/*
   * DECnet       An implementation of the DECnet protocol suite for the LINUX
   *              operating system.  DECnet is implemented using the  BSD Socket
   *              interface as the means of communication with the user level.
   *
   *              DECnet Network Services Protocol (Input)
   *
   * Author:      Eduardo Marcelo Serrat <emserrat@geocities.com>
   *
   * Changes:
   *
   *    Steve Whitehouse:  Split into dn_nsp_in.c and dn_nsp_out.c from
   *                       original dn_nsp.c.
   *    Steve Whitehouse:  Updated to work with my new routing architecture.
   *    Steve Whitehouse:  Add changes from Eduardo Serrat's patches.
   *    Steve Whitehouse:  Put all ack handling code in a common routine.
   *    Steve Whitehouse:  Put other common bits into dn_nsp_rx()
   *    Steve Whitehouse:  More checks on skb->len to catch bogus packets
   *                       Fixed various race conditions and possible nasties.
   *    Steve Whitehouse:  Now handles returned conninit frames.
   *     David S. Miller:  New socket locking
   *    Steve Whitehouse:  Fixed lockup when socket filtering was enabled.
   *         Paul Koning:  Fix to push CC sockets into RUN when acks are
   *                       received.
   *    Steve Whitehouse:
   *   Patrick Caulfield:  Checking conninits for correctness & sending of error
   *                       responses.
   *    Steve Whitehouse:  Added backlog congestion level return codes.
   *   Patrick Caulfield:
   *    Steve Whitehouse:  Added flow control support (outbound)
   *    Steve Whitehouse:  Prepare for nonlinear skbs
   */
  
  /******************************************************************************
      (c) 1995-1998 E.M. Serrat		emserrat@geocities.com

      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
      any later version.
  
      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.
  *******************************************************************************/

  #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/netdevice.h>
  #include <linux/inet.h>
  #include <linux/route.h>

  #include <linux/slab.h>

  #include <net/sock.h>

  #include <net/tcp_states.h>

  #include <asm/system.h>
  #include <linux/fcntl.h>
  #include <linux/mm.h>

  #include <linux/termios.h>

  #include <linux/interrupt.h>
  #include <linux/proc_fs.h>
  #include <linux/stat.h>
  #include <linux/init.h>
  #include <linux/poll.h>
  #include <linux/netfilter_decnet.h>
  #include <net/neighbour.h>
  #include <net/dst.h>
  #include <net/dn.h>
  #include <net/dn_nsp.h>
  #include <net/dn_dev.h>
  #include <net/dn_route.h>
  
  extern int decnet_log_martians;
  
  static void dn_log_martian(struct sk_buff *skb, const char *msg)
  {
  	if (decnet_log_martians && net_ratelimit()) {
  		char *devname = skb->dev ? skb->dev->name : "???";
  		struct dn_skb_cb *cb = DN_SKB_CB(skb);

  		printk(KERN_INFO "DECnet: Martian packet (%s) dev=%s src=0x%04hx dst=0x%04hx srcport=0x%04hx dstport=0x%04hx
  ",
  		       msg, devname, le16_to_cpu(cb->src), le16_to_cpu(cb->dst),
  		       le16_to_cpu(cb->src_port), le16_to_cpu(cb->dst_port));

  	}
  }
  
  /*
   * For this function we've flipped the cross-subchannel bit
   * if the message is an otherdata or linkservice message. Thus
   * we can use it to work out what to update.
   */
  static void dn_ack(struct sock *sk, struct sk_buff *skb, unsigned short ack)
  {
  	struct dn_scp *scp = DN_SK(sk);
  	unsigned short type = ((ack >> 12) & 0x0003);
  	int wakeup = 0;

  	switch (type) {
  	case 0: /* ACK - Data */
  		if (dn_after(ack, scp->ackrcv_dat)) {
  			scp->ackrcv_dat = ack & 0x0fff;
  			wakeup |= dn_nsp_check_xmit_queue(sk, skb,
  							  &scp->data_xmit_queue,
  							  ack);
  		}
  		break;
  	case 1: /* NAK - Data */
  		break;
  	case 2: /* ACK - OtherData */
  		if (dn_after(ack, scp->ackrcv_oth)) {
  			scp->ackrcv_oth = ack & 0x0fff;
  			wakeup |= dn_nsp_check_xmit_queue(sk, skb,
  							  &scp->other_xmit_queue,
  							  ack);
  		}
  		break;
  	case 3: /* NAK - OtherData */
  		break;

