/*
   *	X.25 Packet Layer release 002
   *
   *	This is ALPHA test software. This code may break your machine,
   *	randomly fail to work with new releases, misbehave and/or generally

   *	screw up. It might even work.

   *
   *	This code REQUIRES 2.1.15 or higher
   *
   *	This module:
   *		This module 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.
   *
   *	History
   *	X.25 001	Jonathan Naylor	  Started coding.
   *	X.25 002	Jonathan Naylor	  Centralised disconnection code.
   *					  New timer architecture.

   *	2000-03-20	Daniela Squassoni Disabling/enabling of facilities

   *					  negotiation.
   *	2000-11-10	Henner Eisen	  Check and reset for out-of-sequence
   *					  i-frames.
   */

  #include <linux/slab.h>

  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>

  #include <net/tcp_states.h>

  #include <net/x25.h>
  
  static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
  {
  	struct sk_buff *skbo, *skbn = skb;
  	struct x25_sock *x25 = x25_sk(sk);
  
  	if (more) {
  		x25->fraglen += skb->len;
  		skb_queue_tail(&x25->fragment_queue, skb);
  		skb_set_owner_r(skb, sk);
  		return 0;
  	}
  
  	if (!more && x25->fraglen > 0) {	/* End of fragment */
  		int len = x25->fraglen + skb->len;
  
  		if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL){
  			kfree_skb(skb);
  			return 1;
  		}
  
  		skb_queue_tail(&x25->fragment_queue, skb);

  		skb_reset_transport_header(skbn);

  
  		skbo = skb_dequeue(&x25->fragment_queue);

  		skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len),
  					  skbo->len);

  		kfree_skb(skbo);
  
  		while ((skbo =
  			skb_dequeue(&x25->fragment_queue)) != NULL) {
  			skb_pull(skbo, (x25->neighbour->extended) ?
  					X25_EXT_MIN_LEN : X25_STD_MIN_LEN);

  			skb_copy_from_linear_data(skbo,
  						  skb_put(skbn, skbo->len),
  						  skbo->len);

  			kfree_skb(skbo);
  		}

  		x25->fraglen = 0;

  	}
  
  	skb_set_owner_r(skbn, sk);
  	skb_queue_tail(&sk->sk_receive_queue, skbn);
  	if (!sock_flag(sk, SOCK_DEAD))
  		sk->sk_data_ready(sk, skbn->len);
  
  	return 0;
  }
  
  /*
   * State machine for state 1, Awaiting Call Accepted State.
   * The handling of the timer(s) is in file x25_timer.c.
   * Handling of state 0 and connection release is in af_x25.c.
   */
  static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
  {
  	struct x25_address source_addr, dest_addr;

  	int len;

  	struct x25_sock *x25 = x25_sk(sk);

  
  	switch (frametype) {

  	case X25_CALL_ACCEPTED: {
  
  		x25_stop_timer(sk);
  		x25->condition = 0x00;
  		x25->vs        = 0;
  		x25->va        = 0;
  		x25->vr        = 0;
  		x25->vl        = 0;
  		x25->state     = X25_STATE_3;
  		sk->sk_state   = TCP_ESTABLISHED;
  		/*
  		 *	Parse the data in the frame.
  		 */

  		if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
  			goto out_clear;

  		skb_pull(skb, X25_STD_MIN_LEN);
  
  		len = x25_parse_address_block(skb, &source_addr,
  					      &dest_addr);
  		if (len > 0)
  			skb_pull(skb, len);
  		else if (len < 0)
  			goto out_clear;
  
  		len = x25_parse_facilities(skb, &x25->facilities,
  					   &x25->dte_facilities,
  					   &x25->vc_facil_mask);
  		if (len > 0)
  			skb_pull(skb, len);
  		else if (len < 0)
  			goto out_clear;
  		/*
  		 *	Copy any Call User Data.
  		 */
  		if (skb->len > 0) {

  			if (skb->len > X25_MAX_CUD_LEN)
  				goto out_clear;

  			skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
  				skb->len);

  			x25->calluserdata.cudlength = skb->len;

