net/ax25/ax25_in.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *
  * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
  * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
  */
 #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 <linux/uaccess.h>
 #include <linux/fcntl.h>
 #include <linux/mm.h>
 #include <linux/interrupt.h>

 /*
  *	Given a fragment, queue it on the fragment queue and if the fragment
  *	is complete, send it back to ax25_rx_iframe.
  */
 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
 {
 	struct sk_buff *skbn, *skbo;

 	if (ax25->fragno != 0) {
 		if (!(*skb->data & AX25_SEG_FIRST)) {
 			if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
 				/* Enqueue fragment */
 				ax25->fragno = *skb->data & AX25_SEG_REM;
 				skb_pull(skb, 1);	/* skip fragno */
 				ax25->fraglen += skb->len;
 				skb_queue_tail(&ax25->frag_queue, skb);

 				/* Last fragment received ? */
 				if (ax25->fragno == 0) {
 					skbn = alloc_skb(AX25_MAX_HEADER_LEN +
 							 ax25->fraglen,
 							 GFP_ATOMIC);
 					if (!skbn) {
 						skb_queue_purge(&ax25->frag_queue);
 						return 1;
 					}

 					skb_reserve(skbn, AX25_MAX_HEADER_LEN);

 					skbn->dev   = ax25->ax25_dev->dev;
 					skb_reset_network_header(skbn);
 					skb_reset_transport_header(skbn);

 					/* Copy data from the fragments */
 					while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
 						skb_copy_from_linear_data(skbo,
 							  skb_put(skbn, skbo->len),
 									  skbo->len);
 						kfree_skb(skbo);
 					}

 					ax25->fraglen = 0;

 					if (ax25_rx_iframe(ax25, skbn) == 0)
 						kfree_skb(skbn);
 				}

 				return 1;
 			}
 		}
 	} else {
 		/* First fragment received */
 		if (*skb->data & AX25_SEG_FIRST) {
 			skb_queue_purge(&ax25->frag_queue);
 			ax25->fragno = *skb->data & AX25_SEG_REM;
 			skb_pull(skb, 1);		/* skip fragno */
 			ax25->fraglen = skb->len;
 			skb_queue_tail(&ax25->frag_queue, skb);
 			return 1;
 		}
 	}

 	return 0;
 }

 /*
  *	This is where all valid I frames are sent to, to be dispatched to
  *	whichever protocol requires them.
  */
 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
 {
 	int (*func)(struct sk_buff *, ax25_cb *);
 	unsigned char pid;
 	int queued = 0;

 	if (skb == NULL) return 0;

 	ax25_start_idletimer(ax25);

 	pid = *skb->data;

 	if (pid == AX25_P_IP) {
 		/* working around a TCP bug to keep additional listeners
 		 * happy. TCP re-uses the buffer and destroys the original
 		 * content.
 		 */
 		struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
 		if (skbn != NULL) {
 			kfree_skb(skb);
 			skb = skbn;
 		}

 		skb_pull(skb, 1);	/* Remove PID */
 		skb->mac_header = skb->network_header;
 		skb_reset_network_header(skb);
 		skb->dev      = ax25->ax25_dev->dev;
 		skb->pkt_type = PACKET_HOST;
 		skb->protocol = htons(ETH_P_IP);
 		netif_rx(skb);
 		return 1;
 	}
 	if (pid == AX25_P_SEGMENT) {
 		skb_pull(skb, 1);	/* Remove PID */
 		return ax25_rx_fragment(ax25, skb);
 	}

 	if ((func = ax25_protocol_function(pid)) != NULL) {
 		skb_pull(skb, 1);	/* Remove PID */
 		return (*func)(skb, ax25);
 	}

 	if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
 		if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
 		    ax25->pidincl) {
 			if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
 				queued = 1;
 			else
 				ax25->condition |= AX25_COND_OWN_RX_BUSY;
 		}
 	}

 	return queued;
 }

 /*
  *	Higher level upcall for a LAPB frame
  */
 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
 {
 	int queued = 0;

 	if (ax25->state == AX25_STATE_0)
 		return 0;