  	}
  
  	if (wakeup && !sock_flag(sk, SOCK_DEAD))
  		sk->sk_state_change(sk);
  }
  
  /*
   * This function is a universal ack processor.
   */
  static int dn_process_ack(struct sock *sk, struct sk_buff *skb, int oth)
  {

  	__le16 *ptr = (__le16 *)skb->data;

  	int len = 0;
  	unsigned short ack;
  
  	if (skb->len < 2)
  		return len;

  	if ((ack = le16_to_cpu(*ptr)) & 0x8000) {

  		skb_pull(skb, 2);
  		ptr++;
  		len += 2;
  		if ((ack & 0x4000) == 0) {

  			if (oth)

  				ack ^= 0x2000;
  			dn_ack(sk, skb, ack);
  		}
  	}
  
  	if (skb->len < 2)
  		return len;

  	if ((ack = le16_to_cpu(*ptr)) & 0x8000) {

  		skb_pull(skb, 2);
  		len += 2;
  		if ((ack & 0x4000) == 0) {

  			if (oth)

  				ack ^= 0x2000;
  			dn_ack(sk, skb, ack);
  		}
  	}
  
  	return len;
  }
  
  
  /**
   * dn_check_idf - Check an image data field format is correct.
   * @pptr: Pointer to pointer to image data
   * @len: Pointer to length of image data
   * @max: The maximum allowed length of the data in the image data field
   * @follow_on: Check that this many bytes exist beyond the end of the image data
   *
   * Returns: 0 if ok, -1 on error
   */
  static inline int dn_check_idf(unsigned char **pptr, int *len, unsigned char max, unsigned char follow_on)
  {
  	unsigned char *ptr = *pptr;
  	unsigned char flen = *ptr++;
  
  	(*len)--;
  	if (flen > max)
  		return -1;
  	if ((flen + follow_on) > *len)
  		return -1;
  
  	*len -= flen;
  	*pptr = ptr + flen;
  	return 0;
  }
  
  /*
   * Table of reason codes to pass back to node which sent us a badly
   * formed message, plus text messages for the log. A zero entry in
   * the reason field means "don't reply" otherwise a disc init is sent with
   * the specified reason code.
   */
  static struct {
  	unsigned short reason;
  	const char *text;
  } ci_err_table[] = {
   { 0,             "CI: Truncated message" },
   { NSP_REASON_ID, "CI: Destination username error" },
   { NSP_REASON_ID, "CI: Destination username type" },
   { NSP_REASON_US, "CI: Source username error" },
   { 0,             "CI: Truncated at menuver" },
   { 0,             "CI: Truncated before access or user data" },
   { NSP_REASON_IO, "CI: Access data format error" },
   { NSP_REASON_IO, "CI: User data format error" }
  };
  
  /*
   * This function uses a slightly different lookup method
   * to find its sockets, since it searches on object name/number
   * rather than port numbers. Various tests are done to ensure that
   * the incoming data is in the correct format before it is queued to
   * a socket.
   */
  static struct sock *dn_find_listener(struct sk_buff *skb, unsigned short *reason)
  {
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	struct nsp_conn_init_msg *msg = (struct nsp_conn_init_msg *)skb->data;
  	struct sockaddr_dn dstaddr;
  	struct sockaddr_dn srcaddr;
  	unsigned char type = 0;
  	int dstlen;
  	int srclen;
  	unsigned char *ptr;
  	int len;
  	int err = 0;
  	unsigned char menuver;
  
  	memset(&dstaddr, 0, sizeof(struct sockaddr_dn));
  	memset(&srcaddr, 0, sizeof(struct sockaddr_dn));
  
