1/*
2 * xfrm6_mode_transport.c - Transport 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/dst.h>
14#include <net/ipv6.h>
15#include <net/xfrm.h>
16
17/* Add encapsulation header.
18 *
19 * The IP header and mutable extension headers will be moved forward to make
20 * space for the encapsulation header.
21 */
22static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
23{
24	struct ipv6hdr *iph;
25	u8 *prevhdr;
26	int hdr_len;
27
28	iph = ipv6_hdr(skb);
29
30	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
31	skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
32	skb_set_network_header(skb, -x->props.header_len);
33	skb->transport_header = skb->network_header + hdr_len;
34	__skb_pull(skb, hdr_len);
35	memmove(ipv6_hdr(skb), iph, hdr_len);
36	return 0;
37}
38
39/* Remove encapsulation header.
40 *
41 * The IP header will be moved over the top of the encapsulation header.
42 *
43 * On entry, skb->h shall point to where the IP header should be and skb->nh
44 * shall be set to where the IP header currently is.  skb->data shall point
45 * to the start of the payload.
46 */
47static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
48{
49	int ihl = skb->data - skb_transport_header(skb);
50
51	if (skb->transport_header != skb->network_header) {
52		memmove(skb_transport_header(skb),
53			skb_network_header(skb), ihl);
54		skb->network_header = skb->transport_header;
55	}
56	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
57					   sizeof(struct ipv6hdr));
58	skb_reset_transport_header(skb);
59	return 0;
60}
61
62static struct xfrm_mode xfrm6_transport_mode = {
63	.input = xfrm6_transport_input,
64	.output = xfrm6_transport_output,
65	.owner = THIS_MODULE,
66	.encap = XFRM_MODE_TRANSPORT,
67};
68
69static int __init xfrm6_transport_init(void)
70{
71	return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
72}
73
74static void __exit xfrm6_transport_exit(void)
75{
76	int err;
77
78	err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
79	BUG_ON(err);
80}
81
82module_init(xfrm6_transport_init);
83module_exit(xfrm6_transport_exit);
84MODULE_LICENSE("GPL");
85MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);
86