 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 	case AX25_PROTO_STD_SIMPLEX:
 	case AX25_PROTO_STD_DUPLEX:
 		queued = ax25_std_frame_in(ax25, skb, type);
 		break;

 #ifdef CONFIG_AX25_DAMA_SLAVE
 	case AX25_PROTO_DAMA_SLAVE:
 		if (dama || ax25->ax25_dev->dama.slave)
 			queued = ax25_ds_frame_in(ax25, skb, type);
 		else
 			queued = ax25_std_frame_in(ax25, skb, type);
 		break;
 #endif
 	}

 	return queued;
 }

 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
 	ax25_address *dev_addr, struct packet_type *ptype)
 {
 	ax25_address src, dest, *next_digi = NULL;
 	int type = 0, mine = 0, dama;
 	struct sock *make, *sk;
 	ax25_digi dp, reverse_dp;
 	ax25_cb *ax25;
 	ax25_dev *ax25_dev;

 	/*
 	 *	Process the AX.25/LAPB frame.
 	 */

 	skb_reset_transport_header(skb);

 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
 		goto free;

 	/*
 	 *	Parse the address header.
 	 */

 	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
 		goto free;

 	/*
 	 *	Ours perhaps ?
 	 */
 	if (dp.lastrepeat + 1 < dp.ndigi)		/* Not yet digipeated completely */
 		next_digi = &dp.calls[dp.lastrepeat + 1];

 	/*
 	 *	Pull of the AX.25 headers leaving the CTRL/PID bytes
 	 */
 	skb_pull(skb, ax25_addr_size(&dp));

 	/* For our port addresses ? */
 	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 		mine = 1;

 	/* Also match on any registered callsign from L3/4 */
 	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 		mine = 1;

 	/* UI frame - bypass LAPB processing */
 	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 		skb_set_transport_header(skb, 2); /* skip control and pid */

 		ax25_send_to_raw(&dest, skb, skb->data[1]);

 		if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
 			goto free;

 		/* Now we are pointing at the pid byte */
 		switch (skb->data[1]) {
 		case AX25_P_IP:
 			skb_pull(skb,2);		/* drop PID/CTRL */
 			skb_reset_transport_header(skb);
 			skb_reset_network_header(skb);
 			skb->dev      = dev;
 			skb->pkt_type = PACKET_HOST;
 			skb->protocol = htons(ETH_P_IP);
 			netif_rx(skb);
 			break;

 		case AX25_P_ARP:
 			skb_pull(skb,2);
 			skb_reset_transport_header(skb);
 			skb_reset_network_header(skb);
 			skb->dev      = dev;
 			skb->pkt_type = PACKET_HOST;
 			skb->protocol = htons(ETH_P_ARP);
 			netif_rx(skb);
 			break;
 		case AX25_P_TEXT:
 			/* Now find a suitable dgram socket */
 			sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 			if (sk != NULL) {
 				bh_lock_sock(sk);
 				if (atomic_read(&sk->sk_rmem_alloc) >=
 				    sk->sk_rcvbuf) {
 					kfree_skb(skb);
 				} else {
 					/*
 					 *	Remove the control and PID.
 					 */
 					skb_pull(skb, 2);
 					if (sock_queue_rcv_skb(sk, skb) != 0)
 						kfree_skb(skb);
 				}
 				bh_unlock_sock(sk);
 				sock_put(sk);
 			} else {
 				kfree_skb(skb);
 			}
 			break;

 		default:
 			kfree_skb(skb);	/* Will scan SOCK_AX25 RAW sockets */
 			break;
 		}

 		return 0;
 	}

 	/*
 	 *	Is connected mode supported on this device ?
 	 *	If not, should we DM the incoming frame (except DMs) or
 	 *	silently ignore them. For now we stay quiet.
 	 */
 	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
 		goto free;

