| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* Amanda extension for TCP NAT alteration. |
| * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca> |
| * based on a copy of HW's ip_nat_irc.c as well as other modules |
| * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <linux/udp.h> |
| |
| #include <net/netfilter/nf_conntrack_helper.h> |
| #include <net/netfilter/nf_conntrack_expect.h> |
| #include <net/netfilter/nf_nat_helper.h> |
| #include <linux/netfilter/nf_conntrack_amanda.h> |
| |
| #define NAT_HELPER_NAME "amanda" |
| |
| MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>"); |
| MODULE_DESCRIPTION("Amanda NAT helper"); |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); |
| |
| static struct nf_conntrack_nat_helper nat_helper_amanda = |
| NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); |
| |
| static unsigned int help(struct sk_buff *skb, |
| enum ip_conntrack_info ctinfo, |
| unsigned int protoff, |
| unsigned int matchoff, |
| unsigned int matchlen, |
| struct nf_conntrack_expect *exp) |
| { |
| char buffer[sizeof("65535")]; |
| u_int16_t port; |
| |
| /* Connection comes from client. */ |
| exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; |
| exp->dir = IP_CT_DIR_ORIGINAL; |
| |
| /* When you see the packet, we need to NAT it the same as the |
| * this one (ie. same IP: it will be TCP and master is UDP). */ |
| exp->expectfn = nf_nat_follow_master; |
| |
| /* Try to get same port: if not, try to change it. */ |
| port = nf_nat_exp_find_port(exp, ntohs(exp->saved_proto.tcp.port)); |
| if (port == 0) { |
| nf_ct_helper_log(skb, exp->master, "all ports in use"); |
| return NF_DROP; |
| } |
| |
| sprintf(buffer, "%u", port); |
| if (!nf_nat_mangle_udp_packet(skb, exp->master, ctinfo, |
| protoff, matchoff, matchlen, |
| buffer, strlen(buffer))) { |
| nf_ct_helper_log(skb, exp->master, "cannot mangle packet"); |
| nf_ct_unexpect_related(exp); |
| return NF_DROP; |
| } |
| return NF_ACCEPT; |
| } |
| |
| static void __exit nf_nat_amanda_fini(void) |
| { |
| nf_nat_helper_unregister(&nat_helper_amanda); |
| RCU_INIT_POINTER(nf_nat_amanda_hook, NULL); |
| synchronize_rcu(); |
| } |
| |
| static int __init nf_nat_amanda_init(void) |
| { |
| BUG_ON(nf_nat_amanda_hook != NULL); |
| nf_nat_helper_register(&nat_helper_amanda); |
| RCU_INIT_POINTER(nf_nat_amanda_hook, help); |
| return 0; |
| } |
| |
| module_init(nf_nat_amanda_init); |
| module_exit(nf_nat_amanda_fini); |