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 /* Add encapsulation header.
  27  *
  28  * The top IP header will be constructed per RFC 2401.  The following fields
  29  * in it shall be filled in by x->type->output:
  30  *      tot_len
  31  *      check
  32  *
  33  * On exit, skb->h will be set to the start of the payload to be processed
  34  * by x->type->output and skb->nh will be set to the top IP header.
  35  */
  36 static int xfrm4_tunnel_output(struct sk_buff *skb)
  37 {
  38         struct dst_entry *dst = skb->dst;
  39         struct xfrm_state *x = dst->xfrm;
  40         struct iphdr *iph, *top_iph;
  41         int flags;
  42
  43         iph = skb->nh.iph;
  44         skb->h.ipiph = iph;
  45
  46         skb->nh.raw = skb_push(skb, x->props.header_len);
  47         top_iph = skb->nh.iph;
  48
  49         top_iph->ihl = 5;
  50         top_iph->version = 4;
  51
  52         /* DS disclosed */
  53         top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
  54
  55         flags = x->props.flags;
  56         if (flags & XFRM_STATE_NOECN)
  57                 IP_ECN_clear(top_iph);
  58
  59         top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  60                 0 : (iph->frag_off & htons(IP_DF));
  61         if (!top_iph->frag_off)
  62                 __ip_select_ident(top_iph, dst->child, 0);
  63
  64         top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  65
  66         top_iph->saddr = x->props.saddr.a4;
  67         top_iph->daddr = x->id.daddr.a4;
  68         top_iph->protocol = IPPROTO_IPIP;
  69
  70         memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
  71         return 0;
  72 }
  73
  74 static int xfrm4_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  75 {
  76         struct iphdr *iph = skb->nh.iph;
  77         int err = -EINVAL;
  78
  79         if (iph->protocol != IPPROTO_IPIP)
  80                 goto out;
  81         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  82                 goto out;
  83
  84         if (skb_cloned(skb) &&
  85             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  86                 goto out;
  87
  88         if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  89                 ipv4_copy_dscp(iph, skb->h.ipiph);
  90         if (!(x->props.flags & XFRM_STATE_NOECN))
  91                 ipip_ecn_decapsulate(skb);
  92         skb->mac.raw = memmove(skb->data - skb->mac_len,
  93                                skb->mac.raw, skb->mac_len);
  94         skb->nh.raw = skb->data;
  95         err = 0;
  96
  97 out:
  98         return err;
  99 }
 100
 101 static struct xfrm_mode xfrm4_tunnel_mode = {
 102         .input = xfrm4_tunnel_input,
 103         .output = xfrm4_tunnel_output,
 104         .owner = THIS_MODULE,
 105         .encap = XFRM_MODE_TUNNEL,
 106 };
 107
 108 static int __init xfrm4_tunnel_init(void)
 109 {
 110         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 111 }
 112
 113 static void __exit xfrm4_tunnel_exit(void)
 114 {
 115         int err;
 116
 117         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 118         BUG_ON(err);
 119 }
 120
 121 module_init(xfrm4_tunnel_init);
 122 module_exit(xfrm4_tunnel_exit);
 123 MODULE_LICENSE("GPL");
 124 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);