  	/*
  	 * 1. Decode & remove message header
  	 */
  	cb->src_port = msg->srcaddr;
  	cb->dst_port = msg->dstaddr;
  	cb->services = msg->services;
  	cb->info     = msg->info;

  	cb->segsize  = le16_to_cpu(msg->segsize);

  
  	if (!pskb_may_pull(skb, sizeof(*msg)))
  		goto err_out;
  
  	skb_pull(skb, sizeof(*msg));
  
  	len = skb->len;
  	ptr = skb->data;
  
  	/*
  	 * 2. Check destination end username format
  	 */
  	dstlen = dn_username2sockaddr(ptr, len, &dstaddr, &type);
  	err++;
  	if (dstlen < 0)
  		goto err_out;
  
  	err++;
  	if (type > 1)
  		goto err_out;
  
  	len -= dstlen;
  	ptr += dstlen;
  
  	/*
  	 * 3. Check source end username format
  	 */
  	srclen = dn_username2sockaddr(ptr, len, &srcaddr, &type);
  	err++;
  	if (srclen < 0)
  		goto err_out;
  
  	len -= srclen;
  	ptr += srclen;
  	err++;
  	if (len < 1)
  		goto err_out;
  
  	menuver = *ptr;
  	ptr++;
  	len--;
  
  	/*
  	 * 4. Check that optional data actually exists if menuver says it does
  	 */
  	err++;
  	if ((menuver & (DN_MENUVER_ACC | DN_MENUVER_USR)) && (len < 1))
  		goto err_out;
  
  	/*
  	 * 5. Check optional access data format
  	 */
  	err++;
  	if (menuver & DN_MENUVER_ACC) {
  		if (dn_check_idf(&ptr, &len, 39, 1))
  			goto err_out;
  		if (dn_check_idf(&ptr, &len, 39, 1))
  			goto err_out;
  		if (dn_check_idf(&ptr, &len, 39, (menuver & DN_MENUVER_USR) ? 1 : 0))
  			goto err_out;
  	}
  
  	/*
  	 * 6. Check optional user data format
  	 */
  	err++;
  	if (menuver & DN_MENUVER_USR) {
  		if (dn_check_idf(&ptr, &len, 16, 0))
  			goto err_out;
  	}
  
  	/*
  	 * 7. Look up socket based on destination end username
  	 */
  	return dn_sklist_find_listener(&dstaddr);
  err_out:
  	dn_log_martian(skb, ci_err_table[err].text);
  	*reason = ci_err_table[err].reason;
  	return NULL;
  }
  
  
  static void dn_nsp_conn_init(struct sock *sk, struct sk_buff *skb)
  {
  	if (sk_acceptq_is_full(sk)) {
  		kfree_skb(skb);
  		return;
  	}
  
  	sk->sk_ack_backlog++;
  	skb_queue_tail(&sk->sk_receive_queue, skb);
  	sk->sk_state_change(sk);
  }
  
  static void dn_nsp_conn_conf(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	struct dn_scp *scp = DN_SK(sk);
  	unsigned char *ptr;
  
  	if (skb->len < 4)
  		goto out;
  
  	ptr = skb->data;
  	cb->services = *ptr++;
  	cb->info = *ptr++;

  	cb->segsize = le16_to_cpu(*(__le16 *)ptr);

  
  	if ((scp->state == DN_CI) || (scp->state == DN_CD)) {
  		scp->persist = 0;

  		scp->addrrem = cb->src_port;
  		sk->sk_state = TCP_ESTABLISHED;
  		scp->state = DN_RUN;

  		scp->services_rem = cb->services;
  		scp->info_rem = cb->info;
  		scp->segsize_rem = cb->segsize;
  
  		if ((scp->services_rem & NSP_FC_MASK) == NSP_FC_NONE)
  			scp->max_window = decnet_no_fc_max_cwnd;
  
  		if (skb->len > 0) {

  			u16 dlen = *skb->data;

  			if ((dlen <= 16) && (dlen <= skb->len)) {

  				scp->conndata_in.opt_optl = cpu_to_le16(dlen);

  				skb_copy_from_linear_data_offset(skb, 1,
  					      scp->conndata_in.opt_data, dlen);

