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 disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
48 if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
49 top_iph->tos = 0;
50 else
51 top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
52 top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
53 XFRM_MODE_SKB_CB(skb)->tos);
54
55 flags = x->props.flags;
56 if (flags & XFRM_STATE_NOECN)
57 IP_ECN_clear(top_iph);
58
59 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
60 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
61
62 top_iph->ttl = ip4_dst_hoplimit(dst->child);
63
64 top_iph->saddr = x->props.saddr.a4;
65 top_iph->daddr = x->id.daddr.a4;
66 ip_select_ident(dev_net(dst->dev), skb, NULL);
67
68 return 0;
69 }
70
xfrm4_mode_tunnel_input(struct xfrm_state * x,struct sk_buff * skb)71 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
72 {
73 int err = -EINVAL;
74
75 if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
76 goto out;
77
78 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
79 goto out;
80
81 err = skb_unclone(skb, GFP_ATOMIC);
82 if (err)
83 goto out;
84
85 if (x->props.flags & XFRM_STATE_DECAP_DSCP)
86 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
87 if (!(x->props.flags & XFRM_STATE_NOECN))
88 ipip_ecn_decapsulate(skb);
89
90 skb_reset_network_header(skb);
91 skb_mac_header_rebuild(skb);
92
93 err = 0;
94
95 out:
96 return err;
97 }
98
99 static struct xfrm_mode xfrm4_tunnel_mode = {
100 .input2 = xfrm4_mode_tunnel_input,
101 .input = xfrm_prepare_input,
102 .output2 = xfrm4_mode_tunnel_output,
103 .output = xfrm4_prepare_output,
104 .owner = THIS_MODULE,
105 .encap = XFRM_MODE_TUNNEL,
106 .flags = XFRM_MODE_FLAG_TUNNEL,
107 };
108
xfrm4_mode_tunnel_init(void)109 static int __init xfrm4_mode_tunnel_init(void)
110 {
111 return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
112 }
113
xfrm4_mode_tunnel_exit(void)114 static void __exit xfrm4_mode_tunnel_exit(void)
115 {
116 int err;
117
118 err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
119 BUG_ON(err);
120 }
121
122 module_init(xfrm4_mode_tunnel_init);
123 module_exit(xfrm4_mode_tunnel_exit);
124 MODULE_LICENSE("GPL");
125 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
126