[NETFILTER]: nf_conntrack/nf_nat: add IRC helper port

Add nf_conntrack port of the IRC conntrack/NAT helper. Since DCC doesn't
support IPv6 yet, the helper is still IPv4 only.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter/nf_conntrack_irc.h

@@ -0,0 +1,15 @@
+#ifndef _NF_CONNTRACK_IRC_H
+#define _NF_CONNTRACK_IRC_H
+
+#ifdef __KERNEL__
+
+#define IRC_PORT	6667
+
+extern unsigned int (*nf_nat_irc_hook)(struct sk_buff **pskb,
+				       enum ip_conntrack_info ctinfo,
+				       unsigned int matchoff,
+				       unsigned int matchlen,
+				       struct nf_conntrack_expect *exp);
+
+#endif /* __KERNEL__ */
+#endif /* _NF_CONNTRACK_IRC_H */

net/ipv4/netfilter/Kconfig

@@ -500,6 +500,11 @@ config IP_NF_NAT_IRC
 	default IP_NF_NAT if IP_NF_IRC=y
 	default m if IP_NF_IRC=m
 
+config NF_NAT_IRC
+	tristate
+	depends on IP_NF_IPTABLES && NF_CONNTRACK && NF_NAT
+	default NF_NAT && NF_CONNTRACK_IRC
+
 config IP_NF_NAT_TFTP
 	tristate
 	depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n

net/ipv4/netfilter/Makefile

@@ -53,6 +53,7 @@ obj-$(CONFIG_IP_NF_NAT_SIP) += ip_nat_sip.o
 obj-$(CONFIG_NF_NAT_AMANDA) += nf_nat_amanda.o
 obj-$(CONFIG_NF_NAT_FTP) += nf_nat_ftp.o
 obj-$(CONFIG_NF_NAT_H323) += nf_nat_h323.o
+obj-$(CONFIG_NF_NAT_IRC) += nf_nat_irc.o
 
 # generic IP tables 
 obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o

net/ipv4/netfilter/nf_nat_irc.c

@@ -0,0 +1,101 @@
+/* IRC extension for TCP NAT alteration.
+ *
+ * (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2004 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
+ * based on a copy of RR's ip_nat_ftp.c
+ *
+ * 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/module.h>
+#include <linux/moduleparam.h>
+#include <linux/tcp.h>
+#include <linux/kernel.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_helper.h>
+#include <net/netfilter/nf_nat_rule.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#include <net/netfilter/nf_conntrack_expect.h>
+#include <linux/netfilter/nf_conntrack_irc.h>
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
+MODULE_DESCRIPTION("IRC (DCC) NAT helper");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ip_nat_irc");
+
+static unsigned int help(struct sk_buff **pskb,
+			 enum ip_conntrack_info ctinfo,
+			 unsigned int matchoff,
+			 unsigned int matchlen,
+			 struct nf_conntrack_expect *exp)
+{
+	char buffer[sizeof("4294967296 65635")];
+	u_int32_t ip;
+	u_int16_t port;
+	unsigned int ret;
+
+	DEBUGP("IRC_NAT: info (seq %u + %u) in %u\n",
+	       expect->seq, exp_irc_info->len, ntohl(tcph->seq));
+
+	/* Reply comes from server. */
+	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
+	exp->dir = IP_CT_DIR_REPLY;
+	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++) {
+		exp->tuple.dst.u.tcp.port = htons(port);
+		if (nf_conntrack_expect_related(exp) == 0)
+			break;
+	}
+
+	if (port == 0)
+		return NF_DROP;
+
+	ip = ntohl(exp->master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip);
+	sprintf(buffer, "%u %u", ip, port);
+	DEBUGP("nf_nat_irc: inserting '%s' == %u.%u.%u.%u, port %u\n",
+	       buffer, NIPQUAD(ip), port);
+
+	ret = nf_nat_mangle_tcp_packet(pskb, exp->master, ctinfo,
+				       matchoff, matchlen, buffer,
+				       strlen(buffer));
+	if (ret != NF_ACCEPT)
+		nf_conntrack_unexpect_related(exp);
+	return ret;
+}
+
+static void __exit nf_nat_irc_fini(void)
+{
+	rcu_assign_pointer(nf_nat_irc_hook, NULL);
+	synchronize_rcu();
+}
+
+static int __init nf_nat_irc_init(void)
+{
+	BUG_ON(rcu_dereference(nf_nat_irc_hook));
+	rcu_assign_pointer(nf_nat_irc_hook, help);
+	return 0;
+}
+
+/* Prior to 2.6.11, we had a ports param.  No longer, but don't break users. */
+static int warn_set(const char *val, struct kernel_param *kp)
+{
+	printk(KERN_INFO KBUILD_MODNAME
+	       ": kernel >= 2.6.10 only uses 'ports' for conntrack modules\n");
+	return 0;
+}
+module_param_call(ports, warn_set, NULL, NULL, 0);
+
+module_init(nf_nat_irc_init);
+module_exit(nf_nat_irc_fini);

net/netfilter/Kconfig

@@ -179,6 +179,21 @@ config NF_CONNTRACK_H323
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NF_CONNTRACK_IRC
+	tristate "IRC protocol support (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && NF_CONNTRACK
+	help
+	  There is a commonly-used extension to IRC called
+	  Direct Client-to-Client Protocol (DCC).  This enables users to send
+	  files to each other, and also chat to each other without the need
+	  of a server.  DCC Sending is used anywhere you send files over IRC,
+	  and DCC Chat is most commonly used by Eggdrop bots.  If you are
+	  using NAT, this extension will enable you to send files and initiate
+	  chats.  Note that you do NOT need this extension to get files or
+	  have others initiate chats, or everything else in IRC.
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NF_CT_NETLINK
 	tristate 'Connection tracking netlink interface (EXPERIMENTAL)'
 	depends on EXPERIMENTAL && NF_CONNTRACK && NETFILTER_NETLINK

net/netfilter/Makefile

@@ -25,6 +25,7 @@ nf_conntrack_h323-objs := nf_conntrack_h323_main.o nf_conntrack_h323_asn1.o
 obj-$(CONFIG_NF_CONNTRACK_AMANDA) += nf_conntrack_amanda.o
 obj-$(CONFIG_NF_CONNTRACK_FTP) += nf_conntrack_ftp.o
 obj-$(CONFIG_NF_CONNTRACK_H323) += nf_conntrack_h323.o
+obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
 
 # generic X tables 
 obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o