LXR linux/net/ipv4/xfrm4_mode

   1/*
   2 * xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
   3 *
   4 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   5 */
   6
   7#include <linux/gfp.h>
   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/inet_ecn.h>
  15#include <net/ip.h>
  16#include <net/xfrm.h>
  17
  18static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
  19{
  20        struct iphdr *inner_iph = ipip_hdr(skb);
  21
  22        if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
  23                IP_ECN_set_ce(inner_iph);
  24}
  25
  26/* Add encapsulation header.
  27 *
  28 * The top IP header will be constructed per RFC 2401.
  29 */
  30static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  31{
  32        struct dst_entry *dst = skb_dst(skb);
  33        struct iphdr *top_iph;
  34        int flags;
  35
  36        skb_set_network_header(skb, -x->props.header_len);
  37        skb->mac_header = skb->network_header +
  38                          offsetof(struct iphdr, protocol);
  39        skb->transport_header = skb->network_header + sizeof(*top_iph);
  40        top_iph = ip_hdr(skb);
  41
  42        top_iph->ihl = 5;
  43        top_iph->version = 4;
  44
  45        top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
  46
  47        /* DS disclosed */
  48        top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,
  49                                            XFRM_MODE_SKB_CB(skb)->tos);
  50
  51        flags = x->props.flags;
  52        if (flags & XFRM_STATE_NOECN)
  53                IP_ECN_clear(top_iph);
  54
  55        top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  56                0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
  57        ip_select_ident(top_iph, dst->child, NULL);
  58
  59        top_iph->ttl = ip4_dst_hoplimit(dst->child);
  60
  61        top_iph->saddr = x->props.saddr.a4;
  62        top_iph->daddr = x->id.daddr.a4;
  63
  64        return 0;
  65}
  66
  67static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  68{
  69        const unsigned char *old_mac;
  70        int err = -EINVAL;
  71
  72        if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
  73                goto out;
  74
  75        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  76                goto out;
  77
  78        if (skb_cloned(skb) &&
  79            (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  80                goto out;
  81
  82        if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  83                ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
  84        if (!(x->props.flags & XFRM_STATE_NOECN))
  85                ipip_ecn_decapsulate(skb);
  86
  87        old_mac = skb_mac_header(skb);
  88        skb_set_mac_header(skb, -skb->mac_len);
  89        memmove(skb_mac_header(skb), old_mac, skb->mac_len);
  90        skb_reset_network_header(skb);
  91        err = 0;
  92
  93out:
  94        return err;
  95}
  96
  97static struct xfrm_mode xfrm4_tunnel_mode = {
  98        .input2 = xfrm4_mode_tunnel_input,
  99        .input = xfrm_prepare_input,
 100        .output2 = xfrm4_mode_tunnel_output,
 101        .output = xfrm4_prepare_output,
 102        .owner = THIS_MODULE,
 103        .encap = XFRM_MODE_TUNNEL,
 104        .flags = XFRM_MODE_FLAG_TUNNEL,
 105};
 106
 107static int __init xfrm4_mode_tunnel_init(void)
 108{
 109        return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 110}
 111
 112static void __exit xfrm4_mode_tunnel_exit(void)
 113{
 114        int err;
 115
 116        err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 117        BUG_ON(err);
 118}
 119
 120module_init(xfrm4_mode_tunnel_init);
 121module_exit(xfrm4_mode_tunnel_exit);
 122MODULE_LICENSE("GPL");
 123MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
 124