GNU Linux-libre 4.19.211-gnu1
[releases.git] / net / batman-adv / bitarray.c
1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) 2006-2018  B.A.T.M.A.N. contributors:
3  *
4  * Simon Wunderlich, Marek Lindner
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of version 2 of the GNU General Public
8  * License as published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful, but
11  * WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  * General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program; if not, see <http://www.gnu.org/licenses/>.
17  */
18
19 #include "bitarray.h"
20 #include "main.h"
21
22 #include <linux/bitmap.h>
23
24 #include "log.h"
25
26 /* shift the packet array by n places. */
27 static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)
28 {
29         if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
30                 return;
31
32         bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
33 }
34
35 /**
36  * batadv_bit_get_packet() - receive and process one packet within the sequence
37  *  number window
38  * @priv: the bat priv with all the soft interface information
39  * @seq_bits: pointer to the sequence number receive packet
40  * @seq_num_diff: difference between the current/received sequence number and
41  *  the last sequence number
42  * @set_mark: whether this packet should be marked in seq_bits
43  *
44  * Return: true if the window was moved (either new or very old),
45  *  false if the window was not moved/shifted.
46  */
47 bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
48                            s32 seq_num_diff, int set_mark)
49 {
50         struct batadv_priv *bat_priv = priv;
51
52         /* sequence number is slightly older. We already got a sequence number
53          * higher than this one, so we just mark it.
54          */
55         if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
56                 if (set_mark)
57                         batadv_set_bit(seq_bits, -seq_num_diff);
58                 return false;
59         }
60
61         /* sequence number is slightly newer, so we shift the window and
62          * set the mark if required
63          */
64         if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
65                 batadv_bitmap_shift_left(seq_bits, seq_num_diff);
66
67                 if (set_mark)
68                         batadv_set_bit(seq_bits, 0);
69                 return true;
70         }
71
72         /* sequence number is much newer, probably missed a lot of packets */
73         if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
74             seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
75                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
76                            "We missed a lot of packets (%i) !\n",
77                            seq_num_diff - 1);
78                 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
79                 if (set_mark)
80                         batadv_set_bit(seq_bits, 0);
81                 return true;
82         }
83
84         /* received a much older packet. The other host either restarted
85          * or the old packet got delayed somewhere in the network. The
86          * packet should be dropped without calling this function if the
87          * seqno window is protected.
88          *
89          * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
90          * or
91          * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
92          */
93         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
94                    "Other host probably restarted!\n");
95
96         bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
97         if (set_mark)
98                 batadv_set_bit(seq_bits, 0);
99
100         return true;
101 }