LXR linux/net/ipv4/xfrm4_mode

   1/*
   2 * xfrm4_mode_transport.c - Transport mode encapsulation for IPv4.
   3 *
   4 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   5 */
   6
   7#include <linux/init.h>
   8#include <linux/kernel.h>
   9#include <linux/module.h>
  10#include <linux/skbuff.h>
  11#include <linux/stringify.h>
  12#include <net/dst.h>
  13#include <net/ip.h>
  14#include <net/xfrm.h>
  15
  16/* Add encapsulation header.
  17 *
  18 * The IP header will be moved forward to make space for the encapsulation
  19 * header.
  20 */
  21static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
  22{
  23        struct iphdr *iph = ip_hdr(skb);
  24        int ihl = iph->ihl * 4;
  25
  26        skb_set_network_header(skb, -x->props.header_len);
  27        skb->mac_header = skb->network_header +
  28                          offsetof(struct iphdr, protocol);
  29        skb->transport_header = skb->network_header + ihl;
  30        __skb_pull(skb, ihl);
  31        memmove(skb_network_header(skb), iph, ihl);
  32        return 0;
  33}
  34
  35/* Remove encapsulation header.
  36 *
  37 * The IP header will be moved over the top of the encapsulation header.
  38 *
  39 * On entry, skb->h shall point to where the IP header should be and skb->nh
  40 * shall be set to where the IP header currently is.  skb->data shall point
  41 * to the start of the payload.
  42 */
  43static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  44{
  45        int ihl = skb->data - skb_transport_header(skb);
  46
  47        if (skb->transport_header != skb->network_header) {
  48                memmove(skb_transport_header(skb),
  49                        skb_network_header(skb), ihl);
  50                skb->network_header = skb->transport_header;
  51        }
  52        ip_hdr(skb)->tot_len = htons(skb->len + ihl);
  53        skb_reset_transport_header(skb);
  54        return 0;
  55}
  56
  57static struct xfrm_mode xfrm4_transport_mode = {
  58        .input = xfrm4_transport_input,
  59        .output = xfrm4_transport_output,
  60        .owner = THIS_MODULE,
  61        .encap = XFRM_MODE_TRANSPORT,
  62};
  63
  64static int __init xfrm4_transport_init(void)
  65{
  66        return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
  67}
  68
  69static void __exit xfrm4_transport_exit(void)
  70{
  71        int err;
  72
  73        err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
  74        BUG_ON(err);
  75}
  76
  77module_init(xfrm4_transport_init);
  78module_exit(xfrm4_transport_exit);
  79MODULE_LICENSE("GPL");
  80MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);
  81