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) 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/module.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/if_arp.h>
  #include <linux/skbuff.h>
  #include <net/sock.h>
  #include <asm/uaccess.h>
  #include <linux/fcntl.h>
  #include <linux/termios.h>	/* For TIOCINQ/OUTQ */
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <linux/notifier.h>
  #include <linux/proc_fs.h>
  #include <linux/stat.h>
  #include <linux/sysctl.h>
  #include <net/ip.h>
  #include <net/arp.h>
  
  /*
   *	IP over AX.25 encapsulation.
   */
  
  /*
   *	Shove an AX.25 UI header on an IP packet and handle ARP
   */
  
  #ifdef CONFIG_INET
  
  static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
  			    unsigned short type, const void *daddr,
  			    const void *saddr, unsigned int len)
  {
  	unsigned char *buff;
  
  	/* they sometimes come back to us... */
  	if (type == ETH_P_AX25)
  		return 0;
  
  	/* header is an AX.25 UI frame from us to them */
  	buff = skb_push(skb, AX25_HEADER_LEN);
  	*buff++ = 0x00;	/* KISS DATA */
  
  	if (daddr != NULL)
  		memcpy(buff, daddr, dev->addr_len);	/* Address specified */
  
  	buff[6] &= ~AX25_CBIT;
  	buff[6] &= ~AX25_EBIT;
  	buff[6] |= AX25_SSSID_SPARE;
  	buff    += AX25_ADDR_LEN;
  
  	if (saddr != NULL)
  		memcpy(buff, saddr, dev->addr_len);
  	else
  		memcpy(buff, dev->dev_addr, dev->addr_len);
  
  	buff[6] &= ~AX25_CBIT;
  	buff[6] |= AX25_EBIT;
  	buff[6] |= AX25_SSSID_SPARE;
  	buff    += AX25_ADDR_LEN;
  
  	*buff++  = AX25_UI;	/* UI */
  
  	/* Append a suitable AX.25 PID */
  	switch (type) {
  	case ETH_P_IP:
  		*buff++ = AX25_P_IP;
  		break;
  	case ETH_P_ARP:
  		*buff++ = AX25_P_ARP;
  		break;
  	default:
  		printk(KERN_ERR "AX.25: ax25_hard_header - wrong protocol type 0x%2.2x\n", type);
  		*buff++ = 0;
  		break;
  	}
  
  	if (daddr != NULL)
  		return AX25_HEADER_LEN;
  
  	return -AX25_HEADER_LEN;	/* Unfinished header */
  }
  
  netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
  {
  	struct sk_buff *ourskb;
  	unsigned char *bp  = skb->data;
  	ax25_route *route;
  	struct net_device *dev = NULL;
  	ax25_address *src, *dst;
  	ax25_digi *digipeat = NULL;
  	ax25_dev *ax25_dev;
  	ax25_cb *ax25;
  	char ip_mode = ' ';
  
  	dst = (ax25_address *)(bp + 1);
  	src = (ax25_address *)(bp + 8);
  
  	ax25_route_lock_use();
  	route = ax25_get_route(dst, NULL);
  	if (route) {
  		digipeat = route->digipeat;
  		dev = route->dev;
  		ip_mode = route->ip_mode;
  	}
  
  	if (dev == NULL)
  		dev = skb->dev;
  
  	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
  		kfree_skb(skb);
  		goto put;
  	}
  
  	if (bp[16] == AX25_P_IP) {
  		if (ip_mode == 'V' || (ip_mode == ' ' && ax25_dev->values[AX25_VALUES_IPDEFMODE])) {
  			/*
  			 *	We copy the buffer and release the original thereby
  			 *	keeping it straight
  			 *
  			 *	Note: we report 1 back so the caller will
  			 *	not feed the frame direct to the physical device
  			 *	We don't want that to happen. (It won't be upset
  			 *	as we have pulled the frame from the queue by
  			 *	freeing it).
  			 *
  			 *	NB: TCP modifies buffers that are still
  			 *	on a device queue, thus we use skb_copy()
  			 *      instead of using skb_clone() unless this
  			 *	gets fixed.
  			 */
  
  			ax25_address src_c;
  			ax25_address dst_c;
  
  			if ((ourskb = skb_copy(skb, GFP_ATOMIC)) == NULL) {
  				kfree_skb(skb);
  				goto put;
  			}
  
  			if (skb->sk != NULL)
  				skb_set_owner_w(ourskb, skb->sk);
  
  			kfree_skb(skb);
  			/* dl9sau: bugfix
  			 * after kfree_skb(), dst and src which were pointer
  			 * to bp which is part of skb->data would not be valid
  			 * anymore hope that after skb_pull(ourskb, ..) our
  			 * dsc_c and src_c will not become invalid
  			 */
  			bp  = ourskb->data;
  			dst_c = *(ax25_address *)(bp + 1);
  			src_c = *(ax25_address *)(bp + 8);
  
  			skb_pull(ourskb, AX25_HEADER_LEN - 1);	/* Keep PID */
  			skb_reset_network_header(ourskb);
  
  			ax25=ax25_send_frame(
  			    ourskb,
  			    ax25_dev->values[AX25_VALUES_PACLEN],
  			    &src_c,
  			    &dst_c, digipeat, dev);
  			if (ax25) {
  				ax25_cb_put(ax25);
  			}
  			goto put;
  		}
  	}
  
  	bp[7]  &= ~AX25_CBIT;
  	bp[7]  &= ~AX25_EBIT;
  	bp[7]  |= AX25_SSSID_SPARE;
  
  	bp[14] &= ~AX25_CBIT;
  	bp[14] |= AX25_EBIT;
  	bp[14] |= AX25_SSSID_SPARE;
  
  	skb_pull(skb, AX25_KISS_HEADER_LEN);
  
  	if (digipeat != NULL) {
  		if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL) {
  			kfree_skb(skb);
  			goto put;
  		}
  
  		skb = ourskb;
  	}
  
  	ax25_queue_xmit(skb, dev);
  
  put:
  
  	ax25_route_lock_unuse();
  	return NETDEV_TX_OK;
  }
  
  #else	/* INET */
  
  static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
  			    unsigned short type, const void *daddr,
  			    const void *saddr, unsigned int len)
  {
  	return -AX25_HEADER_LEN;
  }
  
  netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
  {
  	kfree_skb(skb);
  	return NETDEV_TX_OK;
  }
  #endif
  
  static bool ax25_validate_header(const char *header, unsigned int len)
  {
  	ax25_digi digi;
  
  	if (!len)
  		return false;
  
  	if (header[0])
  		return true;
  
  	return ax25_addr_parse(header + 1, len - 1, NULL, NULL, &digi, NULL,
  			       NULL);
  }
  
  const struct header_ops ax25_header_ops = {
  	.create = ax25_hard_header,
  	.validate = ax25_validate_header,
  };
  
  EXPORT_SYMBOL(ax25_header_ops);
  EXPORT_SYMBOL(ax25_ip_xmit);
  
  