text: /*
   * 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 (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 <net/ax25.h>
  #include <linux/inet.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <linux/netfilter.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>
  
  /*
   *	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) {
  		kfree_skb(skb);
  		return 0;
  	}
  
  	/*
  	 *	Parse the address header.
  	 */
  
  	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL) {
  		kfree_skb(skb);
  		return 0;
  	}
  
  	/*
  	 *	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) {
  			kfree_skb(skb);
  			return 0;
  		}
  
  		/* 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) {
  		kfree_skb(skb);
  		return 0;
  	}
  
  	/* 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);
  
  		kfree_skb(skb);
  		return 0;
  	}
  
  	/* 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 = ax25_sk(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) {
  			kfree_skb(skb);
  			return 0;
  		}
  
  		if ((ax25 = ax25_create_cb()) == NULL) {
  			ax25_return_dm(dev, &src, &dest, &dp);
  			kfree_skb(skb);
  			return 0;
  		}
  
  		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, skb->len);
  		sock_put(sk);
  	} else
  		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->sk = NULL;		/* Initially we don't know who it's for */
  	skb->destructor = NULL;	/* Who initializes this, dammit?! */
  
  	if (dev->nd_net != &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);
  }
  