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 ts_state ts;
92	struct nf_conntrack_expect *exp;
93	struct nf_conntrack_tuple *tuple;
94	unsigned int dataoff, start, stop, off, i;
95	char pbuf[sizeof("65535")], *tmp;
96	u_int16_t len;
97	__be16 port;
98	int ret = NF_ACCEPT;
99	typeof(nf_nat_amanda_hook) nf_nat_amanda;
100
101	/* Only look at packets from the Amanda server */
102	if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
103		return NF_ACCEPT;
104
105	/* increase the UDP timeout of the master connection as replies from
106	 * Amanda clients to the server can be quite delayed */
107	nf_ct_refresh(ct, skb, master_timeout * HZ);
108
109	/* No data? */
110	dataoff = protoff + sizeof(struct udphdr);
111	if (dataoff >= skb->len) {
112		net_err_ratelimited("amanda_help: skblen = %u\n", skb->len);
113		return NF_ACCEPT;
114	}
115
116	memset(&ts, 0, sizeof(ts));
117	start = skb_find_text(skb, dataoff, skb->len,
118			      search[SEARCH_CONNECT].ts, &ts);
119	if (start == UINT_MAX)
120		goto out;
121	start += dataoff + search[SEARCH_CONNECT].len;
122
123	memset(&ts, 0, sizeof(ts));
124	stop = skb_find_text(skb, start, skb->len,
125			     search[SEARCH_NEWLINE].ts, &ts);
126	if (stop == UINT_MAX)
127		goto out;
128	stop += start;
129
130	for (i = SEARCH_DATA; i <= SEARCH_INDEX; i++) {
131		memset(&ts, 0, sizeof(ts));
132		off = skb_find_text(skb, start, stop, search[i].ts, &ts);
133		if (off == UINT_MAX)
134			continue;
135		off += start + search[i].len;
136
137		len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
138		if (skb_copy_bits(skb, off, pbuf, len))
139			break;
140		pbuf[len] = '\0';
141
142		port = htons(simple_strtoul(pbuf, &tmp, 10));
143		len = tmp - pbuf;
144		if (port == 0 || len > 5)
145			break;
146
147		exp = nf_ct_expect_alloc(ct);
148		if (exp == NULL) {
149			nf_ct_helper_log(skb, ct, "cannot alloc expectation");
150			ret = NF_DROP;
151			goto out;
152		}
153		tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
154		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
155				  nf_ct_l3num(ct),
156				  &tuple->src.u3, &tuple->dst.u3,
157				  IPPROTO_TCP, NULL, &port);
158
159		nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
160		if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
161			ret = nf_nat_amanda(skb, ctinfo, protoff,
162					    off - dataoff, len, exp);
163		else if (nf_ct_expect_related(exp) != 0) {
164			nf_ct_helper_log(skb, ct, "cannot add expectation");
165			ret = NF_DROP;
166		}
167		nf_ct_expect_put(exp);
168	}
169
170out:
171	return ret;
172}
173
174static const struct nf_conntrack_expect_policy amanda_exp_policy = {
175	.max_expected		= 3,
176	.timeout		= 180,
177};
178
179static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
180	{
181		.name			= "amanda",
182		.me			= THIS_MODULE,
183		.help			= amanda_help,
184		.tuple.src.l3num	= AF_INET,
185		.tuple.src.u.udp.port	= cpu_to_be16(10080),
186		.tuple.dst.protonum	= IPPROTO_UDP,
187		.expect_policy		= &amanda_exp_policy,
188	},
189	{
190		.name			= "amanda",
191		.me			= THIS_MODULE,
192		.help			= amanda_help,
193		.tuple.src.l3num	= AF_INET6,
194		.tuple.src.u.udp.port	= cpu_to_be16(10080),
195		.tuple.dst.protonum	= IPPROTO_UDP,
196		.expect_policy		= &amanda_exp_policy,
197	},
198};
199
200static void __exit nf_conntrack_amanda_fini(void)
201{
202	int i;
203
204	nf_conntrack_helper_unregister(&amanda_helper[0]);
205	nf_conntrack_helper_unregister(&amanda_helper[1]);
206	for (i = 0; i < ARRAY_SIZE(search); i++)
207		textsearch_destroy(search[i].ts);
208}
209
210static int __init nf_conntrack_amanda_init(void)
211{
212	int ret, i;
213
214	for (i = 0; i < ARRAY_SIZE(search); i++) {
215		search[i].ts = textsearch_prepare(ts_algo, search[i].string,
216						  search[i].len,
217						  GFP_KERNEL, TS_AUTOLOAD);
218		if (IS_ERR(search[i].ts)) {
219			ret = PTR_ERR(search[i].ts);
220			goto err1;
221		}
222	}
223	ret = nf_conntrack_helper_register(&amanda_helper[0]);
224	if (ret < 0)
225		goto err1;
226	ret = nf_conntrack_helper_register(&amanda_helper[1]);
227	if (ret < 0)
228		goto err2;
229	return 0;
230
231err2:
232	nf_conntrack_helper_unregister(&amanda_helper[0]);
233err1:
234	while (--i >= 0)
235		textsearch_destroy(search[i].ts);
236
237	return ret;
238}
239
240module_init(nf_conntrack_amanda_init);
241module_exit(nf_conntrack_amanda_fini);
242