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.  The following fields
  37  * in it shall be filled in by x->type->output:
  38  *      payload_len
  39  *
  40  * On exit, skb->h will be set to the start of the encapsulation header to be
  41  * filled in by x->type->output and skb->nh will be set to the nextheader field
  42  * of the extension header directly preceding the encapsulation header, or in
  43  * its absence, that of the top IP header.  The value of skb->data will always
  44  * point to the top IP header.
  45  */
  46 static int xfrm6_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  47 {
  48         struct dst_entry *dst = skb->dst;
  49         struct xfrm_dst *xdst = (struct xfrm_dst*)dst;
  50         struct ipv6hdr *iph, *top_iph;
  51         int dsfield;
  52
  53         skb_push(skb, x->props.header_len);
  54         iph = ipv6_hdr(skb);
  55
  56         skb_reset_network_header(skb);
  57         top_iph = ipv6_hdr(skb);
  58         skb->transport_header = skb->network_header + sizeof(struct ipv6hdr);
  59         skb->network_header   += offsetof(struct ipv6hdr, nexthdr);
  60
  61         top_iph->version = 6;
  62         if (xdst->route->ops->family == AF_INET6) {
  63                 top_iph->priority = iph->priority;
  64                 top_iph->flow_lbl[0] = iph->flow_lbl[0];
  65                 top_iph->flow_lbl[1] = iph->flow_lbl[1];
  66                 top_iph->flow_lbl[2] = iph->flow_lbl[2];
  67                 top_iph->nexthdr = IPPROTO_IPV6;
  68         } else {
  69                 top_iph->priority = 0;
  70                 top_iph->flow_lbl[0] = 0;
  71                 top_iph->flow_lbl[1] = 0;
  72                 top_iph->flow_lbl[2] = 0;
  73                 top_iph->nexthdr = IPPROTO_IPIP;
  74         }
  75         dsfield = ipv6_get_dsfield(top_iph);
  76         dsfield = INET_ECN_encapsulate(dsfield, dsfield);
  77         if (x->props.flags & XFRM_STATE_NOECN)
  78                 dsfield &= ~INET_ECN_MASK;
  79         ipv6_change_dsfield(top_iph, 0, dsfield);
  80         top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
  81         ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
  82         ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
  83         skb->protocol = htons(ETH_P_IPV6);
  84         return 0;
  85 }
  86
  87 static int xfrm6_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  88 {
  89         int err = -EINVAL;
  90         const unsigned char *old_mac;
  91         const unsigned char *nh = skb_network_header(skb);
  92
  93         if (nh[IP6CB(skb)->nhoff] != IPPROTO_IPV6 &&
  94             nh[IP6CB(skb)->nhoff] != IPPROTO_IPIP)
  95                 goto out;
  96         if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
  97                 goto out;
  98
  99         if (skb_cloned(skb) &&
 100             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 101                 goto out;
 102
 103         nh = skb_network_header(skb);
 104         if (nh[IP6CB(skb)->nhoff] == IPPROTO_IPV6) {
 105                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 106                         ipv6_copy_dscp(ipv6_hdr(skb), ipipv6_hdr(skb));
 107                 if (!(x->props.flags & XFRM_STATE_NOECN))
 108                         ipip6_ecn_decapsulate(skb);
 109         } else {
 110                 if (!(x->props.flags & XFRM_STATE_NOECN))
 111                         ip6ip_ecn_decapsulate(skb);
 112                 skb->protocol = htons(ETH_P_IP);
 113         }
 114         old_mac = skb_mac_header(skb);
 115         skb_set_mac_header(skb, -skb->mac_len);
 116         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
 117         skb_reset_network_header(skb);
 118         err = 0;
 119
 120 out:
 121         return err;
 122 }
 123
 124 static struct xfrm_mode xfrm6_tunnel_mode = {
 125         .input = xfrm6_tunnel_input,
 126         .output = xfrm6_tunnel_output,
 127         .owner = THIS_MODULE,
 128         .encap = XFRM_MODE_TUNNEL,
 129 };
 130
 131 static int __init xfrm6_tunnel_init(void)
 132 {
 133         return xfrm_register_mode(&xfrm6_tunnel_mode, AF_INET6);
 134 }
 135
 136 static void __exit xfrm6_tunnel_exit(void)
 137 {
 138         int err;
 139
 140         err = xfrm_unregister_mode(&xfrm6_tunnel_mode, AF_INET6);
 141         BUG_ON(err);
 142 }
 143
 144 module_init(xfrm6_tunnel_init);
 145 module_exit(xfrm6_tunnel_exit);
 146 MODULE_LICENSE("GPL");
 147 MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TUNNEL);