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2874c5fd | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
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2 | /* Amanda extension for TCP NAT alteration. |
3 | * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca> | |
4 | * based on a copy of HW's ip_nat_irc.c as well as other modules | |
f229f6ce | 5 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
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6 | */ |
7 | ||
8 | #include <linux/kernel.h> | |
9 | #include <linux/module.h> | |
10 | #include <linux/skbuff.h> | |
11 | #include <linux/udp.h> | |
12 | ||
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13 | #include <net/netfilter/nf_conntrack_helper.h> |
14 | #include <net/netfilter/nf_conntrack_expect.h> | |
1afc5679 | 15 | #include <net/netfilter/nf_nat_helper.h> |
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16 | #include <linux/netfilter/nf_conntrack_amanda.h> |
17 | ||
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18 | #define NAT_HELPER_NAME "amanda" |
19 | ||
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20 | MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>"); |
21 | MODULE_DESCRIPTION("Amanda NAT helper"); | |
22 | MODULE_LICENSE("GPL"); | |
53b11308 FL |
23 | MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); |
24 | ||
25 | static struct nf_conntrack_nat_helper nat_helper_amanda = | |
26 | NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); | |
16958900 | 27 | |
3db05fea | 28 | static unsigned int help(struct sk_buff *skb, |
16958900 | 29 | enum ip_conntrack_info ctinfo, |
051966c0 | 30 | unsigned int protoff, |
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31 | unsigned int matchoff, |
32 | unsigned int matchlen, | |
33 | struct nf_conntrack_expect *exp) | |
34 | { | |
35 | char buffer[sizeof("65535")]; | |
36 | u_int16_t port; | |
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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); |
3c00fb0b | 51 | res = nf_ct_expect_related(exp, 0); |
ab0cba25 | 52 | if (res == 0) |
5b92b61f | 53 | break; |
ab0cba25 | 54 | else if (res != -EBUSY) { |
5b92b61f | 55 | port = 0; |
16958900 | 56 | break; |
5b92b61f | 57 | } |
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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 | } |
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64 | |
65 | sprintf(buffer, "%u", port); | |
cba81cc4 GF |
66 | if (!nf_nat_mangle_udp_packet(skb, exp->master, ctinfo, |
67 | protoff, matchoff, matchlen, | |
68 | buffer, strlen(buffer))) { | |
b20ab9cc | 69 | nf_ct_helper_log(skb, exp->master, "cannot mangle packet"); |
6823645d | 70 | nf_ct_unexpect_related(exp); |
cba81cc4 | 71 | return NF_DROP; |
b20ab9cc | 72 | } |
cba81cc4 | 73 | return NF_ACCEPT; |
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74 | } |
75 | ||
76 | static void __exit nf_nat_amanda_fini(void) | |
77 | { | |
53b11308 | 78 | nf_nat_helper_unregister(&nat_helper_amanda); |
a9b3cd7f | 79 | RCU_INIT_POINTER(nf_nat_amanda_hook, NULL); |
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80 | synchronize_rcu(); |
81 | } | |
82 | ||
83 | static int __init nf_nat_amanda_init(void) | |
84 | { | |
d1332e0a | 85 | BUG_ON(nf_nat_amanda_hook != NULL); |
53b11308 | 86 | nf_nat_helper_register(&nat_helper_amanda); |
a9b3cd7f | 87 | RCU_INIT_POINTER(nf_nat_amanda_hook, help); |
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88 | return 0; |
89 | } | |
90 | ||
91 | module_init(nf_nat_amanda_init); | |
92 | module_exit(nf_nat_amanda_fini); |