firewall: Fix connection tracking for PPTP

GRE connections were not correctly forwarded without the helper
being enabled. Choosing the wrong protocol here did not allow
us to load it properly.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/initscripts/init.d/firewall

@@ -128,7 +128,7 @@ iptables_init() {
 	if [ "${CONNTRACK_PPTP}" = "on" ]; then
 		iptables -A CONNTRACK -m conntrack --ctstate RELATED \
 			-m helper --helper pptp -j ACCEPT
-		iptables -t raw -A CONNTRACK -p udp --dport 1723 -j CT --helper pptp
+		iptables -t raw -A CONNTRACK -p tcp --dport 1723 -j CT --helper pptp
 	fi
 
 	# TFTP