Refactor port allocation logic a little, deflake tests.

pkg/proxy/winuserspace/port_allocator.go

@@ -57,7 +57,7 @@ func newPortAllocator(r net.PortRange) PortAllocator {
 	if r.Base == 0 {
 		return &randomAllocator{}
 	}
-	return newPortRangeAllocator(r)
+	return newPortRangeAllocator(r, true)
 }
 
 const (
@@ -74,7 +74,7 @@ type rangeAllocator struct {
 	rand  *rand.Rand
 }
 
-func newPortRangeAllocator(r net.PortRange) PortAllocator {
+func newPortRangeAllocator(r net.PortRange, autoFill bool) PortAllocator {
 	if r.Base == 0 || r.Size == 0 {
 		panic("illegal argument: may not specify an empty port range")
 	}
@@ -83,26 +83,31 @@ func newPortRangeAllocator(r net.PortRange) PortAllocator {
 		ports:     make(chan int, portsBufSize),
 		rand:      rand.New(rand.NewSource(time.Now().UnixNano())),
 	}
-	go wait.Until(func() { ra.fillPorts(wait.NeverStop) }, nextFreePortCooldown, wait.NeverStop)
+	if autoFill {
+		go wait.Forever(func() { ra.fillPorts() }, nextFreePortCooldown)
+	}
 	return ra
 }
 
 // fillPorts loops, always searching for the next free port and, if found, fills the ports buffer with it.
-// this func blocks until either there are no remaining free ports, or else the stopCh chan is closed.
-func (r *rangeAllocator) fillPorts(stopCh <-chan struct{}) {
+// this func blocks unless there are no remaining free ports.
+func (r *rangeAllocator) fillPorts() {
 	for {
-		port := r.nextFreePort()
-		if port == -1 {
+		if !r.fillPortsOnce() {
 			return
 		}
-		select {
-		case <-stopCh:
-			return
-		case r.ports <- port:
-		}
 	}
 }
 
+func (r *rangeAllocator) fillPortsOnce() bool {
+	port := r.nextFreePort()
+	if port == -1 {
+		return false
+	}
+	r.ports <- port
+	return true
+}
+
 // nextFreePort finds a free port, first picking a random port. if that port is already in use
 // then the port range is scanned sequentially until either a port is found or the scan completes
 // unsuccessfully. an unsuccessful scan returns a port of -1.