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- /* 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>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
- #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>
- MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
- MODULE_DESCRIPTION("Amanda NAT helper");
- MODULE_LICENSE("GPL");
- MODULE_ALIAS("ip_nat_amanda");
- 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;
- unsigned int ret;
- /* 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. */
- for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
- int res;
- exp->tuple.dst.u.tcp.port = htons(port);
- res = nf_ct_expect_related(exp);
- if (res == 0)
- break;
- else if (res != -EBUSY) {
- port = 0;
- break;
- }
- }
- if (port == 0) {
- nf_ct_helper_log(skb, exp->master, "all ports in use");
- return NF_DROP;
- }
- sprintf(buffer, "%u", port);
- ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
- protoff, matchoff, matchlen,
- buffer, strlen(buffer));
- if (ret != NF_ACCEPT) {
- nf_ct_helper_log(skb, exp->master, "cannot mangle packet");
- nf_ct_unexpect_related(exp);
- }
- return ret;
- }
- static void __exit nf_nat_amanda_fini(void)
- {
- 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);
- RCU_INIT_POINTER(nf_nat_amanda_hook, help);
- return 0;
- }
- module_init(nf_nat_amanda_init);
- module_exit(nf_nat_amanda_fini);
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