net: make -external flag for tests default to true

go test -short # like in the build; no external stuff
go test # long tests, + external
go test -external=false # long tests, no external

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5696079

src/pkg/net/dialgoogle_test.go

@@ -42,9 +42,8 @@ func doDial(t *testing.T, network, addr string) {
 }
 
 func TestLookupCNAME(t *testing.T) {
-	if testing.Short() {
-		// Don't use external network.
-		t.Logf("skipping external network test during -short")
+	if testing.Short() || !*testExternal {
+		t.Logf("skipping test to avoid external network")
 		return
 	}
 	cname, err := LookupCNAME("www.google.com")
@@ -67,9 +66,8 @@ var googleaddrsipv4 = []string{
 }
 
 func TestDialGoogleIPv4(t *testing.T) {
-	if testing.Short() {
-		// Don't use external network.
-		t.Logf("skipping external network test during -short")
+	if testing.Short() || !*testExternal {
+		t.Logf("skipping test to avoid external network")
 		return
 	}
 
@@ -124,9 +122,8 @@ var googleaddrsipv6 = []string{
 }
 
 func TestDialGoogleIPv6(t *testing.T) {
-	if testing.Short() {
-		// Don't use external network.
-		t.Logf("skipping external network test during -short")
+	if testing.Short() || !*testExternal {
+		t.Logf("skipping test to avoid external network")
 		return
 	}
 	// Only run tcp6 if the kernel will take it.

src/pkg/net/lookup_test.go

@@ -12,7 +12,7 @@ import (
 	"testing"
 )
 
-var testExternal = flag.Bool("external", false, "allow use of external networks during test")
+var testExternal = flag.Bool("external", true, "allow use of external networks during long test")
 
 func TestGoogleSRV(t *testing.T) {
 	if testing.Short() || !*testExternal {