/*
   * xfrm6_mode_tunnel.c - Tunnel mode encapsulation for IPv6.
   *
   * Copyright (C) 2002 USAGI/WIDE Project
   * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   */
  
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/stringify.h>
  #include <net/dsfield.h>
  #include <net/dst.h>
  #include <net/inet_ecn.h>
  #include <net/ipv6.h>
  #include <net/xfrm.h>
  
  static inline void ipip6_ecn_decapsulate(struct sk_buff *skb)
  {

  	struct ipv6hdr *outer_iph = ipv6_hdr(skb);

  	struct ipv6hdr *inner_iph = ipipv6_hdr(skb);

  
  	if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
  		IP6_ECN_set_ce(inner_iph);
  }
  
  /* Add encapsulation header.
   *

   * The top IP header will be constructed per RFC 2401.

   */

  static int xfrm6_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)

  {
  	struct dst_entry *dst = skb->dst;

  	struct ipv6hdr *top_iph;

  	int dsfield;

  	skb_set_network_header(skb, -x->props.header_len);

  	skb->mac_header = skb->network_header +
  			  offsetof(struct ipv6hdr, nexthdr);

  	skb->transport_header = skb->network_header + sizeof(*top_iph);

  	top_iph = ipv6_hdr(skb);

  
  	top_iph->version = 6;

  
  	memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
  	       sizeof(top_iph->flow_lbl));

  	top_iph->nexthdr = xfrm_af2proto(skb->dst->ops->family);

  
  	dsfield = XFRM_MODE_SKB_CB(skb)->tos;

  	dsfield = INET_ECN_encapsulate(dsfield, dsfield);
  	if (x->props.flags & XFRM_STATE_NOECN)
  		dsfield &= ~INET_ECN_MASK;
  	ipv6_change_dsfield(top_iph, 0, dsfield);

  	top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
  	ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
  	ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
  	return 0;
  }

  static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)

  {
  	int err = -EINVAL;

  	const unsigned char *old_mac;

  	if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPV6)

  		goto out;
  	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
  		goto out;
  
  	if (skb_cloned(skb) &&
  	    (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  		goto out;

  	if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  		ipv6_copy_dscp(ipv6_get_dsfield(ipv6_hdr(skb)),
  			       ipipv6_hdr(skb));
  	if (!(x->props.flags & XFRM_STATE_NOECN))
  		ipip6_ecn_decapsulate(skb);

  	old_mac = skb_mac_header(skb);

  	skb_set_mac_header(skb, -skb->mac_len);

  	memmove(skb_mac_header(skb), old_mac, skb->mac_len);

  	skb_reset_network_header(skb);

  	err = 0;
  
  out:
  	return err;
  }
  
  static struct xfrm_mode xfrm6_tunnel_mode = {

  	.input2 = xfrm6_mode_tunnel_input,

  	.input = xfrm_prepare_input,

  	.output2 = xfrm6_mode_tunnel_output,

  	.output = xfrm6_prepare_output,

  	.owner = THIS_MODULE,
  	.encap = XFRM_MODE_TUNNEL,

  	.flags = XFRM_MODE_FLAG_TUNNEL,

  };

  static int __init xfrm6_mode_tunnel_init(void)

  {
  	return xfrm_register_mode(&xfrm6_tunnel_mode, AF_INET6);
  }

  static void __exit xfrm6_mode_tunnel_exit(void)

  {
  	int err;
  
  	err = xfrm_unregister_mode(&xfrm6_tunnel_mode, AF_INET6);
  	BUG_ON(err);
  }

  module_init(xfrm6_mode_tunnel_init);
  module_exit(xfrm6_mode_tunnel_exit);

  MODULE_LICENSE("GPL");
  MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TUNNEL);