1/* Copyright (C) 2006-2013 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, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17 * 02110-1301, USA
18 */
19
20#include "main.h"
21#include "bitarray.h"
22
23#include <linux/bitops.h>
24
25/* shift the packet array by n places. */
26static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t 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/* receive and process one packet within the sequence number window.
36 *
37 * returns:
38 *  1 if the window was moved (either new or very old)
39 *  0 if the window was not moved/shifted.
40 */
41int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
42			  int32_t seq_num_diff, int set_mark)
43{
44	struct batadv_priv *bat_priv = priv;
45
46	/* sequence number is slightly older. We already got a sequence number
47	 * higher than this one, so we just mark it.
48	 */
49	if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
50		if (set_mark)
51			batadv_set_bit(seq_bits, -seq_num_diff);
52		return 0;
53	}
54
55	/* sequence number is slightly newer, so we shift the window and
56	 * set the mark if required
57	 */
58	if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
59		batadv_bitmap_shift_left(seq_bits, seq_num_diff);
60
61		if (set_mark)
62			batadv_set_bit(seq_bits, 0);
63		return 1;
64	}
65
66	/* sequence number is much newer, probably missed a lot of packets */
67	if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
68	    seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
69		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
70			   "We missed a lot of packets (%i) !\n",
71			   seq_num_diff - 1);
72		bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
73		if (set_mark)
74			batadv_set_bit(seq_bits, 0);
75		return 1;
76	}
77
78	/* received a much older packet. The other host either restarted
79	 * or the old packet got delayed somewhere in the network. The
80	 * packet should be dropped without calling this function if the
81	 * seqno window is protected.
82	 *
83	 * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
84	 * or
85	 * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
86	 */
87	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
88		   "Other host probably restarted!\n");
89
90	bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
91	if (set_mark)
92		batadv_set_bit(seq_bits, 0);
93
94	return 1;
95}
96