1/*
2 * xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
3 *
4 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
5 */
6
7#include <linux/gfp.h>
8#include <linux/init.h>
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/skbuff.h>
12#include <linux/stringify.h>
13#include <net/dst.h>
14#include <net/inet_ecn.h>
15#include <net/ip.h>
16#include <net/xfrm.h>
17
18static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
19{
20 struct iphdr *inner_iph = ipip_hdr(skb);
21
22 if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
23 IP_ECN_set_ce(inner_iph);
24}
25
26/* Add encapsulation header.
27 *
28 * The top IP header will be constructed per RFC 2401.
29 */
30static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
31{
32 struct dst_entry *dst = skb_dst(skb);
33 struct iphdr *top_iph;
34 int flags;
35
36 skb_set_inner_network_header(skb, skb_network_offset(skb));
37 skb_set_inner_transport_header(skb, skb_transport_offset(skb));
38
39 skb_set_network_header(skb, -x->props.header_len);
40 skb->mac_header = skb->network_header +
41 offsetof(struct iphdr, protocol);
42 skb->transport_header = skb->network_header + sizeof(*top_iph);
43 top_iph = ip_hdr(skb);
44
45 top_iph->ihl = 5;
46 top_iph->version = 4;
47
48 top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
49
50 /* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
51 if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
52 top_iph->tos = 0;
53 else
54 top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
55 top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
56 XFRM_MODE_SKB_CB(skb)->tos);
57
58 flags = x->props.flags;
59 if (flags & XFRM_STATE_NOECN)
60 IP_ECN_clear(top_iph);
61
62 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
63 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
64
65 top_iph->ttl = ip4_dst_hoplimit(xfrm_dst_child(dst));
66
67 top_iph->saddr = x->props.saddr.a4;
68 top_iph->daddr = x->id.daddr.a4;
69 ip_select_ident(dev_net(dst->dev), skb, NULL);
70
71 return 0;
72}
73
74static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
75{
76 int err = -EINVAL;
77
78 if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
79 goto out;
80
81 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
82 goto out;
83
84 err = skb_unclone(skb, GFP_ATOMIC);
85 if (err)
86 goto out;
87
88 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
89 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
90 if (!(x->props.flags & XFRM_STATE_NOECN))
91 ipip_ecn_decapsulate(skb);
92
93 skb_reset_network_header(skb);
94 skb_mac_header_rebuild(skb);
95 if (skb->mac_len)
96 eth_hdr(skb)->h_proto = skb->protocol;
97
98 err = 0;
99
100out:
101 return err;
102}
103
104static struct sk_buff *xfrm4_mode_tunnel_gso_segment(struct xfrm_state *x,
105 struct sk_buff *skb,
106 netdev_features_t features)
107{
108 __skb_push(skb, skb->mac_len);
109 return skb_mac_gso_segment(skb, features);
110}
111
112static void xfrm4_mode_tunnel_xmit(struct xfrm_state *x, struct sk_buff *skb)
113{
114 struct xfrm_offload *xo = xfrm_offload(skb);
115
116 if (xo->flags & XFRM_GSO_SEGMENT)
117 skb->transport_header = skb->network_header +
118 sizeof(struct iphdr);
119
120 skb_reset_mac_len(skb);
121 pskb_pull(skb, skb->mac_len + x->props.header_len);
122}
123
124static struct xfrm_mode xfrm4_tunnel_mode = {
125 .input2 = xfrm4_mode_tunnel_input,
126 .input = xfrm_prepare_input,
127 .output2 = xfrm4_mode_tunnel_output,
128 .output = xfrm4_prepare_output,
129 .gso_segment = xfrm4_mode_tunnel_gso_segment,
130 .xmit = xfrm4_mode_tunnel_xmit,
131 .owner = THIS_MODULE,
132 .encap = XFRM_MODE_TUNNEL,
133 .flags = XFRM_MODE_FLAG_TUNNEL,
134};
135
136static int __init xfrm4_mode_tunnel_init(void)
137{
138 return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
139}
140
141static void __exit xfrm4_mode_tunnel_exit(void)
142{
143 int err;
144
145 err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
146 BUG_ON(err);
147}
148
149module_init(xfrm4_mode_tunnel_init);
150module_exit(xfrm4_mode_tunnel_exit);
151MODULE_LICENSE("GPL");
152MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
153