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16958900 PM |
1 | /* Amanda extension for TCP NAT alteration. |
2 | * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca> | |
3 | * based on a copy of HW's ip_nat_irc.c as well as other modules | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or | |
6 | * modify it under the terms of the GNU General Public License | |
7 | * as published by the Free Software Foundation; either version | |
8 | * 2 of the License, or (at your option) any later version. | |
9 | */ | |
10 | ||
11 | #include <linux/kernel.h> | |
12 | #include <linux/module.h> | |
13 | #include <linux/skbuff.h> | |
14 | #include <linux/udp.h> | |
15 | ||
16 | #include <net/netfilter/nf_nat_helper.h> | |
17 | #include <net/netfilter/nf_nat_rule.h> | |
18 | #include <net/netfilter/nf_conntrack_helper.h> | |
19 | #include <net/netfilter/nf_conntrack_expect.h> | |
20 | #include <linux/netfilter/nf_conntrack_amanda.h> | |
21 | ||
22 | MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>"); | |
23 | MODULE_DESCRIPTION("Amanda NAT helper"); | |
24 | MODULE_LICENSE("GPL"); | |
25 | MODULE_ALIAS("ip_nat_amanda"); | |
26 | ||
3db05fea | 27 | static unsigned int help(struct sk_buff *skb, |
16958900 PM |
28 | enum ip_conntrack_info ctinfo, |
29 | unsigned int matchoff, | |
30 | unsigned int matchlen, | |
31 | struct nf_conntrack_expect *exp) | |
32 | { | |
33 | char buffer[sizeof("65535")]; | |
34 | u_int16_t port; | |
35 | unsigned int ret; | |
36 | ||
37 | /* Connection comes from client. */ | |
38 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; | |
39 | exp->dir = IP_CT_DIR_ORIGINAL; | |
40 | ||
41 | /* When you see the packet, we need to NAT it the same as the | |
42 | * this one (ie. same IP: it will be TCP and master is UDP). */ | |
43 | exp->expectfn = nf_nat_follow_master; | |
44 | ||
45 | /* Try to get same port: if not, try to change it. */ | |
46 | for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { | |
5b92b61f PNA |
47 | int ret; |
48 | ||
16958900 | 49 | exp->tuple.dst.u.tcp.port = htons(port); |
5b92b61f PNA |
50 | ret = nf_ct_expect_related(exp); |
51 | if (ret == 0) | |
52 | break; | |
53 | else if (ret != -EBUSY) { | |
54 | port = 0; | |
16958900 | 55 | break; |
5b92b61f | 56 | } |
16958900 PM |
57 | } |
58 | ||
59 | if (port == 0) | |
60 | return NF_DROP; | |
61 | ||
62 | sprintf(buffer, "%u", port); | |
3db05fea | 63 | ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo, |
16958900 PM |
64 | matchoff, matchlen, |
65 | buffer, strlen(buffer)); | |
66 | if (ret != NF_ACCEPT) | |
6823645d | 67 | nf_ct_unexpect_related(exp); |
16958900 PM |
68 | return ret; |
69 | } | |
70 | ||
71 | static void __exit nf_nat_amanda_fini(void) | |
72 | { | |
73 | rcu_assign_pointer(nf_nat_amanda_hook, NULL); | |
74 | synchronize_rcu(); | |
75 | } | |
76 | ||
77 | static int __init nf_nat_amanda_init(void) | |
78 | { | |
d1332e0a | 79 | BUG_ON(nf_nat_amanda_hook != NULL); |
16958900 PM |
80 | rcu_assign_pointer(nf_nat_amanda_hook, help); |
81 | return 0; | |
82 | } | |
83 | ||
84 | module_init(nf_nat_amanda_init); | |
85 | module_exit(nf_nat_amanda_fini); |