  		}

  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);
  		break;
  	}
  	case X25_CLEAR_REQUEST:

  		if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
  			goto out_clear;

  		x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
  		x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
  		break;

  	default:
  		break;

  	}
  
  	return 0;

  
  out_clear:
  	x25_write_internal(sk, X25_CLEAR_REQUEST);
  	x25->state = X25_STATE_2;
  	x25_start_t23timer(sk);
  	return 0;

  }
  
  /*
   * State machine for state 2, Awaiting Clear Confirmation State.
   * The handling of the timer(s) is in file x25_timer.c
   * Handling of state 0 and connection release is in af_x25.c.
   */
  static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
  {
  	switch (frametype) {
  
  		case X25_CLEAR_REQUEST:

  			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
  				goto out_clear;

  			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
  			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
  			break;
  
  		case X25_CLEAR_CONFIRMATION:
  			x25_disconnect(sk, 0, 0, 0);
  			break;
  
  		default:
  			break;
  	}
  
  	return 0;

  
  out_clear:
  	x25_write_internal(sk, X25_CLEAR_REQUEST);
  	x25_start_t23timer(sk);
  	return 0;

  }
  
  /*
   * State machine for state 3, Connected State.
   * The handling of the timer(s) is in file x25_timer.c
   * Handling of state 0 and connection release is in af_x25.c.
   */
  static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
  {
  	int queued = 0;
  	int modulus;
  	struct x25_sock *x25 = x25_sk(sk);

  	modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS;
  
  	switch (frametype) {
  
  		case X25_RESET_REQUEST:
  			x25_write_internal(sk, X25_RESET_CONFIRMATION);
  			x25_stop_timer(sk);
  			x25->condition = 0x00;
  			x25->vs        = 0;
  			x25->vr        = 0;
  			x25->va        = 0;
  			x25->vl        = 0;
  			x25_requeue_frames(sk);
  			break;
  
  		case X25_CLEAR_REQUEST:

  			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
  				goto out_clear;

  			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
  			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
  			break;
  
  		case X25_RR:
  		case X25_RNR:
  			if (!x25_validate_nr(sk, nr)) {
  				x25_clear_queues(sk);
  				x25_write_internal(sk, X25_RESET_REQUEST);
  				x25_start_t22timer(sk);
  				x25->condition = 0x00;
  				x25->vs        = 0;
  				x25->vr        = 0;
  				x25->va        = 0;
  				x25->vl        = 0;
  				x25->state     = X25_STATE_4;
  			} else {
  				x25_frames_acked(sk, nr);
  				if (frametype == X25_RNR) {
  					x25->condition |= X25_COND_PEER_RX_BUSY;
  				} else {
  					x25->condition &= ~X25_COND_PEER_RX_BUSY;
  				}
  			}
  			break;
  
  		case X25_DATA:	/* XXX */
  			x25->condition &= ~X25_COND_PEER_RX_BUSY;
  			if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) {
  				x25_clear_queues(sk);
  				x25_write_internal(sk, X25_RESET_REQUEST);
  				x25_start_t22timer(sk);
  				x25->condition = 0x00;
  				x25->vs        = 0;
  				x25->vr        = 0;
  				x25->va        = 0;
  				x25->vl        = 0;
  				x25->state     = X25_STATE_4;
  				break;
  			}
  			x25_frames_acked(sk, nr);
  			if (ns == x25->vr) {
  				if (x25_queue_rx_frame(sk, skb, m) == 0) {
  					x25->vr = (x25->vr + 1) % modulus;
  					queued = 1;
  				} else {
  					/* Should never happen */
  					x25_clear_queues(sk);
  					x25_write_internal(sk, X25_RESET_REQUEST);
  					x25_start_t22timer(sk);
  					x25->condition = 0x00;
  					x25->vs        = 0;
  					x25->vr        = 0;
  					x25->va        = 0;
  					x25->vl        = 0;
  					x25->state     = X25_STATE_4;
  					break;
  				}
  				if (atomic_read(&sk->sk_rmem_alloc) >

