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 xfrm_dst *xdst = (struct xfrm_dst*)dst;
  40         struct iphdr *iph, *top_iph;
  41         int flags;
  42
  43         iph = ip_hdr(skb);
  44
  45         skb_set_network_header(skb, -x->props.header_len);
  46         skb->mac_header = skb->network_header +
  47                           offsetof(struct iphdr, protocol);
  48         skb->transport_header = skb->network_header + sizeof(*iph);
  49         top_iph = ip_hdr(skb);
  50
  51         top_iph->ihl = 5;
  52         top_iph->version = 4;
  53
  54         flags = x->props.flags;
  55
  56         /* DS disclosed */
  57         if (xdst->route->ops->family == AF_INET) {
  58                 top_iph->protocol = IPPROTO_IPIP;
  59                 top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
  60                 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  61                         0 : (iph->frag_off & htons(IP_DF));
  62         }
  63 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
  64         else {
  65                 struct ipv6hdr *ipv6h = (struct ipv6hdr*)iph;
  66                 top_iph->protocol = IPPROTO_IPV6;
  67                 top_iph->tos = INET_ECN_encapsulate(iph->tos, ipv6_get_dsfield(ipv6h));
  68                 top_iph->frag_off = 0;
  69         }
  70 #endif
  71
  72         if (flags & XFRM_STATE_NOECN)
  73                 IP_ECN_clear(top_iph);
  74
  75         if (!top_iph->frag_off)
  76                 __ip_select_ident(top_iph, dst->child, 0);
  77
  78         top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  79
  80         top_iph->saddr = x->props.saddr.a4;
  81         top_iph->daddr = x->id.daddr.a4;
  82
  83         skb->protocol = htons(ETH_P_IP);
  84
  85         memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
  86         return 0;
  87 }
  88
  89 static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  90 {
  91         struct iphdr *iph = ip_hdr(skb);
  92         const unsigned char *old_mac;
  93         int err = -EINVAL;
  94
  95         switch (iph->protocol){
  96                 case IPPROTO_IPIP:
  97                         break;
  98 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
  99                 case IPPROTO_IPV6:
 100                         break;
 101 #endif
 102                 default:
 103                         goto out;
 104         }
 105
 106         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 107                 goto out;
 108
 109         if (skb_cloned(skb) &&
 110             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 111                 goto out;
 112
 113         iph = ip_hdr(skb);
 114         if (iph->protocol == IPPROTO_IPIP) {
 115                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 116                         ipv4_copy_dscp(iph, ipip_hdr(skb));
 117                 if (!(x->props.flags & XFRM_STATE_NOECN))
 118                         ipip_ecn_decapsulate(skb);
 119         }
 120 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 121         else {
 122                 if (!(x->props.flags & XFRM_STATE_NOECN))
 123                         ipip6_ecn_decapsulate(iph, skb);
 124                 skb->protocol = htons(ETH_P_IPV6);
 125         }
 126 #endif
 127         old_mac = skb_mac_header(skb);
 128         skb_set_mac_header(skb, -skb->mac_len);
 129         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
 130         skb_reset_network_header(skb);
 131         err = 0;
 132
 133 out:
 134         return err;
 135 }
 136
 137 static struct xfrm_mode xfrm4_tunnel_mode = {
 138         .input = xfrm4_tunnel_input,
 139         .output = xfrm4_tunnel_output,
 140         .owner = THIS_MODULE,
 141         .encap = XFRM_MODE_TUNNEL,
 142 };
 143
 144 static int __init xfrm4_tunnel_init(void)
 145 {
 146         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 147 }
 148
 149 static void __exit xfrm4_tunnel_exit(void)
 150 {
 151         int err;
 152
 153         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 154         BUG_ON(err);
 155 }
 156
 157 module_init(xfrm4_tunnel_init);
 158 module_exit(xfrm4_tunnel_exit);
 159 MODULE_LICENSE("GPL");
 160 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);