Google Cloud Run does not implement NETLINK_ROUTE RTMGRP.
If initialization of the netlink socket or group membership
fails, fall back to a polling implementation.
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
Not great, but lets people working on new ports get going more quickly
without having to do everything up front.
As the link monitor is getting used more, I felt bad having a useless
implementation.
Updates #815
Updates #1427
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Never return "nil, nil" anymore. The caller expected a usable
interface now. I missed some of these earlier.
Also, handle address deletion now.
Updates #532
And make the monitor package portable with no-op implementations on
unsupported operating systems.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
