summaryrefslogtreecommitdiffstats
path: root/net/batman-adv/bitarray.c
blob: 4bc695cda397efd4179e2e52eb52aaefe7e16f88 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2006-2020  B.A.T.M.A.N. contributors:
 *
 * Simon Wunderlich, Marek Lindner
 */

#include "bitarray.h"
#include "main.h"

#include <linux/bitmap.h>

#include "log.h"

/* shift the packet array by n places. */
static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)
{
	if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
		return;

	bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
}

/**
 * batadv_bit_get_packet() - receive and process one packet within the sequence
 *  number window
 * @priv: the bat priv with all the soft interface information
 * @seq_bits: pointer to the sequence number receive packet
 * @seq_num_diff: difference between the current/received sequence number and
 *  the last sequence number
 * @set_mark: whether this packet should be marked in seq_bits
 *
 * Return: true if the window was moved (either new or very old),
 *  false if the window was not moved/shifted.
 */
bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
			   s32 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 false;
	}

	/* 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 true;
	}

	/* 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 true;
	}

	/* 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 true;
}