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 * (C) 2006 Patrick McHardy <kaber@trash.net>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
11 */
12#include <linux/kernel.h>
13#include <linux/module.h>
14#include <linux/moduleparam.h>
15#include <linux/textsearch.h>
16#include <linux/skbuff.h>
17#include <linux/in.h>
18#include <linux/udp.h>
19#include <linux/netfilter.h>
20#include <linux/gfp.h>
21
22#include <net/netfilter/nf_conntrack.h>
23#include <net/netfilter/nf_conntrack_expect.h>
24#include <net/netfilter/nf_conntrack_ecache.h>
25#include <net/netfilter/nf_conntrack_helper.h>
26#include <linux/netfilter/nf_conntrack_amanda.h>
27
28static unsigned int master_timeout __read_mostly = 300;
29static char *ts_algo = "kmp";
30
31MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
32MODULE_DESCRIPTION("Amanda connection tracking module");
33MODULE_LICENSE("GPL");
34MODULE_ALIAS("ip_conntrack_amanda");
35MODULE_ALIAS_NFCT_HELPER("amanda");
36
37module_param(master_timeout, uint, 0600);
38MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
39module_param(ts_algo, charp, 0400);
40MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
41
42unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
43				   enum ip_conntrack_info ctinfo,
44				   unsigned int protoff,
45				   unsigned int matchoff,
46				   unsigned int matchlen,
47				   struct nf_conntrack_expect *exp)
48				   __read_mostly;
49EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
50
51enum amanda_strings {
52	SEARCH_CONNECT,
53	SEARCH_NEWLINE,
54	SEARCH_DATA,
55	SEARCH_MESG,
56	SEARCH_INDEX,
57};
58
59static struct {
60	const char		*string;
61	size_t			len;
62	struct ts_config	*ts;
63} search[] __read_mostly = {
64	[SEARCH_CONNECT] = {
65		.string	= "CONNECT ",
66		.len	= 8,
67	},
68	[SEARCH_NEWLINE] = {
69		.string	= "\n",
70		.len	= 1,
71	},
72	[SEARCH_DATA] = {
73		.string	= "DATA ",
74		.len	= 5,
75	},
76	[SEARCH_MESG] = {
77		.string	= "MESG ",
78		.len	= 5,
79	},
80	[SEARCH_INDEX] = {
81		.string = "INDEX ",
82		.len	= 6,
83	},
84};
85
86static int amanda_help(struct sk_buff *skb,
87		       unsigned int protoff,
88		       struct nf_conn *ct,
89		       enum ip_conntrack_info ctinfo)
90{
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	start = skb_find_text(skb, dataoff, skb->len,
116			      search[SEARCH_CONNECT].ts);
117	if (start == UINT_MAX)
118		goto out;
119	start += dataoff + search[SEARCH_CONNECT].len;
120
121	stop = skb_find_text(skb, start, skb->len,
122			     search[SEARCH_NEWLINE].ts);
123	if (stop == UINT_MAX)
124		goto out;
125	stop += start;
126
127	for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
128		off = skb_find_text(skb, start, stop, search[i].ts);
129		if (off == UINT_MAX)
130			continue;
131		off += start + search[i].len;
132
133		len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
134		if (skb_copy_bits(skb, off, pbuf, len))
135			break;
136		pbuf[len] = '\0';
137
138		port = htons(simple_strtoul(pbuf, &tmp, 10));
139		len = tmp - pbuf;
140		if (port == 0 || len > 5)
141			break;
142
143		exp = nf_ct_expect_alloc(ct);
144		if (exp == NULL) {
145			nf_ct_helper_log(skb, ct, "cannot alloc expectation");
146			ret = NF_DROP;
147			goto out;
148		}
149		tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
150		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
151				  nf_ct_l3num(ct),
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, protoff,
158					    off - dataoff, len, exp);
159		else if (nf_ct_expect_related(exp) != 0) {
160			nf_ct_helper_log(skb, ct, "cannot add expectation");
161			ret = NF_DROP;
162		}
163		nf_ct_expect_put(exp);
164	}
165
166out:
167	return ret;
168}
169
170static const struct nf_conntrack_expect_policy amanda_exp_policy = {
171	.max_expected		= 3,
172	.timeout		= 180,
173};
174
175static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
176	{
177		.name			= "amanda",
178		.me			= THIS_MODULE,
179		.help			= amanda_help,
180		.tuple.src.l3num	= AF_INET,
181		.tuple.src.u.udp.port	= cpu_to_be16(10080),
182		.tuple.dst.protonum	= IPPROTO_UDP,
183		.expect_policy		= &amanda_exp_policy,
184	},
185	{
186		.name			= "amanda",
187		.me			= THIS_MODULE,
188		.help			= amanda_help,
189		.tuple.src.l3num	= AF_INET6,
190		.tuple.src.u.udp.port	= cpu_to_be16(10080),
191		.tuple.dst.protonum	= IPPROTO_UDP,
192		.expect_policy		= &amanda_exp_policy,
193	},
194};
195
196static void __exit nf_conntrack_amanda_fini(void)
197{
198	int i;
199
200	nf_conntrack_helper_unregister(&amanda_helper[0]);
201	nf_conntrack_helper_unregister(&amanda_helper[1]);
202	for (i = 0; i < ARRAY_SIZE(search); i++)
203		textsearch_destroy(search[i].ts);
204}
205
206static int __init nf_conntrack_amanda_init(void)
207{
208	int ret, i;
209
210	for (i = 0; i < ARRAY_SIZE(search); i++) {
211		search[i].ts = textsearch_prepare(ts_algo, search[i].string,
212						  search[i].len,
213						  GFP_KERNEL, TS_AUTOLOAD);
214		if (IS_ERR(search[i].ts)) {
215			ret = PTR_ERR(search[i].ts);
216			goto err1;
217		}
218	}
219	ret = nf_conntrack_helper_register(&amanda_helper[0]);
220	if (ret < 0)
221		goto err1;
222	ret = nf_conntrack_helper_register(&amanda_helper[1]);
223	if (ret < 0)
224		goto err2;
225	return 0;
226
227err2:
228	nf_conntrack_helper_unregister(&amanda_helper[0]);
229err1:
230	while (--i >= 0)
231		textsearch_destroy(search[i].ts);
232
233	return ret;
234}
235
236module_init(nf_conntrack_amanda_init);
237module_exit(nf_conntrack_amanda_fini);
238