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#include <net/protocol.h>
16
17/* Add encapsulation header.
18 *
19 * The IP header will be moved forward to make space for the encapsulation
20 * header.
21 */
22static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
23{
24 struct iphdr *iph = ip_hdr(skb);
25 int ihl = iph->ihl * 4;
26
27 skb_set_inner_transport_header(skb, skb_transport_offset(skb));
28
29 skb_set_network_header(skb, -x->props.header_len);
30 skb->mac_header = skb->network_header +
31 offsetof(struct iphdr, protocol);
32 skb->transport_header = skb->network_header + ihl;
33 __skb_pull(skb, ihl);
34 memmove(skb_network_header(skb), iph, ihl);
35 return 0;
36}
37
38/* Remove encapsulation header.
39 *
40 * The IP header will be moved over the top of the encapsulation header.
41 *
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.
45 */
46static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
47{
48 int ihl = skb->data - skb_transport_header(skb);
49
50 if (skb->transport_header != skb->network_header) {
51 memmove(skb_transport_header(skb),
52 skb_network_header(skb), ihl);
53 skb->network_header = skb->transport_header;
54 }
55 ip_hdr(skb)->tot_len = htons(skb->len + ihl);
56 skb_reset_transport_header(skb);
57 return 0;
58}
59
60static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
61 struct sk_buff *skb,
62 netdev_features_t features)
63{
64 const struct net_offload *ops;
65 struct sk_buff *segs = ERR_PTR(-EINVAL);
66 struct xfrm_offload *xo = xfrm_offload(skb);
67
68 skb->transport_header += x->props.header_len;
69 ops = rcu_dereference(inet_offloads[xo->proto]);
70 if (likely(ops && ops->callbacks.gso_segment))
71 segs = ops->callbacks.gso_segment(skb, features);
72
73 return segs;
74}
75
76static void xfrm4_transport_xmit(struct xfrm_state *x, struct sk_buff *skb)
77{
78 struct xfrm_offload *xo = xfrm_offload(skb);
79
80 skb_reset_mac_len(skb);
81 pskb_pull(skb, skb->mac_len + sizeof(struct iphdr) + x->props.header_len);
82
83 if (xo->flags & XFRM_GSO_SEGMENT) {
84 skb_reset_transport_header(skb);
85 skb->transport_header -= x->props.header_len;
86 }
87}
88
89static struct xfrm_mode xfrm4_transport_mode = {
90 .input = xfrm4_transport_input,
91 .output = xfrm4_transport_output,
92 .gso_segment = xfrm4_transport_gso_segment,
93 .xmit = xfrm4_transport_xmit,
94 .owner = THIS_MODULE,
95 .encap = XFRM_MODE_TRANSPORT,
96};
97
98static int __init xfrm4_transport_init(void)
99{
100 return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
101}
102
103static void __exit xfrm4_transport_exit(void)
104{
105 int err;
106
107 err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
108 BUG_ON(err);
109}
110
111module_init(xfrm4_transport_init);
112module_exit(xfrm4_transport_exit);
113MODULE_LICENSE("GPL");
114MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);
115