1// SPDX-License-Identifier: GPL-2.0-only
2/* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
3 */
4
5#include <linux/module.h>
6#include <linux/udp.h>
7
8#include <net/netfilter/nf_conntrack_helper.h>
9#include <net/netfilter/nf_conntrack_expect.h>
10#include <net/netfilter/nf_nat_helper.h>
11#include <linux/netfilter/nf_conntrack_tftp.h>
12
13#define NAT_HELPER_NAME "tftp"
14
15MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
16MODULE_DESCRIPTION("TFTP NAT helper");
17MODULE_LICENSE("GPL");
18MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
19
20static struct nf_conntrack_nat_helper nat_helper_tftp =
21 NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);
22
23static unsigned int help(struct sk_buff *skb,
24 enum ip_conntrack_info ctinfo,
25 struct nf_conntrack_expect *exp)
26{
27 const struct nf_conn *ct = exp->master;
28
29 exp->saved_proto.udp.port
30 = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
31 exp->dir = IP_CT_DIR_REPLY;
32 exp->expectfn = nf_nat_follow_master;
33 if (nf_ct_expect_related(expect: exp, flags: 0) != 0) {
34 nf_ct_helper_log(skb, ct: exp->master, fmt: "cannot add expectation");
35 return NF_DROP;
36 }
37 return NF_ACCEPT;
38}
39
40static void __exit nf_nat_tftp_fini(void)
41{
42 nf_nat_helper_unregister(nat: &nat_helper_tftp);
43 RCU_INIT_POINTER(nf_nat_tftp_hook, NULL);
44 synchronize_rcu();
45}
46
47static int __init nf_nat_tftp_init(void)
48{
49 BUG_ON(nf_nat_tftp_hook != NULL);
50 nf_nat_helper_register(nat: &nat_helper_tftp);
51 RCU_INIT_POINTER(nf_nat_tftp_hook, help);
52 return 0;
53}
54
55module_init(nf_nat_tftp_init);
56module_exit(nf_nat_tftp_fini);
57

source code of linux/net/netfilter/nf_nat_tftp.c