/*
   * 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 Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   * Copyright Darryl Miles G7LED (dlm@g7led.demon.co.uk)
   */
  #include <linux/errno.h>
  #include <linux/types.h>
  #include <linux/socket.h>
  #include <linux/in.h>
  #include <linux/kernel.h>

  #include <linux/timer.h>
  #include <linux/string.h>
  #include <linux/sockios.h>
  #include <linux/net.h>

  #include <linux/slab.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>
  #include <net/netrom.h>
  
  static int nr_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
  {
  	struct sk_buff *skbo, *skbn = skb;
  	struct nr_sock *nr = nr_sk(sk);
  
  	skb_pull(skb, NR_NETWORK_LEN + NR_TRANSPORT_LEN);
  
  	nr_start_idletimer(sk);
  
  	if (more) {
  		nr->fraglen += skb->len;
  		skb_queue_tail(&nr->frag_queue, skb);
  		return 0;
  	}
  
  	if (!more && nr->fraglen > 0) {	/* End of fragment */
  		nr->fraglen += skb->len;
  		skb_queue_tail(&nr->frag_queue, skb);
  
  		if ((skbn = alloc_skb(nr->fraglen, GFP_ATOMIC)) == NULL)
  			return 1;

  		skb_reset_transport_header(skbn);

  
  		while ((skbo = skb_dequeue(&nr->frag_queue)) != NULL) {

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

  			kfree_skb(skbo);
  		}
  
  		nr->fraglen = 0;
  	}
  
  	return sock_queue_rcv_skb(sk, skbn);
  }
  
  /*
   * State machine for state 1, Awaiting Connection State.
   * The handling of the timer(s) is in file nr_timer.c.
   * Handling of state 0 and connection release is in netrom.c.
   */
  static int nr_state1_machine(struct sock *sk, struct sk_buff *skb,
  	int frametype)
  {
  	switch (frametype) {
  	case NR_CONNACK: {
  		struct nr_sock *nr = nr_sk(sk);
  
  		nr_stop_t1timer(sk);
  		nr_start_idletimer(sk);
  		nr->your_index = skb->data[17];
  		nr->your_id    = skb->data[18];
  		nr->vs	       = 0;
  		nr->va	       = 0;
  		nr->vr	       = 0;
  		nr->vl	       = 0;
  		nr->state      = NR_STATE_3;
  		nr->n2count    = 0;
  		nr->window     = skb->data[20];
  		sk->sk_state   = TCP_ESTABLISHED;
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);
  		break;
  	}
  
  	case NR_CONNACK | NR_CHOKE_FLAG:
  		nr_disconnect(sk, ECONNREFUSED);
  		break;

  	case NR_RESET:

  		if (sysctl_netrom_reset_circuit)

  			nr_disconnect(sk, ECONNRESET);
  		break;

  	default:
  		break;
  	}
  	return 0;
  }
  
  /*
   * State machine for state 2, Awaiting Release State.
   * The handling of the timer(s) is in file nr_timer.c
   * Handling of state 0 and connection release is in netrom.c.
   */
  static int nr_state2_machine(struct sock *sk, struct sk_buff *skb,
  	int frametype)
  {
  	switch (frametype) {
  	case NR_CONNACK | NR_CHOKE_FLAG:
  		nr_disconnect(sk, ECONNRESET);
  		break;
  
  	case NR_DISCREQ:
  		nr_write_internal(sk, NR_DISCACK);
  
  	case NR_DISCACK:
  		nr_disconnect(sk, 0);
  		break;

  	case NR_RESET:

  		if (sysctl_netrom_reset_circuit)

  			nr_disconnect(sk, ECONNRESET);
  		break;

  	default:
  		break;
  	}
  	return 0;
  }
  
  /*
   * State machine for state 3, Connected State.
   * The handling of the timer(s) is in file nr_timer.c
   * Handling of state 0 and connection release is in netrom.c.
   */
  static int nr_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype)
  {
  	struct nr_sock *nrom = nr_sk(sk);
  	struct sk_buff_head temp_queue;
  	struct sk_buff *skbn;
  	unsigned short save_vr;
  	unsigned short nr, ns;
  	int queued = 0;
  
  	nr = skb->data[18];
  	ns = skb->data[17];
  
  	switch (frametype) {
  	case NR_CONNREQ:
  		nr_write_internal(sk, NR_CONNACK);
  		break;
  
  	case NR_DISCREQ:
  		nr_write_internal(sk, NR_DISCACK);
  		nr_disconnect(sk, 0);
  		break;
  
  	case NR_CONNACK | NR_CHOKE_FLAG:
  	case NR_DISCACK:
  		nr_disconnect(sk, ECONNRESET);
  		break;
  
