1 /* 2 * Copyright (C) 2006-2011 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 #include <linux/bitops.h> 26 27 /* returns true if the corresponding bit in the given seq_bits indicates true 28 * and curr_seqno is within range of last_seqno */ 29 uint8_t get_bit_status(unsigned long *seq_bits, uint32_t last_seqno, 30 uint32_t curr_seqno) 31 { 32 int32_t diff, word_offset, word_num; 33 34 diff = last_seqno - curr_seqno; 35 if (diff < 0 || diff >= TQ_LOCAL_WINDOW_SIZE) { 36 return 0; 37 } else { 38 /* which word */ 39 word_num = (last_seqno - curr_seqno) / WORD_BIT_SIZE; 40 /* which position in the selected word */ 41 word_offset = (last_seqno - curr_seqno) % WORD_BIT_SIZE; 42 43 if (test_bit(word_offset, &seq_bits[word_num])) 44 return 1; 45 else 46 return 0; 47 } 48 } 49 50 /* turn corresponding bit on, so we can remember that we got the packet */ 51 void bit_mark(unsigned long *seq_bits, int32_t n) 52 { 53 int32_t word_offset, word_num; 54 55 /* if too old, just drop it */ 56 if (n < 0 || n >= TQ_LOCAL_WINDOW_SIZE) 57 return; 58 59 /* which word */ 60 word_num = n / WORD_BIT_SIZE; 61 /* which position in the selected word */ 62 word_offset = n % WORD_BIT_SIZE; 63 64 set_bit(word_offset, &seq_bits[word_num]); /* turn the position on */ 65 } 66 67 /* shift the packet array by n places. */ 68 static void bit_shift(unsigned long *seq_bits, int32_t n) 69 { 70 int32_t word_offset, word_num; 71 int32_t i; 72 73 if (n <= 0 || n >= TQ_LOCAL_WINDOW_SIZE) 74 return; 75 76 word_offset = n % WORD_BIT_SIZE;/* shift how much inside each word */ 77 word_num = n / WORD_BIT_SIZE; /* shift over how much (full) words */ 78 79 for (i = NUM_WORDS - 1; i > word_num; i--) { 80 /* going from old to new, so we don't overwrite the data we copy 81 * from. 82 * 83 * left is high, right is low: FEDC BA98 7654 3210 84 * ^^ ^^ 85 * vvvv 86 * ^^^^ = from, vvvvv =to, we'd have word_num==1 and 87 * word_offset==WORD_BIT_SIZE/2 ????? in this example. 88 * (=24 bits) 89 * 90 * our desired output would be: 9876 5432 1000 0000 91 * */ 92 93 seq_bits[i] = 94 (seq_bits[i - word_num] << word_offset) + 95 /* take the lower port from the left half, shift it left 96 * to its final position */ 97 (seq_bits[i - word_num - 1] >> 98 (WORD_BIT_SIZE-word_offset)); 99 /* and the upper part of the right half and shift it left to 100 * it's position */ 101 /* for our example that would be: word[0] = 9800 + 0076 = 102 * 9876 */ 103 } 104 /* now for our last word, i==word_num, we only have the it's "left" 105 * half. that's the 1000 word in our example.*/ 106 107 seq_bits[i] = (seq_bits[i - word_num] << word_offset); 108 109 /* pad the rest with 0, if there is anything */ 110 i--; 111 112 for (; i >= 0; i--) 113 seq_bits[i] = 0; 114 } 115 116 static void bit_reset_window(unsigned long *seq_bits) 117 { 118 int i; 119 for (i = 0; i < NUM_WORDS; i++) 120 seq_bits[i] = 0; 121 } 122 123 124 /* receive and process one packet within the sequence number window. 125 * 126 * returns: 127 * 1 if the window was moved (either new or very old) 128 * 0 if the window was not moved/shifted. 129 */ 130 char bit_get_packet(void *priv, unsigned long *seq_bits, 131 int32_t seq_num_diff, int8_t set_mark) 132 { 133 struct bat_priv *bat_priv = (struct bat_priv *)priv; 134 135 /* sequence number is slightly older. We already got a sequence number 136 * higher than this one, so we just mark it. */ 137 138 if ((seq_num_diff <= 0) && (seq_num_diff > -TQ_LOCAL_WINDOW_SIZE)) { 139 if (set_mark) 140 bit_mark(seq_bits, -seq_num_diff); 141 return 0; 142 } 143 144 /* sequence number is slightly newer, so we shift the window and 145 * set the mark if required */ 146 147 if ((seq_num_diff > 0) && (seq_num_diff < TQ_LOCAL_WINDOW_SIZE)) { 148 bit_shift(seq_bits, seq_num_diff); 149 150 if (set_mark) 151 bit_mark(seq_bits, 0); 152 return 1; 153 } 154 155 /* sequence number is much newer, probably missed a lot of packets */ 156 157 if ((seq_num_diff >= TQ_LOCAL_WINDOW_SIZE) 158 || (seq_num_diff < EXPECTED_SEQNO_RANGE)) { 159 bat_dbg(DBG_BATMAN, bat_priv, 160 "We missed a lot of packets (%i) !\n", 161 seq_num_diff - 1); 162 bit_reset_window(seq_bits); 163 if (set_mark) 164 bit_mark(seq_bits, 0); 165 return 1; 166 } 167 168 /* received a much older packet. The other host either restarted 169 * or the old packet got delayed somewhere in the network. The 170 * packet should be dropped without calling this function if the 171 * seqno window is protected. */ 172 173 if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE) 174 || (seq_num_diff >= EXPECTED_SEQNO_RANGE)) { 175 176 bat_dbg(DBG_BATMAN, bat_priv, 177 "Other host probably restarted!\n"); 178 179 bit_reset_window(seq_bits); 180 if (set_mark) 181 bit_mark(seq_bits, 0); 182 183 return 1; 184 } 185 186 /* never reached */ 187 return 0; 188 } 189 190 /* count the hamming weight, how many good packets did we receive? just count 191 * the 1's. 192 */ 193 int bit_packet_count(unsigned long *seq_bits) 194 { 195 int i, hamming = 0; 196 197 for (i = 0; i < NUM_WORDS; i++) 198 hamming += hweight_long(seq_bits[i]); 199 200 return hamming; 201 } 202