Log TCP Connections to WAN in OpenWrt

I have a router running OpenWrt 15.05. I would like to log all the TCP connections. To achieve this, I just need to add a line in the firewall custom rule like:

iptables -A forwarding_lan_rule -p tcp -m state --state NEW -m limit --limit 30/sec -j LOG --log-prefix "NEW Conn "

Then, login the router as root, and restart the firewall with the following command:

/etc/init.d/firewall restart

The following shows how the System Log looks like after enable the custom rule: