linux/net/ipv6/xfrm6_mode_transport.c
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   1/*
   2 * xfrm6_mode_transport.c - Transport mode encapsulation for IPv6.
   3 *
   4 * Copyright (C) 2002 USAGI/WIDE Project
   5 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   6 */
   7
   8#include <linux/init.h>
   9#include <linux/kernel.h>
  10#include <linux/module.h>
  11#include <linux/skbuff.h>
  12#include <linux/stringify.h>
  13#include <net/dst.h>
  14#include <net/ipv6.h>
  15#include <net/xfrm.h>
  16
  17/* Add encapsulation header.
  18 *
  19 * The IP header and mutable extension headers will be moved forward to make
  20 * space for the encapsulation header.
  21 */
  22static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
  23{
  24        struct ipv6hdr *iph;
  25        u8 *prevhdr;
  26        int hdr_len;
  27
  28        iph = ipv6_hdr(skb);
  29
  30        hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
  31        skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
  32        skb_set_network_header(skb, -x->props.header_len);
  33        skb->transport_header = skb->network_header + hdr_len;
  34        __skb_pull(skb, hdr_len);
  35        memmove(ipv6_hdr(skb), iph, hdr_len);
  36        return 0;
  37}
  38
  39/* Remove encapsulation header.
  40 *
  41 * The IP header will be moved over the top of the encapsulation header.
  42 *
  43 * On entry, skb->h shall point to where the IP header should be and skb->nh
  44 * shall be set to where the IP header currently is.  skb->data shall point
  45 * to the start of the payload.
  46 */
  47static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  48{
  49        int ihl = skb->data - skb_transport_header(skb);
  50
  51        if (skb->transport_header != skb->network_header) {
  52                memmove(skb_transport_header(skb),
  53                        skb_network_header(skb), ihl);
  54                skb->network_header = skb->transport_header;
  55        }
  56        ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
  57                                           sizeof(struct ipv6hdr));
  58        skb_reset_transport_header(skb);
  59        return 0;
  60}
  61
  62static struct xfrm_mode xfrm6_transport_mode = {
  63        .input = xfrm6_transport_input,
  64        .output = xfrm6_transport_output,
  65        .owner = THIS_MODULE,
  66        .encap = XFRM_MODE_TRANSPORT,
  67};
  68
  69static int __init xfrm6_transport_init(void)
  70{
  71        return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
  72}
  73
  74static void __exit xfrm6_transport_exit(void)
  75{
  76        int err;
  77
  78        err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
  79        BUG_ON(err);
  80}
  81
  82module_init(xfrm6_transport_init);
  83module_exit(xfrm6_transport_exit);
  84MODULE_LICENSE("GPL");
  85MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);
  86
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