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. */ 24 static 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 33 /* receive and process one packet within the sequence number window. 34 * 35 * returns: 36 * 1 if the window was moved (either new or very old) 37 * 0 if the window was not moved/shifted. 38 */ 39 int batadv_bit_get_packet(void *priv, unsigned long *seq_bits, 40 int32_t seq_num_diff, int set_mark) 41 { 42 struct batadv_priv *bat_priv = priv; 43 44 /* sequence number is slightly older. We already got a sequence number 45 * higher than this one, so we just mark it. 46 */ 47 if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) { 48 if (set_mark) 49 batadv_set_bit(seq_bits, -seq_num_diff); 50 return 0; 51 } 52 53 /* sequence number is slightly newer, so we shift the window and 54 * set the mark if required 55 */ 56 if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) { 57 batadv_bitmap_shift_left(seq_bits, seq_num_diff); 58 59 if (set_mark) 60 batadv_set_bit(seq_bits, 0); 61 return 1; 62 } 63 64 /* sequence number is much newer, probably missed a lot of packets */ 65 if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE && 66 seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) { 67 batadv_dbg(BATADV_DBG_BATMAN, bat_priv, 68 "We missed a lot of packets (%i) !\n", 69 seq_num_diff - 1); 70 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); 71 if (set_mark) 72 batadv_set_bit(seq_bits, 0); 73 return 1; 74 } 75 76 /* received a much older packet. The other host either restarted 77 * or the old packet got delayed somewhere in the network. The 78 * packet should be dropped without calling this function if the 79 * seqno window is protected. 80 * 81 * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE 82 * or 83 * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE 84 */ 85 batadv_dbg(BATADV_DBG_BATMAN, bat_priv, 86 "Other host probably restarted!\n"); 87 88 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); 89 if (set_mark) 90 batadv_set_bit(seq_bits, 0); 91 92 return 1; 93 } 94