1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IP Payload Compression Protocol (IPComp) - RFC3173.
4 *
5 * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
6 *
7 * Todo:
8 *   - Tunable compression parameters.
9 *   - Compression stats.
10 *   - Adaptive compression.
11 */
12#include <linux/module.h>
13#include <linux/err.h>
14#include <linux/rtnetlink.h>
15#include <net/ip.h>
16#include <net/xfrm.h>
17#include <net/icmp.h>
18#include <net/ipcomp.h>
19#include <net/protocol.h>
20#include <net/sock.h>
21
22static int ipcomp4_err(struct sk_buff *skb, u32 info)
23{
24	struct net *net = dev_net(skb->dev);
25	__be32 spi;
26	const struct iphdr *iph = (const struct iphdr *)skb->data;
27	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
28	struct xfrm_state *x;
29
30	switch (icmp_hdr(skb)->type) {
31	case ICMP_DEST_UNREACH:
32		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
33			return 0;
34		break;
35	case ICMP_REDIRECT:
36		break;
37	default:
38		return 0;
39	}
40
41	spi = htonl(ntohs(ipch->cpi));
42	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
43			      spi, IPPROTO_COMP, AF_INET);
44	if (!x)
45		return 0;
46
47	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
48		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_COMP);
49	else
50		ipv4_redirect(skb, net, 0, IPPROTO_COMP);
51	xfrm_state_put(x);
52
53	return 0;
54}
55
56/* We always hold one tunnel user reference to indicate a tunnel */
57static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
58{
59	struct net *net = xs_net(x);
60	struct xfrm_state *t;
61
62	t = xfrm_state_alloc(net);
63	if (!t)
64		goto out;
65
66	t->id.proto = IPPROTO_IPIP;
67	t->id.spi = x->props.saddr.a4;
68	t->id.daddr.a4 = x->id.daddr.a4;
69	memcpy(&t->sel, &x->sel, sizeof(t->sel));
70	t->props.family = AF_INET;
71	t->props.mode = x->props.mode;
72	t->props.saddr.a4 = x->props.saddr.a4;
73	t->props.flags = x->props.flags;
74	t->props.extra_flags = x->props.extra_flags;
75	memcpy(&t->mark, &x->mark, sizeof(t->mark));
76	t->if_id = x->if_id;
77
78	if (xfrm_init_state(t))
79		goto error;
80
81	atomic_set(&t->tunnel_users, 1);
82out:
83	return t;
84
85error:
86	t->km.state = XFRM_STATE_DEAD;
87	xfrm_state_put(t);
88	t = NULL;
89	goto out;
90}
91
92/*
93 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
94 * always incremented on success.
95 */
96static int ipcomp_tunnel_attach(struct xfrm_state *x)
97{
98	struct net *net = xs_net(x);
99	int err = 0;
100	struct xfrm_state *t;
101	u32 mark = x->mark.v & x->mark.m;
102
103	t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
104			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
105	if (!t) {
106		t = ipcomp_tunnel_create(x);
107		if (!t) {
108			err = -EINVAL;
109			goto out;
110		}
111		xfrm_state_insert(t);
112		xfrm_state_hold(t);
113	}
114	x->tunnel = t;
115	atomic_inc(&t->tunnel_users);
116out:
117	return err;
118}
119
120static int ipcomp4_init_state(struct xfrm_state *x,
121			      struct netlink_ext_ack *extack)
122{
123	int err = -EINVAL;
124
125	x->props.header_len = 0;
126	switch (x->props.mode) {
127	case XFRM_MODE_TRANSPORT:
128		break;
129	case XFRM_MODE_TUNNEL:
130		x->props.header_len += sizeof(struct iphdr);
131		break;
132	default:
133		NL_SET_ERR_MSG(extack, "Unsupported XFRM mode for IPcomp");
134		goto out;
135	}
136
137	err = ipcomp_init_state(x, extack);
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			NL_SET_ERR_MSG(extack, "Kernel error: failed to initialize the associated state");
145			goto out;
146		}
147	}
148
149	err = 0;
150out:
151	return err;
152}
153
154static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
155{
156	return 0;
157}
158
159static const struct xfrm_type ipcomp_type = {
160	.owner		= THIS_MODULE,
161	.proto	     	= IPPROTO_COMP,
162	.init_state	= ipcomp4_init_state,
163	.destructor	= ipcomp_destroy,
164	.input		= ipcomp_input,
165	.output		= ipcomp_output
166};
167
168static struct xfrm4_protocol ipcomp4_protocol = {
169	.handler	=	xfrm4_rcv,
170	.input_handler	=	xfrm_input,
171	.cb_handler	=	ipcomp4_rcv_cb,
172	.err_handler	=	ipcomp4_err,
173	.priority	=	0,
174};
175
176static int __init ipcomp4_init(void)
177{
178	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
179		pr_info("%s: can't add xfrm type\n", __func__);
180		return -EAGAIN;
181	}
182	if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
183		pr_info("%s: can't add protocol\n", __func__);
184		xfrm_unregister_type(&ipcomp_type, AF_INET);
185		return -EAGAIN;
186	}
187	return 0;
188}
189
190static void __exit ipcomp4_fini(void)
191{
192	if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
193		pr_info("%s: can't remove protocol\n", __func__);
194	xfrm_unregister_type(&ipcomp_type, AF_INET);
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