 	/* LAPB */

 	/* AX.25 state 1-4 */

 	ax25_digi_invert(&dp, &reverse_dp);

 	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 		/*
 		 *	Process the frame. If it is queued up internally it
 		 *	returns one otherwise we free it immediately. This
 		 *	routine itself wakes the user context layers so we do
 		 *	no further work
 		 */
 		if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 			kfree_skb(skb);

 		ax25_cb_put(ax25);
 		return 0;
 	}

 	/* AX.25 state 0 (disconnected) */

 	/* a) received not a SABM(E) */

 	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 	    (*skb->data & ~AX25_PF) != AX25_SABME) {
 		/*
 		 *	Never reply to a DM. Also ignore any connects for
 		 *	addresses that are not our interfaces and not a socket.
 		 */
 		if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 			ax25_return_dm(dev, &src, &dest, &dp);

 		goto free;
 	}

 	/* b) received SABM(E) */

 	if (dp.lastrepeat + 1 == dp.ndigi)
 		sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 	else
 		sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);

 	if (sk != NULL) {
 		bh_lock_sock(sk);
 		if (sk_acceptq_is_full(sk) ||
 		    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 			if (mine)
 				ax25_return_dm(dev, &src, &dest, &dp);
 			kfree_skb(skb);
 			bh_unlock_sock(sk);
 			sock_put(sk);

 			return 0;
 		}

 		ax25 = sk_to_ax25(make);
 		skb_set_owner_r(skb, make);
 		skb_queue_head(&sk->sk_receive_queue, skb);

 		make->sk_state = TCP_ESTABLISHED;

 		sk->sk_ack_backlog++;
 		bh_unlock_sock(sk);
 	} else {
 		if (!mine)
 			goto free;

 		if ((ax25 = ax25_create_cb()) == NULL) {
 			ax25_return_dm(dev, &src, &dest, &dp);
 			goto free;
 		}

 		ax25_fillin_cb(ax25, ax25_dev);
 	}

 	ax25->source_addr = dest;
 	ax25->dest_addr   = src;

 	/*
 	 *	Sort out any digipeated paths.
 	 */
 	if (dp.ndigi && !ax25->digipeat &&
 	    (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 		kfree_skb(skb);
 		ax25_destroy_socket(ax25);
 		if (sk)
 			sock_put(sk);
 		return 0;
 	}

 	if (dp.ndigi == 0) {
 		kfree(ax25->digipeat);
 		ax25->digipeat = NULL;
 	} else {
 		/* Reverse the source SABM's path */
 		memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 	}

 	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 		ax25->modulus = AX25_EMODULUS;
 		ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 	} else {
 		ax25->modulus = AX25_MODULUS;
 		ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 	}

 	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);

 #ifdef CONFIG_AX25_DAMA_SLAVE
 	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 		ax25_dama_on(ax25);
 #endif

 	ax25->state = AX25_STATE_3;

 	ax25_cb_add(ax25);

 	ax25_start_heartbeat(ax25);
 	ax25_start_t3timer(ax25);
 	ax25_start_idletimer(ax25);

 	if (sk) {
 		if (!sock_flag(sk, SOCK_DEAD))
 			sk->sk_data_ready(sk);
 		sock_put(sk);
 	} else {
 free:
 		kfree_skb(skb);
 	}
 	return 0;
 }

 /*
  *	Receive an AX.25 frame via a SLIP interface.
  */
 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 		  struct packet_type *ptype, struct net_device *orig_dev)
 {
 	skb_orphan(skb);

 	if (!net_eq(dev_net(dev), &init_net)) {
 		kfree_skb(skb);
 		return 0;
 	}

 	if ((*skb->data & 0x0F) != 0) {
 		kfree_skb(skb);	/* Not a KISS data frame */
 		return 0;
 	}

 	skb_pull(skb, AX25_KISS_HEADER_LEN);	/* Remove the KISS byte */

 	return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	*
	* Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
	* Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
	* Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
	* Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
	*/
	#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 <linux/uaccess.h>
	#include <linux/fcntl.h>
	#include <linux/mm.h>
	#include <linux/interrupt.h>

