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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
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
