/*
   * 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)
   */
  #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 <linux/fcntl.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <net/netrom.h>
  
  /*
   *	This routine purges all of the queues of frames.
   */
  void nr_clear_queues(struct sock *sk)
  {
  	struct nr_sock *nr = nr_sk(sk);
  
  	skb_queue_purge(&sk->sk_write_queue);
  	skb_queue_purge(&nr->ack_queue);
  	skb_queue_purge(&nr->reseq_queue);
  	skb_queue_purge(&nr->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 nr_frames_acked(struct sock *sk, unsigned short nr)
  {
  	struct nr_sock *nrom = nr_sk(sk);
  	struct sk_buff *skb;
  
  	/*
  	 * Remove all the ack-ed frames from the ack queue.
  	 */
  	if (nrom->va != nr) {
  		while (skb_peek(&nrom->ack_queue) != NULL && nrom->va != nr) {
  			skb = skb_dequeue(&nrom->ack_queue);
  			kfree_skb(skb);
  			nrom->va = (nrom->va + 1) % NR_MODULUS;
  		}
  	}
  }
  
  /*
   * Requeue all the un-ack-ed frames on the output queue to be picked
   * up by nr_kick called from the timer. This arrangement handles the
   * possibility of an empty output queue.
   */
  void nr_requeue_frames(struct sock *sk)
  {
  	struct sk_buff *skb, *skb_prev = NULL;
  
  	while ((skb = skb_dequeue(&nr_sk(sk)->ack_queue)) != NULL) {
  		if (skb_prev == NULL)
  			skb_queue_head(&sk->sk_write_queue, skb);
  		else
  			skb_append(skb_prev, skb, &sk->sk_write_queue);
  		skb_prev = skb;
  	}
  }
  
  /*
   *	Validate that the value of nr is between va and vs. Return true or
   *	false for testing.
   */
  int nr_validate_nr(struct sock *sk, unsigned short nr)
  {
  	struct nr_sock *nrom = nr_sk(sk);
  	unsigned short vc = nrom->va;
  
  	while (vc != nrom->vs) {
  		if (nr == vc) return 1;
  		vc = (vc + 1) % NR_MODULUS;
  	}
  
  	return nr == nrom->vs;
  }
  
  /*
   *	Check that ns is within the receive window.
   */
  int nr_in_rx_window(struct sock *sk, unsigned short ns)
  {
  	struct nr_sock *nr = nr_sk(sk);
  	unsigned short vc = nr->vr;
  	unsigned short vt = (nr->vl + nr->window) % NR_MODULUS;
  
  	while (vc != vt) {
  		if (ns == vc) return 1;
  		vc = (vc + 1) % NR_MODULUS;
  	}
  
  	return 0;
  }
  
  /*
   *  This routine is called when the HDLC layer internally generates a
   *  control frame.
   */
  void nr_write_internal(struct sock *sk, int frametype)
  {
  	struct nr_sock *nr = nr_sk(sk);
  	struct sk_buff *skb;
  	unsigned char  *dptr;
  	int len, timeout;
  
  	len = NR_NETWORK_LEN + NR_TRANSPORT_LEN;
  
  	switch (frametype & 0x0F) {
  	case NR_CONNREQ:
  		len += 17;
  		break;
  	case NR_CONNACK:
  		len += (nr->bpqext) ? 2 : 1;
  		break;
  	case NR_DISCREQ:
  	case NR_DISCACK:
  	case NR_INFOACK:
  		break;
  	default:
  		printk(KERN_ERR "NET/ROM: nr_write_internal - invalid frame type %d
  ", frametype);
  		return;
  	}
  
  	if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
  		return;
  
