// SPDX-License-Identifier: GPL-2.0-or-later
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/* IRC extension for TCP NAT alteration.
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*
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* (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
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* (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
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* based on a copy of RR's ip_nat_ftp.c
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/tcp.h>
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#include <linux/kernel.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_helper.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#include <linux/netfilter/nf_conntrack_irc.h>
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#define NAT_HELPER_NAME "irc"
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MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
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MODULE_DESCRIPTION("IRC (DCC) NAT helper");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
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static struct nf_conntrack_nat_helper nat_helper_irc =
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NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);
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static unsigned int help(struct sk_buff *skb,
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enum ip_conntrack_info ctinfo,
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unsigned int protoff,
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unsigned int matchoff,
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unsigned int matchlen,
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struct nf_conntrack_expect *exp)
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{
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char buffer[sizeof("4294967296 65635")];
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struct nf_conn *ct = exp->master;
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union nf_inet_addr newaddr;
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u_int16_t port;
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/* Reply comes from server. */
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newaddr = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3;
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exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
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exp->dir = IP_CT_DIR_REPLY;
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exp->expectfn = nf_nat_follow_master;
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/* Try to get same port: if not, try to change it. */
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for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
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int ret;
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exp->tuple.dst.u.tcp.port = htons(port);
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ret = nf_ct_expect_related(exp, 0);
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if (ret == 0)
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break;
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else if (ret != -EBUSY) {
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port = 0;
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break;
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}
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}
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if (port == 0) {
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nf_ct_helper_log(skb, ct, "all ports in use");
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return NF_DROP;
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}
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/* strlen("\1DCC CHAT chat AAAAAAAA P\1\n")=27
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* strlen("\1DCC SCHAT chat AAAAAAAA P\1\n")=28
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* strlen("\1DCC SEND F AAAAAAAA P S\1\n")=26
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* strlen("\1DCC MOVE F AAAAAAAA P S\1\n")=26
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* strlen("\1DCC TSEND F AAAAAAAA P S\1\n")=27
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*
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* AAAAAAAAA: bound addr (1.0.0.0==16777216, min 8 digits,
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* 255.255.255.255==4294967296, 10 digits)
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* P: bound port (min 1 d, max 5d (65635))
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* F: filename (min 1 d )
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* S: size (min 1 d )
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* 0x01, \n: terminators
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*/
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/* AAA = "us", ie. where server normally talks to. */
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snprintf(buffer, sizeof(buffer), "%u %u", ntohl(newaddr.ip), port);
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pr_debug("inserting '%s' == %pI4, port %u\n",
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buffer, &newaddr.ip, port);
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if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
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matchlen, buffer, strlen(buffer))) {
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nf_ct_helper_log(skb, ct, "cannot mangle packet");
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nf_ct_unexpect_related(exp);
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return NF_DROP;
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}
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return NF_ACCEPT;
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}
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static void __exit nf_nat_irc_fini(void)
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{
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nf_nat_helper_unregister(&nat_helper_irc);
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RCU_INIT_POINTER(nf_nat_irc_hook, NULL);
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synchronize_rcu();
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}
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static int __init nf_nat_irc_init(void)
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{
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BUG_ON(nf_nat_irc_hook != NULL);
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nf_nat_helper_register(&nat_helper_irc);
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RCU_INIT_POINTER(nf_nat_irc_hook, help);
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return 0;
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}
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/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */
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static int warn_set(const char *val, const struct kernel_param *kp)
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{
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pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
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return 0;
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}
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module_param_call(ports, warn_set, NULL, NULL, 0);
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module_init(nf_nat_irc_init);
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module_exit(nf_nat_irc_fini);
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