net: delete usableLocalPort from test

The old way to find a port was to listen :0 and then
look at what port it picked, close the listener, and then
immediately try to listen on that port.

On some Windows 7 machines that sequence fails at
the second listen, because the first one is still lingering
in the TCP/IP stack somewhere.  (Ironically, most of these
are used in tests of a "second listen", which in this case
ends up being the third listen.)

Instead of this race, just return the listener from the
function, replacing usableLocalPort+Listen with
usableListenPort.

Fixes #3219.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5769045

diff --git a/src/pkg/net/unicast_test.go b/src/pkg/net/unicast_test.go
index f164f34825fac1a575263d4e834d46c02ce485c4..a23bc5adaf28dceb89793df354554ee0f1060531 100644 (file)
--- a/src/pkg/net/unicast_test.go
+++ b/src/pkg/net/unicast_test.go
@@ -56,11 +56,7 @@ func TestTCPListener(t *testing.T) {
                if tt.ipv6 && !supportsIPv6 {
                        continue
                }
-               port := usableLocalPort(t, tt.net, tt.laddr)
-               l1, err := Listen(tt.net, tt.laddr+":"+port)
-               if err != nil {
-                       t.Fatalf("First Listen(%q, %q) failed: %v", tt.net, tt.laddr+":"+port, err)
-               }
+               l1, port := usableListenPort(t, tt.net, tt.laddr)
                checkFirstListener(t, tt.net, tt.laddr+":"+port, l1)
                l2, err := Listen(tt.net, tt.laddr+":"+port)
                checkSecondListener(t, tt.net, tt.laddr+":"+port, err, l2)
@@ -105,11 +101,7 @@ func TestUDPListener(t *testing.T) {
                        continue
                }
                tt.net = toudpnet(tt.net)
-               port := usableLocalPort(t, tt.net, tt.laddr)
-               l1, err := ListenPacket(tt.net, tt.laddr+":"+port)
-               if err != nil {
-                       t.Fatalf("First ListenPacket(%q, %q) failed: %v", tt.net, tt.laddr+":"+port, err)
-               }
+               l1, port := usableListenPacketPort(t, tt.net, tt.laddr)
                checkFirstListener(t, tt.net, tt.laddr+":"+port, l1)
                l2, err := ListenPacket(tt.net, tt.laddr+":"+port)
                checkSecondListener(t, tt.net, tt.laddr+":"+port, err, l2)
@@ -138,11 +130,7 @@ func TestSimpleTCPListener(t *testing.T) {
                if tt.ipv6 {
                        continue
                }
-               port := usableLocalPort(t, tt.net, tt.laddr)
-               l1, err := Listen(tt.net, tt.laddr+":"+port)
-               if err != nil {
-                       t.Fatalf("First Listen(%q, %q) failed: %v", tt.net, tt.laddr+":"+port, err)
-               }
+               l1, port := usableListenPort(t, tt.net, tt.laddr)
                checkFirstListener(t, tt.net, tt.laddr+":"+port, l1)
                l2, err := Listen(tt.net, tt.laddr+":"+port)
                checkSecondListener(t, tt.net, tt.laddr+":"+port, err, l2)
@@ -177,11 +165,7 @@ func TestSimpleUDPListener(t *testing.T) {
                        continue
                }
                tt.net = toudpnet(tt.net)
-               port := usableLocalPort(t, tt.net, tt.laddr)
-               l1, err := ListenPacket(tt.net, tt.laddr+":"+port)
-               if err != nil {
-                       t.Fatalf("First ListenPacket(%q, %q) failed: %v", tt.net, tt.laddr+":"+port, err)
-               }
+               l1, port := usableListenPacketPort(t, tt.net, tt.laddr)
                checkFirstListener(t, tt.net, tt.laddr+":"+port, l1)
                l2, err := ListenPacket(tt.net, tt.laddr+":"+port)
                checkSecondListener(t, tt.net, tt.laddr+":"+port, err, l2)
@@ -276,12 +260,8 @@ func TestDualStackTCPListener(t *testing.T) {
                                tt.xerr = nil
                        }
                }
-               port := usableLocalPort(t, tt.net1, tt.laddr1)
+               l1, port := usableListenPort(t, tt.net1, tt.laddr1)
                laddr := tt.laddr1 + ":" + port
-               l1, err := Listen(tt.net1, laddr)
-               if err != nil {
-                       t.Fatalf("First Listen(%q, %q) failed: %v", tt.net1, laddr, err)
-               }
                checkFirstListener(t, tt.net1, laddr, l1)
                laddr = tt.laddr2 + ":" + port
                l2, err := Listen(tt.net2, laddr)
@@ -327,12 +307,8 @@ func TestDualStackUDPListener(t *testing.T) {
                                tt.xerr = nil
                        }
                }
-               port := usableLocalPort(t, tt.net1, tt.laddr1)
+               l1, port := usableListenPacketPort(t, tt.net1, tt.laddr1)
                laddr := tt.laddr1 + ":" + port
-               l1, err := ListenPacket(tt.net1, laddr)
-               if err != nil {
-                       t.Fatalf("First ListenPacket(%q, %q) failed: %v", tt.net1, laddr, err)
-               }
                checkFirstListener(t, tt.net1, laddr, l1)
                laddr = tt.laddr2 + ":" + port
                l2, err := ListenPacket(tt.net2, laddr)
@@ -341,29 +317,44 @@ func TestDualStackUDPListener(t *testing.T) {
        }
 }
 
