1 files changed, 934 insertions, 0 deletions

diff --git a/net/decnet/dn_nsp_in.c b/net/decnet/dn_nsp_in.c
new file mode 100644
index 00000000000..202dbde9850
--- /dev/null
+++ b/net/decnet/dn_nsp_in.c
@@ -0,0 +1,934 @@
+/*
+ * 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/config.h>
+#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 <linux/netdevice.h>
+#include <linux/inet.h>
+#include <linux/route.h>
+#include <net/sock.h>
+#include <net/tcp.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\n", msg, devname, cb->src, cb->dst, cb->src_port, 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)
+{
+	unsigned short *ptr = (unsigned short *)skb->data;
+	int len = 0;
+	unsigned short ack;
+
+	if (skb->len < 2)
+		return len;
+
+	if ((ack = dn_ntohs(*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 = dn_ntohs(*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  = dn_ntohs(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 = dn_ntohs(*(__u16 *)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) {
+			unsigned char dlen = *skb->data;
+			if ((dlen <= 16) && (dlen <= skb->len)) {
+				scp->conndata_in.opt_optl = dlen;
+				memcpy(scp->conndata_in.opt_data, skb->data + 1, 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 = dn_ntohs(*(__u16 *)skb->data);
+	skb_pull(skb, 2);
+
+	scp->discdata_in.opt_status = reason;
+	scp->discdata_in.opt_optl   = 0;
+	memset(scp->discdata_in.opt_data, 0, 16);
+
+	if (skb->len > 0) {
+		unsigned char dlen = *skb->data;
+		if ((dlen <= 16) && (dlen <= skb->len)) {
+			scp->discdata_in.opt_optl = dlen;
+			memcpy(scp->discdata_in.opt_data, skb->data + 1, 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 = dn_ntohs(*(__u16 *)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 = dn_ntohs(*(__u16 *)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;
+	
+        /* 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, 0);
+	if (err)
+		goto out;
+
+        skb_set_owner_r(skb, sk);
+        skb_queue_tail(queue, skb);
+
+	/* This code only runs from BH or BH protected context.
+	 * Therefore the plain read_lock is ok here. -DaveM
+	 */
+	read_lock(&sk->sk_callback_lock);
+        if (!sock_flag(sk, SOCK_DEAD)) {
+		struct socket *sock = sk->sk_socket;
+		wake_up_interruptible(sk->sk_sleep);
+		if (sock && sock->fasync_list &&
+		    !test_bit(SOCK_ASYNC_WAITDATA, &sock->flags))
+			__kill_fasync(sock->fasync_list, sig, 
+				    (sig == SIGURG) ? POLL_PRI : POLL_IN);
+	}
+	read_unlock(&sk->sk_callback_lock);
+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 = dn_ntohs(*(__u16 *)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 = dn_ntohs(*(__u16 *)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->h.raw    = skb->data;
+	cb->nsp_flags = *ptr++;
+
+	if (decnet_debug_level & 2)
+		printk(KERN_DEBUG "dn_nsp_rx: Message type 0x%02x\n", (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 = *(unsigned short *)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 = *(unsigned short *)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)) {
+		unsigned short 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);
+		int ret;
+
+		/* Reset backoff */
+		scp->nsp_rxtshift = 0;
+
+		/*
+		 * We linearize everything except data segments here.
+		 */
+		if (cb->nsp_flags & ~0x60) {
+			if (unlikely(skb_is_nonlinear(skb)) &&
+			    skb_linearize(skb, GFP_ATOMIC) != 0)
+				goto free_out;
+		}
+
+		bh_lock_sock(sk);
+		ret = NET_RX_SUCCESS;
+		if (decnet_debug_level & 8)
+			printk(KERN_DEBUG "NSP: 0x%02x 0x%02x 0x%04x 0x%04x %d\n",
+				(int)cb->rt_flags, (int)cb->nsp_flags, 
+				(int)cb->src_port, (int)cb->dst_port, 
+				!!sock_owned_by_user(sk));
+		if (!sock_owned_by_user(sk))
+			ret = dn_nsp_backlog_rcv(sk, skb);
+		else
+			sk_add_backlog(sk, skb);
+		bh_unlock_sock(sk);
+		sock_put(sk);
+
+		return ret;
+	}
+
+	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(PF_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;
+}
+