  			}
  		}

  		dn_nsp_send_link(sk, DN_NOCHANGE, 0);
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);
  	}

  
  out:

  	kfree_skb(skb);

  }
  
  static void dn_nsp_conn_ack(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  
  	if (scp->state == DN_CI) {
  		scp->state = DN_CD;
  		scp->persist = 0;
  	}
  
  	kfree_skb(skb);
  }
  
  static void dn_nsp_disc_init(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	unsigned short reason;
  
  	if (skb->len < 2)
  		goto out;

  	reason = le16_to_cpu(*(__le16 *)skb->data);

  	skb_pull(skb, 2);

  	scp->discdata_in.opt_status = cpu_to_le16(reason);

  	scp->discdata_in.opt_optl   = 0;
  	memset(scp->discdata_in.opt_data, 0, 16);
  
  	if (skb->len > 0) {

  		u16 dlen = *skb->data;

  		if ((dlen <= 16) && (dlen <= skb->len)) {

  			scp->discdata_in.opt_optl = cpu_to_le16(dlen);

  			skb_copy_from_linear_data_offset(skb, 1, scp->discdata_in.opt_data, dlen);

  		}
  	}
  
  	scp->addrrem = cb->src_port;
  	sk->sk_state = TCP_CLOSE;

  	switch (scp->state) {
  	case DN_CI:
  	case DN_CD:
  		scp->state = DN_RJ;
  		sk->sk_err = ECONNREFUSED;
  		break;
  	case DN_RUN:
  		sk->sk_shutdown |= SHUTDOWN_MASK;
  		scp->state = DN_DN;
  		break;
  	case DN_DI:
  		scp->state = DN_DIC;
  		break;

  	}
  
  	if (!sock_flag(sk, SOCK_DEAD)) {
  		if (sk->sk_socket->state != SS_UNCONNECTED)
  			sk->sk_socket->state = SS_DISCONNECTING;
  		sk->sk_state_change(sk);
  	}

  	/*

  	 * It appears that its possible for remote machines to send disc
  	 * init messages with no port identifier if we are in the CI and
  	 * possibly also the CD state. Obviously we shouldn't reply with
  	 * a message if we don't know what the end point is.
  	 */
  	if (scp->addrrem) {
  		dn_nsp_send_disc(sk, NSP_DISCCONF, NSP_REASON_DC, GFP_ATOMIC);
  	}
  	scp->persist_fxn = dn_destroy_timer;
  	scp->persist = dn_nsp_persist(sk);
  
  out:
  	kfree_skb(skb);
  }
  
  /*
   * disc_conf messages are also called no_resources or no_link
   * messages depending upon the "reason" field.
   */
  static void dn_nsp_disc_conf(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  	unsigned short reason;
  
  	if (skb->len != 2)
  		goto out;

  	reason = le16_to_cpu(*(__le16 *)skb->data);

  
  	sk->sk_state = TCP_CLOSE;

  	switch (scp->state) {
  	case DN_CI:
  		scp->state = DN_NR;
  		break;
  	case DN_DR:
  		if (reason == NSP_REASON_DC)
  			scp->state = DN_DRC;
  		if (reason == NSP_REASON_NL)

  			scp->state = DN_CN;

  		break;
  	case DN_DI:
  		scp->state = DN_DIC;
  		break;
  	case DN_RUN:
  		sk->sk_shutdown |= SHUTDOWN_MASK;
  	case DN_CC:
  		scp->state = DN_CN;

  	}
  
  	if (!sock_flag(sk, SOCK_DEAD)) {
  		if (sk->sk_socket->state != SS_UNCONNECTED)
  			sk->sk_socket->state = SS_DISCONNECTING;
  		sk->sk_state_change(sk);
  	}
  
  	scp->persist_fxn = dn_destroy_timer;
  	scp->persist = dn_nsp_persist(sk);
  
  out:
  	kfree_skb(skb);
  }
  
  static void dn_nsp_linkservice(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  	unsigned short segnum;
  	unsigned char lsflags;
  	signed char fcval;
  	int wake_up = 0;
  	char *ptr = skb->data;
  	unsigned char fctype = scp->services_rem & NSP_FC_MASK;
  
  	if (skb->len != 4)
  		goto out;

  	segnum = le16_to_cpu(*(__le16 *)ptr);

  	ptr += 2;
  	lsflags = *(unsigned char *)ptr++;
  	fcval = *ptr;
  
