Nick Khyl ab2380a631 net/dns,util/coalescedop: serialize and coalesce DNS flush calls on Windows ...

Previously, ipconfig /flushdns and ipconfig /registerdns were called
from multiple sites without coordination: the DNS manager's SetDNS
(in a fire-and-forget goroutine), the router's winRouter.Set (synchronously
on every route change), the link change handler, and session unlock.
These could fire concurrently or in rapid succession, spawning multiple
ipconfig processes and putting excessive pressure on the Dnscache service.

In this PR, we introduce a new util/coalescedop.CoalescedOp type that provides
"one in-flight, at most one pending" semantics: Do() is non-blocking,
at most one execution runs at a time, and concurrent/rapid successive
requests coalesce into a single follow-up execution.

We then use CoalescedOp for both ipconfig /flushdns and ipconfig /registerdns,
replacing the fire-and-forget goroutine in windowsManager.SetDNS
and in the session unlock handler in tailscaled.

We also remove the redundant dns.Flush() call from winRouter.Set, since every
meaningful router.Set is followed by dns.Set in Reconfig, which already
flushes.

Updates #21001

Signed-off-by: Nick Khyl <nickk@tailscale.com>

2026-09-30 10:44:22 -07:00

..

depaware.txt

net/dns,util/coalescedop: serialize and coalesce DNS flush calls on Windows

2026-09-30 10:44:22 -07:00

stund.go

all: remove AUTHORS file and references to it

2026-01-23 15:49:45 -08:00