1/* Copyright (C) 2006-2014 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 "main.h"
19#include "bitarray.h"
20
21#include <linux/bitops.h>
22
23/* shift the packet array by n places. */
24static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t 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/* receive and process one packet within the sequence number window.
33 *
34 * returns:
35 *  1 if the window was moved (either new or very old)
36 *  0 if the window was not moved/shifted.
37 */
38int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
39			  int32_t seq_num_diff, int set_mark)
40{
41	struct batadv_priv *bat_priv = priv;
42
43	/* sequence number is slightly older. We already got a sequence number
44	 * higher than this one, so we just mark it.
45	 */
46	if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
47		if (set_mark)
48			batadv_set_bit(seq_bits, -seq_num_diff);
49		return 0;
50	}
51
52	/* sequence number is slightly newer, so we shift the window and
53	 * set the mark if required
54	 */
55	if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
56		batadv_bitmap_shift_left(seq_bits, seq_num_diff);
57
58		if (set_mark)
59			batadv_set_bit(seq_bits, 0);
60		return 1;
61	}
62
63	/* sequence number is much newer, probably missed a lot of packets */
64	if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
65	    seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
66		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
67			   "We missed a lot of packets (%i) !\n",
68			   seq_num_diff - 1);
69		bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
70		if (set_mark)
71			batadv_set_bit(seq_bits, 0);
72		return 1;
73	}
74
75	/* received a much older packet. The other host either restarted
76	 * or the old packet got delayed somewhere in the network. The
77	 * packet should be dropped without calling this function if the
78	 * seqno window is protected.
79	 *
80	 * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
81	 * or
82	 * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
83	 */
84	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
85		   "Other host probably restarted!\n");
86
87	bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
88	if (set_mark)
89		batadv_set_bit(seq_bits, 0);
90
91	return 1;
92}
93