	/*
	* Given a fragment, queue it on the fragment queue and if the fragment
	* is complete, send it back to ax25_rx_iframe.
	*/
	static int ax25_rx_fragment(ax25_cb ax25, struct sk_buff skb)
	{
	struct sk_buff skbn, skbo;

	if (ax25->fragno != 0) {
	if (!(*skb->data & AX25_SEG_FIRST)) {
	if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
	/* Enqueue fragment */
	ax25->fragno = *skb->data & AX25_SEG_REM;
	skb_pull(skb, 1); /* skip fragno */
	ax25->fraglen += skb->len;
	skb_queue_tail(&ax25->frag_queue, skb);

	/* Last fragment received ? */
	if (ax25->fragno == 0) {
	skbn = alloc_skb(AX25_MAX_HEADER_LEN +
	ax25->fraglen,
	GFP_ATOMIC);
	if (!skbn) {
	skb_queue_purge(&ax25->frag_queue);
	return 1;
	}

	skb_reserve(skbn, AX25_MAX_HEADER_LEN);

	skbn->dev = ax25->ax25_dev->dev;
	skb_reset_network_header(skbn);
	skb_reset_transport_header(skbn);

	/* Copy data from the fragments */
	while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
	skb_copy_from_linear_data(skbo,
	skb_put(skbn, skbo->len),
	skbo->len);
	kfree_skb(skbo);
	}

	ax25->fraglen = 0;

	if (ax25_rx_iframe(ax25, skbn) == 0)
	kfree_skb(skbn);
	}

	return 1;
	}
	}
	} else {
	/* First fragment received */
	if (*skb->data & AX25_SEG_FIRST) {
	skb_queue_purge(&ax25->frag_queue);
	ax25->fragno = *skb->data & AX25_SEG_REM;
	skb_pull(skb, 1); /* skip fragno */
	ax25->fraglen = skb->len;
	skb_queue_tail(&ax25->frag_queue, skb);
	return 1;
	}
	}

	return 0;
	}

	/*
	* This is where all valid I frames are sent to, to be dispatched to
	* whichever protocol requires them.
	*/
	int ax25_rx_iframe(ax25_cb ax25, struct sk_buff skb)
	{
	int (func)(struct sk_buff , ax25_cb *);
	unsigned char pid;
	int queued = 0;

	if (skb == NULL) return 0;

	ax25_start_idletimer(ax25);

	pid = *skb->data;

	if (pid == AX25_P_IP) {
	/* working around a TCP bug to keep additional listeners
	* happy. TCP re-uses the buffer and destroys the original
	* content.
	*/
	struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
	if (skbn != NULL) {
	kfree_skb(skb);
	skb = skbn;
	}

	skb_pull(skb, 1); /* Remove PID */
	skb->mac_header = skb->network_header;
	skb_reset_network_header(skb);
	skb->dev = ax25->ax25_dev->dev;
	skb->pkt_type = PACKET_HOST;
	skb->protocol = htons(ETH_P_IP);
	netif_rx(skb);
	return 1;
	}
	if (pid == AX25_P_SEGMENT) {
	skb_pull(skb, 1); /* Remove PID */
	return ax25_rx_fragment(ax25, skb);
	}

	if ((func = ax25_protocol_function(pid)) != NULL) {
	skb_pull(skb, 1); /* Remove PID */
	return (*func)(skb, ax25);
	}

	if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
	if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) \|\|
	ax25->pidincl) {
	if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
	queued = 1;
	else
	ax25->condition \|= AX25_COND_OWN_RX_BUSY;
	}
	}

	return queued;
	}

	/*
	* Higher level upcall for a LAPB frame
	*/
	static int ax25_process_rx_frame(ax25_cb ax25, struct sk_buff skb, int type, int dama)
	{
	int queued = 0;

	if (ax25->state == AX25_STATE_0)
	return 0;