-func usableLocalPort(t *testing.T, net, laddr string) string {
+func usableListenPort(t *testing.T, net, laddr string) (l Listener, port string) {
        var nladdr string
+       var err error
        switch net {
+       default:
+               panic("usableListenPort net=" + net)
        case "tcp", "tcp4", "tcp6":
-               l, err := Listen(net, laddr+":0")
+               l, err = Listen(net, laddr+":0")
                if err != nil {
                        t.Fatalf("Probe Listen(%q, %q) failed: %v", net, laddr, err)
                }
-               defer l.Close()
                nladdr = l.(*TCPListener).Addr().String()
+       }
+       _, port, err = SplitHostPort(nladdr)
+       if err != nil {
+               t.Fatalf("SplitHostPort failed: %v", err)
+       }
+       return l, port
+}
+
+func usableListenPacketPort(t *testing.T, net, laddr string) (l PacketConn, port string) {
+       var nladdr string
+       var err error
+       switch net {
+       default:
+               panic("usableListenPacketPort net=" + net)
        case "udp", "udp4", "udp6":
-               c, err := ListenPacket(net, laddr+":0")
+               l, err = ListenPacket(net, laddr+":0")
                if err != nil {
                        t.Fatalf("Probe ListenPacket(%q, %q) failed: %v", net, laddr, err)
                }
-               defer c.Close()
-               nladdr = c.(*UDPConn).LocalAddr().String()
+               nladdr = l.(*UDPConn).LocalAddr().String()
        }
-       _, port, err := SplitHostPort(nladdr)
+       _, port, err = SplitHostPort(nladdr)
        if err != nil {
                t.Fatalf("SplitHostPort failed: %v", err)
        }
-       return port
+       return l, port
 }
 
 func differentWildcardAddr(i, j string) bool {
@@ -535,15 +526,11 @@ func TestProhibitionaryDialArgs(t *testing.T) {
                return
        }
 
-       port := usableLocalPort(t, "tcp", "[::]")
-       l, err := Listen("tcp", "[::]"+":"+port)
-       if err != nil {
-               t.Fatalf("Listen failed: %v", err)
-       }
+       l, port := usableListenPort(t, "tcp", "[::]")
        defer l.Close()
 
        for _, tt := range prohibitionaryDialArgTests {
-               _, err = Dial(tt.net, tt.addr+":"+port)
+               _, err := Dial(tt.net, tt.addr+":"+port)
                if err == nil {
                        t.Fatalf("Dial(%q, %q) should fail", tt.net, tt.addr)
                }