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 */
xfrm4_transport_output(struct xfrm_state * x,struct sk_buff * skb)21 static 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 */
xfrm4_transport_input(struct xfrm_state * x,struct sk_buff * skb)43 static 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
57 static 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
xfrm4_transport_init(void)64 static int __init xfrm4_transport_init(void)
65 {
66 return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
67 }
68
xfrm4_transport_exit(void)69 static 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
77 module_init(xfrm4_transport_init);
78 module_exit(xfrm4_transport_exit);
79 MODULE_LICENSE("GPL");
80 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);
81