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