  	/*
  	 * Here we ignore erronous packets which should really

  	 * should cause a connection abort. It is not critical

  	 * for now though.
  	 */
  	if (lsflags & 0xf8)
  		goto out;
  
  	if (seq_next(scp->numoth_rcv, segnum)) {
  		seq_add(&scp->numoth_rcv, 1);
  		switch(lsflags & 0x04) { /* FCVAL INT */
  		case 0x00: /* Normal Request */
  			switch(lsflags & 0x03) { /* FCVAL MOD */

  			case 0x00: /* Request count */

  				if (fcval < 0) {
  					unsigned char p_fcval = -fcval;
  					if ((scp->flowrem_dat > p_fcval) &&
  					    (fctype == NSP_FC_SCMC)) {
  						scp->flowrem_dat -= p_fcval;
  					}
  				} else if (fcval > 0) {
  					scp->flowrem_dat += fcval;
  					wake_up = 1;
  				}

  				break;

  			case 0x01: /* Stop outgoing data */
  				scp->flowrem_sw = DN_DONTSEND;
  				break;
  			case 0x02: /* Ok to start again */
  				scp->flowrem_sw = DN_SEND;
  				dn_nsp_output(sk);
  				wake_up = 1;
  			}
  			break;
  		case 0x04: /* Interrupt Request */
  			if (fcval > 0) {
  				scp->flowrem_oth += fcval;
  				wake_up = 1;
  			}
  			break;

  		}

  		if (wake_up && !sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);

  	}

  
  	dn_nsp_send_oth_ack(sk);
  
  out:
  	kfree_skb(skb);
  }
  
  /*
   * Copy of sock_queue_rcv_skb (from sock.h) without
   * bh_lock_sock() (its already held when this is called) which
   * also allows data and other data to be queued to a socket.
   */
  static __inline__ int dn_queue_skb(struct sock *sk, struct sk_buff *skb, int sig, struct sk_buff_head *queue)
  {
  	int err;

  	int skb_len;

  
  	/* Cast skb->rcvbuf to unsigned... It's pointless, but reduces
  	   number of warnings when compiling with -W --ANK
  	 */
  	if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=

  	    (unsigned)sk->sk_rcvbuf) {

  		err = -ENOMEM;
  		goto out;
  	}

  	err = sk_filter(sk, skb);

  	if (err)
  		goto out;

  	skb_len = skb->len;

  	skb_set_owner_r(skb, sk);
  	skb_queue_tail(queue, skb);

  	if (!sock_flag(sk, SOCK_DEAD))
  		sk->sk_data_ready(sk, skb_len);

  out:

  	return err;

  }
  
  static void dn_nsp_otherdata(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  	unsigned short segnum;
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	int queued = 0;
  
  	if (skb->len < 2)
  		goto out;

  	cb->segnum = segnum = le16_to_cpu(*(__le16 *)skb->data);

  	skb_pull(skb, 2);
  
  	if (seq_next(scp->numoth_rcv, segnum)) {
  
  		if (dn_queue_skb(sk, skb, SIGURG, &scp->other_receive_queue) == 0) {
  			seq_add(&scp->numoth_rcv, 1);
  			scp->other_report = 0;
  			queued = 1;
  		}
  	}
  
  	dn_nsp_send_oth_ack(sk);
  out:
  	if (!queued)
  		kfree_skb(skb);
  }
  
  static void dn_nsp_data(struct sock *sk, struct sk_buff *skb)
  {
  	int queued = 0;
  	unsigned short segnum;
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	struct dn_scp *scp = DN_SK(sk);
  
  	if (skb->len < 2)
  		goto out;

  	cb->segnum = segnum = le16_to_cpu(*(__le16 *)skb->data);

  	skb_pull(skb, 2);
  
  	if (seq_next(scp->numdat_rcv, segnum)) {

  		if (dn_queue_skb(sk, skb, SIGIO, &sk->sk_receive_queue) == 0) {

  			seq_add(&scp->numdat_rcv, 1);

  			queued = 1;
  		}

  
  		if ((scp->flowloc_sw == DN_SEND) && dn_congested(sk)) {
  			scp->flowloc_sw = DN_DONTSEND;
  			dn_nsp_send_link(sk, DN_DONTSEND, 0);
  		}

