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_is_gso(skb) && skb->len > mtu) ||
33 (skb_is_gso(skb) &&
34 !skb_gso_validate_network_len(skb, ip_skb_dst_mtu(skb->sk, skb)))) {
35 skb->protocol = htons(ETH_P_IP);
36
37 if (skb->sk)
38 xfrm_local_error(skb, mtu);
39 else
40 icmp_send(skb, ICMP_DEST_UNREACH,
41 ICMP_FRAG_NEEDED, htonl(mtu));
42 ret = -EMSGSIZE;
43 }
44out:
45 return ret;
46}
47
48int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
49{
50 int err;
51
52 err = xfrm4_tunnel_check_size(skb);
53 if (err)
54 return err;
55
56 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
57
58 return xfrm4_extract_header(skb);
59}
60
61int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
62{
63 int err;
64
65 err = xfrm_inner_extract_output(x, skb);
66 if (err)
67 return err;
68
69 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
70 skb->protocol = htons(ETH_P_IP);
71
72 return x->outer_mode->output2(x, skb);
73}
74EXPORT_SYMBOL(xfrm4_prepare_output);
75
76int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)
77{
78 memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
79
80#ifdef CONFIG_NETFILTER
81 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
82#endif
83
84 return xfrm_output(sk, skb);
85}
86
87static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
88{
89 struct xfrm_state *x = skb_dst(skb)->xfrm;
90
91#ifdef CONFIG_NETFILTER
92 if (!x) {
93 IPCB(skb)->flags |= IPSKB_REROUTED;
94 return dst_output(net, sk, skb);
95 }
96#endif
97
98 return x->outer_mode->afinfo->output_finish(sk, skb);
99}
100
101int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
102{
103 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
104 net, sk, skb, NULL, skb_dst(skb)->dev,
105 __xfrm4_output,
106 !(IPCB(skb)->flags & IPSKB_REROUTED));
107}
108
109void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
110{
111 struct iphdr *hdr;
112
113 hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
114 ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
115 inet_sk(skb->sk)->inet_dport, mtu);
116}
117