xt_conntrack.c revision df54aae02210e1acf3a1d2ffac9b29003835710c 
1/* Kernel module to match connection tracking information.
2 * Superset of Rusty's minimalistic state match.
3 *
4 * (C) 2001  Marc Boucher (marc@mbsi.ca).
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <linux/module.h>
12#include <linux/skbuff.h>
13#include <linux/netfilter/x_tables.h>
14#include <linux/netfilter/xt_conntrack.h>
15#include <net/netfilter/nf_conntrack.h>
16
17MODULE_LICENSE("GPL");
18MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
19MODULE_DESCRIPTION("iptables connection tracking match module");
20MODULE_ALIAS("ipt_conntrack");
21
22static bool
23conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
24             const struct net_device *out, const struct xt_match *match,
25             const void *matchinfo, int offset, unsigned int protoff,
26             bool *hotdrop)
27{
28	const struct xt_conntrack_info *sinfo = matchinfo;
29	const struct nf_conn *ct;
30	enum ip_conntrack_info ctinfo;
31	unsigned int statebit;
32
33	ct = nf_ct_get(skb, &ctinfo);
34
35#define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
36
37	if (ct == &nf_conntrack_untracked)
38		statebit = XT_CONNTRACK_STATE_UNTRACKED;
39	else if (ct)
40		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
41	else
42		statebit = XT_CONNTRACK_STATE_INVALID;
43
44	if (sinfo->flags & XT_CONNTRACK_STATE) {
45		if (ct) {
46			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
47				statebit |= XT_CONNTRACK_STATE_SNAT;
48			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
49				statebit |= XT_CONNTRACK_STATE_DNAT;
50		}
51		if (FWINV((statebit & sinfo->statemask) == 0,
52			  XT_CONNTRACK_STATE))
53			return false;
54	}
55
56	if (ct == NULL) {
57		if (sinfo->flags & ~XT_CONNTRACK_STATE)
58			return false;
59		return true;
60	}
61
62	if (sinfo->flags & XT_CONNTRACK_PROTO &&
63	    FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
64		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
65		  XT_CONNTRACK_PROTO))
66		return false;
67
68	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
69	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
70		   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
71		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
72		  XT_CONNTRACK_ORIGSRC))
73		return false;
74
75	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
76	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
77		   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
78		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
79		  XT_CONNTRACK_ORIGDST))
80		return false;
81
82	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
83	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
84		   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
85		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
86		  XT_CONNTRACK_REPLSRC))
87		return false;
88
89	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
90	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
91		   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
92		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
93		  XT_CONNTRACK_REPLDST))
94		return false;
95
96	if (sinfo->flags & XT_CONNTRACK_STATUS &&
97	    FWINV((ct->status & sinfo->statusmask) == 0,
98		  XT_CONNTRACK_STATUS))
99		return false;
100
101	if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
102		unsigned long expires = timer_pending(&ct->timeout) ?
103					(ct->timeout.expires - jiffies)/HZ : 0;
104
105		if (FWINV(!(expires >= sinfo->expires_min &&
106			    expires <= sinfo->expires_max),
107			  XT_CONNTRACK_EXPIRES))
108			return false;
109	}
110	return true;
111}
112
113static bool
114conntrack_mt_check(const char *tablename, const void *ip,
115                   const struct xt_match *match, void *matchinfo,
116                   unsigned int hook_mask)
117{
118	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
119		printk(KERN_WARNING "can't load conntrack support for "
120				    "proto=%u\n", match->family);
121		return false;
122	}
123	return true;
124}
125
126static void
127conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
128{
129	nf_ct_l3proto_module_put(match->family);
130}
131
132#ifdef CONFIG_COMPAT
133struct compat_xt_conntrack_info
134{
135	compat_uint_t			statemask;
136	compat_uint_t			statusmask;
137	struct ip_conntrack_old_tuple	tuple[IP_CT_DIR_MAX];
138	struct in_addr			sipmsk[IP_CT_DIR_MAX];
139	struct in_addr			dipmsk[IP_CT_DIR_MAX];
140	compat_ulong_t			expires_min;
141	compat_ulong_t			expires_max;
142	u_int8_t			flags;
143	u_int8_t			invflags;
144};
145
146static void conntrack_mt_compat_from_user(void *dst, void *src)
147{
148	const struct compat_xt_conntrack_info *cm = src;
149	struct xt_conntrack_info m = {
150		.statemask	= cm->statemask,
151		.statusmask	= cm->statusmask,
152		.expires_min	= cm->expires_min,
153		.expires_max	= cm->expires_max,
154		.flags		= cm->flags,
155		.invflags	= cm->invflags,
156	};
157	memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
158	memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
159	memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
160	memcpy(dst, &m, sizeof(m));
161}
162
163static int conntrack_mt_compat_to_user(void __user *dst, void *src)
164{
165	const struct xt_conntrack_info *m = src;
166	struct compat_xt_conntrack_info cm = {
167		.statemask	= m->statemask,
168		.statusmask	= m->statusmask,
169		.expires_min	= m->expires_min,
170		.expires_max	= m->expires_max,
171		.flags		= m->flags,
172		.invflags	= m->invflags,
173	};
174	memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
175	memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
176	memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
177	return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
178}
179#endif
180
181static struct xt_match conntrack_mt_reg __read_mostly = {
182	.name		= "conntrack",
183	.match		= conntrack_mt,
184	.checkentry	= conntrack_mt_check,
185	.destroy	= conntrack_mt_destroy,
186	.matchsize	= sizeof(struct xt_conntrack_info),
187#ifdef CONFIG_COMPAT
188	.compatsize	= sizeof(struct compat_xt_conntrack_info),
189	.compat_from_user = conntrack_mt_compat_from_user,
190	.compat_to_user	= conntrack_mt_compat_to_user,
191#endif
192	.family		= AF_INET,
193	.me		= THIS_MODULE,
194};
195
196static int __init conntrack_mt_init(void)
197{
198	return xt_register_match(&conntrack_mt_reg);
199}
200
201static void __exit conntrack_mt_exit(void)
202{
203	xt_unregister_match(&conntrack_mt_reg);
204}
205
206module_init(conntrack_mt_init);
207module_exit(conntrack_mt_exit);
208