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.  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->transport_header = skb->network_header;
  51
  52         skb_set_network_header(skb, -x->props.header_len);
  53         top_iph = ip_hdr(skb);
  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         skb->protocol = htons(ETH_P_IP);
  88
  89         memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
  90         return 0;
  91 }
  92
  93 static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  94 {
  95         struct iphdr *iph = ip_hdr(skb);
  96         const unsigned char *old_mac;
  97         int err = -EINVAL;
  98
  99         switch (iph->protocol){
 100                 case IPPROTO_IPIP:
 101                         break;
 102 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 103                 case IPPROTO_IPV6:
 104                         break;
 105 #endif
 106                 default:
 107                         goto out;
 108         }
 109
 110         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 111                 goto out;
 112
 113         if (skb_cloned(skb) &&
 114             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
 115                 goto out;
 116
 117         iph = ip_hdr(skb);
 118         if (iph->protocol == IPPROTO_IPIP) {
 119                 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 120                         ipv4_copy_dscp(iph, ipip_hdr(skb));
 121                 if (!(x->props.flags & XFRM_STATE_NOECN))
 122                         ipip_ecn_decapsulate(skb);
 123         }
 124 #if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
 125         else {
 126                 if (!(x->props.flags & XFRM_STATE_NOECN))
 127                         ipip6_ecn_decapsulate(iph, skb);
 128                 skb->protocol = htons(ETH_P_IPV6);
 129         }
 130 #endif
 131         old_mac = skb_mac_header(skb);
 132         skb_set_mac_header(skb, -skb->mac_len);
 133         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
 134         skb_reset_network_header(skb);
 135         err = 0;
 136
 137 out:
 138         return err;
 139 }
 140
 141 static struct xfrm_mode xfrm4_tunnel_mode = {
 142         .input = xfrm4_tunnel_input,
 143         .output = xfrm4_tunnel_output,
 144         .owner = THIS_MODULE,
 145         .encap = XFRM_MODE_TUNNEL,
 146 };
 147
 148 static int __init xfrm4_tunnel_init(void)
 149 {
 150         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 151 }
 152
 153 static void __exit xfrm4_tunnel_exit(void)
 154 {
 155         int err;
 156
 157         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 158         BUG_ON(err);
 159 }
 160
 161 module_init(xfrm4_tunnel_init);
 162 module_exit(xfrm4_tunnel_exit);
 163 MODULE_LICENSE("GPL");
 164 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);