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/net/ipv4/xfrm4_mode_transport.c

http://github.com/mirrors/linux
C | 80 lines | 52 code | 10 blank | 18 comment | 2 complexity | da1c024ff03b0b9dcaaa28d4c83f400b MD5 | raw file
 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 */
21static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
22{
23	struct iphdr *iph = ip_hdr(skb);
24	int ihl = iph->ihl * 4;
25
26	skb_set_network_header(skb, -x->props.header_len);
27	skb->mac_header = skb->network_header +
28			  offsetof(struct iphdr, protocol);
29	skb->transport_header = skb->network_header + ihl;
30	__skb_pull(skb, ihl);
31	memmove(skb_network_header(skb), iph, ihl);
32	return 0;
33}
34
35/* Remove encapsulation header.
36 *
37 * The IP header will be moved over the top of the encapsulation header.
38 *
39 * On entry, skb->h shall point to where the IP header should be and skb->nh
40 * shall be set to where the IP header currently is.  skb->data shall point
41 * to the start of the payload.
42 */
43static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
44{
45	int ihl = skb->data - skb_transport_header(skb);
46
47	if (skb->transport_header != skb->network_header) {
48		memmove(skb_transport_header(skb),
49			skb_network_header(skb), ihl);
50		skb->network_header = skb->transport_header;
51	}
52	ip_hdr(skb)->tot_len = htons(skb->len + ihl);
53	skb_reset_transport_header(skb);
54	return 0;
55}
56
57static struct xfrm_mode xfrm4_transport_mode = {
58	.input = xfrm4_transport_input,
59	.output = xfrm4_transport_output,
60	.owner = THIS_MODULE,
61	.encap = XFRM_MODE_TRANSPORT,
62};
63
64static int __init xfrm4_transport_init(void)
65{
66	return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
67}
68
69static void __exit xfrm4_transport_exit(void)
70{
71	int err;
72
73	err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
74	BUG_ON(err);
75}
76
77module_init(xfrm4_transport_init);
78module_exit(xfrm4_transport_exit);
79MODULE_LICENSE("GPL");
80MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);