1/* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
2 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License version 2 as
5 * published by the Free Software Foundation.
6 */
7
8#include <linux/module.h>
9#include <linux/moduleparam.h>
10#include <linux/in.h>
11#include <linux/udp.h>
12#include <linux/netfilter.h>
13
14#include <net/netfilter/nf_conntrack.h>
15#include <net/netfilter/nf_conntrack_tuple.h>
16#include <net/netfilter/nf_conntrack_expect.h>
17#include <net/netfilter/nf_conntrack_ecache.h>
18#include <net/netfilter/nf_conntrack_helper.h>
19#include <linux/netfilter/nf_conntrack_tftp.h>
20
21MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
22MODULE_DESCRIPTION("TFTP connection tracking helper");
23MODULE_LICENSE("GPL");
24MODULE_ALIAS("ip_conntrack_tftp");
25MODULE_ALIAS_NFCT_HELPER("tftp");
26
27#define MAX_PORTS 8
28static unsigned short ports[MAX_PORTS];
29static unsigned int ports_c;
30module_param_array(ports, ushort, &ports_c, 0400);
31MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
32
33unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
34				 enum ip_conntrack_info ctinfo,
35				 struct nf_conntrack_expect *exp) __read_mostly;
36EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
37
38static int tftp_help(struct sk_buff *skb,
39		     unsigned int protoff,
40		     struct nf_conn *ct,
41		     enum ip_conntrack_info ctinfo)
42{
43	const struct tftphdr *tfh;
44	struct tftphdr _tftph;
45	struct nf_conntrack_expect *exp;
46	struct nf_conntrack_tuple *tuple;
47	unsigned int ret = NF_ACCEPT;
48	typeof(nf_nat_tftp_hook) nf_nat_tftp;
49
50	tfh = skb_header_pointer(skb, protoff + sizeof(struct udphdr),
51				 sizeof(_tftph), &_tftph);
52	if (tfh == NULL)
53		return NF_ACCEPT;
54
55	switch (ntohs(tfh->opcode)) {
56	case TFTP_OPCODE_READ:
57	case TFTP_OPCODE_WRITE:
58		/* RRQ and WRQ works the same way */
59		nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
60		nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
61
62		exp = nf_ct_expect_alloc(ct);
63		if (exp == NULL) {
64			nf_ct_helper_log(skb, ct, "cannot alloc expectation");
65			return NF_DROP;
66		}
67		tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
68		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
69				  nf_ct_l3num(ct),
70				  &tuple->src.u3, &tuple->dst.u3,
71				  IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
72
73		pr_debug("expect: ");
74		nf_ct_dump_tuple(&exp->tuple);
75
76		nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
77		if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
78			ret = nf_nat_tftp(skb, ctinfo, exp);
79		else if (nf_ct_expect_related(exp) != 0) {
80			nf_ct_helper_log(skb, ct, "cannot add expectation");
81			ret = NF_DROP;
82		}
83		nf_ct_expect_put(exp);
84		break;
85	case TFTP_OPCODE_DATA:
86	case TFTP_OPCODE_ACK:
87		pr_debug("Data/ACK opcode\n");
88		break;
89	case TFTP_OPCODE_ERROR:
90		pr_debug("Error opcode\n");
91		break;
92	default:
93		pr_debug("Unknown opcode\n");
94	}
95	return ret;
96}
97
98static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
99
100static const struct nf_conntrack_expect_policy tftp_exp_policy = {
101	.max_expected	= 1,
102	.timeout	= 5 * 60,
103};
104
105static void nf_conntrack_tftp_fini(void)
106{
107	int i, j;
108
109	for (i = 0; i < ports_c; i++) {
110		for (j = 0; j < 2; j++)
111			nf_conntrack_helper_unregister(&tftp[i][j]);
112	}
113}
114
115static int __init nf_conntrack_tftp_init(void)
116{
117	int i, j, ret;
118
119	if (ports_c == 0)
120		ports[ports_c++] = TFTP_PORT;
121
122	for (i = 0; i < ports_c; i++) {
123		memset(&tftp[i], 0, sizeof(tftp[i]));
124
125		tftp[i][0].tuple.src.l3num = AF_INET;
126		tftp[i][1].tuple.src.l3num = AF_INET6;
127		for (j = 0; j < 2; j++) {
128			tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
129			tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
130			tftp[i][j].expect_policy = &tftp_exp_policy;
131			tftp[i][j].me = THIS_MODULE;
132			tftp[i][j].help = tftp_help;
133
134			if (ports[i] == TFTP_PORT)
135				sprintf(tftp[i][j].name, "tftp");
136			else
137				sprintf(tftp[i][j].name, "tftp-%u", i);
138
139			ret = nf_conntrack_helper_register(&tftp[i][j]);
140			if (ret) {
141				printk(KERN_ERR "nf_ct_tftp: failed to register"
142				       " helper for pf: %u port: %u\n",
143					tftp[i][j].tuple.src.l3num, ports[i]);
144				nf_conntrack_tftp_fini();
145				return ret;
146			}
147		}
148	}
149	return 0;
150}
151
152module_init(nf_conntrack_tftp_init);
153module_exit(nf_conntrack_tftp_fini);
154