xt_conntrack.c revision 93bbce1ad0cd788190dd7d6c17d289f771fe3d0d 
1/*
2 *	xt_conntrack - Netfilter module to match connection tracking
3 *	information. (Superset of Rusty's minimalistic state match.)
4 *
5 *	(C) 2001  Marc Boucher (marc@mbsi.ca).
6 *	Copyright © CC Computer Consultants GmbH, 2007 - 2008
7 *
8 *	This program is free software; you can redistribute it and/or modify
9 *	it under the terms of the GNU General Public License version 2 as
10 *	published by the Free Software Foundation.
11 */
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13#include <linux/module.h>
14#include <linux/skbuff.h>
15#include <net/ipv6.h>
16#include <linux/netfilter/x_tables.h>
17#include <linux/netfilter/xt_conntrack.h>
18#include <net/netfilter/nf_conntrack.h>
19
20MODULE_LICENSE("GPL");
21MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
22MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
23MODULE_DESCRIPTION("Xtables: connection tracking state match");
24MODULE_ALIAS("ipt_conntrack");
25MODULE_ALIAS("ip6t_conntrack");
26
27static bool
28conntrack_addrcmp(const union nf_inet_addr *kaddr,
29                  const union nf_inet_addr *uaddr,
30                  const union nf_inet_addr *umask, unsigned int l3proto)
31{
32	if (l3proto == NFPROTO_IPV4)
33		return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
34	else if (l3proto == NFPROTO_IPV6)
35		return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
36		       &uaddr->in6) == 0;
37	else
38		return false;
39}
40
41static inline bool
42conntrack_mt_origsrc(const struct nf_conn *ct,
43                     const struct xt_conntrack_mtinfo2 *info,
44		     u_int8_t family)
45{
46	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
47	       &info->origsrc_addr, &info->origsrc_mask, family);
48}
49
50static inline bool
51conntrack_mt_origdst(const struct nf_conn *ct,
52                     const struct xt_conntrack_mtinfo2 *info,
53		     u_int8_t family)
54{
55	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
56	       &info->origdst_addr, &info->origdst_mask, family);
57}
58
59static inline bool
60conntrack_mt_replsrc(const struct nf_conn *ct,
61                     const struct xt_conntrack_mtinfo2 *info,
62		     u_int8_t family)
63{
64	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
65	       &info->replsrc_addr, &info->replsrc_mask, family);
66}
67
68static inline bool
69conntrack_mt_repldst(const struct nf_conn *ct,
70                     const struct xt_conntrack_mtinfo2 *info,
71		     u_int8_t family)
72{
73	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
74	       &info->repldst_addr, &info->repldst_mask, family);
75}
76
77static inline bool
78ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
79                    const struct nf_conn *ct)
80{
81	const struct nf_conntrack_tuple *tuple;
82
83	tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
84	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
85	    (nf_ct_protonum(ct) == info->l4proto) ^
86	    !(info->invert_flags & XT_CONNTRACK_PROTO))
87		return false;
88
89	/* Shortcut to match all recognized protocols by using ->src.all. */
90	if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
91	    (tuple->src.u.all == info->origsrc_port) ^
92	    !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
93		return false;
94
95	if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
96	    (tuple->dst.u.all == info->origdst_port) ^
97	    !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
98		return false;
99
100	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
101
102	if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
103	    (tuple->src.u.all == info->replsrc_port) ^
104	    !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
105		return false;
106
107	if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
108	    (tuple->dst.u.all == info->repldst_port) ^
109	    !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
110		return false;
111
112	return true;
113}
114
115static inline bool
116port_match(u16 min, u16 max, u16 port, bool invert)
117{
118	return (port >= min && port <= max) ^ invert;
119}
120
121static inline bool
122ct_proto_port_check_v3(const struct xt_conntrack_mtinfo3 *info,
123		       const struct nf_conn *ct)
124{
125	const struct nf_conntrack_tuple *tuple;
126
127	tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
128	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
129	    (nf_ct_protonum(ct) == info->l4proto) ^
130	    !(info->invert_flags & XT_CONNTRACK_PROTO))
131		return false;
132
133	/* Shortcut to match all recognized protocols by using ->src.all. */
134	if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
135	    !port_match(info->origsrc_port, info->origsrc_port_high,
136			ntohs(tuple->src.u.all),
137			info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
138		return false;
139
140	if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
141	    !port_match(info->origdst_port, info->origdst_port_high,
142			ntohs(tuple->dst.u.all),
143			info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
144		return false;
145
146	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
147
148	if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
149	    !port_match(info->replsrc_port, info->replsrc_port_high,
150			ntohs(tuple->src.u.all),
151			info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
152		return false;
153
