B.A.T.M.A.N. (better approach to mobile ad-hoc networking) is a routing protocol for multi-hop ad-hoc mesh networks. The networks may be wired or wireless. See http://www.open-mesh.org/ for more information and user space tools. Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
201 lines
5.3 KiB
C
201 lines
5.3 KiB
C
/*
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* Copyright (C) 2006-2010 B.A.T.M.A.N. contributors:
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*
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* Simon Wunderlich, Marek Lindner
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA
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*
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*/
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#include "main.h"
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#include "bitarray.h"
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#include <linux/bitops.h>
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/* returns true if the corresponding bit in the given seq_bits indicates true
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* and curr_seqno is within range of last_seqno */
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uint8_t get_bit_status(unsigned long *seq_bits, uint32_t last_seqno,
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uint32_t curr_seqno)
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{
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int32_t diff, word_offset, word_num;
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diff = last_seqno - curr_seqno;
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if (diff < 0 || diff >= TQ_LOCAL_WINDOW_SIZE) {
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return 0;
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} else {
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/* which word */
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word_num = (last_seqno - curr_seqno) / WORD_BIT_SIZE;
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/* which position in the selected word */
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word_offset = (last_seqno - curr_seqno) % WORD_BIT_SIZE;
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if (test_bit(word_offset, &seq_bits[word_num]))
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return 1;
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else
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return 0;
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}
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}
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/* turn corresponding bit on, so we can remember that we got the packet */
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void bit_mark(unsigned long *seq_bits, int32_t n)
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{
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int32_t word_offset, word_num;
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/* if too old, just drop it */
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if (n < 0 || n >= TQ_LOCAL_WINDOW_SIZE)
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return;
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/* which word */
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word_num = n / WORD_BIT_SIZE;
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/* which position in the selected word */
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word_offset = n % WORD_BIT_SIZE;
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set_bit(word_offset, &seq_bits[word_num]); /* turn the position on */
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}
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/* shift the packet array by n places. */
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static void bit_shift(unsigned long *seq_bits, int32_t n)
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{
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int32_t word_offset, word_num;
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int32_t i;
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if (n <= 0 || n >= TQ_LOCAL_WINDOW_SIZE)
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return;
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word_offset = n % WORD_BIT_SIZE;/* shift how much inside each word */
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word_num = n / WORD_BIT_SIZE; /* shift over how much (full) words */
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for (i = NUM_WORDS - 1; i > word_num; i--) {
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/* going from old to new, so we don't overwrite the data we copy
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* from.
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*
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* left is high, right is low: FEDC BA98 7654 3210
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* ^^ ^^
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* vvvv
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* ^^^^ = from, vvvvv =to, we'd have word_num==1 and
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* word_offset==WORD_BIT_SIZE/2 ????? in this example.
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* (=24 bits)
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*
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* our desired output would be: 9876 5432 1000 0000
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* */
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seq_bits[i] =
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(seq_bits[i - word_num] << word_offset) +
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/* take the lower port from the left half, shift it left
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* to its final position */
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(seq_bits[i - word_num - 1] >>
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(WORD_BIT_SIZE-word_offset));
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/* and the upper part of the right half and shift it left to
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* it's position */
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/* for our example that would be: word[0] = 9800 + 0076 =
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* 9876 */
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}
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/* now for our last word, i==word_num, we only have the it's "left"
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* half. that's the 1000 word in our example.*/
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seq_bits[i] = (seq_bits[i - word_num] << word_offset);
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/* pad the rest with 0, if there is anything */
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i--;
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for (; i >= 0; i--)
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seq_bits[i] = 0;
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}
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static void bit_reset_window(unsigned long *seq_bits)
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{
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int i;
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for (i = 0; i < NUM_WORDS; i++)
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seq_bits[i] = 0;
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}
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/* receive and process one packet within the sequence number window.
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*
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* returns:
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* 1 if the window was moved (either new or very old)
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* 0 if the window was not moved/shifted.
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*/
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char bit_get_packet(void *priv, unsigned long *seq_bits,
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int32_t seq_num_diff, int8_t set_mark)
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{
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struct bat_priv *bat_priv = (struct bat_priv *)priv;
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/* sequence number is slightly older. We already got a sequence number
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* higher than this one, so we just mark it. */
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if ((seq_num_diff <= 0) && (seq_num_diff > -TQ_LOCAL_WINDOW_SIZE)) {
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if (set_mark)
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bit_mark(seq_bits, -seq_num_diff);
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return 0;
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}
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/* sequence number is slightly newer, so we shift the window and
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* set the mark if required */
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if ((seq_num_diff > 0) && (seq_num_diff < TQ_LOCAL_WINDOW_SIZE)) {
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bit_shift(seq_bits, seq_num_diff);
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if (set_mark)
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bit_mark(seq_bits, 0);
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return 1;
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}
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/* sequence number is much newer, probably missed a lot of packets */
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if ((seq_num_diff >= TQ_LOCAL_WINDOW_SIZE)
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|| (seq_num_diff < EXPECTED_SEQNO_RANGE)) {
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bat_dbg(DBG_BATMAN, bat_priv,
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"We missed a lot of packets (%i) !\n",
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seq_num_diff - 1);
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bit_reset_window(seq_bits);
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if (set_mark)
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bit_mark(seq_bits, 0);
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return 1;
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}
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/* received a much older packet. The other host either restarted
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* or the old packet got delayed somewhere in the network. The
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* packet should be dropped without calling this function if the
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* seqno window is protected. */
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if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE)
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|| (seq_num_diff >= EXPECTED_SEQNO_RANGE)) {
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bat_dbg(DBG_BATMAN, bat_priv,
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"Other host probably restarted!\n");
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bit_reset_window(seq_bits);
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if (set_mark)
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bit_mark(seq_bits, 0);
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return 1;
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}
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/* never reached */
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return 0;
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}
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/* count the hamming weight, how many good packets did we receive? just count
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* the 1's.
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*/
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int bit_packet_count(unsigned long *seq_bits)
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{
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int i, hamming = 0;
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for (i = 0; i < NUM_WORDS; i++)
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hamming += hweight_long(seq_bits[i]);
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return hamming;
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}
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