I have steup wrt firewall.user to log all outbound traffice on br0, but I can not figure out how to send it to a log file without freezing the router. 

Here is the ipdtable line: forwarding_rule -i br0 -j LOG --log-prefix "OUTBOUND: "

I run logread -f | grep OUT >> test.log &, but it slows down the router, or freezes it. 

Can anyone give me an idea on how to streamline this?