i've upgraded openwrt to 19.07, and now it has built-in VPN/WAN policy-based routing! it works really well (remember to allow the forwards in firewall) and is indispensable in modern world full of state censorship
@okoeroo Dd-wrt? Please, don't. Replace it asap. It's a bloated mostly non-working crap I've used. Instead, do OpenWRT. They're busy with 5.x kernel now. With lots of recoding to phy net. A Dutch hw guy has made SFP cage of Ubiquity ER-X-SFP working with OpenWRT on 5.x kernel