Since f343b496c3 ("wgengine, all: remove LazyWG, use wireguard-go
callback API for on-demand peers"), Reconfig is fully synchronous:
magicConn.UpdatePeers, wgdev.RemovePeer, router.Set, and dns.Set all
return when the work is done, and the peer list is updated under
wgLock before Reconfig returns. So after Reconfig with empty configs,
len(st.Peers) is already 0.
The old loop also waited for st.DERPs to drain to 0, but UpdatePeers
only edits maps; active DERP connections idle out on their own
timeout. The sole caller (LocalBackend.stopEngineAndWait) doesn't
inspect st.DERPs anyway; it just hands the Status to
setWgengineStatusLocked. So the drain-wait was for nothing observable
and could theoretically (or at least appear to readers to) loop
forever holding b.mu. Remove that reader confusion by removing
the backoff loop entirely.
Updates #19759
Change-Id: Ibfac3f0baabcad7604b713c934a8fc37932e0a50
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick
fa49009eee