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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 | ||
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 | ||
69 | static void __exit nf_nat_irc_fini(void) | |
70 | { | |
71 | rcu_assign_pointer(nf_nat_irc_hook, NULL); | |
72 | synchronize_rcu(); | |
73 | } | |
74 | ||
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. */ | |
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); |