nf_conntrack_amanda.c revision 58c0fb0ddd92e5105d61fc85b6e7af7b1f669067 
1/* Amanda extension for IP connection tracking
2 *
3 * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
4 * based on HW's ip_conntrack_irc.c as well as other modules
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/moduleparam.h>
14#include <linux/textsearch.h>
15#include <linux/skbuff.h>
16#include <linux/in.h>
17#include <linux/udp.h>
18#include <linux/netfilter.h>
19
20#include <net/netfilter/nf_conntrack.h>
21#include <net/netfilter/nf_conntrack_expect.h>
22#include <net/netfilter/nf_conntrack_ecache.h>
23#include <net/netfilter/nf_conntrack_helper.h>
24#include <linux/netfilter/nf_conntrack_amanda.h>
25
26static unsigned int master_timeout __read_mostly = 300;
27static char *ts_algo = "kmp";
28
29MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
30MODULE_DESCRIPTION("Amanda connection tracking module");
31MODULE_LICENSE("GPL");
32MODULE_ALIAS("ip_conntrack_amanda");
33
34module_param(master_timeout, uint, 0600);
35MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
36module_param(ts_algo, charp, 0400);
37MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
38
39unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
40				   enum ip_conntrack_info ctinfo,
41				   unsigned int matchoff,
42				   unsigned int matchlen,
43				   struct nf_conntrack_expect *exp)
44				   __read_mostly;
45EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
46
47enum amanda_strings {
48	SEARCH_CONNECT,
49	SEARCH_NEWLINE,
50	SEARCH_DATA,
51	SEARCH_MESG,
52	SEARCH_INDEX,
53};
54
55static struct {
56	const char		*string;
57	size_t			len;
58	struct ts_config	*ts;
59} search[] __read_mostly = {
60	[SEARCH_CONNECT] = {
61		.string	= "CONNECT ",
62		.len	= 8,
63	},
64	[SEARCH_NEWLINE] = {
65		.string	= "\n",
66		.len	= 1,
67	},
68	[SEARCH_DATA] = {
69		.string	= "DATA ",
70		.len	= 5,
71	},
72	[SEARCH_MESG] = {
73		.string	= "MESG ",
74		.len	= 5,
75	},
76	[SEARCH_INDEX] = {
77		.string = "INDEX ",
78		.len	= 6,
79	},
80};
81
82static int amanda_help(struct sk_buff *skb,
83		       unsigned int protoff,
84		       struct nf_conn *ct,
85		       enum ip_conntrack_info ctinfo)
86{
87	struct ts_state ts;
88	struct nf_conntrack_expect *exp;
89	struct nf_conntrack_tuple *tuple;
90	unsigned int dataoff, start, stop, off, i;
91	char pbuf[sizeof("65535")], *tmp;
92	u_int16_t len;
93	__be16 port;
94	int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
95	int ret = NF_ACCEPT;
96	typeof(nf_nat_amanda_hook) nf_nat_amanda;
97
98	/* Only look at packets from the Amanda server */
99	if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
100		return NF_ACCEPT;
101
102	/* increase the UDP timeout of the master connection as replies from
103	 * Amanda clients to the server can be quite delayed */
104	nf_ct_refresh(ct, skb, master_timeout * HZ);
105
106	/* No data? */
107	dataoff = protoff + sizeof(struct udphdr);
108	if (dataoff >= skb->len) {
109		if (net_ratelimit())
110			printk("amanda_help: skblen = %u\n", skb->len);
111		return NF_ACCEPT;
112	}
113
114	memset(&ts, 0, sizeof(ts));
115	start = skb_find_text(skb, dataoff, skb->len,
116			      search[SEARCH_CONNECT].ts, &ts);
117	if (start == UINT_MAX)
118		goto out;
119	start += dataoff + search[SEARCH_CONNECT].len;
120
121	memset(&ts, 0, sizeof(ts));
122	stop = skb_find_text(skb, start, skb->len,
123			     search[SEARCH_NEWLINE].ts, &ts);
124	if (stop == UINT_MAX)
125		goto out;
126	stop += start;
127
128	for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
129		memset(&ts, 0, sizeof(ts));
130		off = skb_find_text(skb, start, stop, search[i].ts, &ts);
131		if (off == UINT_MAX)
132			continue;
133		off += start + search[i].len;
134
135		len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
136		if (skb_copy_bits(skb, off, pbuf, len))
137			break;
138		pbuf[len] = '\0';
139
140		port = htons(simple_strtoul(pbuf, &tmp, 10));
141		len = tmp - pbuf;
142		if (port == 0 || len > 5)
143			break;
144
145		exp = nf_ct_expect_alloc(ct);
146		if (exp == NULL) {
147			ret = NF_DROP;
148			goto out;
149		}
150		tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
151		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, family,
152				  &tuple->src.u3, &tuple->dst.u3,
153				  IPPROTO_TCP, NULL, &port);
154
155		nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
156		if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
157			ret = nf_nat_amanda(skb, ctinfo, off - dataoff,
158					    len, exp);
159		else if (nf_ct_expect_related(exp) != 0)
160			ret = NF_DROP;
161		nf_ct_expect_put(exp);
162	}
163
164out:
165	return ret;
166}
167
168static const struct nf_conntrack_expect_policy amanda_exp_policy = {
169	.max_expected		= 3,
170	.timeout		= 180,
171};
172
173static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
174	{
175		.name			= "amanda",
176		.me			= THIS_MODULE,
177		.help			= amanda_help,
178		.tuple.src.l3num	= AF_INET,
179		.tuple.src.u.udp.port	= __constant_htons(10080),
180		.tuple.dst.protonum	= IPPROTO_UDP,
181		.expect_policy		= &amanda_exp_policy,
182	},
183	{
184		.name			= "amanda",
185		.me			= THIS_MODULE,
186		.help			= amanda_help,
187		.tuple.src.l3num	= AF_INET6,
188		.tuple.src.u.udp.port	= __constant_htons(10080),
189		.tuple.dst.protonum	= IPPROTO_UDP,
190		.expect_policy		= &amanda_exp_policy,
191	},
192};
193
194static void __exit nf_conntrack_amanda_fini(void)
195{
196	int i;
197
198	nf_conntrack_helper_unregister(&amanda_helper[0]);
199	nf_conntrack_helper_unregister(&amanda_helper[1]);
200	for (i = 0; i < ARRAY_SIZE(search); i++)
201		textsearch_destroy(search[i].ts);
202}
203
204static int __init nf_conntrack_amanda_init(void)
205{
206	int ret, i;
207
208	for (i = 0; i < ARRAY_SIZE(search); i++) {
209		search[i].ts = textsearch_prepare(ts_algo, search[i].string,
210						  search[i].len,
211						  GFP_KERNEL, TS_AUTOLOAD);
212		if (IS_ERR(search[i].ts)) {
213			ret = PTR_ERR(search[i].ts);
214			goto err1;
215		}
216	}
217	ret = nf_conntrack_helper_register(&amanda_helper[0]);
218	if (ret < 0)
219		goto err1;
220	ret = nf_conntrack_helper_register(&amanda_helper[1]);
221	if (ret < 0)
222		goto err2;
223	return 0;
224
225err2:
226	nf_conntrack_helper_unregister(&amanda_helper[0]);
227err1:
228	while (--i >= 0)
229		textsearch_destroy(search[i].ts);
230
231	return ret;
232}
233
234module_init(nf_conntrack_amanda_init);
235module_exit(nf_conntrack_amanda_fini);
236