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/if_ether.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
15 #include <linux/netfilter_ipv4.h>
16 #include <net/dst.h>
17 #include <net/ip.h>
18 #include <net/xfrm.h>
19 #include <net/icmp.h>
20
xfrm4_tunnel_check_size(struct sk_buff * skb)21 static int xfrm4_tunnel_check_size(struct sk_buff *skb)
22 {
23 int mtu, ret = 0;
24 struct dst_entry *dst;
25
26 if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
27 goto out;
28
29 if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->local_df)
30 goto out;
31
32 dst = skb_dst(skb);
33 mtu = dst_mtu(dst);
34 if (skb->len > mtu) {
35 if (skb->sk)
36 ip_local_error(skb->sk, EMSGSIZE, ip_hdr(skb)->daddr,
37 inet_sk(skb->sk)->inet_dport, mtu);
38 else
39 icmp_send(skb, ICMP_DEST_UNREACH,
40 ICMP_FRAG_NEEDED, htonl(mtu));
41 ret = -EMSGSIZE;
42 }
43 out:
44 return ret;
45 }
46
xfrm4_extract_output(struct xfrm_state * x,struct sk_buff * skb)47 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
48 {
49 int err;
50
51 err = xfrm4_tunnel_check_size(skb);
52 if (err)
53 return err;
54
55 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
56
57 return xfrm4_extract_header(skb);
58 }
59
xfrm4_prepare_output(struct xfrm_state * x,struct sk_buff * skb)60 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
61 {
62 int err;
63
64 err = xfrm_inner_extract_output(x, skb);
65 if (err)
66 return err;
67
68 memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
69 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED;
70
71 skb->protocol = htons(ETH_P_IP);
72
73 return x->outer_mode->output2(x, skb);
74 }
75 EXPORT_SYMBOL(xfrm4_prepare_output);
76
xfrm4_output_finish(struct sk_buff * skb)77 int xfrm4_output_finish(struct sk_buff *skb)
78 {
79 #ifdef CONFIG_NETFILTER
80 if (!skb_dst(skb)->xfrm) {
81 IPCB(skb)->flags |= IPSKB_REROUTED;
82 return dst_output(skb);
83 }
84
85 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
86 #endif
87
88 skb->protocol = htons(ETH_P_IP);
89 return xfrm_output(skb);
90 }
91
xfrm4_output(struct sk_buff * skb)92 int xfrm4_output(struct sk_buff *skb)
93 {
94 struct dst_entry *dst = skb_dst(skb);
95 struct xfrm_state *x = dst->xfrm;
96
97 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb,
98 NULL, dst->dev,
99 x->outer_mode->afinfo->output_finish,
100 !(IPCB(skb)->flags & IPSKB_REROUTED));
101 }
102