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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 | |
f229f6ce | 4 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
16958900 PM |
5 | * |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public License | |
8 | * as published by the Free Software Foundation; either version | |
9 | * 2 of the License, or (at your option) any later version. | |
10 | */ | |
11 | ||
12 | #include <linux/kernel.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/skbuff.h> | |
15 | #include <linux/udp.h> | |
16 | ||
16958900 PM |
17 | #include <net/netfilter/nf_conntrack_helper.h> |
18 | #include <net/netfilter/nf_conntrack_expect.h> | |
1afc5679 | 19 | #include <net/netfilter/nf_nat_helper.h> |
16958900 PM |
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 | 28 | enum ip_conntrack_info ctinfo, |
051966c0 | 29 | unsigned int protoff, |
16958900 PM |
30 | unsigned int matchoff, |
31 | unsigned int matchlen, | |
32 | struct nf_conntrack_expect *exp) | |
33 | { | |
34 | char buffer[sizeof("65535")]; | |
35 | u_int16_t port; | |
36 | unsigned int ret; | |
37 | ||
38 | /* Connection comes from client. */ | |
39 | exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; | |
40 | exp->dir = IP_CT_DIR_ORIGINAL; | |
41 | ||
42 | /* When you see the packet, we need to NAT it the same as the | |
43 | * this one (ie. same IP: it will be TCP and master is UDP). */ | |
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++) { | |
ab0cba25 | 48 | int res; |
5b92b61f | 49 | |
16958900 | 50 | exp->tuple.dst.u.tcp.port = htons(port); |
ab0cba25 ED |
51 | res = nf_ct_expect_related(exp); |
52 | if (res == 0) | |
5b92b61f | 53 | break; |
ab0cba25 | 54 | else if (res != -EBUSY) { |
5b92b61f | 55 | port = 0; |
16958900 | 56 | break; |
5b92b61f | 57 | } |
16958900 PM |
58 | } |
59 | ||
b20ab9cc PNA |
60 | if (port == 0) { |
61 | nf_ct_helper_log(skb, exp->master, "all ports in use"); | |
16958900 | 62 | return NF_DROP; |
b20ab9cc | 63 | } |
16958900 PM |
64 | |
65 | sprintf(buffer, "%u", port); | |
3db05fea | 66 | ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo, |
051966c0 | 67 | protoff, matchoff, matchlen, |
16958900 | 68 | buffer, strlen(buffer)); |
b20ab9cc PNA |
69 | if (ret != NF_ACCEPT) { |
70 | nf_ct_helper_log(skb, exp->master, "cannot mangle packet"); | |
6823645d | 71 | nf_ct_unexpect_related(exp); |
b20ab9cc | 72 | } |
16958900 PM |
73 | return ret; |
74 | } | |
75 | ||
76 | static void __exit nf_nat_amanda_fini(void) | |
77 | { | |
a9b3cd7f | 78 | RCU_INIT_POINTER(nf_nat_amanda_hook, NULL); |
16958900 PM |
79 | synchronize_rcu(); |
80 | } | |
81 | ||
82 | static int __init nf_nat_amanda_init(void) | |
83 | { | |
d1332e0a | 84 | BUG_ON(nf_nat_amanda_hook != NULL); |
a9b3cd7f | 85 | RCU_INIT_POINTER(nf_nat_amanda_hook, help); |
16958900 PM |
86 | return 0; |
87 | } | |
88 | ||
89 | module_init(nf_nat_amanda_init); | |
90 | module_exit(nf_nat_amanda_fini); |