From a9977eca9145b9f061ceb1d1604f59efba1b2949 Mon Sep 17 00:00:00 2001
From: Jo-Philipp Wich <jow@openwrt.org>
Date: Tue, 12 Apr 2011 20:03:59 +0000
Subject: [PATCH] firewall: allow local redirection of ports

Allow a redirect like:

config redirect
        option src 'wan'
        option dest 'lan'
        option src_dport '22001'
        option dest_port '22'
        option proto 'tcp'

note the absence of the "dest_ip" field, meaning to terminate the connection on the firewall itself.

This patch makes three changes:

(1) moves the conntrack module into the conntrack package (but not any of the conntrack_* helpers).
(2) fixes a bug where the wrong table is used when the "dest_ip" field is absent.
(3) accepts incoming connections on the destination port on the input_ZONE table, but only for DNATted
    connections.

In the above example,

ssh -p 22 root@myrouter

would fail from the outside, but:

ssh -p 22001 root@myrouter

would succeed.  This is handy if:

(1) you want to avoid ssh probes on your router, or
(2) you want to redirect incoming connections on port 22 to some machine inside your firewall, but
    still want to allow firewall access from outside.

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

SVN-Revision: 26617
---
 include/netfilter.mk                        | 4 ++--
 package/firewall/files/lib/core_redirect.sh | 5 ++---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/netfilter.mk b/include/netfilter.mk
index fe468fca31..9da455a07a 100644
--- a/include/netfilter.mk
+++ b/include/netfilter.mk
@@ -60,6 +60,8 @@ $(eval $(call nf_add,IPT_CONNTRACK,CONFIG_NETFILTER_XT_MATCH_STATE, $(P_XT)xt_st
 $(eval $(call nf_add,IPT_CONNTRACK,CONFIG_IP_NF_RAW, $(P_V4)iptable_raw))
 $(eval $(call nf_add,IPT_CONNTRACK,CONFIG_IP_NF_TARGET_NOTRACK, $(P_V4)ipt_NOTRACK))
 $(eval $(call nf_add,IPT_CONNTRACK,CONFIG_NETFILTER_XT_TARGET_NOTRACK, $(P_XT)xt_NOTRACK))
+$(eval $(call nf_add,IPT_CONNTRACK,CONFIG_IP_NF_MATCH_CONNTRACK, $(P_V4)ipt_conntrack))
+$(eval $(call nf_add,IPT_CONNTRACK,CONFIG_NETFILTER_XT_MATCH_CONNTRACK, $(P_XT)xt_conntrack))
 
 
 # conntrack-extra
@@ -68,8 +70,6 @@ $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_IP_NF_MATCH_CONNBYTES, $(P_V4)ip
 $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_NETFILTER_XT_MATCH_CONNBYTES, $(P_XT)xt_connbytes))
 $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_IP_NF_MATCH_CONNMARK, $(P_V4)ipt_connmark))
 $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_NETFILTER_XT_MATCH_CONNMARK, $(P_XT)xt_connmark))
-$(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_IP_NF_MATCH_CONNTRACK, $(P_V4)ipt_conntrack))
-$(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_NETFILTER_XT_MATCH_CONNTRACK, $(P_XT)xt_conntrack))
 $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_IP_NF_MATCH_HELPER, $(P_V4)ipt_helper))
 $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_NETFILTER_XT_MATCH_HELPER, $(P_XT)xt_helper))
 $(eval $(call nf_add,IPT_CONNTRACK_EXTRA,CONFIG_IP_NF_MATCH_RECENT, $(P_V4)ipt_recent))
diff --git a/package/firewall/files/lib/core_redirect.sh b/package/firewall/files/lib/core_redirect.sh
index 87941a2a17..64c619e434 100644
--- a/package/firewall/files/lib/core_redirect.sh
+++ b/package/firewall/files/lib/core_redirect.sh
@@ -34,7 +34,7 @@ fw_load_redirect() {
 			return 0
 		}
 
-		fwdchain="zone_${redirect_src}_forward"
+		fwdchain="zone_${redirect_src}${redirect_dest_ip:+_forward}"
 
 		natopt="--to-destination"
 		natchain="zone_${redirect_src}_prerouting"
@@ -100,9 +100,8 @@ fw_load_redirect() {
 			$natopt $nataddr${natports:+:$natports} \
 		}
 
-		[ -n "$destaddr" ] && \
 		fw add $mode f ${fwdchain:-forward} ACCEPT ^ { $redirect_src_ip $redirect_dest_ip } { \
-			$srcaddr $destaddr \
+			$srcaddr ${destaddr:--m conntrack --ctstate DNAT} \
 			${redirect_proto:+-p $redirect_proto} \
 			${srcports:+--sport $srcports} \
 			${destports:+--dport $destports} \