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
ipip_ecn_decapsulate(struct sk_buff * skb)18 static 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 */
xfrm4_mode_tunnel_output(struct xfrm_state * x,struct sk_buff * skb)30 static 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_network_header(skb, -x->props.header_len);
37 skb->mac_header = skb->network_header +
38 offsetof(struct iphdr, protocol);
39 skb->transport_header = skb->network_header + sizeof(*top_iph);
40 top_iph = ip_hdr(skb);
41
42 top_iph->ihl = 5;
43 top_iph->version = 4;
44
45 top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
46
47 /* DS disclosed */
48 top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,
49 XFRM_MODE_SKB_CB(skb)->tos);
50
51 flags = x->props.flags;
52 if (flags & XFRM_STATE_NOECN)
53 IP_ECN_clear(top_iph);
54
55 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
56 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
57 ip_select_ident(top_iph, dst->child, NULL);
58
59 top_iph->ttl = ip4_dst_hoplimit(dst->child);
60
61 top_iph->saddr = x->props.saddr.a4;
62 top_iph->daddr = x->id.daddr.a4;
63
64 return 0;
65 }
66
xfrm4_mode_tunnel_input(struct xfrm_state * x,struct sk_buff * skb)67 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
68 {
69 int err = -EINVAL;
70
71 if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
72 goto out;
73
74 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
75 goto out;
76
77 if (skb_cloned(skb) &&
78 (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
79 goto out;
80
81 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
82 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
83 if (!(x->props.flags & XFRM_STATE_NOECN))
84 ipip_ecn_decapsulate(skb);
85
86 skb_reset_network_header(skb);
87 skb_mac_header_rebuild(skb);
88
89 err = 0;
90
91 out:
92 return err;
93 }
94
95 static struct xfrm_mode xfrm4_tunnel_mode = {
96 .input2 = xfrm4_mode_tunnel_input,
97 .input = xfrm_prepare_input,
98 .output2 = xfrm4_mode_tunnel_output,
99 .output = xfrm4_prepare_output,
100 .owner = THIS_MODULE,
101 .encap = XFRM_MODE_TUNNEL,
102 .flags = XFRM_MODE_FLAG_TUNNEL,
103 };
104
xfrm4_mode_tunnel_init(void)105 static int __init xfrm4_mode_tunnel_init(void)
106 {
107 return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
108 }
109
xfrm4_mode_tunnel_exit(void)110 static void __exit xfrm4_mode_tunnel_exit(void)
111 {
112 int err;
113
114 err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
115 BUG_ON(err);
116 }
117
118 module_init(xfrm4_mode_tunnel_init);
119 module_exit(xfrm4_mode_tunnel_exit);
120 MODULE_LICENSE("GPL");
121 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
122