1 // SPDX-License-Identifier: GPL-2.0-or-later
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
5 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <linux/udp.h>
13 #include <net/netfilter/nf_conntrack_helper.h>
14 #include <net/netfilter/nf_conntrack_expect.h>
15 #include <net/netfilter/nf_nat_helper.h>
16 #include <linux/netfilter/nf_conntrack_amanda.h>
18 #define NAT_HELPER_NAME "amanda"
20 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
21 MODULE_DESCRIPTION("Amanda NAT helper");
22 MODULE_LICENSE("GPL");
23 MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME
);
25 static struct nf_conntrack_nat_helper nat_helper_amanda
=
26 NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME
);
28 static unsigned int help(struct sk_buff
*skb
,
29 enum ip_conntrack_info ctinfo
,
31 unsigned int matchoff
,
32 unsigned int matchlen
,
33 struct nf_conntrack_expect
*exp
)
35 char buffer
[sizeof("65535")];
38 /* Connection comes from client. */
39 exp
->saved_proto
.tcp
.port
= exp
->tuple
.dst
.u
.tcp
.port
;
40 exp
->dir
= IP_CT_DIR_ORIGINAL
;
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
;
46 /* Try to get same port: if not, try to change it. */
47 for (port
= ntohs(exp
->saved_proto
.tcp
.port
); port
!= 0; port
++) {
50 exp
->tuple
.dst
.u
.tcp
.port
= htons(port
);
51 res
= nf_ct_expect_related(exp
, 0);
54 else if (res
!= -EBUSY
) {
61 nf_ct_helper_log(skb
, exp
->master
, "all ports in use");
65 sprintf(buffer
, "%u", port
);
66 if (!nf_nat_mangle_udp_packet(skb
, exp
->master
, ctinfo
,
67 protoff
, matchoff
, matchlen
,
68 buffer
, strlen(buffer
))) {
69 nf_ct_helper_log(skb
, exp
->master
, "cannot mangle packet");
70 nf_ct_unexpect_related(exp
);
76 static void __exit
nf_nat_amanda_fini(void)
78 nf_nat_helper_unregister(&nat_helper_amanda
);
79 RCU_INIT_POINTER(nf_nat_amanda_hook
, NULL
);
83 static int __init
nf_nat_amanda_init(void)
85 BUG_ON(nf_nat_amanda_hook
!= NULL
);
86 nf_nat_helper_register(&nat_helper_amanda
);
87 RCU_INIT_POINTER(nf_nat_amanda_hook
, help
);
91 module_init(nf_nat_amanda_init
);
92 module_exit(nf_nat_amanda_fini
);