ipcomp.c

  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 lock_class_key xfrm_state_lock_key;
 58static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 59{
 60	struct net *net = xs_net(x);
 61	struct xfrm_state *t;
 62
 63	t = xfrm_state_alloc(net);
 64	if (!t)
 65		goto out;
 66	lockdep_set_class(&t->lock, &xfrm_state_lock_key);
 67
 68	t->id.proto = IPPROTO_IPIP;
 69	t->id.spi = x->props.saddr.a4;
 70	t->id.daddr.a4 = x->id.daddr.a4;
 71	memcpy(&t->sel, &x->sel, sizeof(t->sel));
 72	t->props.family = AF_INET;
 73	t->props.mode = x->props.mode;
 74	t->props.saddr.a4 = x->props.saddr.a4;
 75	t->props.flags = x->props.flags;
 76	t->props.extra_flags = x->props.extra_flags;
 77	memcpy(&t->mark, &x->mark, sizeof(t->mark));
 78	t->if_id = x->if_id;
 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			      struct netlink_ext_ack *extack)
124{
125	int err = -EINVAL;
126
127	x->props.header_len = 0;
128	switch (x->props.mode) {
129	case XFRM_MODE_TRANSPORT:
130		break;
131	case XFRM_MODE_TUNNEL:
132		x->props.header_len += sizeof(struct iphdr);
133		break;
134	default:
135		NL_SET_ERR_MSG(extack, "Unsupported XFRM mode for IPcomp");
136		goto out;
137	}
138
139	err = ipcomp_init_state(x, extack);
140	if (err)
141		goto out;
142
143	if (x->props.mode == XFRM_MODE_TUNNEL) {
144		err = ipcomp_tunnel_attach(x);
145		if (err) {
146			NL_SET_ERR_MSG(extack, "Kernel error: failed to initialize the associated state");
147			goto out;
148		}
149	}
150
151	err = 0;
152out:
153	return err;
154}
155
156static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
157{
158	return 0;
159}
160
161static const struct xfrm_type ipcomp_type = {
162	.owner		= THIS_MODULE,
163	.proto	     	= IPPROTO_COMP,
164	.init_state	= ipcomp4_init_state,
165	.destructor	= ipcomp_destroy,
166	.input		= ipcomp_input,
167	.output		= ipcomp_output
168};
169
170static struct xfrm4_protocol ipcomp4_protocol = {
171	.handler	=	xfrm4_rcv,
172	.input_handler	=	xfrm_input,
173	.cb_handler	=	ipcomp4_rcv_cb,
174	.err_handler	=	ipcomp4_err,
175	.priority	=	0,
176};
177
178static int __init ipcomp4_init(void)
179{
180	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
181		pr_info("%s: can't add xfrm type\n", __func__);
182		return -EAGAIN;
183	}
184	if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
185		pr_info("%s: can't add protocol\n", __func__);
186		xfrm_unregister_type(&ipcomp_type, AF_INET);
187		return -EAGAIN;
188	}
189	return 0;
190}
191
192static void __exit ipcomp4_fini(void)
193{
194	if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
195		pr_info("%s: can't remove protocol\n", __func__);
196	xfrm_unregister_type(&ipcomp_type, AF_INET);
197}
198
199module_init(ipcomp4_init);
200module_exit(ipcomp4_fini);
201
202MODULE_LICENSE("GPL");
203MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
204MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
205
206MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);