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
62	top_iph->ttl = ip4_dst_hoplimit(dst->child);
63
64	top_iph->saddr = x->props.saddr.a4;
65	top_iph->daddr = x->id.daddr.a4;
66	ip_select_ident(skb, NULL);
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);
126