Fix the race condition

Signed-off-by: David Gageot <[email protected]>

pkg/skaffold/util/port.go

@@ -32,7 +32,6 @@ import (
 // See https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt,
 func GetAvailablePort(port int, forwardedPorts *sync.Map) int {
 	if isPortAvailable(port, forwardedPorts) {
-		forwardedPorts.Store(port, true)
 		return port
 	}
 
@@ -41,14 +40,12 @@ func GetAvailablePort(port int, forwardedPorts *sync.Map) int {
 		port++
 		if isPortAvailable(port, forwardedPorts) {
 			logrus.Debugf("found open port: %d", port)
-			forwardedPorts.Store(port, true)
 			return port
 		}
 	}
 
 	for port = 4503; port <= 4533; port++ {
 		if isPortAvailable(port, forwardedPorts) {
-			forwardedPorts.Store(port, true)
 			return port
 		}
 	}
@@ -58,18 +55,16 @@ func GetAvailablePort(port int, forwardedPorts *sync.Map) int {
 		return -1
 	}
 
-	l.Close()
-	// Here, we introduce a race condition by closing before we
-	// update the `forwardedPorts` map.
-	// Another go routine could try the same port and succeed.
-
 	p := l.Addr().(*net.TCPAddr).Port
+
 	forwardedPorts.Store(p, true)
+	l.Close()
 	return p
 }
 
 func isPortAvailable(p int, forwardedPorts *sync.Map) bool {
-	if _, ok := forwardedPorts.Load(p); ok {
+	alreadyUsed, loaded := forwardedPorts.LoadOrStore(p, true)
+	if loaded && alreadyUsed.(bool) {
 		return false
 	}
 
@@ -79,9 +74,5 @@ func isPortAvailable(p int, forwardedPorts *sync.Map) bool {
 	}
 
 	l.Close()
-	// Here, we introduce a race condition by closing before we
-	// update the `forwardedPorts` map.
-	// Another go routine could try the same port and succeed.
-
 	return true
 }