154	if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
155	    !port_match(info->repldst_port, info->repldst_port_high,
156			ntohs(tuple->dst.u.all),
157			info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
158		return false;
159
160	return true;
161}
162
163static bool
164conntrack_mt(const struct sk_buff *skb, struct xt_action_param *par,
165             u16 state_mask, u16 status_mask)
166{
167	const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
168	enum ip_conntrack_info ctinfo;
169	const struct nf_conn *ct;
170	unsigned int statebit;
171
172	ct = nf_ct_get(skb, &ctinfo);
173
174	if (ct) {
175		if (nf_ct_is_untracked(ct))
176			statebit = XT_CONNTRACK_STATE_UNTRACKED;
177		else
178			statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
179	} else
180		statebit = XT_CONNTRACK_STATE_INVALID;
181
182	if (info->match_flags & XT_CONNTRACK_STATE) {
183		if (ct != NULL) {
184			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
185				statebit |= XT_CONNTRACK_STATE_SNAT;
186			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
187				statebit |= XT_CONNTRACK_STATE_DNAT;
188		}
189		if (!!(state_mask & statebit) ^
190		    !(info->invert_flags & XT_CONNTRACK_STATE))
191			return false;
192	}
193
194	if (ct == NULL)
195		return info->match_flags & XT_CONNTRACK_STATE;
196	if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
197	    (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
198	    !(info->invert_flags & XT_CONNTRACK_DIRECTION))
199		return false;
200
201	if (info->match_flags & XT_CONNTRACK_ORIGSRC)
202		if (conntrack_mt_origsrc(ct, info, par->family) ^
203		    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
204			return false;
205
206	if (info->match_flags & XT_CONNTRACK_ORIGDST)
207		if (conntrack_mt_origdst(ct, info, par->family) ^
208		    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
209			return false;
210
211	if (info->match_flags & XT_CONNTRACK_REPLSRC)
212		if (conntrack_mt_replsrc(ct, info, par->family) ^
213		    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
214			return false;
215
216	if (info->match_flags & XT_CONNTRACK_REPLDST)
217		if (conntrack_mt_repldst(ct, info, par->family) ^
218		    !(info->invert_flags & XT_CONNTRACK_REPLDST))
219			return false;
220
221	if (par->match->revision != 3) {
222		if (!ct_proto_port_check(info, ct))
223			return false;
224	} else {
225		if (!ct_proto_port_check_v3(par->matchinfo, ct))
226			return false;
227	}
228
229	if ((info->match_flags & XT_CONNTRACK_STATUS) &&
230	    (!!(status_mask & ct->status) ^
231	    !(info->invert_flags & XT_CONNTRACK_STATUS)))
232		return false;
233
234	if (info->match_flags & XT_CONNTRACK_EXPIRES) {
235		unsigned long expires = 0;
236
237		if (timer_pending(&ct->timeout))
238			expires = (ct->timeout.expires - jiffies) / HZ;
239		if ((expires >= info->expires_min &&
240		    expires <= info->expires_max) ^
241		    !(info->invert_flags & XT_CONNTRACK_EXPIRES))
242			return false;
243	}
244	return true;
245}
246
247static bool
248conntrack_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
249{
250	const struct xt_conntrack_mtinfo1 *info = par->matchinfo;
251
252	return conntrack_mt(skb, par, info->state_mask, info->status_mask);
253}
254
255static bool
256conntrack_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)
257{
258	const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
259
260	return conntrack_mt(skb, par, info->state_mask, info->status_mask);
261}
262
263static bool
264conntrack_mt_v3(const struct sk_buff *skb, struct xt_action_param *par)
265{
266	const struct xt_conntrack_mtinfo3 *info = par->matchinfo;
267
268	return conntrack_mt(skb, par, info->state_mask, info->status_mask);
269}
270
271static int conntrack_mt_check(const struct xt_mtchk_param *par)
272{
273	int ret;
274
275	ret = nf_ct_l3proto_try_module_get(par->family);
276	if (ret < 0)
277		pr_info("cannot load conntrack support for proto=%u\n",
278			par->family);
279	return ret;
280}
281
282static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
283{
284	nf_ct_l3proto_module_put(par->family);
285}
286
287static struct xt_match conntrack_mt_reg[] __read_mostly = {
288	{
289		.name       = "conntrack",
290		.revision   = 1,
291		.family     = NFPROTO_UNSPEC,
292		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
293		.match      = conntrack_mt_v1,
294		.checkentry = conntrack_mt_check,
295		.destroy    = conntrack_mt_destroy,
296		.me         = THIS_MODULE,
297	},
298	{
299		.name       = "conntrack",
300		.revision   = 2,
301		.family     = NFPROTO_UNSPEC,
302		.matchsize  = sizeof(struct xt_conntrack_mtinfo2),
303		.match      = conntrack_mt_v2,
304		.checkentry = conntrack_mt_check,
305		.destroy    = conntrack_mt_destroy,
306		.me         = THIS_MODULE,
307	},
308	{
309		.name       = "conntrack",
310		.revision   = 3,
311		.family     = NFPROTO_UNSPEC,
312		.matchsize  = sizeof(struct xt_conntrack_mtinfo3),
313		.match      = conntrack_mt_v3,
314		.checkentry = conntrack_mt_check,
315		.destroy    = conntrack_mt_destroy,
316		.me         = THIS_MODULE,
317	},
318};
319
320static int __init conntrack_mt_init(void)
321{
322	return xt_register_matches(conntrack_mt_reg,
323	       ARRAY_SIZE(conntrack_mt_reg));
324}
325
326static void __exit conntrack_mt_exit(void)
327{
328	xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
329}
330
331module_init(conntrack_mt_init);
332module_exit(conntrack_mt_exit);
333