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 int ipcomp4_err(struct sk_buff *skb, u32 info)
27{
28	struct net *net = dev_net(skb->dev);
29	__be32 spi;
30	const struct iphdr *iph = (const struct iphdr *)skb->data;
31	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
32	struct xfrm_state *x;
33
34	switch (icmp_hdr(skb)->type) {
35	case ICMP_DEST_UNREACH:
36		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
37			return 0;
38	case ICMP_REDIRECT:
39		break;
40	default:
41		return 0;
42	}
43
44	spi = htonl(ntohs(ipch->cpi));
45	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
46			      spi, IPPROTO_COMP, AF_INET);
47	if (!x)
48		return 0;
49
50	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
51		ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_COMP, 0);
52	else
53		ipv4_redirect(skb, net, 0, 0, IPPROTO_COMP, 0);
54	xfrm_state_put(x);
55
56	return 0;
57}
58
59/* We always hold one tunnel user reference to indicate a tunnel */
60static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
61{
62	struct net *net = xs_net(x);
63	struct xfrm_state *t;
64
65	t = xfrm_state_alloc(net);
66	if (!t)
67		goto out;
68
69	t->id.proto = IPPROTO_IPIP;
70	t->id.spi = x->props.saddr.a4;
71	t->id.daddr.a4 = x->id.daddr.a4;
72	memcpy(&t->sel, &x->sel, sizeof(t->sel));
73	t->props.family = AF_INET;
74	t->props.mode = x->props.mode;
75	t->props.saddr.a4 = x->props.saddr.a4;
76	t->props.flags = x->props.flags;
77	t->props.extra_flags = x->props.extra_flags;
78	memcpy(&t->mark, &x->mark, sizeof(t->mark));
79
80	if (xfrm_init_state(t))
81		goto error;
82
83	atomic_set(&t->tunnel_users, 1);
84out:
85	return t;
86
87error:
88	t->km.state = XFRM_STATE_DEAD;
89	xfrm_state_put(t);
90	t = NULL;
91	goto out;
92}
93
94/*
95 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
96 * always incremented on success.
97 */
98static int ipcomp_tunnel_attach(struct xfrm_state *x)
99{
100	struct net *net = xs_net(x);
101	int err = 0;
102	struct xfrm_state *t;
103	u32 mark = x->mark.v & x->mark.m;
104
105	t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
106			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
107	if (!t) {
108		t = ipcomp_tunnel_create(x);
109		if (!t) {
110			err = -EINVAL;
111			goto out;
112		}
113		xfrm_state_insert(t);
114		xfrm_state_hold(t);
115	}
116	x->tunnel = t;
117	atomic_inc(&t->tunnel_users);
118out:
119	return err;
120}
121
122static int ipcomp4_init_state(struct xfrm_state *x)
123{
124	int err = -EINVAL;
125
126	x->props.header_len = 0;
127	switch (x->props.mode) {
128	case XFRM_MODE_TRANSPORT:
129		break;
130	case XFRM_MODE_TUNNEL:
131		x->props.header_len += sizeof(struct iphdr);
132		break;
133	default:
134		goto out;
135	}
136
137	err = ipcomp_init_state(x);
138	if (err)
139		goto out;
140
141	if (x->props.mode == XFRM_MODE_TUNNEL) {
142		err = ipcomp_tunnel_attach(x);
143		if (err)
144			goto out;
145	}
146
147	err = 0;
148out:
149	return err;
150}
151
152static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
153{
154	return 0;
155}
156
157static const struct xfrm_type ipcomp_type = {
158	.description	= "IPCOMP4",
159	.owner		= THIS_MODULE,
160	.proto	     	= IPPROTO_COMP,
161	.init_state	= ipcomp4_init_state,
162	.destructor	= ipcomp_destroy,
163	.input		= ipcomp_input,
164	.output		= ipcomp_output
165};
166
167static struct xfrm4_protocol ipcomp4_protocol = {
168	.handler	=	xfrm4_rcv,
169	.input_handler	=	xfrm_input,
170	.cb_handler	=	ipcomp4_rcv_cb,
171	.err_handler	=	ipcomp4_err,
172	.priority	=	0,
173};
174
175static int __init ipcomp4_init(void)
176{
177	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
178		pr_info("%s: can't add xfrm type\n", __func__);
179		return -EAGAIN;
180	}
181	if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
182		pr_info("%s: can't add protocol\n", __func__);
183		xfrm_unregister_type(&ipcomp_type, AF_INET);
184		return -EAGAIN;
185	}
186	return 0;
187}
188
189static void __exit ipcomp4_fini(void)
190{
191	if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
192		pr_info("%s: can't remove protocol\n", __func__);
193	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
194		pr_info("%s: can't remove xfrm type\n", __func__);
195}
196
197module_init(ipcomp4_init);
198module_exit(ipcomp4_fini);
199
200MODULE_LICENSE("GPL");
201MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
202MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
203
204MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);
205