nf_conntrack_amanda.c revision 051966c0c644a1c96092d4206e00704ade813c9a 
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#include <linux/gfp.h>
20
21#include <net/netfilter/nf_conntrack.h>
22#include <net/netfilter/nf_conntrack_expect.h>
23#include <net/netfilter/nf_conntrack_ecache.h>
24#include <net/netfilter/nf_conntrack_helper.h>
25#include <linux/netfilter/nf_conntrack_amanda.h>
26
27static unsigned int master_timeout __read_mostly = 300;
28static char *ts_algo = "kmp";
29
30MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
31MODULE_DESCRIPTION("Amanda connection tracking module");
32MODULE_LICENSE("GPL");
33MODULE_ALIAS("ip_conntrack_amanda");
34MODULE_ALIAS_NFCT_HELPER("amanda");
35
36module_param(master_timeout, uint, 0600);
37MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
38module_param(ts_algo, charp, 0400);
39MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
40
41unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
42				   enum ip_conntrack_info ctinfo,
43				   unsigned int protoff,
44				   unsigned int matchoff,
45				   unsigned int matchlen,
46				   struct nf_conntrack_expect *exp)
47				   __read_mostly;
48EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
49
50enum amanda_strings {
51	SEARCH_CONNECT,
52	SEARCH_NEWLINE,
53	SEARCH_DATA,
54	SEARCH_MESG,
55	SEARCH_INDEX,
56};
57
58static struct {
59	const char		*string;
60	size_t			len;
61	struct ts_config	*ts;
62} search[] __read_mostly = {
63	[SEARCH_CONNECT] = {
64		.string	= "CONNECT ",
65		.len	= 8,
66	},
67	[SEARCH_NEWLINE] = {
68		.string	= "\n",
69		.len	= 1,
70	},
71	[SEARCH_DATA] = {
72		.string	= "DATA ",
73		.len	= 5,
74	},
75	[SEARCH_MESG] = {
76		.string	= "MESG ",
77		.len	= 5,
78	},
79	[SEARCH_INDEX] = {
80		.string = "INDEX ",
81		.len	= 6,
82	},
83};
84
85static int amanda_help(struct sk_buff *skb,
86		       unsigned int protoff,
87		       struct nf_conn *ct,
88		       enum ip_conntrack_info ctinfo)
89{
90	struct ts_state ts;
91	struct nf_conntrack_expect *exp;
92	struct nf_conntrack_tuple *tuple;
93	unsigned int dataoff, start, stop, off, i;
94	char pbuf[sizeof("65535")], *tmp;
95	u_int16_t len;
96	__be16 port;
97	int ret = NF_ACCEPT;
98	typeof(nf_nat_amanda_hook) nf_nat_amanda;
99
100	/* Only look at packets from the Amanda server */
101	if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
102		return NF_ACCEPT;
103
104	/* increase the UDP timeout of the master connection as replies from
105	 * Amanda clients to the server can be quite delayed */
106	nf_ct_refresh(ct, skb, master_timeout * HZ);
107
108	/* No data? */
109	dataoff = protoff + sizeof(struct udphdr);
110	if (dataoff >= skb->len) {
111		net_err_ratelimited("amanda_help: skblen = %u\n", skb->len);
112		return NF_ACCEPT;
113	}
114
115	memset(&ts, 0, sizeof(ts));
116	start = skb_find_text(skb, dataoff, skb->len,
117			      search[SEARCH_CONNECT].ts, &ts);
118	if (start == UINT_MAX)
119		goto out;
120	start += dataoff + search[SEARCH_CONNECT].len;
121
122	memset(&ts, 0, sizeof(ts));
123	stop = skb_find_text(skb, start, skb->len,
124			     search[SEARCH_NEWLINE].ts, &ts);
125	if (stop == UINT_MAX)
126		goto out;
127	stop += start;
128
129	for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
130		memset(&ts, 0, sizeof(ts));
131		off = skb_find_text(skb, start, stop, search[i].ts, &ts);
132		if (off == UINT_MAX)
133			continue;
134		off += start + search[i].len;
135
136		len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
137		if (skb_copy_bits(skb, off, pbuf, len))
138			break;
139		pbuf[len] = '\0';
140
141		port = htons(simple_strtoul(pbuf, &tmp, 10));
142		len = tmp - pbuf;
143		if (port == 0 || len > 5)
144			break;
145
146		exp = nf_ct_expect_alloc(ct);
147		if (exp == NULL) {
148			ret = NF_DROP;
149			goto out;
150		}
151		tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
152		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
153				  nf_ct_l3num(ct),
154				  &tuple->src.u3, &tuple->dst.u3,
155				  IPPROTO_TCP, NULL, &port);
156
157		nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
158		if (nf_nat_amanda && nf_ct_l3num(ct) == NFPROTO_IPV4 &&
159		    ct->status & IPS_NAT_MASK)
160			ret = nf_nat_amanda(skb, ctinfo, protoff,
161					    off - dataoff, len, exp);
162		else if (nf_ct_expect_related(exp) != 0)
163			ret = NF_DROP;
164		nf_ct_expect_put(exp);
165	}
166
167out:
168	return ret;
169}
170
171static const struct nf_conntrack_expect_policy amanda_exp_policy = {
172	.max_expected		= 3,
173	.timeout		= 180,
174};
175
176static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
177	{
178		.name			= "amanda",
179		.me			= THIS_MODULE,
180		.help			= amanda_help,
181		.tuple.src.l3num	= AF_INET,
182		.tuple.src.u.udp.port	= cpu_to_be16(10080),
183		.tuple.dst.protonum	= IPPROTO_UDP,
184		.expect_policy		= &amanda_exp_policy,
185	},
186	{
187		.name			= "amanda",
188		.me			= THIS_MODULE,
189		.help			= amanda_help,
190		.tuple.src.l3num	= AF_INET6,
191		.tuple.src.u.udp.port	= cpu_to_be16(10080),
192		.tuple.dst.protonum	= IPPROTO_UDP,
193		.expect_policy		= &amanda_exp_policy,
194	},
195};
196
197static void __exit nf_conntrack_amanda_fini(void)
198{
199	int i;
200
201	nf_conntrack_helper_unregister(&amanda_helper[0]);
202	nf_conntrack_helper_unregister(&amanda_helper[1]);
203	for (i = 0; i < ARRAY_SIZE(search); i++)
204		textsearch_destroy(search[i].ts);
205}
206
207static int __init nf_conntrack_amanda_init(void)
208{
209	int ret, i;
210
211	for (i = 0; i < ARRAY_SIZE(search); i++) {
212		search[i].ts = textsearch_prepare(ts_algo, search[i].string,
213						  search[i].len,
214						  GFP_KERNEL, TS_AUTOLOAD);
215		if (IS_ERR(search[i].ts)) {
216			ret = PTR_ERR(search[i].ts);
217			goto err1;
218		}
219	}
220	ret = nf_conntrack_helper_register(&amanda_helper[0]);
221	if (ret < 0)
222		goto err1;
223	ret = nf_conntrack_helper_register(&amanda_helper[1]);
224	if (ret < 0)
225		goto err2;
226	return 0;
227
228err2:
229	nf_conntrack_helper_unregister(&amanda_helper[0]);
230err1:
231	while (--i >= 0)
232		textsearch_destroy(search[i].ts);
233
234	return ret;
235}
236
237module_init(nf_conntrack_amanda_init);
238module_exit(nf_conntrack_amanda_fini);
239