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

Add IPv4 and IPv6 capable nf_conntrack port of the Amanda conntrack/NAT helper.

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

3 files changed, 84 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 52f876d..6993ec5 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -512,6 +512,11 @@ config IP_NF_NAT_AMANDA
 	default IP_NF_NAT if IP_NF_AMANDA=y
 	default m if IP_NF_AMANDA=m
 
+config NF_NAT_AMANDA
+	tristate
+	depends on IP_NF_IPTABLES && NF_CONNTRACK && NF_NAT
+	default NF_NAT && NF_CONNTRACK_AMANDA
+
 config IP_NF_NAT_PPTP
 	tristate
 	depends on IP_NF_NAT!=n && IP_NF_PPTP!=n
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index c0c6194..8893249b 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_IP_NF_NAT_IRC) += ip_nat_irc.o
 obj-$(CONFIG_IP_NF_NAT_SIP) += ip_nat_sip.o
 
 # NAT helpers (nf_conntrack)
+obj-$(CONFIG_NF_NAT_AMANDA) += nf_nat_amanda.o
 obj-$(CONFIG_NF_NAT_FTP) += nf_nat_ftp.o
 
 # generic IP tables 
diff --git a/net/ipv4/netfilter/nf_nat_amanda.c b/net/ipv4/netfilter/nf_nat_amanda.c
new file mode 100644
index 0000000..0f17098
--- /dev/null
+++ b/net/ipv4/netfilter/nf_nat_amanda.c
@@ -0,0 +1,78 @@
+/* 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
+ *
+ * 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_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_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 **pskb,
+			 enum ip_conntrack_info ctinfo,
+			 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++) {
+		exp->tuple.dst.u.tcp.port = htons(port);
+		if (nf_conntrack_expect_related(exp) == 0)
+			break;
+	}
+
+	if (port == 0)
+		return NF_DROP;
+
+	sprintf(buffer, "%u", port);
+	ret = nf_nat_mangle_udp_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_amanda_fini(void)
+{
+	rcu_assign_pointer(nf_nat_amanda_hook, NULL);
+	synchronize_rcu();
+}
+
+static int __init nf_nat_amanda_init(void)
+{
+	BUG_ON(rcu_dereference(nf_nat_amanda_hook));
+	rcu_assign_pointer(nf_nat_amanda_hook, help);
+	return 0;
+}
+
+module_init(nf_nat_amanda_init);
+module_exit(nf_nat_amanda_fini);