  	case NR_INFOACK:
  	case NR_INFOACK | NR_CHOKE_FLAG:
  	case NR_INFOACK | NR_NAK_FLAG:
  	case NR_INFOACK | NR_NAK_FLAG | NR_CHOKE_FLAG:
  		if (frametype & NR_CHOKE_FLAG) {
  			nrom->condition |= NR_COND_PEER_RX_BUSY;
  			nr_start_t4timer(sk);
  		} else {
  			nrom->condition &= ~NR_COND_PEER_RX_BUSY;
  			nr_stop_t4timer(sk);
  		}
  		if (!nr_validate_nr(sk, nr)) {
  			break;
  		}
  		if (frametype & NR_NAK_FLAG) {
  			nr_frames_acked(sk, nr);
  			nr_send_nak_frame(sk);
  		} else {
  			if (nrom->condition & NR_COND_PEER_RX_BUSY) {
  				nr_frames_acked(sk, nr);
  			} else {
  				nr_check_iframes_acked(sk, nr);
  			}
  		}
  		break;
  
  	case NR_INFO:
  	case NR_INFO | NR_NAK_FLAG:
  	case NR_INFO | NR_CHOKE_FLAG:
  	case NR_INFO | NR_MORE_FLAG:
  	case NR_INFO | NR_NAK_FLAG | NR_CHOKE_FLAG:
  	case NR_INFO | NR_CHOKE_FLAG | NR_MORE_FLAG:
  	case NR_INFO | NR_NAK_FLAG | NR_MORE_FLAG:
  	case NR_INFO | NR_NAK_FLAG | NR_CHOKE_FLAG | NR_MORE_FLAG:
  		if (frametype & NR_CHOKE_FLAG) {
  			nrom->condition |= NR_COND_PEER_RX_BUSY;
  			nr_start_t4timer(sk);
  		} else {
  			nrom->condition &= ~NR_COND_PEER_RX_BUSY;
  			nr_stop_t4timer(sk);
  		}
  		if (nr_validate_nr(sk, nr)) {
  			if (frametype & NR_NAK_FLAG) {
  				nr_frames_acked(sk, nr);
  				nr_send_nak_frame(sk);
  			} else {
  				if (nrom->condition & NR_COND_PEER_RX_BUSY) {
  					nr_frames_acked(sk, nr);
  				} else {
  					nr_check_iframes_acked(sk, nr);
  				}
  			}
  		}
  		queued = 1;
  		skb_queue_head(&nrom->reseq_queue, skb);
  		if (nrom->condition & NR_COND_OWN_RX_BUSY)
  			break;
  		skb_queue_head_init(&temp_queue);
  		do {
  			save_vr = nrom->vr;
  			while ((skbn = skb_dequeue(&nrom->reseq_queue)) != NULL) {
  				ns = skbn->data[17];
  				if (ns == nrom->vr) {
  					if (nr_queue_rx_frame(sk, skbn, frametype & NR_MORE_FLAG) == 0) {
  						nrom->vr = (nrom->vr + 1) % NR_MODULUS;
  					} else {
  						nrom->condition |= NR_COND_OWN_RX_BUSY;
  						skb_queue_tail(&temp_queue, skbn);
  					}
  				} else if (nr_in_rx_window(sk, ns)) {
  					skb_queue_tail(&temp_queue, skbn);
  				} else {
  					kfree_skb(skbn);
  				}
  			}
  			while ((skbn = skb_dequeue(&temp_queue)) != NULL) {
  				skb_queue_tail(&nrom->reseq_queue, skbn);
  			}
  		} while (save_vr != nrom->vr);
  		/*
  		 * Window is full, ack it immediately.
  		 */
  		if (((nrom->vl + nrom->window) % NR_MODULUS) == nrom->vr) {
  			nr_enquiry_response(sk);
  		} else {
  			if (!(nrom->condition & NR_COND_ACK_PENDING)) {
  				nrom->condition |= NR_COND_ACK_PENDING;
  				nr_start_t2timer(sk);
  			}
  		}
  		break;

  	case NR_RESET:

  		if (sysctl_netrom_reset_circuit)

  			nr_disconnect(sk, ECONNRESET);
  		break;

  	default:
  		break;
  	}
  	return queued;
  }
  
  /* Higher level upcall for a LAPB frame - called with sk locked */
  int nr_process_rx_frame(struct sock *sk, struct sk_buff *skb)
  {
  	struct nr_sock *nr = nr_sk(sk);
  	int queued = 0, frametype;
  
  	if (nr->state == NR_STATE_0)
  		return 0;
  
  	frametype = skb->data[19];
  
  	switch (nr->state) {
  	case NR_STATE_1:
  		queued = nr_state1_machine(sk, skb, frametype);
  		break;
  	case NR_STATE_2:
  		queued = nr_state2_machine(sk, skb, frametype);
  		break;
  	case NR_STATE_3:
  		queued = nr_state3_machine(sk, skb, frametype);
  		break;
  	}
  
  	nr_kick(sk);
  
  	return queued;
  }