FR: I want to bind TS tunnels to specific IP(s) or Interface(s)

### What are you trying to do?

Basically i have an exit node inside a typical home LAN. this exit node also has a GRE tunnel that is configured with a default route and can access internet through it. I want all the tailscale tunnels to be configured on via my home public ip not the public ip of the other side of the GRE tunnel. it seems that now there is hair pinning with the TS tunnels being built over the GRE tunnel and then going right back out. i want a two legged solution where the ts tunnel traffic (to the exit node) comes in the regular internet and then is routed to the gre tunnel for internet.

### How should we solve this?

Being able to bind restrict the ip endpoints tailscale sees, or to bind to the tailscale tunnels interface itself

### What is the impact of not solving this?

Low impact niche issue.

### Anything else?

i suppose this could be related to a dual wan situation, but with a very specific policy.