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 #include <linux/module.h>
14 #include <linux/moduleparam.h>
15 #include <linux/tcp.h>
16 #include <linux/kernel.h>
17
18 #include <net/netfilter/nf_nat.h>
19 #include <net/netfilter/nf_nat_helper.h>
20 #include <net/netfilter/nf_nat_rule.h>
21 #include <net/netfilter/nf_conntrack_helper.h>
22 #include <net/netfilter/nf_conntrack_expect.h>
23 #include <linux/netfilter/nf_conntrack_irc.h>
24
25 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
26 MODULE_DESCRIPTION("IRC (DCC) NAT helper");
27 MODULE_LICENSE("GPL");
28 MODULE_ALIAS("ip_nat_irc");
29
help(struct sk_buff * skb,enum ip_conntrack_info ctinfo,unsigned int matchoff,unsigned int matchlen,struct nf_conntrack_expect * exp)30 static unsigned int help(struct sk_buff *skb,
31 enum ip_conntrack_info ctinfo,
32 unsigned int matchoff,
33 unsigned int matchlen,
34 struct nf_conntrack_expect *exp)
35 {
36 char buffer[sizeof("4294967296 65635")];
37 u_int32_t ip;
38 u_int16_t port;
39 unsigned int ret;
40
41 /* Reply comes from server. */
42 exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
43 exp->dir = IP_CT_DIR_REPLY;
44 exp->expectfn = nf_nat_follow_master;
45
46 /* Try to get same port: if not, try to change it. */
47 for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
48 exp->tuple.dst.u.tcp.port = htons(port);
49 if (nf_ct_expect_related(exp) == 0)
50 break;
51 }
52
53 if (port == 0)
54 return NF_DROP;
55
56 ip = ntohl(exp->master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip);
57 sprintf(buffer, "%u %u", ip, port);
58 pr_debug("nf_nat_irc: inserting '%s' == %pI4, port %u\n",
59 buffer, &ip, port);
60
61 ret = nf_nat_mangle_tcp_packet(skb, exp->master, ctinfo,
62 matchoff, matchlen, buffer,
63 strlen(buffer));
64 if (ret != NF_ACCEPT)
65 nf_ct_unexpect_related(exp);
66 return ret;
67 }
68
nf_nat_irc_fini(void)69 static void __exit nf_nat_irc_fini(void)
70 {
71 rcu_assign_pointer(nf_nat_irc_hook, NULL);
72 synchronize_rcu();
73 }
74
nf_nat_irc_init(void)75 static int __init nf_nat_irc_init(void)
76 {
77 BUG_ON(nf_nat_irc_hook != NULL);
78 rcu_assign_pointer(nf_nat_irc_hook, help);
79 return 0;
80 }
81
82 /* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
warn_set(const char * val,struct kernel_param * kp)83 static int warn_set(const char *val, struct kernel_param *kp)
84 {
85 printk(KERN_INFO KBUILD_MODNAME
86 ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
87 return 0;
88 }
89 module_param_call(ports, warn_set, NULL, NULL, 0);
90
91 module_init(nf_nat_irc_init);
92 module_exit(nf_nat_irc_fini);
93