	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
	case AX25_PROTO_STD_SIMPLEX:
	case AX25_PROTO_STD_DUPLEX:
	queued = ax25_std_frame_in(ax25, skb, type);
	break;

	#ifdef CONFIG_AX25_DAMA_SLAVE
	case AX25_PROTO_DAMA_SLAVE:
	if (dama \|\| ax25->ax25_dev->dama.slave)
	queued = ax25_ds_frame_in(ax25, skb, type);
	else
	queued = ax25_std_frame_in(ax25, skb, type);
	break;
	#endif
	}

	return queued;
	}

	static int ax25_rcv(struct sk_buff skb, struct net_device dev,
	ax25_address dev_addr, struct packet_type ptype)
	{
	ax25_address src, dest, *next_digi = NULL;
	int type = 0, mine = 0, dama;
	struct sock make, sk;
	ax25_digi dp, reverse_dp;
	ax25_cb *ax25;
	ax25_dev *ax25_dev;

	/*
	* Process the AX.25/LAPB frame.
	*/

	skb_reset_transport_header(skb);

	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
	goto free;

	/*
	* Parse the address header.
	*/

	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
	goto free;

	/*
	* Ours perhaps ?
	*/
	if (dp.lastrepeat + 1 < dp.ndigi) /* Not yet digipeated completely */
	next_digi = &dp.calls[dp.lastrepeat + 1];

	/*
	* Pull of the AX.25 headers leaving the CTRL/PID bytes
	*/
	skb_pull(skb, ax25_addr_size(&dp));

	/* For our port addresses ? */
	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
	mine = 1;

	/* Also match on any registered callsign from L3/4 */
	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
	mine = 1;

	/* UI frame - bypass LAPB processing */
	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
	skb_set_transport_header(skb, 2); /* skip control and pid */

	ax25_send_to_raw(&dest, skb, skb->data[1]);

	if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
	goto free;

	/* Now we are pointing at the pid byte */
	switch (skb->data[1]) {
	case AX25_P_IP:
	skb_pull(skb,2); /* drop PID/CTRL */
	skb_reset_transport_header(skb);
	skb_reset_network_header(skb);
	skb->dev = dev;
	skb->pkt_type = PACKET_HOST;
	skb->protocol = htons(ETH_P_IP);
	netif_rx(skb);
	break;

	case AX25_P_ARP:
	skb_pull(skb,2);
	skb_reset_transport_header(skb);
	skb_reset_network_header(skb);
	skb->dev = dev;
	skb->pkt_type = PACKET_HOST;
	skb->protocol = htons(ETH_P_ARP);
	netif_rx(skb);
	break;
	case AX25_P_TEXT:
	/* Now find a suitable dgram socket */
	sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
	if (sk != NULL) {
	bh_lock_sock(sk);
	if (atomic_read(&sk->sk_rmem_alloc) >=
	sk->sk_rcvbuf) {
	kfree_skb(skb);
	} else {
	/*
	* Remove the control and PID.
	*/
	skb_pull(skb, 2);
	if (sock_queue_rcv_skb(sk, skb) != 0)
	kfree_skb(skb);
	}
	bh_unlock_sock(sk);
	sock_put(sk);
	} else {
	kfree_skb(skb);
	}
	break;

	default:
	kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
	break;
	}

	return 0;
	}

	/*
	* Is connected mode supported on this device ?
	* If not, should we DM the incoming frame (except DMs) or
	* silently ignore them. For now we stay quiet.
	*/
	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
	goto free;

