1 /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
2 *
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
21 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
22 MODULE_DESCRIPTION("TFTP connection tracking helper");
23 MODULE_LICENSE("GPL");
24 MODULE_ALIAS("ip_conntrack_tftp");
25 MODULE_ALIAS_NFCT_HELPER("tftp");
26
27 #define MAX_PORTS 8
28 static unsigned short ports[MAX_PORTS];
29 static unsigned int ports_c;
30 module_param_array(ports, ushort, &ports_c, 0400);
31 MODULE_PARM_DESC(ports, "Port numbers of TFTP servers");
32
33 unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb,
34 enum ip_conntrack_info ctinfo,
35 struct nf_conntrack_expect *exp) __read_mostly;
36 EXPORT_SYMBOL_GPL(nf_nat_tftp_hook);
37
tftp_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)38 static 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 return NF_DROP;
65 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
66 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
67 nf_ct_l3num(ct),
68 &tuple->src.u3, &tuple->dst.u3,
69 IPPROTO_UDP, NULL, &tuple->dst.u.udp.port);
70
71 pr_debug("expect: ");
72 nf_ct_dump_tuple(&exp->tuple);
73
74 nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook);
75 if (nf_nat_tftp && ct->status & IPS_NAT_MASK)
76 ret = nf_nat_tftp(skb, ctinfo, exp);
77 else if (nf_ct_expect_related(exp) != 0)
78 ret = NF_DROP;
79 nf_ct_expect_put(exp);
80 break;
81 case TFTP_OPCODE_DATA:
82 case TFTP_OPCODE_ACK:
83 pr_debug("Data/ACK opcode\n");
84 break;
85 case TFTP_OPCODE_ERROR:
86 pr_debug("Error opcode\n");
87 break;
88 default:
89 pr_debug("Unknown opcode\n");
90 }
91 return ret;
92 }
93
94 static struct nf_conntrack_helper tftp[MAX_PORTS][2] __read_mostly;
95 static char tftp_names[MAX_PORTS][2][sizeof("tftp-65535")] __read_mostly;
96
97 static const struct nf_conntrack_expect_policy tftp_exp_policy = {
98 .max_expected = 1,
99 .timeout = 5 * 60,
100 };
101
nf_conntrack_tftp_fini(void)102 static void nf_conntrack_tftp_fini(void)
103 {
104 int i, j;
105
106 for (i = 0; i < ports_c; i++) {
107 for (j = 0; j < 2; j++)
108 nf_conntrack_helper_unregister(&tftp[i][j]);
109 }
110 }
111
nf_conntrack_tftp_init(void)112 static int __init nf_conntrack_tftp_init(void)
113 {
114 int i, j, ret;
115 char *tmpname;
116
117 if (ports_c == 0)
118 ports[ports_c++] = TFTP_PORT;
119
120 for (i = 0; i < ports_c; i++) {
121 memset(&tftp[i], 0, sizeof(tftp[i]));
122
123 tftp[i][0].tuple.src.l3num = AF_INET;
124 tftp[i][1].tuple.src.l3num = AF_INET6;
125 for (j = 0; j < 2; j++) {
126 tftp[i][j].tuple.dst.protonum = IPPROTO_UDP;
127 tftp[i][j].tuple.src.u.udp.port = htons(ports[i]);
128 tftp[i][j].expect_policy = &tftp_exp_policy;
129 tftp[i][j].me = THIS_MODULE;
130 tftp[i][j].help = tftp_help;
131
132 tmpname = &tftp_names[i][j][0];
133 if (ports[i] == TFTP_PORT)
134 sprintf(tmpname, "tftp");
135 else
136 sprintf(tmpname, "tftp-%u", i);
137 tftp[i][j].name = tmpname;
138
139 ret = nf_conntrack_helper_register(&tftp[i][j]);
140 if (ret) {
141 printk("nf_ct_tftp: failed to register helper "
142 "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
152 module_init(nf_conntrack_tftp_init);
153 module_exit(nf_conntrack_tftp_fini);
154