/*
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
   */
  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/in.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/timer.h>
  #include <linux/string.h>
  #include <linux/sockios.h>
  #include <linux/net.h>
  #include <net/ax25.h>
  #include <linux/inet.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>

  #include <net/tcp_states.h>

  #include <asm/uaccess.h>
  #include <asm/system.h>
  #include <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  
  /*
   *	This routine purges all the queues of frames.
   */
  void ax25_clear_queues(ax25_cb *ax25)
  {
  	skb_queue_purge(&ax25->write_queue);
  	skb_queue_purge(&ax25->ack_queue);
  	skb_queue_purge(&ax25->reseq_queue);
  	skb_queue_purge(&ax25->frag_queue);
  }
  
  /*
   * This routine purges the input queue of those frames that have been
   * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
   * SDL diagram.
   */
  void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
  {
  	struct sk_buff *skb;
  
  	/*
  	 * Remove all the ack-ed frames from the ack queue.
  	 */
  	if (ax25->va != nr) {
  		while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
  		        skb = skb_dequeue(&ax25->ack_queue);
  			kfree_skb(skb);
  			ax25->va = (ax25->va + 1) % ax25->modulus;
  		}
  	}
  }
  
  void ax25_requeue_frames(ax25_cb *ax25)
  {
          struct sk_buff *skb, *skb_prev = NULL;
  
  	/*
  	 * Requeue all the un-ack-ed frames on the output queue to be picked
  	 * up by ax25_kick called from the timer. This arrangement handles the
  	 * possibility of an empty output queue.
  	 */
  	while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) {
  		if (skb_prev == NULL)
  			skb_queue_head(&ax25->write_queue, skb);
  		else

  			skb_append(skb_prev, skb, &ax25->write_queue);

  		skb_prev = skb;
  	}
  }
  
  /*
   *	Validate that the value of nr is between va and vs. Return true or
   *	false for testing.
   */
  int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  {
  	unsigned short vc = ax25->va;
  
  	while (vc != ax25->vs) {
  		if (nr == vc) return 1;
  		vc = (vc + 1) % ax25->modulus;
  	}
  
  	if (nr == ax25->vs) return 1;
  
  	return 0;
  }
  
  /*
   *	This routine is the centralised routine for parsing the control
   *	information for the different frame formats.
   */
  int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
  {
  	unsigned char *frame;
  	int frametype = AX25_ILLEGAL;
  
  	frame = skb->data;
  	*ns = *nr = *pf = 0;
  
  	if (ax25->modulus == AX25_MODULUS) {
  		if ((frame[0] & AX25_S) == 0) {
  			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
  			*ns = (frame[0] >> 1) & 0x07;
  			*nr = (frame[0] >> 5) & 0x07;
  			*pf = frame[0] & AX25_PF;
  		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
  			frametype = frame[0] & 0x0F;
  			*nr = (frame[0] >> 5) & 0x07;
  			*pf = frame[0] & AX25_PF;
  		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
  			frametype = frame[0] & ~AX25_PF;
  			*pf = frame[0] & AX25_PF;
  		}
  		skb_pull(skb, 1);
  	} else {
  		if ((frame[0] & AX25_S) == 0) {
  			frametype = AX25_I;			/* I frame - carries NR/NS/PF */
  			*ns = (frame[0] >> 1) & 0x7F;
  			*nr = (frame[1] >> 1) & 0x7F;
  			*pf = frame[1] & AX25_EPF;
  			skb_pull(skb, 2);
  		} else if ((frame[0] & AX25_U) == 1) { 	/* S frame - take out PF/NR */
  			frametype = frame[0] & 0x0F;
  			*nr = (frame[1] >> 1) & 0x7F;
  			*pf = frame[1] & AX25_EPF;
  			skb_pull(skb, 2);
  		} else if ((frame[0] & AX25_U) == 3) { 	/* U frame - take out PF */
  			frametype = frame[0] & ~AX25_PF;
  			*pf = frame[0] & AX25_PF;
  			skb_pull(skb, 1);
  		}
  	}
  
  	return frametype;
  }
  
  /*
   *	This routine is called when the HDLC layer internally  generates a
   *	command or  response  for  the remote machine ( eg. RR, UA etc. ).
   *	Only supervisory or unnumbered frames are processed.
   */
  void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
  {
  	struct sk_buff *skb;
  	unsigned char  *dptr;
  
  	if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
  		return;
  
  	skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
  
  	skb->nh.raw = skb->data;
  
