/*
   * xfrm6_mode_transport.c - Transport 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/dst.h>
  #include <net/ipv6.h>
  #include <net/xfrm.h>

  #include <net/protocol.h>

  
  /* Add encapsulation header.
   *
   * The IP header and mutable extension headers will be moved forward to make
   * space for the encapsulation header.

   */

  static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)

  {

  	struct ipv6hdr *iph;
  	u8 *prevhdr;
  	int hdr_len;

  	iph = ipv6_hdr(skb);

  	skb_set_inner_transport_header(skb, skb_transport_offset(skb));

  	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);

  	if (hdr_len < 0)
  		return hdr_len;

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

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

  	skb->transport_header = skb->network_header + hdr_len;

  	__skb_pull(skb, hdr_len);
  	memmove(ipv6_hdr(skb), iph, hdr_len);

  	return 0;
  }

  /* Remove encapsulation header.
   *
   * The IP header will be moved over the top of the encapsulation header.
   *
   * On entry, skb->h shall point to where the IP header should be and skb->nh
   * shall be set to where the IP header currently is.  skb->data shall point
   * to the start of the payload.
   */

  static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  {

  	int ihl = skb->data - skb_transport_header(skb);

  	if (skb->transport_header != skb->network_header) {

  		memmove(skb_transport_header(skb),
  			skb_network_header(skb), ihl);

  		skb->network_header = skb->transport_header;

  	}

  	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -

  					   sizeof(struct ipv6hdr));

  	skb_reset_transport_header(skb);

  	return 0;
  }

  static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
  						   struct sk_buff *skb,
  						   netdev_features_t features)
  {
  	const struct net_offload *ops;
  	struct sk_buff *segs = ERR_PTR(-EINVAL);
  	struct xfrm_offload *xo = xfrm_offload(skb);
  
  	skb->transport_header += x->props.header_len;
  	ops = rcu_dereference(inet6_offloads[xo->proto]);
  	if (likely(ops && ops->callbacks.gso_segment))
  		segs = ops->callbacks.gso_segment(skb, features);
  
  	return segs;
  }
  
  static void xfrm6_transport_xmit(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct xfrm_offload *xo = xfrm_offload(skb);
  
  	skb_reset_mac_len(skb);
  	pskb_pull(skb, skb->mac_len + sizeof(struct ipv6hdr) + x->props.header_len);
  
  	if (xo->flags & XFRM_GSO_SEGMENT) {
  		 skb_reset_transport_header(skb);
  		 skb->transport_header -= x->props.header_len;
  	}
  }

  static struct xfrm_mode xfrm6_transport_mode = {
  	.input = xfrm6_transport_input,
  	.output = xfrm6_transport_output,

  	.gso_segment = xfrm4_transport_gso_segment,
  	.xmit = xfrm6_transport_xmit,

  	.owner = THIS_MODULE,
  	.encap = XFRM_MODE_TRANSPORT,
  };
  
  static int __init xfrm6_transport_init(void)
  {
  	return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
  }
  
  static void __exit xfrm6_transport_exit(void)
  {
  	int err;
  
  	err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
  	BUG_ON(err);
  }
  
  module_init(xfrm6_transport_init);
  module_exit(xfrm6_transport_exit);
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);