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
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 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
36 ret = -EMSGSIZE;
37 }
38 out:
39 return ret;
40 }
41
42 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
43 {
44 int err;
45
46 err = xfrm4_tunnel_check_size(skb);
47 if (err)
48 return err;
49
50 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
51
52 return xfrm4_extract_header(skb);
53 }
54
55 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
56 {
57 int err;
58
59 err = xfrm_inner_extract_output(x, skb);
60 if (err)
61 return err;
62
63 memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
64 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED;
65
66 skb->protocol = htons(ETH_P_IP);
67
68 return x->outer_mode->output2(x, skb);
69 }
70 EXPORT_SYMBOL(xfrm4_prepare_output);
71
72 static int xfrm4_output_finish(struct sk_buff *skb)
73 {
74 #ifdef CONFIG_NETFILTER
75 if (!skb_dst(skb)->xfrm) {
76 IPCB(skb)->flags |= IPSKB_REROUTED;
77 return dst_output(skb);
78 }
79
80 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
81 #endif
82
83 skb->protocol = htons(ETH_P_IP);
84 return xfrm_output(skb);
85 }
86
87 int xfrm4_output(struct sk_buff *skb)
88 {
89 return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb,
90 NULL, skb_dst(skb)->dev, xfrm4_output_finish,
91 !(IPCB(skb)->flags & IPSKB_REROUTED));
92 }
93
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