Some netmap updates are guaranteed to affect only the "static" parts of the
netmap, and so should not require us to walk through all the peers and user
profiles when updating the cache. To support this, the new UpdateSelfOnly
method updates only the Self node and other tailnet settings that are not
dependent on the peers and profiles.
Use this when updating the cache on DERP home changes.
Updates #12542
Change-Id: Ifed522b29d579fb76e010b4ff738cc4e0a72d27f
Signed-off-by: M. J. Fromberger <fromberger@tailscale.com>
With netmap caching, the home DERP of the self node was neither saved to
the cache or loaded from it, making nodes not stick to a DERP when
starting without a connection to control.
Instead, make sure that when a cache is available, load that cache,
before looking for DERP servers. This is implemented by allowing a skip
of ReSTUN in setting the DERP map (we must have a DERP map before
setting the home DERP), so the DERP from cache will set itself and be
sticky until a connection to control is established.
Making DERP only change when connected to control is handled by existing
code from f072d017bd.
Updates #19490
Signed-off-by: Claus Lensbøl <claus@tailscale.com>
