1/*
2 * xfrm6_mode_tunnel.c - Tunnel mode encapsulation for IPv6.
3 *
4 * Copyright (C) 2002 USAGI/WIDE Project
5 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
6 */
7
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/dsfield.h>
14#include <net/dst.h>
15#include <net/inet_ecn.h>
16#include <net/ipv6.h>
17#include <net/xfrm.h>
18
19static inline void ipip6_ecn_decapsulate(struct sk_buff *skb)
20{
21	struct ipv6hdr *outer_iph = ipv6_hdr(skb);
22	struct ipv6hdr *inner_iph = ipipv6_hdr(skb);
23
24	if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
25		IP6_ECN_set_ce(inner_iph);
26}
27
28static inline void ip6ip_ecn_decapsulate(struct sk_buff *skb)
29{
30	if (INET_ECN_is_ce(ipv6_get_dsfield(ipv6_hdr(skb))))
31			IP_ECN_set_ce(ipip_hdr(skb));
32}
33
34/* Add encapsulation header.
35 *
36 * The top IP header will be constructed per RFC 2401.  The following fields
37 * in it shall be filled in by x->type->output:
38 *	payload_len
39 *
40 * On exit, skb->h will be set to the start of the encapsulation header to be
41 * filled in by x->type->output and skb->nh will be set to the nextheader field
42 * of the extension header directly preceding the encapsulation header, or in
43 * its absence, that of the top IP header.  The value of skb->data will always
44 * point to the top IP header.
45 */
46static int xfrm6_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
47{
48	struct dst_entry *dst = skb->dst;
49	struct xfrm_dst *xdst = (struct xfrm_dst*)dst;
50	struct ipv6hdr *iph, *top_iph;
51	int dsfield;
52
53	skb_push(skb, x->props.header_len);
54	iph = ipv6_hdr(skb);
55
56	skb_reset_network_header(skb);
57	top_iph = ipv6_hdr(skb);
58	skb->transport_header = skb->network_header + sizeof(struct ipv6hdr);
59	skb->network_header   += offsetof(struct ipv6hdr, nexthdr);
60
61	top_iph->version = 6;
62	if (xdst->route->ops->family == AF_INET6) {
63		top_iph->priority = iph->priority;
64		top_iph->flow_lbl[0] = iph->flow_lbl[0];
65		top_iph->flow_lbl[1] = iph->flow_lbl[1];
66		top_iph->flow_lbl[2] = iph->flow_lbl[2];
67		top_iph->nexthdr = IPPROTO_IPV6;
68	} else {
69		top_iph->priority = 0;
70		top_iph->flow_lbl[0] = 0;
71		top_iph->flow_lbl[1] = 0;
72		top_iph->flow_lbl[2] = 0;
73		top_iph->nexthdr = IPPROTO_IPIP;
74	}
75	dsfield = ipv6_get_dsfield(top_iph);
76	dsfield = INET_ECN_encapsulate(dsfield, dsfield);
77	if (x->props.flags & XFRM_STATE_NOECN)
78		dsfield &= ~INET_ECN_MASK;
79	ipv6_change_dsfield(top_iph, 0, dsfield);
80	top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
81	ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
82	ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
83	skb->protocol = htons(ETH_P_IPV6);
84	return 0;
85}
86
87static int xfrm6_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
88{
89	int err = -EINVAL;
90	const unsigned char *old_mac;
91	const unsigned char *nh = skb_network_header(skb);
92
93	if (nh[IP6CB(skb)->nhoff] != IPPROTO_IPV6 &&
94	    nh[IP6CB(skb)->nhoff] != IPPROTO_IPIP)
95		goto out;
96	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
97		goto out;
98
99	if (skb_cloned(skb) &&
100	    (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
101		goto out;
102
103	nh = skb_network_header(skb);
104	if (nh[IP6CB(skb)->nhoff] == IPPROTO_IPV6) {
105		if (x->props.flags & XFRM_STATE_DECAP_DSCP)
106			ipv6_copy_dscp(ipv6_hdr(skb), ipipv6_hdr(skb));
107		if (!(x->props.flags & XFRM_STATE_NOECN))
108			ipip6_ecn_decapsulate(skb);
109	} else {
110		if (!(x->props.flags & XFRM_STATE_NOECN))
111			ip6ip_ecn_decapsulate(skb);
112		skb->protocol = htons(ETH_P_IP);
113	}
114	old_mac = skb_mac_header(skb);
115	skb_set_mac_header(skb, -skb->mac_len);
116	memmove(skb_mac_header(skb), old_mac, skb->mac_len);
117	skb_reset_network_header(skb);
118	err = 0;
119
120out:
121	return err;
122}
123
124static struct xfrm_mode xfrm6_tunnel_mode = {
125	.input = xfrm6_tunnel_input,
126	.output = xfrm6_tunnel_output,
127	.owner = THIS_MODULE,
128	.encap = XFRM_MODE_TUNNEL,
129};
130
131static int __init xfrm6_tunnel_init(void)
132{
133	return xfrm_register_mode(&xfrm6_tunnel_mode, AF_INET6);
134}
135
136static void __exit xfrm6_tunnel_exit(void)
137{
138	int err;
139
140	err = xfrm_unregister_mode(&xfrm6_tunnel_mode, AF_INET6);
141	BUG_ON(err);
142}
143
144module_init(xfrm6_tunnel_init);
145module_exit(xfrm6_tunnel_exit);
146MODULE_LICENSE("GPL");
147MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TUNNEL);
148