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