1 /* Copyright (C) 2006-2012 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, write to the Free Software 16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 17 * 02110-1301, USA 18 */ 19 20 #include "main.h" 21 #include "bitarray.h" 22 23 #include <linux/bitops.h> 24 25 /* shift the packet array by n places. */ 26 static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t n) 27 { 28 if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE) 29 return; 30 31 bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE); 32 } 33 34 35 /* receive and process one packet within the sequence number window. 36 * 37 * returns: 38 * 1 if the window was moved (either new or very old) 39 * 0 if the window was not moved/shifted. 40 */ 41 int batadv_bit_get_packet(void *priv, unsigned long *seq_bits, 42 int32_t seq_num_diff, int set_mark) 43 { 44 struct batadv_priv *bat_priv = priv; 45 46 /* sequence number is slightly older. We already got a sequence number 47 * higher than this one, so we just mark it. 48 */ 49 if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) { 50 if (set_mark) 51 batadv_set_bit(seq_bits, -seq_num_diff); 52 return 0; 53 } 54 55 /* sequence number is slightly newer, so we shift the window and 56 * set the mark if required 57 */ 58 if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) { 59 batadv_bitmap_shift_left(seq_bits, seq_num_diff); 60 61 if (set_mark) 62 batadv_set_bit(seq_bits, 0); 63 return 1; 64 } 65 66 /* sequence number is much newer, probably missed a lot of packets */ 67 if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE && 68 seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) { 69 batadv_dbg(BATADV_DBG_BATMAN, bat_priv, 70 "We missed a lot of packets (%i) !\n", 71 seq_num_diff - 1); 72 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); 73 if (set_mark) 74 batadv_set_bit(seq_bits, 0); 75 return 1; 76 } 77 78 /* received a much older packet. The other host either restarted 79 * or the old packet got delayed somewhere in the network. The 80 * packet should be dropped without calling this function if the 81 * seqno window is protected. 82 * 83 * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE 84 * or 85 * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE 86 */ 87 batadv_dbg(BATADV_DBG_BATMAN, bat_priv, 88 "Other host probably restarted!\n"); 89 90 bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); 91 if (set_mark) 92 batadv_set_bit(seq_bits, 0); 93 94 return 1; 95 } 96