  				    (sk->sk_rcvbuf >> 1))

  					x25->condition |= X25_COND_OWN_RX_BUSY;
  			}
  			/*
  			 *	If the window is full Ack it immediately, else
  			 *	start the holdback timer.
  			 */
  			if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) {
  				x25->condition &= ~X25_COND_ACK_PENDING;
  				x25_stop_timer(sk);
  				x25_enquiry_response(sk);
  			} else {
  				x25->condition |= X25_COND_ACK_PENDING;
  				x25_start_t2timer(sk);
  			}
  			break;
  
  		case X25_INTERRUPT_CONFIRMATION:

  			clear_bit(X25_INTERRUPT_FLAG, &x25->flags);

  			break;
  
  		case X25_INTERRUPT:
  			if (sock_flag(sk, SOCK_URGINLINE))
  				queued = !sock_queue_rcv_skb(sk, skb);
  			else {
  				skb_set_owner_r(skb, sk);
  				skb_queue_tail(&x25->interrupt_in_queue, skb);
  				queued = 1;
  			}
  			sk_send_sigurg(sk);
  			x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION);
  			break;
  
  		default:
  			printk(KERN_WARNING "x25: unknown %02X in state 3
  ", frametype);
  			break;
  	}
  
  	return queued;

  
  out_clear:
  	x25_write_internal(sk, X25_CLEAR_REQUEST);
  	x25->state = X25_STATE_2;
  	x25_start_t23timer(sk);
  	return 0;

  }
  
  /*
   * State machine for state 4, Awaiting Reset Confirmation State.
   * The handling of the timer(s) is in file x25_timer.c
   * Handling of state 0 and connection release is in af_x25.c.
   */
  static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
  {

  	struct x25_sock *x25 = x25_sk(sk);

  	switch (frametype) {
  
  		case X25_RESET_REQUEST:
  			x25_write_internal(sk, X25_RESET_CONFIRMATION);
  		case X25_RESET_CONFIRMATION: {

  			x25_stop_timer(sk);
  			x25->condition = 0x00;
  			x25->va        = 0;
  			x25->vr        = 0;
  			x25->vs        = 0;
  			x25->vl        = 0;
  			x25->state     = X25_STATE_3;
  			x25_requeue_frames(sk);
  			break;
  		}
  		case X25_CLEAR_REQUEST:

  			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
  				goto out_clear;

  			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
  			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
  			break;
  
  		default:
  			break;
  	}
  
  	return 0;

  
  out_clear:
  	x25_write_internal(sk, X25_CLEAR_REQUEST);
  	x25->state = X25_STATE_2;
  	x25_start_t23timer(sk);
  	return 0;

  }
  
  /* Higher level upcall for a LAPB frame */
  int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb)
  {
  	struct x25_sock *x25 = x25_sk(sk);
  	int queued = 0, frametype, ns, nr, q, d, m;
  
  	if (x25->state == X25_STATE_0)
  		return 0;
  
  	frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m);
  
  	switch (x25->state) {

  	case X25_STATE_1:
  		queued = x25_state1_machine(sk, skb, frametype);
  		break;
  	case X25_STATE_2:
  		queued = x25_state2_machine(sk, skb, frametype);
  		break;
  	case X25_STATE_3:
  		queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
  		break;
  	case X25_STATE_4:
  		queued = x25_state4_machine(sk, skb, frametype);
  		break;

  	}
  
  	x25_kick(sk);
  
  	return queued;
  }
  
  int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	int queued = x25_process_rx_frame(sk, skb);
  
  	if (!queued)
  		kfree_skb(skb);
  
  	return 0;
  }