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 = skb->nh.iph;
  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 = skb->nh.iph;
  50         skb->h.ipiph = iph;
  51
  52         skb->nh.raw = skb_push(skb, x->props.header_len);
  53         top_iph = skb->nh.iph;
  54
  55         top_iph->ihl = 5;
  56         top_iph->version = 4;
  57
  58         flags = x->props.flags;
  59
  60         /* DS disclosed */
  61         if (xdst->route->ops->family == AF_INET) {
  62                 top_iph->protocol = IPPROTO_IPIP;
  63                 top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
  64                 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  65                         0 : (iph->frag_off & htons(IP_DF));
  66         }
  67 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
  68         else {
  69                 struct ipv6hdr *ipv6h = (struct ipv6hdr*)iph;
  70                 top_iph->protocol = IPPROTO_IPV6;
  71                 top_iph->tos = INET_ECN_encapsulate(iph->tos, ipv6_get_dsfield(ipv6h));
  72                 top_iph->frag_off = 0;
  73         }
  74 #endif
  75
  76         if (flags & XFRM_STATE_NOECN)
  77                 IP_ECN_clear(top_iph);
  78
  79         if (!top_iph->frag_off)
  80                 __ip_select_ident(top_iph, dst->child, 0);
  81
  82         top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  83
  84         top_iph->saddr = x->props.saddr.a4;
  85         top_iph->daddr = x->id.daddr.a4;
  86
  87         memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
  88         return 0;
  89 }
  90
  91 static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  92 {
  93         struct iphdr *iph = skb->nh.iph;
  94         int err = -EINVAL;
  95
  96         switch(iph->protocol){
  97                 case IPPROTO_IPIP:
  98                         break;
  99 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 100                 case IPPROTO_IPV6:
 101                         break;
 102 #endif
 103                 default:
 104                         goto out;
 105         }
 106
 107         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 108                 goto out;
 109
 110         if (skb_cloned(skb) &&
 111             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 112                 goto out;
 113
 114         iph = skb->nh.iph;
 115         if (iph->protocol == IPPROTO_IPIP) {
 116                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 117                         ipv4_copy_dscp(iph, skb->h.ipiph);
 118                 if (!(x->props.flags & XFRM_STATE_NOECN))
 119                         ipip_ecn_decapsulate(skb);
 120         }
 121 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 122         else {
 123                 if (!(x->props.flags & XFRM_STATE_NOECN))
 124                         ipip6_ecn_decapsulate(iph, skb);
 125                 skb->protocol = htons(ETH_P_IPV6);
 126         }
 127 #endif
 128         skb->mac.raw = memmove(skb->data - skb->mac_len,
 129                                skb->mac.raw, skb->mac_len);
 130         skb->nh.raw = skb->data;
 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);