2 * xfrm4_mode_transport.c - Transport mode encapsulation for IPv4.
4 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
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>
16 /* Add encapsulation header.
18 * The IP header will be moved forward to make space for the encapsulation
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.
24 static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
26 struct iphdr *iph = ip_hdr(skb);
27 int ihl = iph->ihl * 4;
29 skb->h.raw = skb->nh.raw;
32 skb_push(skb, x->props.header_len);
33 skb_reset_network_header(skb);
34 memmove(skb_network_header(skb), iph, ihl);
38 /* Remove encapsulation header.
40 * The IP header will be moved over the top of the encapsulation header.
42 * On entry, skb->h shall point to where the IP header should be and skb->nh
43 * shall be set to where the IP header currently is. skb->data shall point
44 * to the start of the payload.
46 static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
48 int ihl = skb->data - skb->h.raw;
50 if (skb->h.raw != skb->nh.raw) {
51 memmove(skb->h.raw, skb_network_header(skb), ihl);
52 skb->nh.raw = skb->h.raw;
54 ip_hdr(skb)->tot_len = htons(skb->len + ihl);
55 skb->h.raw = skb->data;
59 static struct xfrm_mode xfrm4_transport_mode = {
60 .input = xfrm4_transport_input,
61 .output = xfrm4_transport_output,
63 .encap = XFRM_MODE_TRANSPORT,
66 static int __init xfrm4_transport_init(void)
68 return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
71 static void __exit xfrm4_transport_exit(void)
75 err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
79 module_init(xfrm4_transport_init);
80 module_exit(xfrm4_transport_exit);
81 MODULE_LICENSE("GPL");
82 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);