  	}

  
  	dn_nsp_send_data_ack(sk);
  out:
  	if (!queued)
  		kfree_skb(skb);
  }
  
  /*
   * If one of our conninit messages is returned, this function
   * deals with it. It puts the socket into the NO_COMMUNICATION
   * state.
   */
  static void dn_returned_conn_init(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  
  	if (scp->state == DN_CI) {
  		scp->state = DN_NC;
  		sk->sk_state = TCP_CLOSE;
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);
  	}
  
  	kfree_skb(skb);
  }
  
  static int dn_nsp_no_socket(struct sk_buff *skb, unsigned short reason)
  {
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	int ret = NET_RX_DROP;
  
  	/* Must not reply to returned packets */
  	if (cb->rt_flags & DN_RT_F_RTS)
  		goto out;
  
  	if ((reason != NSP_REASON_OK) && ((cb->nsp_flags & 0x0c) == 0x08)) {

  		switch (cb->nsp_flags & 0x70) {
  		case 0x10:
  		case 0x60: /* (Retransmitted) Connect Init */
  			dn_nsp_return_disc(skb, NSP_DISCINIT, reason);
  			ret = NET_RX_SUCCESS;
  			break;
  		case 0x20: /* Connect Confirm */
  			dn_nsp_return_disc(skb, NSP_DISCCONF, reason);
  			ret = NET_RX_SUCCESS;
  			break;

  		}
  	}
  
  out:
  	kfree_skb(skb);
  	return ret;
  }
  
  static int dn_nsp_rx_packet(struct sk_buff *skb)
  {
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  	struct sock *sk = NULL;
  	unsigned char *ptr = (unsigned char *)skb->data;
  	unsigned short reason = NSP_REASON_NL;
  
  	if (!pskb_may_pull(skb, 2))
  		goto free_out;

  	skb_reset_transport_header(skb);

  	cb->nsp_flags = *ptr++;
  
  	if (decnet_debug_level & 2)
  		printk(KERN_DEBUG "dn_nsp_rx: Message type 0x%02x
  ", (int)cb->nsp_flags);

  	if (cb->nsp_flags & 0x83)

  		goto free_out;
  
  	/*
  	 * Filter out conninits and useless packet types
  	 */
  	if ((cb->nsp_flags & 0x0c) == 0x08) {

  		switch (cb->nsp_flags & 0x70) {
  		case 0x00: /* NOP */
  		case 0x70: /* Reserved */
  		case 0x50: /* Reserved, Phase II node init */
  			goto free_out;
  		case 0x10:
  		case 0x60:
  			if (unlikely(cb->rt_flags & DN_RT_F_RTS))

  				goto free_out;

  			sk = dn_find_listener(skb, &reason);
  			goto got_it;

  		}
  	}
  
  	if (!pskb_may_pull(skb, 3))
  		goto free_out;
  
  	/*
  	 * Grab the destination address.
  	 */

  	cb->dst_port = *(__le16 *)ptr;

  	cb->src_port = 0;
  	ptr += 2;
  
  	/*
  	 * If not a connack, grab the source address too.
  	 */
  	if (pskb_may_pull(skb, 5)) {

  		cb->src_port = *(__le16 *)ptr;

  		ptr += 2;
  		skb_pull(skb, 5);
  	}
  
  	/*
  	 * Returned packets...
  	 * Swap src & dst and look up in the normal way.
  	 */
  	if (unlikely(cb->rt_flags & DN_RT_F_RTS)) {

