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