xt_conntrack.c revision fe0b9294c9f951a64c768f8a5879154235efe63f 
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
14#if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
15#include <linux/netfilter_ipv4/ip_conntrack.h>
16#include <linux/netfilter_ipv4/ip_conntrack_tuple.h>
17#else
18#include <net/netfilter/nf_conntrack.h>
19#endif
20
21#include <linux/netfilter/x_tables.h>
22#include <linux/netfilter/xt_conntrack.h>
23#include <net/netfilter/nf_conntrack_compat.h>
24
25MODULE_LICENSE("GPL");
26MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
27MODULE_DESCRIPTION("iptables connection tracking match module");
28MODULE_ALIAS("ipt_conntrack");
29
30#if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
31
32static int
33match(const struct sk_buff *skb,
34      const struct net_device *in,
35      const struct net_device *out,
36      const struct xt_match *match,
37      const void *matchinfo,
38      int offset,
39      unsigned int protoff,
40      int *hotdrop)
41{
42	const struct xt_conntrack_info *sinfo = matchinfo;
43	struct ip_conntrack *ct;
44	enum ip_conntrack_info ctinfo;
45	unsigned int statebit;
46
47	ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
48
49#define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & invflg))
50
51	if (ct == &ip_conntrack_untracked)
52		statebit = XT_CONNTRACK_STATE_UNTRACKED;
53	else if (ct)
54 		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
55 	else
56 		statebit = XT_CONNTRACK_STATE_INVALID;
57
58	if (sinfo->flags & XT_CONNTRACK_STATE) {
59		if (ct) {
60			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
61				statebit |= XT_CONNTRACK_STATE_SNAT;
62			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
63				statebit |= XT_CONNTRACK_STATE_DNAT;
64		}
65		if (FWINV((statebit & sinfo->statemask) == 0,
66			  XT_CONNTRACK_STATE))
67			return 0;
68	}
69
70	if (ct == NULL) {
71		if (sinfo->flags & ~XT_CONNTRACK_STATE)
72			return 0;
73		return 1;
74	}
75
76	if (sinfo->flags & XT_CONNTRACK_PROTO &&
77	    FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
78		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
79		  XT_CONNTRACK_PROTO))
80                return 0;
81
82	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
83	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip &
84		   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
85		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
86		  XT_CONNTRACK_ORIGSRC))
87		return 0;
88
89	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
90	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip &
91		   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
92		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
93		  XT_CONNTRACK_ORIGDST))
94		return 0;
95
96	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
97	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip &
98		   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
99		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
100		  XT_CONNTRACK_REPLSRC))
101		return 0;
102
103	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
104	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip &
105		   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
106		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
107		  XT_CONNTRACK_REPLDST))
108		return 0;
109
110	if (sinfo->flags & XT_CONNTRACK_STATUS &&
111	    FWINV((ct->status & sinfo->statusmask) == 0,
112		  XT_CONNTRACK_STATUS))
113		return 0;
114
115	if (sinfo->flags & XT_CONNTRACK_EXPIRES) {
116		unsigned long expires = timer_pending(&ct->timeout) ?
117					(ct->timeout.expires - jiffies)/HZ : 0;
118
119		if (FWINV(!(expires >= sinfo->expires_min &&
120			    expires <= sinfo->expires_max),
121			  XT_CONNTRACK_EXPIRES))
122			return 0;
123	}
124	return 1;
125}
126
127#else /* CONFIG_IP_NF_CONNTRACK */
128static int
129match(const struct sk_buff *skb,
130      const struct net_device *in,
131      const struct net_device *out,
132      const struct xt_match *match,
133      const void *matchinfo,
134      int offset,
135      unsigned int protoff,
136      int *hotdrop)
137{
138	const struct xt_conntrack_info *sinfo = matchinfo;
139	struct nf_conn *ct;
140	enum ip_conntrack_info ctinfo;
141	unsigned int statebit;
142
143	ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
144
145#define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
146
147	if (ct == &nf_conntrack_untracked)
148		statebit = XT_CONNTRACK_STATE_UNTRACKED;
149	else if (ct)
150 		statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
151 	else
152 		statebit = XT_CONNTRACK_STATE_INVALID;
153
154	if (sinfo->flags & XT_CONNTRACK_STATE) {
155		if (ct) {
156			if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
157				statebit |= XT_CONNTRACK_STATE_SNAT;
158			if (test_bit(IPS_DST_NAT_BIT, &ct->status))
159				statebit |= XT_CONNTRACK_STATE_DNAT;
160		}
161		if (FWINV((statebit & sinfo->statemask) == 0,
162			  XT_CONNTRACK_STATE))
163			return 0;
164	}
165
166	if (ct == NULL) {
167		if (sinfo->flags & ~XT_CONNTRACK_STATE)
168			return 0;
169		return 1;
170	}
171
172	if (sinfo->flags & XT_CONNTRACK_PROTO &&
173	    FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
174	    	  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
175		  XT_CONNTRACK_PROTO))
176                return 0;
177
178	if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
179	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
180	    	   sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
181		  sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
182		  XT_CONNTRACK_ORIGSRC))
183		return 0;
184
185	if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
186	    FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
187	    	   sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
188		  sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
189		  XT_CONNTRACK_ORIGDST))
190		return 0;
191
192	if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
193	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
194	    	   sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
195		  sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
196		  XT_CONNTRACK_REPLSRC))
197		return 0;
198
199	if (sinfo->flags & XT_CONNTRACK_REPLDST &&
200	    FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
201	    	   sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
202		  sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
203		  XT_CONNTRACK_REPLDST))
204		return 0;
205
206	if (sinfo->flags & XT_CONNTRACK_STATUS &&
207	    FWINV((ct->status & sinfo->statusmask) == 0,
208	    	  XT_CONNTRACK_STATUS))
209		return 0;
210
211	if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
212		unsigned long expires = timer_pending(&ct->timeout) ?
213					(ct->timeout.expires - jiffies)/HZ : 0;
214
215		if (FWINV(!(expires >= sinfo->expires_min &&
216			    expires <= sinfo->expires_max),
217			  XT_CONNTRACK_EXPIRES))
218			return 0;
219	}
220	return 1;
221}
222
223#endif /* CONFIG_NF_IP_CONNTRACK */
224
225static int
226checkentry(const char *tablename,
227	   const void *ip,
228	   const struct xt_match *match,
229	   void *matchinfo,
230	   unsigned int hook_mask)
231{
232	if (nf_ct_l3proto_try_module_get(match->family) < 0) {
233		printk(KERN_WARNING "can't load conntrack support for "
234				    "proto=%d\n", match->family);
235		return 0;
236	}
237	return 1;
238}
239
240static void destroy(const struct xt_match *match, void *matchinfo)
241{
242	nf_ct_l3proto_module_put(match->family);
243}
244
245static struct xt_match conntrack_match = {
246	.name		= "conntrack",
247	.match		= match,
248	.checkentry	= checkentry,
249	.destroy	= destroy,
250	.matchsize	= sizeof(struct xt_conntrack_info),
251	.family		= AF_INET,
252	.me		= THIS_MODULE,
253};
254
255static int __init xt_conntrack_init(void)
256{
257	return xt_register_match(&conntrack_match);
258}
259
260static void __exit xt_conntrack_fini(void)
261{
262	xt_unregister_match(&conntrack_match);
263}
264
265module_init(xt_conntrack_init);
266module_exit(xt_conntrack_fini);
267