xt_conntrack.c revision 64eb12f9972d45f3b9b0f0a33a966e311c3d5275 
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 *	Jan Engelhardt <jengelh@computergmbh.de>
8 *
9 *	This program is free software; you can redistribute it and/or modify
10 *	it under the terms of the GNU General Public License version 2 as
11 *	published by the Free Software Foundation.
12 */
13
14#include <linux/module.h>
15#include <linux/skbuff.h>
16#include <net/ipv6.h>
17#include <linux/netfilter/x_tables.h>
18#include <linux/netfilter/xt_conntrack.h>
19#include <net/netfilter/nf_conntrack.h>
20
21MODULE_LICENSE("GPL");
22MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
23MODULE_DESCRIPTION("iptables connection tracking match module");
24MODULE_ALIAS("ipt_conntrack");
25MODULE_ALIAS("ip6t_conntrack");
26
27static bool
28conntrack_mt_v0(const struct sk_buff *skb, const struct net_device *in,
29                const struct net_device *out, const struct xt_match *match,
30                const void *matchinfo, int offset, unsigned int protoff,
31                bool *hotdrop)
32{
33	const struct xt_conntrack_info *sinfo = matchinfo;
34	const struct nf_conn *ct;
35	enum ip_conntrack_info ctinfo;
36	unsigned int statebit;
37
38	ct = nf_ct_get(skb, &ctinfo);
39
40#define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))
41
42	if (ct == &nf_conntrack_untracked)
43		statebit = XT_CONNTRACK_STATE_UNTRACKED;
44	else if (ct)
45		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
46	else
47		statebit = XT_CONNTRACK_STATE_INVALID;
48
49	if (sinfo->flags & XT_CONNTRACK_STATE) {
50		if (ct) {
51			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
52				statebit |= XT_CONNTRACK_STATE_SNAT;
53			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
54				statebit |= XT_CONNTRACK_STATE_DNAT;
55		}
56		if (FWINV((statebit & sinfo->statemask) == 0,
57			  XT_CONNTRACK_STATE))
58			return false;
59	}
60
61	if (ct == NULL) {
62		if (sinfo->flags & ~XT_CONNTRACK_STATE)
63			return false;
64		return true;
65	}
66
67	if (sinfo->flags & XT_CONNTRACK_PROTO &&
68	    FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
69		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
70		  XT_CONNTRACK_PROTO))
71		return false;
72
73	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
74	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
75		   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
76		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
77		  XT_CONNTRACK_ORIGSRC))
78		return false;
79
80	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
81	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
82		   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
83		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
84		  XT_CONNTRACK_ORIGDST))
85		return false;
86
87	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
88	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
89		   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
90		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
91		  XT_CONNTRACK_REPLSRC))
92		return false;
93
94	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
95	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
96		   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
97		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
98		  XT_CONNTRACK_REPLDST))
99		return false;
100
101	if (sinfo->flags & XT_CONNTRACK_STATUS &&
102	    FWINV((ct->status & sinfo->statusmask) == 0,
103		  XT_CONNTRACK_STATUS))
104		return false;
105
106	if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
107		unsigned long expires = timer_pending(&ct->timeout) ?
108					(ct->timeout.expires - jiffies)/HZ : 0;
109
110		if (FWINV(!(expires >= sinfo->expires_min &&
111			    expires <= sinfo->expires_max),
112			  XT_CONNTRACK_EXPIRES))
113			return false;
114	}
115	return true;
116#undef FWINV
117}
118
119static bool
120conntrack_addrcmp(const union nf_inet_addr *kaddr,
121                  const union nf_inet_addr *uaddr,
122                  const union nf_inet_addr *umask, unsigned int l3proto)
123{
124	if (l3proto == AF_INET)
125		return (kaddr->ip & umask->ip) == uaddr->ip;
126	else if (l3proto == AF_INET6)
127		return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
128		       &uaddr->in6) == 0;
129	else
130		return false;
131}
132
133static inline bool
134conntrack_mt_origsrc(const struct nf_conn *ct,
135                     const struct xt_conntrack_mtinfo1 *info,
136                     unsigned int family)
137{
138	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
139	       &info->origsrc_addr, &info->origsrc_mask, family);
140}
141
142static inline bool
143conntrack_mt_origdst(const struct nf_conn *ct,
144                     const struct xt_conntrack_mtinfo1 *info,
145                     unsigned int family)
146{
147	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
148	       &info->origdst_addr, &info->origdst_mask, family);
149}
150
151static inline bool
152conntrack_mt_replsrc(const struct nf_conn *ct,
153                     const struct xt_conntrack_mtinfo1 *info,
154                     unsigned int family)
155{
156	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
157	       &info->replsrc_addr, &info->replsrc_mask, family);
158}
159
160static inline bool
161conntrack_mt_repldst(const struct nf_conn *ct,
162                     const struct xt_conntrack_mtinfo1 *info,
163                     unsigned int family)
164{
165	return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
166	       &info->repldst_addr, &info->repldst_mask, family);
167}
168
169static bool
170conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
171             const struct net_device *out, const struct xt_match *match,
