nf_conntrack_amanda.c revision 09640e6365c679b5642b1c41b6d7078f51689ddf 
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");
33MODULE_ALIAS_NFCT_HELPER("amanda");
34
35module_param(master_timeout, uint, 0600);
36MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
37module_param(ts_algo, charp, 0400);
38MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
39
40unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
41				   enum ip_conntrack_info ctinfo,
42				   unsigned int matchoff,
43				   unsigned int matchlen,
44				   struct nf_conntrack_expect *exp)
45				   __read_mostly;
46EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
47
48enum amanda_strings {
49	SEARCH_CONNECT,
50	SEARCH_NEWLINE,
51	SEARCH_DATA,
52	SEARCH_MESG,
53	SEARCH_INDEX,
54};
55
56static struct {
57	const char		*string;
58	size_t			len;
59	struct ts_config	*ts;
60} search[] __read_mostly = {
61	[SEARCH_CONNECT] = {
62		.string	= "CONNECT ",
63		.len	= 8,
64	},
65	[SEARCH_NEWLINE] = {
66		.string	= "\n",
67		.len	= 1,
68	},
69	[SEARCH_DATA] = {
70		.string	= "DATA ",
71		.len	= 5,
72	},
73	[SEARCH_MESG] = {
74		.string	= "MESG ",
75		.len	= 5,
76	},
77	[SEARCH_INDEX] = {
78		.string = "INDEX ",
79		.len	= 6,
80	},
81};
82
83static int amanda_help(struct sk_buff *skb,
84		       unsigned int protoff,
85		       struct nf_conn *ct,
86		       enum ip_conntrack_info ctinfo)
87{
88	struct ts_state ts;
89	struct nf_conntrack_expect *exp;
90	struct nf_conntrack_tuple *tuple;
91	unsigned int dataoff, start, stop, off, i;
92	char pbuf[sizeof("65535")], *tmp;
93	u_int16_t len;
94	__be16 port;
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,
152				  nf_ct_l3num(ct),
153				  &tuple->src.u3, &tuple->dst.u3,
154				  IPPROTO_TCP, NULL, &port);
155
156		nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
157		if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
158			ret = nf_nat_amanda(skb, ctinfo, off - dataoff,
159					    len, exp);
160		else if (nf_ct_expect_related(exp) != 0)
161			ret = NF_DROP;
162		nf_ct_expect_put(exp);
163	}
164
165out:
166	return ret;
167}
168
169static const struct nf_conntrack_expect_policy amanda_exp_policy = {
170	.max_expected		= 3,
171	.timeout		= 180,
172};
173
174static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
175	{
176		.name			= "amanda",
177		.me			= THIS_MODULE,
178		.help			= amanda_help,
179		.tuple.src.l3num	= AF_INET,
180		.tuple.src.u.udp.port	= cpu_to_be16(10080),
181		.tuple.dst.protonum	= IPPROTO_UDP,
182		.expect_policy		= &amanda_exp_policy,
183	},
184	{
185		.name			= "amanda",
186		.me			= THIS_MODULE,
187		.help			= amanda_help,
188		.tuple.src.l3num	= AF_INET6,
189		.tuple.src.u.udp.port	= cpu_to_be16(10080),
190		.tuple.dst.protonum	= IPPROTO_UDP,
191		.expect_policy		= &amanda_exp_policy,
192	},
193};
194
195static void __exit nf_conntrack_amanda_fini(void)
196{
197	int i;
198
199	nf_conntrack_helper_unregister(&amanda_helper[0]);
200	nf_conntrack_helper_unregister(&amanda_helper[1]);
201	for (i = 0; i < ARRAY_SIZE(search); i++)
202		textsearch_destroy(search[i].ts);
203}
204
205static int __init nf_conntrack_amanda_init(void)
206{
207	int ret, i;
208
209	for (i = 0; i < ARRAY_SIZE(search); i++) {
210		search[i].ts = textsearch_prepare(ts_algo, search[i].string,
211						  search[i].len,
212						  GFP_KERNEL, TS_AUTOLOAD);
213		if (IS_ERR(search[i].ts)) {
214			ret = PTR_ERR(search[i].ts);
215			goto err1;
216		}
217	}
218	ret = nf_conntrack_helper_register(&amanda_helper[0]);
219	if (ret < 0)
220		goto err1;
221	ret = nf_conntrack_helper_register(&amanda_helper[1]);
222	if (ret < 0)
223		goto err2;
224	return 0;
225
226err2:
227	nf_conntrack_helper_unregister(&amanda_helper[0]);
228err1:
229	while (--i >= 0)
230		textsearch_destroy(search[i].ts);
231
232	return ret;
233}
234
235module_init(nf_conntrack_amanda_init);
236module_exit(nf_conntrack_amanda_fini);
237