net/ipv4/xfrm4_mode_tunnel.c

   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
  18 static 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  */
  30 static 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 = dst_metric(dst->child, RTAX_HOPLIMIT);
  60
  61         top_iph->saddr = x->props.saddr.a4;
  62         top_iph->daddr = x->id.daddr.a4;
  63
  64         return 0;
  65 }
  66
  67 static 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
  93 out:
  94         return err;
  95 }
  96
  97 static 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
 107 static int __init xfrm4_mode_tunnel_init(void)
 108 {
 109         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 110 }
 111
 112 static 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
 120 module_init(xfrm4_mode_tunnel_init);
 121 module_exit(xfrm4_mode_tunnel_exit);
 122 MODULE_LICENSE("GPL");
 123 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);