172             const void *matchinfo, int offset, unsigned int protoff,
173             bool *hotdrop)
174{
175	const struct xt_conntrack_mtinfo1 *info = matchinfo;
176	enum ip_conntrack_info ctinfo;
177	const struct nf_conn *ct;
178	unsigned int statebit;
179
180	ct = nf_ct_get(skb, &ctinfo);
181
182	if (ct == &nf_conntrack_untracked)
183		statebit = XT_CONNTRACK_STATE_UNTRACKED;
184	else if (ct != NULL)
185		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
186	else
187		statebit = XT_CONNTRACK_STATE_INVALID;
188
189	if (info->match_flags & XT_CONNTRACK_STATE) {
190		if (ct != NULL) {
191			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
192				statebit |= XT_CONNTRACK_STATE_SNAT;
193			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
194				statebit |= XT_CONNTRACK_STATE_DNAT;
195		}
196		if ((info->state_mask & statebit) ^
197		    !(info->invert_flags & XT_CONNTRACK_STATE))
198			return false;
199	}
200
201	if (ct == NULL)
202		return info->match_flags & XT_CONNTRACK_STATE;
203
204	if ((info->match_flags & XT_CONNTRACK_PROTO) &&
205	    ((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum ==
206	    info->l4proto) ^ !(info->invert_flags & XT_CONNTRACK_PROTO)))
207		return false;
208
209	if (info->match_flags & XT_CONNTRACK_ORIGSRC)
210		if (conntrack_mt_origsrc(ct, info, match->family) ^
211		    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
212			return false;
213
214	if (info->match_flags & XT_CONNTRACK_ORIGDST)
215		if (conntrack_mt_origdst(ct, info, match->family) ^
216		    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
217			return false;
218
219	if (info->match_flags & XT_CONNTRACK_REPLSRC)
220		if (conntrack_mt_replsrc(ct, info, match->family) ^
221		    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
222			return false;
223
224	if (info->match_flags & XT_CONNTRACK_REPLDST)
225		if (conntrack_mt_repldst(ct, info, match->family) ^
226		    !(info->invert_flags & XT_CONNTRACK_REPLDST))
227			return false;
228
229	if ((info->match_flags & XT_CONNTRACK_STATUS) &&
230	    (!!(info->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_check(const char *tablename, const void *ip,
249                   const struct xt_match *match, void *matchinfo,
250                   unsigned int hook_mask)
251{
252	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
253		printk(KERN_WARNING "can't load conntrack support for "
254				    "proto=%u\n", match->family);
255		return false;
256	}
257	return true;
258}
259
260static void
261conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
262{
263	nf_ct_l3proto_module_put(match->family);
264}
265
266#ifdef CONFIG_COMPAT
267struct compat_xt_conntrack_info
268{
269	compat_uint_t			statemask;
270	compat_uint_t			statusmask;
271	struct ip_conntrack_old_tuple	tuple[IP_CT_DIR_MAX];
272	struct in_addr			sipmsk[IP_CT_DIR_MAX];
273	struct in_addr			dipmsk[IP_CT_DIR_MAX];
274	compat_ulong_t			expires_min;
275	compat_ulong_t			expires_max;
276	u_int8_t			flags;
277	u_int8_t			invflags;
278};
279
280static void conntrack_mt_compat_from_user_v0(void *dst, void *src)
281{
282	const struct compat_xt_conntrack_info *cm = src;
283	struct xt_conntrack_info m = {
284		.statemask	= cm->statemask,
285		.statusmask	= cm->statusmask,
286		.expires_min	= cm->expires_min,
287		.expires_max	= cm->expires_max,
288		.flags		= cm->flags,
289		.invflags	= cm->invflags,
290	};
291	memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
292	memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
293	memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
294	memcpy(dst, &m, sizeof(m));
295}
296
297static int conntrack_mt_compat_to_user_v0(void __user *dst, void *src)
298{
299	const struct xt_conntrack_info *m = src;
300	struct compat_xt_conntrack_info cm = {
301		.statemask	= m->statemask,
302		.statusmask	= m->statusmask,
303		.expires_min	= m->expires_min,
304		.expires_max	= m->expires_max,
305		.flags		= m->flags,
306		.invflags	= m->invflags,
307	};
308	memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
309	memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
310	memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
311	return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
312}
313#endif
314
315static struct xt_match conntrack_mt_reg[] __read_mostly = {
316	{
317		.name       = "conntrack",
318		.revision   = 0,
319		.family     = AF_INET,
320		.match      = conntrack_mt_v0,
321		.checkentry = conntrack_mt_check,
322		.destroy    = conntrack_mt_destroy,
323		.matchsize  = sizeof(struct xt_conntrack_info),
324		.me         = THIS_MODULE,
325#ifdef CONFIG_COMPAT
326		.compatsize       = sizeof(struct compat_xt_conntrack_info),
327		.compat_from_user = conntrack_mt_compat_from_user_v0,
328		.compat_to_user   = conntrack_mt_compat_to_user_v0,
329#endif
330	},
331	{
332		.name       = "conntrack",
333		.revision   = 1,
334		.family     = AF_INET,
335		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
336		.match      = conntrack_mt,
337		.checkentry = conntrack_mt_check,
338		.destroy    = conntrack_mt_destroy,
339		.me         = THIS_MODULE,
340	},
341	{
342		.name       = "conntrack",
343		.revision   = 1,
344		.family     = AF_INET6,
345		.matchsize  = sizeof(struct xt_conntrack_mtinfo1),
346		.match      = conntrack_mt,
347		.checkentry = conntrack_mt_check,
348		.destroy    = conntrack_mt_destroy,
349		.me         = THIS_MODULE,
350	},
351};
352
353static int __init conntrack_mt_init(void)
354{
355	return xt_register_matches(conntrack_mt_reg,
356	       ARRAY_SIZE(conntrack_mt_reg));
357}
358
359static void __exit conntrack_mt_exit(void)
360{
361	xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
362}
363
364module_init(conntrack_mt_init);
365module_exit(conntrack_mt_exit);
366