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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Patrick McHardy16a66772006-01-06 23:01:48 -080011#include <linux/compiler.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070012#include <linux/skbuff.h>
13#include <linux/spinlock.h>
Patrick McHardy16a66772006-01-06 23:01:48 -080014#include <linux/netfilter_ipv4.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#include <net/inet_ecn.h>
16#include <net/ip.h>
17#include <net/xfrm.h>
18#include <net/icmp.h>
19
20/* Add encapsulation header.
21 *
22 * In transport mode, the IP header will be moved forward to make space
23 * for the encapsulation header.
24 *
25 * In tunnel mode, the top IP header will be constructed per RFC 2401.
26 * The following fields in it shall be filled in by x->type->output:
27 * tot_len
28 * check
29 *
30 * On exit, skb->h will be set to the start of the payload to be processed
31 * by x->type->output and skb->nh will be set to the top IP header.
32 */
33static void xfrm4_encap(struct sk_buff *skb)
34{
35 struct dst_entry *dst = skb->dst;
36 struct xfrm_state *x = dst->xfrm;
37 struct iphdr *iph, *top_iph;
Herbert Xudd871472005-06-20 13:21:43 -070038 int flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -070039
40 iph = skb->nh.iph;
41 skb->h.ipiph = iph;
42
43 skb->nh.raw = skb_push(skb, x->props.header_len);
44 top_iph = skb->nh.iph;
45
46 if (!x->props.mode) {
47 skb->h.raw += iph->ihl*4;
48 memmove(top_iph, iph, iph->ihl*4);
49 return;
50 }
51
52 top_iph->ihl = 5;
53 top_iph->version = 4;
54
55 /* DS disclosed */
56 top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
Herbert Xudd871472005-06-20 13:21:43 -070057
58 flags = x->props.flags;
59 if (flags & XFRM_STATE_NOECN)
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 IP_ECN_clear(top_iph);
61
Herbert Xudd871472005-06-20 13:21:43 -070062 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
63 0 : (iph->frag_off & htons(IP_DF));
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 if (!top_iph->frag_off)
65 __ip_select_ident(top_iph, dst, 0);
66
67 top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
68
69 top_iph->saddr = x->props.saddr.a4;
70 top_iph->daddr = x->id.daddr.a4;
71 top_iph->protocol = IPPROTO_IPIP;
72
73 memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
74}
75
76static int xfrm4_tunnel_check_size(struct sk_buff *skb)
77{
78 int mtu, ret = 0;
79 struct dst_entry *dst;
80 struct iphdr *iph = skb->nh.iph;
81
82 if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
83 goto out;
84
85 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
86
87 if (!(iph->frag_off & htons(IP_DF)) || skb->local_df)
88 goto out;
89
90 dst = skb->dst;
91 mtu = dst_mtu(dst);
92 if (skb->len > mtu) {
93 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
94 ret = -EMSGSIZE;
95 }
96out:
97 return ret;
98}
99
Patrick McHardy16a66772006-01-06 23:01:48 -0800100static int xfrm4_output_one(struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101{
102 struct dst_entry *dst = skb->dst;
103 struct xfrm_state *x = dst->xfrm;
104 int err;
105
106 if (skb->ip_summed == CHECKSUM_HW) {
107 err = skb_checksum_help(skb, 0);
108 if (err)
109 goto error_nolock;
110 }
111
112 if (x->props.mode) {
113 err = xfrm4_tunnel_check_size(skb);
114 if (err)
115 goto error_nolock;
116 }
117
Patrick McHardy16a66772006-01-06 23:01:48 -0800118 do {
119 spin_lock_bh(&x->lock);
120 err = xfrm_state_check(x, skb);
121 if (err)
122 goto error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123
Patrick McHardy16a66772006-01-06 23:01:48 -0800124 xfrm4_encap(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
Patrick McHardy16a66772006-01-06 23:01:48 -0800126 err = x->type->output(x, skb);
127 if (err)
128 goto error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129
Patrick McHardy16a66772006-01-06 23:01:48 -0800130 x->curlft.bytes += skb->len;
131 x->curlft.packets++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132
Patrick McHardy16a66772006-01-06 23:01:48 -0800133 spin_unlock_bh(&x->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134
Patrick McHardy16a66772006-01-06 23:01:48 -0800135 if (!(skb->dst = dst_pop(dst))) {
136 err = -EHOSTUNREACH;
137 goto error_nolock;
138 }
139 dst = skb->dst;
140 x = dst->xfrm;
141 } while (x && !x->props.mode);
142
Patrick McHardy3e3850e2006-01-06 23:04:54 -0800143 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
Patrick McHardy16a66772006-01-06 23:01:48 -0800144 err = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145
146out_exit:
147 return err;
148error:
149 spin_unlock_bh(&x->lock);
150error_nolock:
151 kfree_skb(skb);
152 goto out_exit;
153}
Patrick McHardy16a66772006-01-06 23:01:48 -0800154
Patrick McHardy48d5cad2006-02-15 15:10:22 -0800155static int xfrm4_output_finish(struct sk_buff *skb)
Patrick McHardy16a66772006-01-06 23:01:48 -0800156{
157 int err;
158
Patrick McHardy48d5cad2006-02-15 15:10:22 -0800159#ifdef CONFIG_NETFILTER
160 if (!skb->dst->xfrm) {
161 IPCB(skb)->flags |= IPSKB_REROUTED;
162 return dst_output(skb);
163 }
164#endif
Patrick McHardy16a66772006-01-06 23:01:48 -0800165 while (likely((err = xfrm4_output_one(skb)) == 0)) {
166 nf_reset(skb);
167
168 err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, &skb, NULL,
169 skb->dst->dev, dst_output);
170 if (unlikely(err != 1))
171 break;
172
173 if (!skb->dst->xfrm)
174 return dst_output(skb);
175
176 err = nf_hook(PF_INET, NF_IP_POST_ROUTING, &skb, NULL,
177 skb->dst->dev, xfrm4_output_finish);
178 if (unlikely(err != 1))
179 break;
180 }
181
182 return err;
183}
184
185int xfrm4_output(struct sk_buff *skb)
186{
Patrick McHardy48d5cad2006-02-15 15:10:22 -0800187 return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
188 xfrm4_output_finish,
189 !(IPCB(skb)->flags & IPSKB_REROUTED));
Patrick McHardy16a66772006-01-06 23:01:48 -0800190}