fff-firewall: Fix match in ip6tables and add dependencies

The syntax " -m state --state " seems to be not supported anymore.

The replace should not change behavior compared to
lede-17.01-based firmware.

Added required dependency.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Tim Niemeyer <tim@tn-x.org>
Reviewed-by: Fabian Bläse <fabian@blaese.de>

src/packages/fff/fff-firewall/Makefile

 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=fff-firewall
-PKG_VERSION:=2
+PKG_VERSION:=3
 PKG_RELEASE:=1
 
 PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)
@@ -16,7 +16,8 @@ define Package/$(PKG_NAME)
     DEPENDS:=+arptables \
              +ebtables +ebtables-utils \
              +kmod-ebtables-ipv4 +kmod-ebtables-ipv6 \
-             +iptables-mod-filter +iptables-mod-ipopt +iptables-mod-conntrack-extra
+             +iptables-mod-filter +iptables-mod-ipopt +iptables-mod-conntrack-extra \
+             +kmod-nf-conntrack6
 endef
 
 define Package/$(PKG_NAME)/description

src/packages/fff/fff-firewall/files/usr/lib/firewall.d/20-filter-ssh

@@ -3,5 +3,5 @@ iptables -A INPUT -i $IF_WAN -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEP
 iptables -A INPUT -i $IF_WAN -j REJECT
 
 # Limit ssh to 6 new connections per 60 seconds
-/usr/sbin/ip6tables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --set --name dropbear
-/usr/sbin/ip6tables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 60 --hitcount 6 --rttl --name dropbear -j DROP
+/usr/sbin/ip6tables -A INPUT -p tcp --dport 22 -m conntrack --ctstate NEW -m recent --set --name dropbear
+/usr/sbin/ip6tables -A INPUT -p tcp --dport 22 -m conntrack --ctstate NEW -m recent --update --seconds 60 --hitcount 6 --rttl --name dropbear -j DROP