// SPDX-License-Identifier: GPL-2.0

  /* Copyright (C) 2006-2020  B.A.T.M.A.N. contributors:

   *
   * Simon Wunderlich, Marek Lindner

   */

  #include "bitarray.h"

  #include "main.h"

  #include <linux/bitmap.h>

  #include "log.h"

  /* shift the packet array by n places. */

  static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)

  {

  	if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)

  		return;

  	bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);

  }

  /**

   * batadv_bit_get_packet() - receive and process one packet within the sequence

   *  number window
   * @priv: the bat priv with all the soft interface information
   * @seq_bits: pointer to the sequence number receive packet
   * @seq_num_diff: difference between the current/received sequence number and
   *  the last sequence number
   * @set_mark: whether this packet should be marked in seq_bits

   *

   * Return: true if the window was moved (either new or very old),
   *  false if the window was not moved/shifted.

   */

  bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
  			   s32 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 false;

  	}
  
  	/* 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 true;

  	}
  
  	/* 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) !
  ",
  			   seq_num_diff - 1);

  		bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);

  		if (set_mark)

  			batadv_set_bit(seq_bits, 0);

  		return true;

  	}
  
  	/* 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!
  ");

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

  	return true;

  }