[IPSEC] xfrm: Abstract out encapsulation modes
[linux-2.6.git] / net / ipv4 / xfrm4_output.c
1 /*
2  * xfrm4_output.c - Common IPsec encapsulation code for IPv4.
3  * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
4  * 
5  * This program is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU General Public License
7  * as published by the Free Software Foundation; either version
8  * 2 of the License, or (at your option) any later version.
9  */
10
11 #include <linux/compiler.h>
12 #include <linux/skbuff.h>
13 #include <linux/spinlock.h>
14 #include <linux/netfilter_ipv4.h>
15 #include <net/ip.h>
16 #include <net/xfrm.h>
17 #include <net/icmp.h>
18
19 static int xfrm4_tunnel_check_size(struct sk_buff *skb)
20 {
21         int mtu, ret = 0;
22         struct dst_entry *dst;
23         struct iphdr *iph = skb->nh.iph;
24
25         if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
26                 goto out;
27
28         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
29         
30         if (!(iph->frag_off & htons(IP_DF)) || skb->local_df)
31                 goto out;
32
33         dst = skb->dst;
34         mtu = dst_mtu(dst);
35         if (skb->len > mtu) {
36                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
37                 ret = -EMSGSIZE;
38         }
39 out:
40         return ret;
41 }
42
43 static int xfrm4_output_one(struct sk_buff *skb)
44 {
45         struct dst_entry *dst = skb->dst;
46         struct xfrm_state *x = dst->xfrm;
47         int err;
48         
49         if (skb->ip_summed == CHECKSUM_HW) {
50                 err = skb_checksum_help(skb, 0);
51                 if (err)
52                         goto error_nolock;
53         }
54
55         if (x->props.mode) {
56                 err = xfrm4_tunnel_check_size(skb);
57                 if (err)
58                         goto error_nolock;
59         }
60
61         do {
62                 spin_lock_bh(&x->lock);
63                 err = xfrm_state_check(x, skb);
64                 if (err)
65                         goto error;
66
67                 err = x->mode->output(skb);
68                 if (err)
69                         goto error;
70
71                 err = x->type->output(x, skb);
72                 if (err)
73                         goto error;
74
75                 x->curlft.bytes += skb->len;
76                 x->curlft.packets++;
77
78                 spin_unlock_bh(&x->lock);
79         
80                 if (!(skb->dst = dst_pop(dst))) {
81                         err = -EHOSTUNREACH;
82                         goto error_nolock;
83                 }
84                 dst = skb->dst;
85                 x = dst->xfrm;
86         } while (x && !x->props.mode);
87
88         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
89         err = 0;
90
91 out_exit:
92         return err;
93 error:
94         spin_unlock_bh(&x->lock);
95 error_nolock:
96         kfree_skb(skb);
97         goto out_exit;
98 }
99
100 static int xfrm4_output_finish(struct sk_buff *skb)
101 {
102         int err;
103
104 #ifdef CONFIG_NETFILTER
105         if (!skb->dst->xfrm) {
106                 IPCB(skb)->flags |= IPSKB_REROUTED;
107                 return dst_output(skb);
108         }
109 #endif
110         while (likely((err = xfrm4_output_one(skb)) == 0)) {
111                 nf_reset(skb);
112
113                 err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, &skb, NULL,
114                               skb->dst->dev, dst_output);
115                 if (unlikely(err != 1))
116                         break;
117
118                 if (!skb->dst->xfrm)
119                         return dst_output(skb);
120
121                 err = nf_hook(PF_INET, NF_IP_POST_ROUTING, &skb, NULL,
122                               skb->dst->dev, xfrm4_output_finish);
123                 if (unlikely(err != 1))
124                         break;
125         }
126
127         return err;
128 }
129
130 int xfrm4_output(struct sk_buff *skb)
131 {
132         return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
133                             xfrm4_output_finish,
134                             !(IPCB(skb)->flags & IPSKB_REROUTED));
135 }