ipcomp.c revision 221df1ed33c9284fc7a6f6e47ca7f8d5f3665d43 
1/*
2 * IP Payload Compression Protocol (IPComp) - RFC3173.
3 *
4 * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the Free
8 * Software Foundation; either version 2 of the License, or (at your option)
9 * any later version.
10 *
11 * Todo:
12 *   - Tunable compression parameters.
13 *   - Compression stats.
14 *   - Adaptive compression.
15 */
16#include <linux/module.h>
17#include <linux/err.h>
18#include <linux/rtnetlink.h>
19#include <net/ip.h>
20#include <net/xfrm.h>
21#include <net/icmp.h>
22#include <net/ipcomp.h>
23#include <net/protocol.h>
24#include <net/sock.h>
25
26static void ipcomp4_err(struct sk_buff *skb, u32 info)
27{
28	__be32 spi;
29	struct iphdr *iph = (struct iphdr *)skb->data;
30	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
31	struct xfrm_state *x;
32
33	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
34	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
35		return;
36
37	spi = htonl(ntohs(ipch->cpi));
38	x = xfrm_state_lookup(&init_net, (xfrm_address_t *)&iph->daddr,
39			      spi, IPPROTO_COMP, AF_INET);
40	if (!x)
41		return;
42	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%pI4\n",
43		 spi, &iph->daddr);
44	xfrm_state_put(x);
45}
46
47/* We always hold one tunnel user reference to indicate a tunnel */
48static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
49{
50	struct xfrm_state *t;
51
52	t = xfrm_state_alloc(&init_net);
53	if (t == NULL)
54		goto out;
55
56	t->id.proto = IPPROTO_IPIP;
57	t->id.spi = x->props.saddr.a4;
58	t->id.daddr.a4 = x->id.daddr.a4;
59	memcpy(&t->sel, &x->sel, sizeof(t->sel));
60	t->props.family = AF_INET;
61	t->props.mode = x->props.mode;
62	t->props.saddr.a4 = x->props.saddr.a4;
63	t->props.flags = x->props.flags;
64
65	if (xfrm_init_state(t))
66		goto error;
67
68	atomic_set(&t->tunnel_users, 1);
69out:
70	return t;
71
72error:
73	t->km.state = XFRM_STATE_DEAD;
74	xfrm_state_put(t);
75	t = NULL;
76	goto out;
77}
78
79/*
80 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
81 * always incremented on success.
82 */
83static int ipcomp_tunnel_attach(struct xfrm_state *x)
84{
85	int err = 0;
86	struct xfrm_state *t;
87
88	t = xfrm_state_lookup(&init_net, (xfrm_address_t *)&x->id.daddr.a4,
89			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
90	if (!t) {
91		t = ipcomp_tunnel_create(x);
92		if (!t) {
93			err = -EINVAL;
94			goto out;
95		}
96		xfrm_state_insert(t);
97		xfrm_state_hold(t);
98	}
99	x->tunnel = t;
100	atomic_inc(&t->tunnel_users);
101out:
102	return err;
103}
104
105static int ipcomp4_init_state(struct xfrm_state *x)
106{
107	int err = -EINVAL;
108
109	x->props.header_len = 0;
110	switch (x->props.mode) {
111	case XFRM_MODE_TRANSPORT:
112		break;
113	case XFRM_MODE_TUNNEL:
114		x->props.header_len += sizeof(struct iphdr);
115		break;
116	default:
117		goto out;
118	}
119
120	err = ipcomp_init_state(x);
121	if (err)
122		goto out;
123
124	if (x->props.mode == XFRM_MODE_TUNNEL) {
125		err = ipcomp_tunnel_attach(x);
126		if (err)
127			goto error_tunnel;
128	}
129
130	err = 0;
131out:
132	return err;
133
134error_tunnel:
135	ipcomp_destroy(x);
136	goto out;
137}
138
139static const struct xfrm_type ipcomp_type = {
140	.description	= "IPCOMP4",
141	.owner		= THIS_MODULE,
142	.proto	     	= IPPROTO_COMP,
143	.init_state	= ipcomp4_init_state,
144	.destructor	= ipcomp_destroy,
145	.input		= ipcomp_input,
146	.output		= ipcomp_output
147};
148
149static struct net_protocol ipcomp4_protocol = {
150	.handler	=	xfrm4_rcv,
151	.err_handler	=	ipcomp4_err,
152	.no_policy	=	1,
153};
154
155static int __init ipcomp4_init(void)
156{
157	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
158		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
159		return -EAGAIN;
160	}
161	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
162		printk(KERN_INFO "ipcomp init: can't add protocol\n");
163		xfrm_unregister_type(&ipcomp_type, AF_INET);
164		return -EAGAIN;
165	}
166	return 0;
167}
168
169static void __exit ipcomp4_fini(void)
170{
171	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
172		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
173	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
174		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
175}
176
177module_init(ipcomp4_init);
178module_exit(ipcomp4_fini);
179
180MODULE_LICENSE("GPL");
181MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
182MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
183
184MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);
185