  	/*
  	 *	Space for AX.25 and NET/ROM network header
  	 */
  	skb_reserve(skb, NR_NETWORK_LEN);
  
  	dptr = skb_put(skb, skb_tailroom(skb));
  
  	switch (frametype & 0x0F) {
  	case NR_CONNREQ:
  		timeout  = nr->t1 / HZ;
  		*dptr++  = nr->my_index;
  		*dptr++  = nr->my_id;
  		*dptr++  = 0;
  		*dptr++  = 0;
  		*dptr++  = frametype;
  		*dptr++  = nr->window;
  		memcpy(dptr, &nr->user_addr, AX25_ADDR_LEN);
  		dptr[6] &= ~AX25_CBIT;
  		dptr[6] &= ~AX25_EBIT;
  		dptr[6] |= AX25_SSSID_SPARE;
  		dptr    += AX25_ADDR_LEN;
  		memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
  		dptr[6] &= ~AX25_CBIT;
  		dptr[6] &= ~AX25_EBIT;
  		dptr[6] |= AX25_SSSID_SPARE;
  		dptr    += AX25_ADDR_LEN;
  		*dptr++  = timeout % 256;
  		*dptr++  = timeout / 256;
  		break;
  
  	case NR_CONNACK:
  		*dptr++ = nr->your_index;
  		*dptr++ = nr->your_id;
  		*dptr++ = nr->my_index;
  		*dptr++ = nr->my_id;
  		*dptr++ = frametype;
  		*dptr++ = nr->window;
  		if (nr->bpqext) *dptr++ = sysctl_netrom_network_ttl_initialiser;
  		break;
  
  	case NR_DISCREQ:
  	case NR_DISCACK:
  		*dptr++ = nr->your_index;
  		*dptr++ = nr->your_id;
  		*dptr++ = 0;
  		*dptr++ = 0;
  		*dptr++ = frametype;
  		break;
  
  	case NR_INFOACK:
  		*dptr++ = nr->your_index;
  		*dptr++ = nr->your_id;
  		*dptr++ = 0;
  		*dptr++ = nr->vr;
  		*dptr++ = frametype;
  		break;
  	}
  
  	nr_transmit_buffer(sk, skb);
  }
  
  /*
   * This routine is called to send an error reply.
   */
  void __nr_transmit_reply(struct sk_buff *skb, int mine, unsigned char cmdflags)
  {
  	struct sk_buff *skbn;
  	unsigned char *dptr;
  	int len;
  
  	len = NR_NETWORK_LEN + NR_TRANSPORT_LEN + 1;
  
  	if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL)
  		return;
  
  	skb_reserve(skbn, 0);
  
  	dptr = skb_put(skbn, NR_NETWORK_LEN + NR_TRANSPORT_LEN);
  
  	skb_copy_from_linear_data_offset(skb, 7, dptr, AX25_ADDR_LEN);
  	dptr[6] &= ~AX25_CBIT;
  	dptr[6] &= ~AX25_EBIT;
  	dptr[6] |= AX25_SSSID_SPARE;
  	dptr += AX25_ADDR_LEN;
  
  	skb_copy_from_linear_data(skb, dptr, AX25_ADDR_LEN);
  	dptr[6] &= ~AX25_CBIT;
  	dptr[6] |= AX25_EBIT;
  	dptr[6] |= AX25_SSSID_SPARE;
  	dptr += AX25_ADDR_LEN;
  
  	*dptr++ = sysctl_netrom_network_ttl_initialiser;
  
  	if (mine) {
  		*dptr++ = 0;
  		*dptr++ = 0;
  		*dptr++ = skb->data[15];
  		*dptr++ = skb->data[16];
  	} else {
  		*dptr++ = skb->data[15];
  		*dptr++ = skb->data[16];
  		*dptr++ = 0;
  		*dptr++ = 0;
  	}
  
  	*dptr++ = cmdflags;
  	*dptr++ = 0;
  
  	if (!nr_route_frame(skbn, NULL))
  		kfree_skb(skbn);
  }
  
  void nr_disconnect(struct sock *sk, int reason)
  {
  	nr_stop_t1timer(sk);
  	nr_stop_t2timer(sk);
  	nr_stop_t4timer(sk);
  	nr_stop_idletimer(sk);
  
  	nr_clear_queues(sk);
  
  	nr_sk(sk)->state = NR_STATE_0;
  
  	sk->sk_state     = TCP_CLOSE;
  	sk->sk_err       = reason;
  	sk->sk_shutdown |= SEND_SHUTDOWN;
  
  	if (!sock_flag(sk, SOCK_DEAD)) {
  		sk->sk_state_change(sk);
  		sock_set_flag(sk, SOCK_DEAD);
  	}
  }