/*
   * xfrm6_mode_beet.c - BEET mode encapsulation for IPv6.
   *
   * Copyright (c) 2006 Diego Beltrami <diego.beltrami@gmail.com>
   *                    Miika Komu     <miika@iki.fi>
   *                    Herbert Xu     <herbert@gondor.apana.org.au>
   *                    Abhinav Pathak <abhinav.pathak@hiit.fi>
   *                    Jeff Ahrenholz <ahrenholz@gmail.com>
   */
  
  #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>
  
  /* Add encapsulation header.
   *
   * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
   * The following fields in it shall be filled in by x->type->output:
   *	payload_len
   *
   * On exit, skb->h will be set to the start of the encapsulation header to be
   * filled in by x->type->output and skb->nh will be set to the nextheader field
   * of the extension header directly preceding the encapsulation header, or in
   * its absence, that of the top IP header.  The value of skb->data will always
   * point to the top IP header.
   */
  static int xfrm6_beet_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ipv6hdr *iph, *top_iph;
  	u8 *prevhdr;
  	int hdr_len;
  
  	skb_push(skb, x->props.header_len);

  	iph = ipv6_hdr(skb);

  
  	hdr_len = ip6_find_1stfragopt(skb, &prevhdr);

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

  	skb_set_transport_header(skb, hdr_len);

  	memmove(skb->data, iph, hdr_len);

  	skb_reset_network_header(skb);

  	top_iph = ipv6_hdr(skb);

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

  
  	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_beet_input(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ipv6hdr *ip6h;

  	const unsigned char *old_mac;

  	int size = sizeof(struct ipv6hdr);
  	int err = -EINVAL;
  
  	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
  		goto out;
  
  	skb_push(skb, size);

  	memmove(skb->data, skb_network_header(skb), size);

  	skb_reset_network_header(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);

  	ip6h = ipv6_hdr(skb);

  	ip6h->payload_len = htons(skb->len - size);
  	ipv6_addr_copy(&ip6h->daddr, (struct in6_addr *) &x->sel.daddr.a6);
  	ipv6_addr_copy(&ip6h->saddr, (struct in6_addr *) &x->sel.saddr.a6);
  	err = 0;
  out:
  	return err;
  }
  
  static struct xfrm_mode xfrm6_beet_mode = {
  	.input = xfrm6_beet_input,
  	.output = xfrm6_beet_output,
  	.owner = THIS_MODULE,
  	.encap = XFRM_MODE_BEET,
  };
  
  static int __init xfrm6_beet_init(void)
  {
  	return xfrm_register_mode(&xfrm6_beet_mode, AF_INET6);
  }
  
  static void __exit xfrm6_beet_exit(void)
  {
  	int err;
  
  	err = xfrm_unregister_mode(&xfrm6_beet_mode, AF_INET6);
  	BUG_ON(err);
  }
  
  module_init(xfrm6_beet_init);
  module_exit(xfrm6_beet_exit);
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_BEET);