How do I tell openconnect to use the VPN only for its route and DNS?

[Robert James]

Hi.  Thank you for developing openconnect - it's great to have an open
alternative to Cisco's client!

I would like to set up openconnect in a secondary way.  That is, it should:
* Only use the tun device for the specific nets on the VPN, but keep
my default device and route for all other IPs
* Not change any DNS settings

In other words: add a route for the specific networks that are
internal to the VPN, but make no other changes.

How can I configure this?

Thanks