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 *
22 * On exit, skb->h will be set to the start of the encapsulation header to be
23 * filled in by x->type->output and skb->nh will be set to the nextheader field
24 * of the extension header directly preceding the encapsulation header, or in
25 * its absence, that of the top IP header.  The value of skb->data will always
26 * point to the top IP header.
27 */
28static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
29{
30	struct ipv6hdr *iph;
31	u8 *prevhdr;
32	int hdr_len;
33
34	skb_push(skb, x->props.header_len);
35	iph = ipv6_hdr(skb);
36
37	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
38	skb_set_network_header(skb,
39			       (prevhdr - x->props.header_len) - skb->data);
40	skb_set_transport_header(skb, hdr_len);
41	memmove(skb->data, iph, hdr_len);
42	return 0;
43}
44
45/* Remove encapsulation header.
46 *
47 * The IP header will be moved over the top of the encapsulation header.
48 *
49 * On entry, skb->h shall point to where the IP header should be and skb->nh
50 * shall be set to where the IP header currently is.  skb->data shall point
51 * to the start of the payload.
52 */
53static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
54{
55	int ihl = skb->data - skb_transport_header(skb);
56
57	if (skb->transport_header != skb->network_header) {
58		memmove(skb_transport_header(skb),
59			skb_network_header(skb), ihl);
60		skb->network_header = skb->transport_header;
61	}
62	ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
63					   sizeof(struct ipv6hdr));
64	skb_reset_transport_header(skb);
65	return 0;
66}
67
68static struct xfrm_mode xfrm6_transport_mode = {
69	.input = xfrm6_transport_input,
70	.output = xfrm6_transport_output,
71	.owner = THIS_MODULE,
72	.encap = XFRM_MODE_TRANSPORT,
73};
74
75static int __init xfrm6_transport_init(void)
76{
77	return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
78}
79
80static void __exit xfrm6_transport_exit(void)
81{
82	int err;
83
84	err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
85	BUG_ON(err);
86}
87
88module_init(xfrm6_transport_init);
89module_exit(xfrm6_transport_exit);
90MODULE_LICENSE("GPL");
91MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);
92