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
21static int xfrm4_tunnel_check_size(struct sk_buff *skb)
22{
23	int mtu, ret = 0;
24
25	if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
26		goto out;
27
28	if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->ignore_df)
29		goto out;
30
31	mtu = dst_mtu(skb_dst(skb));
32	if (skb->len > mtu) {
33		if (skb->sk)
34			xfrm_local_error(skb, mtu);
35		else
36			icmp_send(skb, ICMP_DEST_UNREACH,
37				  ICMP_FRAG_NEEDED, htonl(mtu));
38		ret = -EMSGSIZE;
39	}
40out:
41	return ret;
42}
43
44int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
45{
46	int err;
47
48	err = xfrm4_tunnel_check_size(skb);
49	if (err)
50		return err;
51
52	XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
53
54	return xfrm4_extract_header(skb);
55}
56
57int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
58{
59	int err;
60
61	err = xfrm_inner_extract_output(x, skb);
62	if (err)
63		return err;
64
65	IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
66	skb->protocol = htons(ETH_P_IP);
67
68	return x->outer_mode->output2(x, skb);
69}
70EXPORT_SYMBOL(xfrm4_prepare_output);
71
72int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)
73{
74	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
75
76#ifdef CONFIG_NETFILTER
77	IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
78#endif
79
80	return xfrm_output(sk, skb);
81}
82
83static int __xfrm4_output(struct sock *sk, struct sk_buff *skb)
84{
85	struct xfrm_state *x = skb_dst(skb)->xfrm;
86
87#ifdef CONFIG_NETFILTER
88	if (!x) {
89		IPCB(skb)->flags |= IPSKB_REROUTED;
90		return dst_output_sk(sk, skb);
91	}
92#endif
93
94	return x->outer_mode->afinfo->output_finish(sk, skb);
95}
96
97int xfrm4_output(struct sock *sk, struct sk_buff *skb)
98{
99	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, sk, skb,
100			    NULL, skb_dst(skb)->dev, __xfrm4_output,
101			    !(IPCB(skb)->flags & IPSKB_REROUTED));
102}
103
104void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
105{
106	struct iphdr *hdr;
107
108	hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
109	ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
110		       inet_sk(skb->sk)->inet_dport, mtu);
111}
112