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 disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
  48         if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
  49                 top_iph->tos = 0;
  50         else
  51                 top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
  52         top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
  53                                             XFRM_MODE_SKB_CB(skb)->tos);
  54
  55         flags = x->props.flags;
  56         if (flags & XFRM_STATE_NOECN)
  57                 IP_ECN_clear(top_iph);
  58
  59         top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  60                 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
  61
  62         top_iph->ttl = ip4_dst_hoplimit(dst->child);
  63
  64         top_iph->saddr = x->props.saddr.a4;
  65         top_iph->daddr = x->id.daddr.a4;
  66         ip_select_ident(skb, NULL);
  67
  68         return 0;
  69 }
  70
  71 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  72 {
  73         int err = -EINVAL;
  74
  75         if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
  76                 goto out;
  77
  78         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  79                 goto out;
  80
  81         err = skb_unclone(skb, GFP_ATOMIC);
  82         if (err)
  83                 goto out;
  84
  85         if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  86                 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
  87         if (!(x->props.flags & XFRM_STATE_NOECN))
  88                 ipip_ecn_decapsulate(skb);
  89
  90         skb_reset_network_header(skb);
  91         skb_mac_header_rebuild(skb);
  92
  93         err = 0;
  94
  95 out:
  96         return err;
  97 }
  98
  99 static struct xfrm_mode xfrm4_tunnel_mode = {
 100         .input2 = xfrm4_mode_tunnel_input,
 101         .input = xfrm_prepare_input,
 102         .output2 = xfrm4_mode_tunnel_output,
 103         .output = xfrm4_prepare_output,
 104         .owner = THIS_MODULE,
 105         .encap = XFRM_MODE_TUNNEL,
 106         .flags = XFRM_MODE_FLAG_TUNNEL,
 107 };
 108
 109 static int __init xfrm4_mode_tunnel_init(void)
 110 {
 111         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 112 }
 113
 114 static void __exit xfrm4_mode_tunnel_exit(void)
 115 {
 116         int err;
 117
 118         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 119         BUG_ON(err);
 120 }
 121
 122 module_init(xfrm4_mode_tunnel_init);
 123 module_exit(xfrm4_mode_tunnel_exit);
 124 MODULE_LICENSE("GPL");
 125 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);