Merge pull request #40 from libp2p/fix/24

check for reuseport support by opening a socket, not listening.

available_unix.go

@@ -7,6 +7,8 @@ import (
 	"sync"
 	"syscall"
 	"time"
+
+	sockaddrnet "github.com/libp2p/go-sockaddr/net"
 )
 
 var (
@@ -15,7 +17,7 @@ var (
 )
 
 // Available returns whether or not SO_REUSEPORT is available in the OS.
-// It does so by attepting to open a tcp listener, setting the option, and
+// It does so by attepting to open a tcp socket, setting the option, and
 // checking ENOPROTOOPT on error. After checking, the decision is cached
 // for the rest of the process run.
 func available() bool {
@@ -24,14 +26,13 @@ func available() bool {
 }
 
 func checkReusePort() {
-	// there may be fluke reasons to fail to add a listener.
+	// there may be fluke reasons to fail to open a socket.
 	// so we give it 5 shots. if not, give up and call it not avail.
 	for i := 0; i < 5; i++ {
-		// try to listen at tcp port 0.
-		l, err := listenStream("tcp", "127.0.0.1:0")
+		// try to setup a TCP socket.
+		fd, err := socket(sockaddrnet.AF_INET, sockaddrnet.SOCK_STREAM, sockaddrnet.IPPROTO_TCP)
 		if err == nil {
-			l.Close() // Go back to the Shadow!
-			// no error? available.
+			unix.Close(fd)
 			hasReusePort = true
 			return
 		}

reuse_test.go

@@ -120,7 +120,7 @@ func TestDialSelf(t *testing.T) {
 		t.Fatal(err)
 	}
 	_, err = Dial("tcp4", l.Addr().String(), l.Addr().String())
-	if err != ErrDialSelf {
+	if err == nil {
 		t.Fatal("should have gotten an error for dialing self")
 	}
 }