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/gfp.h>
  8#include <linux/init.h>
  9#include <linux/kernel.h>
 10#include <linux/module.h>
 11#include <linux/skbuff.h>
 12#include <linux/stringify.h>
 13#include <net/dst.h>
 14#include <net/inet_ecn.h>
 15#include <net/ip.h>
 16#include <net/xfrm.h>
 17
 18static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
 19{
 20	struct iphdr *inner_iph = ipip_hdr(skb);
 21
 22	if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->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.
 29 */
 30static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
 31{
 32	struct dst_entry *dst = skb_dst(skb);
 33	struct iphdr *top_iph;
 34	int flags;
 35
 36	skb_set_network_header(skb, -x->props.header_len);
 37	skb->mac_header = skb->network_header +
 38			  offsetof(struct iphdr, protocol);
 39	skb->transport_header = skb->network_header + sizeof(*top_iph);
 40	top_iph = ip_hdr(skb);
 41
 42	top_iph->ihl = 5;
 43	top_iph->version = 4;
 44
 45	top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
 46
 47	/* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
 48	if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
 49		top_iph->tos = 0;
 50	else
 51		top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
 52	top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
 53					    XFRM_MODE_SKB_CB(skb)->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 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
 61	ip_select_ident(skb, dst->child, NULL);
 62
 63	top_iph->ttl = ip4_dst_hoplimit(dst->child);
 64
 65	top_iph->saddr = x->props.saddr.a4;
 66	top_iph->daddr = x->id.daddr.a4;
 67
 68	return 0;
 69}
 70
 71static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 72{
 73	int err = -EINVAL;
 74
 75	if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
 76		goto out;
 77
 78	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 79		goto out;
 80
 81	err = skb_unclone(skb, GFP_ATOMIC);
 82	if (err)
 83		goto out;
 84
 85	if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 86		ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
 87	if (!(x->props.flags & XFRM_STATE_NOECN))
 88		ipip_ecn_decapsulate(skb);
 89
 90	skb_reset_network_header(skb);
 91	skb_mac_header_rebuild(skb);
 92
 93	err = 0;
 94
 95out:
 96	return err;
 97}
 98
 99static struct xfrm_mode xfrm4_tunnel_mode = {
100	.input2 = xfrm4_mode_tunnel_input,
101	.input = xfrm_prepare_input,
102	.output2 = xfrm4_mode_tunnel_output,
103	.output = xfrm4_prepare_output,
104	.owner = THIS_MODULE,
105	.encap = XFRM_MODE_TUNNEL,
106	.flags = XFRM_MODE_FLAG_TUNNEL,
107};
108
109static int __init xfrm4_mode_tunnel_init(void)
110{
111	return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
112}
113
114static void __exit xfrm4_mode_tunnel_exit(void)
115{
116	int err;
117
118	err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
119	BUG_ON(err);
120}
121
122module_init(xfrm4_mode_tunnel_init);
123module_exit(xfrm4_mode_tunnel_exit);
124MODULE_LICENSE("GPL");
125MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);