	/* LAPB */

	/* AX.25 state 1-4 */

	ax25_digi_invert(&dp, &reverse_dp);

	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
	/*
	* Process the frame. If it is queued up internally it
	* returns one otherwise we free it immediately. This
	* routine itself wakes the user context layers so we do
	* no further work
	*/
	if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
	kfree_skb(skb);

	ax25_cb_put(ax25);
	return 0;
	}

	/* AX.25 state 0 (disconnected) */

	/* a) received not a SABM(E) */

	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
	(*skb->data & ~AX25_PF) != AX25_SABME) {
	/*
	* Never reply to a DM. Also ignore any connects for
	* addresses that are not our interfaces and not a socket.
	*/
	if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
	ax25_return_dm(dev, &src, &dest, &dp);

	goto free;
	}

	/* b) received SABM(E) */

	if (dp.lastrepeat + 1 == dp.ndigi)
	sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
	else
	sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);

	if (sk != NULL) {
	bh_lock_sock(sk);
	if (sk_acceptq_is_full(sk) \|\|
	(make = ax25_make_new(sk, ax25_dev)) == NULL) {
	if (mine)
	ax25_return_dm(dev, &src, &dest, &dp);
	kfree_skb(skb);
	bh_unlock_sock(sk);
	sock_put(sk);

	return 0;
	}

	ax25 = sk_to_ax25(make);
	skb_set_owner_r(skb, make);
	skb_queue_head(&sk->sk_receive_queue, skb);

	make->sk_state = TCP_ESTABLISHED;

	sk->sk_ack_backlog++;
	bh_unlock_sock(sk);
	} else {
	if (!mine)
	goto free;

	if ((ax25 = ax25_create_cb()) == NULL) {
	ax25_return_dm(dev, &src, &dest, &dp);
	goto free;
	}

	ax25_fillin_cb(ax25, ax25_dev);
	}

	ax25->source_addr = dest;
	ax25->dest_addr = src;

	/*
	* Sort out any digipeated paths.
	*/
	if (dp.ndigi && !ax25->digipeat &&
	(ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
	kfree_skb(skb);
	ax25_destroy_socket(ax25);
	if (sk)
	sock_put(sk);
	return 0;
	}

	if (dp.ndigi == 0) {
	kfree(ax25->digipeat);
	ax25->digipeat = NULL;
	} else {
	/* Reverse the source SABM's path */
	memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
	}

	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
	ax25->modulus = AX25_EMODULUS;
	ax25->window = ax25_dev->values[AX25_VALUES_EWINDOW];
	} else {
	ax25->modulus = AX25_MODULUS;
	ax25->window = ax25_dev->values[AX25_VALUES_WINDOW];
	}

	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);

	#ifdef CONFIG_AX25_DAMA_SLAVE
	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
	ax25_dama_on(ax25);
	#endif

	ax25->state = AX25_STATE_3;

	ax25_cb_add(ax25);

	ax25_start_heartbeat(ax25);
	ax25_start_t3timer(ax25);
	ax25_start_idletimer(ax25);

	if (sk) {
	if (!sock_flag(sk, SOCK_DEAD))
	sk->sk_data_ready(sk);
	sock_put(sk);
	} else {
	free:
	kfree_skb(skb);
	}
	return 0;
	}

	/*
	* Receive an AX.25 frame via a SLIP interface.
	*/
	int ax25_kiss_rcv(struct sk_buff skb, struct net_device dev,
	struct packet_type ptype, struct net_device orig_dev)
	{
	skb_orphan(skb);

	if (!net_eq(dev_net(dev), &init_net)) {
	kfree_skb(skb);
	return 0;
	}

	if ((*skb->data & 0x0F) != 0) {
	kfree_skb(skb); /* Not a KISS data frame */
	return 0;
	}

	skb_pull(skb, AX25_KISS_HEADER_LEN); /* Remove the KISS byte */

	return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
	}