net/ipv6/xfrm6_mode_tunnel.c

   1 /*
   2  * xfrm6_mode_tunnel.c - Tunnel mode encapsulation for IPv6.
   3  *
   4  * Copyright (C) 2002 USAGI/WIDE Project
   5  * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   6  */
   7
   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/dsfield.h>
  14 #include <net/dst.h>
  15 #include <net/inet_ecn.h>
  16 #include <net/ipv6.h>
  17 #include <net/xfrm.h>
  18
  19 static inline void ipip6_ecn_decapsulate(struct sk_buff *skb)
  20 {
  21         struct ipv6hdr *outer_iph = ipv6_hdr(skb);
  22         struct ipv6hdr *inner_iph = ipipv6_hdr(skb);
  23
  24         if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
  25                 IP6_ECN_set_ce(inner_iph);
  26 }
  27
  28 static inline void ip6ip_ecn_decapsulate(struct sk_buff *skb)
  29 {
  30         if (INET_ECN_is_ce(ipv6_get_dsfield(ipv6_hdr(skb))))
  31                         IP_ECN_set_ce(ipip_hdr(skb));
  32 }
  33
  34 /* Add encapsulation header.
  35  *
  36  * The top IP header will be constructed per RFC 2401.
  37  */
  38 static int xfrm6_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  39 {
  40         struct dst_entry *dst = skb->dst;
  41         struct ipv6hdr *top_iph;
  42         int dsfield;
  43
  44         skb_set_network_header(skb, -x->props.header_len);
  45         skb->mac_header = skb->network_header +
  46                           offsetof(struct ipv6hdr, nexthdr);
  47         skb->transport_header = skb->network_header + sizeof(*top_iph);
  48         top_iph = ipv6_hdr(skb);
  49
  50         top_iph->version = 6;
  51
  52         memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
  53                sizeof(top_iph->flow_lbl));
  54         top_iph->nexthdr = x->inner_mode->afinfo->proto;
  55
  56         dsfield = XFRM_MODE_SKB_CB(skb)->tos;
  57         dsfield = INET_ECN_encapsulate(dsfield, dsfield);
  58         if (x->props.flags & XFRM_STATE_NOECN)
  59                 dsfield &= ~INET_ECN_MASK;
  60         ipv6_change_dsfield(top_iph, 0, dsfield);
  61         top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
  62         ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
  63         ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
  64         return 0;
  65 }
  66
  67 static int xfrm6_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  68 {
  69         int err = -EINVAL;
  70         const unsigned char *old_mac;
  71         const unsigned char *nh = skb_network_header(skb);
  72
  73         if (nh[IP6CB(skb)->nhoff] != IPPROTO_IPV6 &&
  74             nh[IP6CB(skb)->nhoff] != IPPROTO_IPIP)
  75                 goto out;
  76         if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
  77                 goto out;
  78
  79         if (skb_cloned(skb) &&
  80             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  81                 goto out;
  82
  83         nh = skb_network_header(skb);
  84         if (nh[IP6CB(skb)->nhoff] == IPPROTO_IPV6) {
  85                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  86                         ipv6_copy_dscp(ipv6_get_dsfield(ipv6_hdr(skb)),
  87                                        ipipv6_hdr(skb));
  88                 if (!(x->props.flags & XFRM_STATE_NOECN))
  89                         ipip6_ecn_decapsulate(skb);
  90         } else {
  91                 if (!(x->props.flags & XFRM_STATE_NOECN))
  92                         ip6ip_ecn_decapsulate(skb);
  93                 skb->protocol = htons(ETH_P_IP);
  94         }
  95         old_mac = skb_mac_header(skb);
  96         skb_set_mac_header(skb, -skb->mac_len);
  97         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
  98         skb_reset_network_header(skb);
  99         err = 0;
 100
 101 out:
 102         return err;
 103 }
 104
 105 static struct xfrm_mode xfrm6_tunnel_mode = {
 106         .input = xfrm6_tunnel_input,
 107         .output2 = xfrm6_tunnel_output,
 108         .output = xfrm6_prepare_output,
 109         .owner = THIS_MODULE,
 110         .encap = XFRM_MODE_TUNNEL,
 111         .flags = XFRM_MODE_FLAG_TUNNEL,
 112 };
 113
 114 static int __init xfrm6_tunnel_init(void)
 115 {
 116         return xfrm_register_mode(&xfrm6_tunnel_mode, AF_INET6);
 117 }
 118
 119 static void __exit xfrm6_tunnel_exit(void)
 120 {
 121         int err;
 122
 123         err = xfrm_unregister_mode(&xfrm6_tunnel_mode, AF_INET6);
 124         BUG_ON(err);
 125 }
 126
 127 module_init(xfrm6_tunnel_init);
 128 module_exit(xfrm6_tunnel_exit);
 129 MODULE_LICENSE("GPL");
 130 MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TUNNEL);