bitarray.c
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/* Copyright (C) 2006-2014 B.A.T.M.A.N. contributors:
*
* Simon Wunderlich, Marek Lindner
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "main.h"
#include "bitarray.h"
#include <linux/bitops.h>
/* shift the packet array by n places. */
static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t n)
{
if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
return;
bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
}
/* receive and process one packet within the sequence number window.
*
* returns:
* 1 if the window was moved (either new or very old)
* 0 if the window was not moved/shifted.
*/
int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
int32_t seq_num_diff, int set_mark)
{
struct batadv_priv *bat_priv = priv;
/* sequence number is slightly older. We already got a sequence number
* higher than this one, so we just mark it.
*/
if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
if (set_mark)
batadv_set_bit(seq_bits, -seq_num_diff);
return 0;
}
/* sequence number is slightly newer, so we shift the window and
* set the mark if required
*/
if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
batadv_bitmap_shift_left(seq_bits, seq_num_diff);
if (set_mark)
batadv_set_bit(seq_bits, 0);
return 1;
}
/* sequence number is much newer, probably missed a lot of packets */
if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
"We missed a lot of packets (%i) !\n",
seq_num_diff - 1);
bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
if (set_mark)
batadv_set_bit(seq_bits, 0);
return 1;
}
/* received a much older packet. The other host either restarted
* or the old packet got delayed somewhere in the network. The
* packet should be dropped without calling this function if the
* seqno window is protected.
*
* seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
* or
* seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
*/
batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
"Other host probably restarted!\n");
bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
if (set_mark)
batadv_set_bit(seq_bits, 0);
return 1;
}