1 /* IRC extension for TCP NAT alteration.
2 *
3 * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
4 * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
5 * based on a copy of RR's ip_nat_ftp.c
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
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15 #include <linux/module.h>
16 #include <linux/moduleparam.h>
17 #include <linux/tcp.h>
18 #include <linux/kernel.h>
19
20 #include <net/netfilter/nf_nat.h>
21 #include <net/netfilter/nf_nat_helper.h>
22 #include <net/netfilter/nf_conntrack_helper.h>
23 #include <net/netfilter/nf_conntrack_expect.h>
24 #include <linux/netfilter/nf_conntrack_irc.h>
25
26 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
27 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
28 MODULE_LICENSE("GPL");
29 MODULE_ALIAS("ip_nat_irc");
30
help(struct sk_buff * skb,enum ip_conntrack_info ctinfo,unsigned int protoff,unsigned int matchoff,unsigned int matchlen,struct nf_conntrack_expect * exp)31 static unsigned int help(struct sk_buff *skb,
32 enum ip_conntrack_info ctinfo,
33 unsigned int protoff,
34 unsigned int matchoff,
35 unsigned int matchlen,
36 struct nf_conntrack_expect *exp)
37 {
38 char buffer[sizeof("4294967296 65635")];
39 struct nf_conn *ct = exp->master;
40 union nf_inet_addr newaddr;
41 u_int16_t port;
42
43 /* Reply comes from server. */
44 newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
45
46 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
47 exp->dir = IP_CT_DIR_REPLY;
48 exp->expectfn = nf_nat_follow_master;
49
50 /* Try to get same port: if not, try to change it. */
51 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
52 int ret;
53
54 exp->tuple.dst.u.tcp.port = htons(port);
55 ret = nf_ct_expect_related(exp);
56 if (ret == 0)
57 break;
58 else if (ret != -EBUSY) {
59 port = 0;
60 break;
61 }
62 }
63
64 if (port == 0) {
65 nf_ct_helper_log(skb, ct, "all ports in use");
66 return NF_DROP;
67 }
68
69 /* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27
70 * strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28
71 * strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
72 * strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
73 * strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
74 *
75 * AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits,
76 * 255.255.255.255==4294967296, 10 digits)
77 * P: bound port (min 1 d, max 5d (65635))
78 * F: filename (min 1 d )
79 * S: size (min 1 d )
80 * 0x01, \n: terminators
81 */
82 /* AAA = "us", ie. where server normally talks to. */
83 snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port);
84 pr_debug("inserting '%s' == %pI4, port %u\n",
85 buffer, &newaddr.ip, port);
86
87 if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
88 matchlen, buffer, strlen(buffer))) {
89 nf_ct_helper_log(skb, ct, "cannot mangle packet");
90 nf_ct_unexpect_related(exp);
91 return NF_DROP;
92 }
93
94 return NF_ACCEPT;
95 }
96
nf_nat_irc_fini(void)97 static void __exit nf_nat_irc_fini(void)
98 {
99 RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
100 synchronize_rcu();
101 }
102
nf_nat_irc_init(void)103 static int __init nf_nat_irc_init(void)
104 {
105 BUG_ON(nf_nat_irc_hook != NULL);
106 RCU_INIT_POINTER(nf_nat_irc_hook, help);
107 return 0;
108 }
109
110 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
warn_set(const char * val,const struct kernel_param * kp)111 static int warn_set(const char *val, const struct kernel_param *kp)
112 {
113 pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
114 return 0;
115 }
116 module_param_call(ports, warn_set, NULL, NULL, 0);
117
118 module_init(nf_nat_irc_init);
119 module_exit(nf_nat_irc_fini);
120
