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 = skb->h.ipiph;
  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(skb->nh.ipv6h);
  30 }
  31
  32 /* Add encapsulation header.
  33  *
  34  * The top IP header will be constructed per RFC 2401.  The following fields
  35  * in it shall be filled in by x->type->output:
  36  *      tot_len
  37  *      check
  38  *
  39  * On exit, skb->h will be set to the start of the payload to be processed
  40  * by x->type->output and skb->nh will be set to the top IP header.
  41  */
  42 static int xfrm4_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  43 {
  44         struct dst_entry *dst = skb->dst;
  45         struct xfrm_dst *xdst = (struct xfrm_dst*)dst;
  46         struct iphdr *iph, *top_iph;
  47         int flags;
  48
  49         iph = ip_hdr(skb);
  50         skb->h.ipiph = iph;
  51
  52         skb_push(skb, x->props.header_len);
  53         skb_reset_network_header(skb);
  54         top_iph = ip_hdr(skb);
  55
  56         top_iph->ihl = 5;
  57         top_iph->version = 4;
  58
  59         flags = x->props.flags;
  60
  61         /* DS disclosed */
  62         if (xdst->route->ops->family == AF_INET) {
  63                 top_iph->protocol = IPPROTO_IPIP;
  64                 top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
  65                 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  66                         0 : (iph->frag_off & htons(IP_DF));
  67         }
  68 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
  69         else {
  70                 struct ipv6hdr *ipv6h = (struct ipv6hdr*)iph;
  71                 top_iph->protocol = IPPROTO_IPV6;
  72                 top_iph->tos = INET_ECN_encapsulate(iph->tos, ipv6_get_dsfield(ipv6h));
  73                 top_iph->frag_off = 0;
  74         }
  75 #endif
  76
  77         if (flags & XFRM_STATE_NOECN)
  78                 IP_ECN_clear(top_iph);
  79
  80         if (!top_iph->frag_off)
  81                 __ip_select_ident(top_iph, dst->child, 0);
  82
  83         top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  84
  85         top_iph->saddr = x->props.saddr.a4;
  86         top_iph->daddr = x->id.daddr.a4;
  87
  88         memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
  89         return 0;
  90 }
  91
  92 static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  93 {
  94         struct iphdr *iph = ip_hdr(skb);
  95         const unsigned char *old_mac;
  96         int err = -EINVAL;
  97
  98         switch (iph->protocol){
  99                 case IPPROTO_IPIP:
 100                         break;
 101 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 102                 case IPPROTO_IPV6:
 103                         break;
 104 #endif
 105                 default:
 106                         goto out;
 107         }
 108
 109         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 110                 goto out;
 111
 112         if (skb_cloned(skb) &&
 113             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 114                 goto out;
 115
 116         iph = ip_hdr(skb);
 117         if (iph->protocol == IPPROTO_IPIP) {
 118                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 119                         ipv4_copy_dscp(iph, skb->h.ipiph);
 120                 if (!(x->props.flags & XFRM_STATE_NOECN))
 121                         ipip_ecn_decapsulate(skb);
 122         }
 123 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 124         else {
 125                 if (!(x->props.flags & XFRM_STATE_NOECN))
 126                         ipip6_ecn_decapsulate(iph, skb);
 127                 skb->protocol = htons(ETH_P_IPV6);
 128         }
 129 #endif
 130         old_mac = skb_mac_header(skb);
 131         skb_set_mac_header(skb, -skb->mac_len);
 132         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
 133         skb_reset_network_header(skb);
 134         err = 0;
 135
 136 out:
 137         return err;
 138 }
 139
 140 static struct xfrm_mode xfrm4_tunnel_mode = {
 141         .input = xfrm4_tunnel_input,
 142         .output = xfrm4_tunnel_output,
 143         .owner = THIS_MODULE,
 144         .encap = XFRM_MODE_TUNNEL,
 145 };
 146
 147 static int __init xfrm4_tunnel_init(void)
 148 {
 149         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 150 }
 151
 152 static void __exit xfrm4_tunnel_exit(void)
 153 {
 154         int err;
 155
 156         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 157         BUG_ON(err);
 158 }
 159
 160 module_init(xfrm4_tunnel_init);
 161 module_exit(xfrm4_tunnel_exit);
 162 MODULE_LICENSE("GPL");
 163 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);