1/*
2 * xfrm4_mode_transport.c - Transport mode encapsulation for IPv4.
3 *
4 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
5 */
6
7#include <linux/init.h>
8#include <linux/kernel.h>
9#include <linux/module.h>
10#include <linux/skbuff.h>
11#include <linux/stringify.h>
12#include <net/dst.h>
13#include <net/ip.h>
14#include <net/xfrm.h>
15
16/* Add encapsulation header.
17 *
18 * The IP header will be moved forward to make space for the encapsulation
19 * header.
20 *
21 * On exit, skb->h will be set to the start of the payload to be processed
22 * by x->type->output and skb->nh will be set to the top IP header.
23 */
24static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
25{
26	struct iphdr *iph = ip_hdr(skb);
27	int ihl = iph->ihl * 4;
28
29	skb->transport_header = skb->network_header + ihl;
30	skb_push(skb, x->props.header_len);
31	skb_reset_network_header(skb);
32	memmove(skb_network_header(skb), iph, ihl);
33	return 0;
34}
35
36/* Remove encapsulation header.
37 *
38 * The IP header will be moved over the top of the encapsulation header.
39 *
40 * On entry, skb->h shall point to where the IP header should be and skb->nh
41 * shall be set to where the IP header currently is.  skb->data shall point
42 * to the start of the payload.
43 */
44static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
45{
46	int ihl = skb->data - skb_transport_header(skb);
47
48	if (skb->transport_header != skb->network_header) {
49		memmove(skb_transport_header(skb),
50			skb_network_header(skb), ihl);
51		skb->network_header = skb->transport_header;
52	}
53	ip_hdr(skb)->tot_len = htons(skb->len + ihl);
54	skb_reset_transport_header(skb);
55	return 0;
56}
57
58static struct xfrm_mode xfrm4_transport_mode = {
59	.input = xfrm4_transport_input,
60	.output = xfrm4_transport_output,
61	.owner = THIS_MODULE,
62	.encap = XFRM_MODE_TRANSPORT,
63};
64
65static int __init xfrm4_transport_init(void)
66{
67	return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
68}
69
70static void __exit xfrm4_transport_exit(void)
71{
72	int err;
73
74	err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
75	BUG_ON(err);
76}
77
78module_init(xfrm4_transport_init);
79module_exit(xfrm4_transport_exit);
80MODULE_LICENSE("GPL");
81MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);
82