A home node behind NAT (no Endpoint → not Reachable) that took over a
tunnel must still listen on that tunnel's port: its LAN peers dial it
there. ListenPort was gated on Reachable, which conflated 'a peer dials
me here' with 'the hub can dial me' — so the takeover guard refused
overlay-up, and the guard's suggested remedy (re-place with an
endpoint) breaks a NAT'd node's path: it stops keepalive and hands the
hub a private LAN address to dial. TakeOver now carries the found
tunnel's port (already known to the controller), and the interface
listens on it when the node is not otherwise reachable. Two tests;
Endpoint-reachable nodes keep the old path unchanged.
jschoubben
cc252472e2