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tailcat: avoid repeated process-wide netns.SetEnabled side effect #10

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tailcat: avoid repeated process-wide netns.SetEnabled side effect #10

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9 changes: 8 additions & 1 deletion tailcat.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1334,6 +1334,13 @@ func newNetstack(logf logger.Logf, sys *tsd.System) (*netstack.Impl, error) {
)
}

// disableNetNSOnce ensures we only call netns.SetEnabled(false) once for
// the process. tailcat uses userspace networking and does not want
// Tailscale-created sockets bound in a separate network namespace.
// Calling it on every engine creation would be an observable global side
// effect for library callers that create multiple Server/Client instances.
var disableNetNSOnce sync.Once

// createEngine creates the wgengine.Engine with userspace networking.
func createEngine(logf logger.Logf, lb *locoBackend) (err error) {
sys := &lb.sys
Expand All @@ -1358,7 +1365,7 @@ func createEngine(logf logger.Logf, lb *locoBackend) (err error) {
// call-me-maybe messages that advertise our UDP endpoints (see
// locoBackend.advertiseEndpoints).
conf.ForceDiscoKey = nodePrivateAsDiscoPrivate(lb.priv)
netns.SetEnabled(false)
disableNetNSOnce.Do(func() { netns.SetEnabled(false) })
e, err := wgengine.NewUserspaceEngine(logf, conf)
if err != nil {
logf("wgengine.NewUserspaceEngine(tun %q) error: %v", "userspace-networking", err)
Expand Down