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. */
batadv_bitmap_shift_left(unsigned long * seq_bits,s32 n)15 static 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  */
batadv_bit_get_packet(void * priv,unsigned long * seq_bits,s32 seq_num_diff,int set_mark)35 bool 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