  		__le16 tmp = cb->dst_port;

  		cb->dst_port = cb->src_port;
  		cb->src_port = tmp;
  		tmp = cb->dst;
  		cb->dst = cb->src;
  		cb->src = tmp;
  	}
  
  	/*
  	 * Find the socket to which this skb is destined.
  	 */
  	sk = dn_find_by_skb(skb);
  got_it:
  	if (sk != NULL) {
  		struct dn_scp *scp = DN_SK(sk);

  
  		/* Reset backoff */
  		scp->nsp_rxtshift = 0;
  
  		/*
  		 * We linearize everything except data segments here.
  		 */
  		if (cb->nsp_flags & ~0x60) {

  			if (unlikely(skb_linearize(skb)))

  				goto free_out;
  		}

  		return sk_receive_skb(sk, skb, 0);

  	}
  
  	return dn_nsp_no_socket(skb, reason);
  
  free_out:
  	kfree_skb(skb);
  	return NET_RX_DROP;
  }
  
  int dn_nsp_rx(struct sk_buff *skb)
  {

  	return NF_HOOK(NFPROTO_DECNET, NF_DN_LOCAL_IN, skb, skb->dev, NULL,
  		       dn_nsp_rx_packet);

  }
  
  /*
   * This is the main receive routine for sockets. It is called
   * from the above when the socket is not busy, and also from
   * sock_release() when there is a backlog queued up.
   */
  int dn_nsp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_scp *scp = DN_SK(sk);
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  
  	if (cb->rt_flags & DN_RT_F_RTS) {
  		if (cb->nsp_flags == 0x18 || cb->nsp_flags == 0x68)
  			dn_returned_conn_init(sk, skb);
  		else
  			kfree_skb(skb);
  		return NET_RX_SUCCESS;
  	}
  
  	/*
  	 * Control packet.
  	 */
  	if ((cb->nsp_flags & 0x0c) == 0x08) {

  		switch (cb->nsp_flags & 0x70) {
  		case 0x10:
  		case 0x60:
  			dn_nsp_conn_init(sk, skb);
  			break;
  		case 0x20:
  			dn_nsp_conn_conf(sk, skb);
  			break;
  		case 0x30:
  			dn_nsp_disc_init(sk, skb);
  			break;
  		case 0x40:
  			dn_nsp_disc_conf(sk, skb);
  			break;

  		}
  
  	} else if (cb->nsp_flags == 0x24) {
  		/*
  		 * Special for connacks, 'cos they don't have
  		 * ack data or ack otherdata info.
  		 */
  		dn_nsp_conn_ack(sk, skb);
  	} else {
  		int other = 1;
  
  		/* both data and ack frames can kick a CC socket into RUN */
  		if ((scp->state == DN_CC) && !sock_flag(sk, SOCK_DEAD)) {
  			scp->state = DN_RUN;
  			sk->sk_state = TCP_ESTABLISHED;
  			sk->sk_state_change(sk);
  		}
  
  		if ((cb->nsp_flags & 0x1c) == 0)
  			other = 0;
  		if (cb->nsp_flags == 0x04)
  			other = 0;
  
  		/*
  		 * Read out ack data here, this applies equally
  		 * to data, other data, link serivce and both
  		 * ack data and ack otherdata.
  		 */
  		dn_process_ack(sk, skb, other);
  
  		/*
  		 * If we've some sort of data here then call a
  		 * suitable routine for dealing with it, otherwise
  		 * the packet is an ack and can be discarded.
  		 */
  		if ((cb->nsp_flags & 0x0c) == 0) {
  
  			if (scp->state != DN_RUN)
  				goto free_out;

  			switch (cb->nsp_flags) {
  			case 0x10: /* LS */
  				dn_nsp_linkservice(sk, skb);
  				break;
  			case 0x30: /* OD */
  				dn_nsp_otherdata(sk, skb);
  				break;
  			default:
  				dn_nsp_data(sk, skb);

  			}
  
  		} else { /* Ack, chuck it out here */
  free_out:
  			kfree_skb(skb);
  		}
  	}
  
  	return NET_RX_SUCCESS;
  }