OpenVPN, OpenWRT, and comp-lzo

When setting up a VPN client on my OpenWRT box, I was getting the following error message in /var/log/daemon.log on the server and, consequently, no packets could get through:

Bad LZO decompression header byte: 42

The reason is that while vanilla OpenVPN uses dashes in option names, the OpenWRT config uses underscores instead and my option comp-lzo 1 got simply ignored.

Remedy: use option comp_lzo 1 in /etc/config/openvpn on the OpenWRT box.