  	/* Assume a response - address structure for DTE */
  	if (ax25->modulus == AX25_MODULUS) {
  		dptr = skb_put(skb, 1);
  		*dptr = frametype;
  		*dptr |= (poll_bit) ? AX25_PF : 0;
  		if ((frametype & AX25_U) == AX25_S)		/* S frames carry NR */
  			*dptr |= (ax25->vr << 5);
  	} else {
  		if ((frametype & AX25_U) == AX25_U) {
  			dptr = skb_put(skb, 1);
  			*dptr = frametype;
  			*dptr |= (poll_bit) ? AX25_PF : 0;
  		} else {
  			dptr = skb_put(skb, 2);
  			dptr[0] = frametype;
  			dptr[1] = (ax25->vr << 1);
  			dptr[1] |= (poll_bit) ? AX25_EPF : 0;
  		}
  	}
  
  	ax25_transmit_buffer(ax25, skb, type);
  }
  
  /*
   *	Send a 'DM' to an unknown connection attempt, or an invalid caller.
   *
   *	Note: src here is the sender, thus it's the target of the DM
   */
  void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
  {
  	struct sk_buff *skb;
  	char *dptr;
  	ax25_digi retdigi;
  
  	if (dev == NULL)
  		return;
  
  	if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
  		return;	/* Next SABM will get DM'd */
  
  	skb_reserve(skb, dev->hard_header_len);
  	skb->nh.raw = skb->data;
  
  	ax25_digi_invert(digi, &retdigi);
  
  	dptr = skb_put(skb, 1);
  
  	*dptr = AX25_DM | AX25_PF;
  
  	/*
  	 *	Do the address ourselves
  	 */
  	dptr  = skb_push(skb, ax25_addr_size(digi));
  	dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);

  	ax25_queue_xmit(skb, dev);

  }
  
  /*
   *	Exponential backoff for AX.25
   */
  void ax25_calculate_t1(ax25_cb *ax25)
  {
  	int n, t = 2;
  
  	switch (ax25->backoff) {
  	case 0:
  		break;
  
  	case 1:
  		t += 2 * ax25->n2count;
  		break;
  
  	case 2:
  		for (n = 0; n < ax25->n2count; n++)
  			t *= 2;
  		if (t > 8) t = 8;
  		break;
  	}
  
  	ax25->t1 = t * ax25->rtt;
  }
  
  /*
   *	Calculate the Round Trip Time
   */
  void ax25_calculate_rtt(ax25_cb *ax25)
  {
  	if (ax25->backoff == 0)
  		return;
  
  	if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
  		ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
  
  	if (ax25->rtt < AX25_T1CLAMPLO)
  		ax25->rtt = AX25_T1CLAMPLO;
  
  	if (ax25->rtt > AX25_T1CLAMPHI)
  		ax25->rtt = AX25_T1CLAMPHI;
  }
  
  void ax25_disconnect(ax25_cb *ax25, int reason)
  {
  	ax25_clear_queues(ax25);
  
  	ax25_stop_t1timer(ax25);
  	ax25_stop_t2timer(ax25);
  	ax25_stop_t3timer(ax25);
  	ax25_stop_idletimer(ax25);
  
  	ax25->state = AX25_STATE_0;
  
  	ax25_link_failed(ax25, reason);
  
  	if (ax25->sk != NULL) {
  		bh_lock_sock(ax25->sk);
  		ax25->sk->sk_state     = TCP_CLOSE;
  		ax25->sk->sk_err       = reason;
  		ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
  		if (!sock_flag(ax25->sk, SOCK_DEAD)) {
  			ax25->sk->sk_state_change(ax25->sk);
  			sock_set_flag(ax25->sk, SOCK_DEAD);
  		}
  		bh_unlock_sock(ax25->sk);
  	}
  }