/*
   * xfrm4_output.c - Common IPsec encapsulation code for IPv4.
   * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>

   *

   * 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.
   */

  #include <linux/if_ether.h>
  #include <linux/kernel.h>

  #include <linux/module.h>

  #include <linux/skbuff.h>

  #include <linux/netfilter_ipv4.h>

  #include <net/dst.h>

  #include <net/ip.h>
  #include <net/xfrm.h>
  #include <net/icmp.h>

  static int xfrm4_tunnel_check_size(struct sk_buff *skb)
  {
  	int mtu, ret = 0;

  
  	if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
  		goto out;

  	if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->ignore_df)

  		goto out;

  	mtu = dst_mtu(skb_dst(skb));

  	if (skb->len > mtu) {

  		skb->protocol = htons(ETH_P_IP);

  		if (skb->sk)

  			xfrm_local_error(skb, mtu);

  		else
  			icmp_send(skb, ICMP_DEST_UNREACH,
  				  ICMP_FRAG_NEEDED, htonl(mtu));

  		ret = -EMSGSIZE;
  	}
  out:
  	return ret;
  }

  int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int err;
  
  	err = xfrm4_tunnel_check_size(skb);
  	if (err)
  		return err;

  	XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;

  	return xfrm4_extract_header(skb);
  }
  
  int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int err;

  	err = xfrm_inner_extract_output(x, skb);

  	if (err)
  		return err;

  	IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;

  	skb->protocol = htons(ETH_P_IP);

  
  	return x->outer_mode->output2(x, skb);
  }
  EXPORT_SYMBOL(xfrm4_prepare_output);

  int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)

  {

  	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));

  
  #ifdef CONFIG_NETFILTER
  	IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  #endif

  	return xfrm_output(sk, skb);

  }

  static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)

  {
  	struct xfrm_state *x = skb_dst(skb)->xfrm;

  #ifdef CONFIG_NETFILTER

  	if (!x) {

  		IPCB(skb)->flags |= IPSKB_REROUTED;

  		return dst_output(net, sk, skb);

  	}

  #endif

  	return x->outer_mode->afinfo->output_finish(sk, skb);

  }

  int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)

  {

  	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
  			    net, sk, skb, NULL, skb_dst(skb)->dev,
  			    __xfrm4_output,

  			    !(IPCB(skb)->flags & IPSKB_REROUTED));

  }

  
  void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
  {
  	struct iphdr *hdr;
  
  	hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
  	ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
  		       inet_sk(skb->sk)->inet_dport, mtu);
  }