Provide mechanism for users to exclude interfaces from disco + endpoint advertisements #1552
Description
User wishes to exclude an interface from being used for disco + endpoint advertisement:
Perhaps we could add TS_AVOID_PREFIX=10.5.4.0/24, which people could add to their /etc/default/tailscale. And then we could check that IPSet for discoverEndpoints and sending disco messages.
An IPSet is probably easier than an interface name. But I suppose we could also accept an interface name and map it to a prefix on start-up (or on a timer or major link change?).
@danderson, thoughts?