new file mode 100644

@@ -0,0 +1,42 @@

+package portallocator

+

+import (

+	"bytes"

+	"fmt"

+	"os/exec"

+)

+

+func getDynamicPortRange() (start int, end int, err error) {

+	portRangeKernelSysctl := []string{"net.inet.ip.portrange.hifirst", "net.ip.portrange.hilast"}

+	portRangeFallback := fmt.Sprintf("using fallback port range %d-%d", DefaultPortRangeStart, DefaultPortRangeEnd)

+	portRangeLowCmd := exec.Command("/sbin/sysctl", portRangeKernelSysctl[0])

+	var portRangeLowOut bytes.Buffer

+	portRangeLowCmd.Stdout = &portRangeLowOut

+	cmdErr := portRangeLowCmd.Run()

+	if cmdErr != nil {

+		return 0, 0, fmt.Errorf("port allocator - sysctl net.inet.ip.portrange.hifirst failed - %s: %v", portRangeFallback, err)

+	}

+	n, err := fmt.Sscanf(portRangeLowOut.String(), "%d", &start)

+	if n != 1 || err != nil {

+		if err == nil {

+			err = fmt.Errorf("unexpected count of parsed numbers (%d)", n)

+		}

+		return 0, 0, fmt.Errorf("port allocator - failed to parse system ephemeral port range start from %s - %s: %v", portRangeLowOut.String(), portRangeFallback, err)

+	}

+

+	portRangeHighCmd := exec.Command("/sbin/sysctl", portRangeKernelSysctl[1])

+	var portRangeHighOut bytes.Buffer

+	portRangeHighCmd.Stdout = &portRangeHighOut

+	cmdErr = portRangeHighCmd.Run()

+	if cmdErr != nil {

+		return 0, 0, fmt.Errorf("port allocator - sysctl net.inet.ip.portrange.hilast failed - %s: %v", portRangeFallback, err)

+	}

+	n, err = fmt.Sscanf(portRangeHighOut.String(), "%d", &end)

+	if n != 1 || err != nil {

+		if err == nil {

+			err = fmt.Errorf("unexpected count of parsed numbers (%d)", n)

+		}

+		return 0, 0, fmt.Errorf("port allocator - failed to parse system ephemeral port range end from %s - %s: %v", portRangeHighOut.String(), portRangeFallback, err)

+	}

+	return start, end, nil

+}