarted
  73         * or the old packet got delayed somewhere in the network. The
  74         * packet should be dropped without calling this function if the
  75         * seqno window is protected.
  76         *
  77         * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
  78         * or
  79         * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
  80         */
  81        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  82                   "Other host probably restarted!\n");
  83
  84        bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
  85        if (set_mark)
  86                batadv_set_bit(seq_bits, 0);
  87
  88        return true;
  89}
  90