zapret/init.d/sysv/custom.d.examples/10-keenetic-udp-fix

# This script fixes keenetic issue with nfqws generated udp packets
# Keenetic uses proprietary ndmmark and does not masquerade without this mark
# If not masqueraded packets go to WAN with LAN IP and get dropped by ISP

# It's advised to set IFACE_WAN in config

zapret_custom_firewall()
{
	# $1 - 1 - add, 0 - stop

	local wan wanif rule

	[ "$DISABLE_IPV4" = "1" ] || {
		# use IFACE_WAN if defined. if not - search for interfaces with default route.
		wanif=${IFACE_WAN:-$(sed -nre 's/^([^\t]+)\t00000000\t[0-9A-F]{8}\t[0-9A-F]{4}\t[0-9]+\t[0-9]+\t[0-9]+\t00000000.*$/\1/p' /proc/net/route | sort -u | xargs)}
		for wan in $wanif; do
			rule="-o $wan -p udp -m mark --mark $DESYNC_MARK/$DESYNC_MARK"
			ipt_print_op $1 "$rule" "keenetic udp fix"
			ipt_add_del $1 POSTROUTING -t nat $rule -j MASQUERADE
		done
	}
}