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 *outer_iph = ip_hdr(skb);
  20         struct iphdr *inner_iph = ipip_hdr(skb);
  21
  22         if (INET_ECN_is_ce(outer_iph->tos))
  23                 IP_ECN_set_ce(inner_iph);
  24 }
  25
  26 static inline void ipip6_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
  27 {
  28         if (INET_ECN_is_ce(iph->tos))
  29                 IP6_ECN_set_ce(ipv6_hdr(skb));
  30 }
  31
  32 /* Add encapsulation header.
  33  *
  34  * The top IP header will be constructed per RFC 2401.
  35  */
  36 static int xfrm4_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  37 {
  38         struct dst_entry *dst = skb->dst;
  39         struct iphdr *top_iph;
  40         int flags;
  41
  42         skb_set_network_header(skb, -x->props.header_len);
  43         skb->mac_header = skb->network_header +
  44                           offsetof(struct iphdr, protocol);
  45         skb->transport_header = skb->network_header + sizeof(*top_iph);
  46         top_iph = ip_hdr(skb);
  47
  48         top_iph->ihl = 5;
  49         top_iph->version = 4;
  50
  51         top_iph->protocol = x->inner_mode->afinfo->proto;
  52
  53         /* DS disclosed */
  54         top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,
  55                                             XFRM_MODE_SKB_CB(skb)->tos);
  56
  57         flags = x->props.flags;
  58         if (flags & XFRM_STATE_NOECN)
  59                 IP_ECN_clear(top_iph);
  60
  61         top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  62                             0 : XFRM_MODE_SKB_CB(skb)->frag_off;
  63         ip_select_ident(top_iph, dst->child, NULL);
  64
  65         top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  66
  67         top_iph->saddr = x->props.saddr.a4;
  68         top_iph->daddr = x->id.daddr.a4;
  69
  70         return 0;
  71 }
  72
  73 static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  74 {
  75         struct iphdr *iph = ip_hdr(skb);
  76         const unsigned char *old_mac;
  77         int err = -EINVAL;
  78
  79         switch (iph->protocol){
  80                 case IPPROTO_IPIP:
  81                         break;
  82 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
  83                 case IPPROTO_IPV6:
  84                         break;
  85 #endif
  86                 default:
  87                         goto out;
  88         }
  89
  90         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  91                 goto out;
  92
  93         if (skb_cloned(skb) &&
  94             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  95                 goto out;
  96
  97         iph = ip_hdr(skb);
  98         if (iph->protocol == IPPROTO_IPIP) {
  99                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 100                         ipv4_copy_dscp(ipv4_get_dsfield(iph), ipip_hdr(skb));
 101                 if (!(x->props.flags & XFRM_STATE_NOECN))
 102                         ipip_ecn_decapsulate(skb);
 103         }
 104 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 105         else {
 106                 if (!(x->props.flags & XFRM_STATE_NOECN))
 107                         ipip6_ecn_decapsulate(iph, skb);
 108                 skb->protocol = htons(ETH_P_IPV6);
 109         }
 110 #endif
 111         old_mac = skb_mac_header(skb);
 112         skb_set_mac_header(skb, -skb->mac_len);
 113         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
 114         skb_reset_network_header(skb);
 115         err = 0;
 116
 117 out:
 118         return err;
 119 }
 120
 121 static struct xfrm_mode xfrm4_tunnel_mode = {
 122         .input = xfrm4_tunnel_input,
 123         .output2 = xfrm4_tunnel_output,
 124         .output = xfrm4_prepare_output,
 125         .owner = THIS_MODULE,
 126         .encap = XFRM_MODE_TUNNEL,
 127         .flags = XFRM_MODE_FLAG_TUNNEL,
 128 };
 129
 130 static int __init xfrm4_tunnel_init(void)
 131 {
 132         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 133 }
 134
 135 static void __exit xfrm4_tunnel_exit(void)
 136 {
 137         int err;
 138
 139         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 140         BUG_ON(err);
 141 }
 142
 143 module_init(xfrm4_tunnel_init);
 144 module_exit(xfrm4_tunnel_exit);
 145 MODULE_LICENSE("GPL");
 146 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);