1/* 2 * Copyright (C) 2006-2010 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, write to the Free Software 17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 18 * 02110-1301, USA 19 * 20 */ 21 22#include "main.h" 23#include "bitarray.h" 24 25/* returns true if the corresponding bit in the given seq_bits indicates true 26 * and curr_seqno is within range of last_seqno */ 27uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint32_t last_seqno, 28 uint32_t curr_seqno) 29{ 30 int32_t diff, word_offset, word_num; 31 32 diff = last_seqno - curr_seqno; 33 if (diff < 0 || diff >= TQ_LOCAL_WINDOW_SIZE) { 34 return 0; 35 } else { 36 /* which word */ 37 word_num = (last_seqno - curr_seqno) / WORD_BIT_SIZE; 38 /* which position in the selected word */ 39 word_offset = (last_seqno - curr_seqno) % WORD_BIT_SIZE; 40 41 if (seq_bits[word_num] & 1 << word_offset) 42 return 1; 43 else 44 return 0; 45 } 46} 47 48/* turn corresponding bit on, so we can remember that we got the packet */ 49void bit_mark(TYPE_OF_WORD *seq_bits, int32_t n) 50{ 51 int32_t word_offset, word_num; 52 53 /* if too old, just drop it */ 54 if (n < 0 || n >= TQ_LOCAL_WINDOW_SIZE) 55 return; 56 57 /* which word */ 58 word_num = n / WORD_BIT_SIZE; 59 /* which position in the selected word */ 60 word_offset = n % WORD_BIT_SIZE; 61 62 seq_bits[word_num] |= 1 << word_offset; /* turn the position on */ 63} 64 65/* shift the packet array by n places. */ 66static void bit_shift(TYPE_OF_WORD *seq_bits, int32_t n) 67{ 68 int32_t word_offset, word_num; 69 int32_t i; 70 71 if (n <= 0 || n >= TQ_LOCAL_WINDOW_SIZE) 72 return; 73 74 word_offset = n % WORD_BIT_SIZE;/* shift how much inside each word */ 75 word_num = n / WORD_BIT_SIZE; /* shift over how much (full) words */ 76 77 for (i = NUM_WORDS - 1; i > word_num; i--) { 78 /* going from old to new, so we don't overwrite the data we copy 79 * from. 80 * 81 * left is high, right is low: FEDC BA98 7654 3210 82 * ^^ ^^ 83 * vvvv 84 * ^^^^ = from, vvvvv =to, we'd have word_num==1 and 85 * word_offset==WORD_BIT_SIZE/2 ????? in this example. 86 * (=24 bits) 87 * 88 * our desired output would be: 9876 5432 1000 0000 89 * */ 90 91 seq_bits[i] = 92 (seq_bits[i - word_num] << word_offset) + 93 /* take the lower port from the left half, shift it left 94 * to its final position */ 95 (seq_bits[i - word_num - 1] >> 96 (WORD_BIT_SIZE-word_offset)); 97 /* and the upper part of the right half and shift it left to 98 * it's position */ 99 /* for our example that would be: word[0] = 9800 + 0076 = 100 * 9876 */ 101 } 102 /* now for our last word, i==word_num, we only have the it's "left" 103 * half. that's the 1000 word in our example.*/ 104 105 seq_bits[i] = (seq_bits[i - word_num] << word_offset); 106 107 /* pad the rest with 0, if there is anything */ 108 i--; 109 110 for (; i >= 0; i--) 111 seq_bits[i] = 0; 112} 113 114static void bit_reset_window(TYPE_OF_WORD *seq_bits) 115{ 116 int i; 117 for (i = 0; i < NUM_WORDS; i++) 118 seq_bits[i] = 0; 119} 120 121 122/* receive and process one packet within the sequence number window. 123 * 124 * returns: 125 * 1 if the window was moved (either new or very old) 126 * 0 if the window was not moved/shifted. 127 */ 128char bit_get_packet(TYPE_OF_WORD *seq_bits, int32_t seq_num_diff, 129 int8_t set_mark) 130{ 131 struct bat_priv *bat_priv = netdev_priv(soft_device); 132 133 /* sequence number is slightly older. We already got a sequence number 134 * higher than this one, so we just mark it. */ 135 136 if ((seq_num_diff <= 0) && (seq_num_diff > -TQ_LOCAL_WINDOW_SIZE)) { 137 if (set_mark) 138 bit_mark(seq_bits, -seq_num_diff); 139 return 0; 140 } 141 142 /* sequence number is slightly newer, so we shift the window and 143 * set the mark if required */ 144 145 if ((seq_num_diff > 0) && (seq_num_diff < TQ_LOCAL_WINDOW_SIZE)) { 146 bit_shift(seq_bits, seq_num_diff); 147 148 if (set_mark) 149 bit_mark(seq_bits, 0); 150 return 1; 151 } 152 153 /* sequence number is much newer, probably missed a lot of packets */ 154 155 if ((seq_num_diff >= TQ_LOCAL_WINDOW_SIZE) 156 || (seq_num_diff < EXPECTED_SEQNO_RANGE)) { 157 bat_dbg(DBG_BATMAN, bat_priv, 158 "We missed a lot of packets (%i) !\n", 159 seq_num_diff - 1); 160 bit_reset_window(seq_bits); 161 if (set_mark) 162 bit_mark(seq_bits, 0); 163 return 1; 164 } 165 166 /* received a much older packet. The other host either restarted 167 * or the old packet got delayed somewhere in the network. The 168 * packet should be dropped without calling this function if the 169 * seqno window is protected. */ 170 171 if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE) 172 || (seq_num_diff >= EXPECTED_SEQNO_RANGE)) { 173 174 bat_dbg(DBG_BATMAN, bat_priv, 175 "Other host probably restarted!\n"); 176 177 bit_reset_window(seq_bits); 178 if (set_mark) 179 bit_mark(seq_bits, 0); 180 181 return 1; 182 } 183 184 /* never reached */ 185 return 0; 186} 187 188/* count the hamming weight, how many good packets did we receive? just count 189 * the 1's. The inner loop uses the Kernighan algorithm, see 190 * http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan 191 */ 192int bit_packet_count(TYPE_OF_WORD *seq_bits) 193{ 194 int i, hamming = 0; 195 TYPE_OF_WORD word; 196 197 for (i = 0; i < NUM_WORDS; i++) { 198 word = seq_bits[i]; 199 200 while (word) { 201 word &= word-1; 202 hamming++; 203 } 204 } 205 return hamming; 206} 207