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