Raspberry Pi Forums

Code: Select all

unsigned long *word;
*w = bitmap_weight(word, BATADV_TQ_LOCAL_WINDOW_SIZE);


/* shift the packet array by n places. */
static void batadv_bitmap_shift_left(unsigned long *seq_bits, int32_t n)
{
	if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
		return;

	bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
}


/* receive and process one packet within the sequence number window.
 *
 * returns:
 *  1 if the window was moved (either new or very old)
 *  0 if the window was not moved/shifted.
 */
int batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
			  int32_t seq_num_diff, int set_mark)
{
	struct batadv_priv *bat_priv = priv;

	/* sequence number is slightly older. We already got a sequence number
	 * higher than this one, so we just mark it.
	 */
	if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
		if (set_mark)
			batadv_set_bit(seq_bits, -seq_num_diff);
		return 0;
	}

	/* sequence number is slightly newer, so we shift the window and
	 * set the mark if required
	 */
	if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
		batadv_bitmap_shift_left(seq_bits, seq_num_diff);

		if (set_mark)
			batadv_set_bit(seq_bits, 0);
		return 1;
	}

	/* sequence number is much newer, probably missed a lot of packets */
	if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
	    seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
			   "We missed a lot of packets (%i) !\n",
			   seq_num_diff - 1);
		bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
		if (set_mark)
			batadv_set_bit(seq_bits, 0);
		return 1;
	}

	/* received a much older packet. The other host either restarted
	 * or the old packet got delayed somewhere in the network. The
	 * packet should be dropped without calling this function if the
	 * seqno window is protected.
	 *
	 * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
	 * or
	 * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
	 */
	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
		   "Other host probably restarted!\n");

	bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
	if (set_mark)
		batadv_set_bit(seq_bits, 0);

	return 1;
}

Code: Select all

#define DECLARE_BITMAP(name,bits) \
unsigned long name[BITS_TO_LONGS(bits)]

#define BITS_TO_LONGS(nr)       DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
#define BITS_PER_BYTE 8

Code: Select all

#define DECLARE_BITMAP(name,bits) unsigned long name[(((bits) + ({number of bits in long}) -1) / ({number of bits in long}))]