ipv6: document that package ipv6 doesn't support Darwin kernel version 12 or below

This change also uses nettest.SupportsIPv6MulticastDeliveryOnLoopback
to disable multicast packet delivery tests on some platform that doesn't
support the feature.

Fixes golang/go#17015.

Change-Id: Ia547efc2ac3779a96592bbc3874533fb65b711af
Reviewed-on: https://go-review.googlesource.com/33251
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

ipv6/doc.go

@@ -16,6 +16,9 @@
 // MLDv1 and MLDv2 are defined in RFC 2710 and RFC 3810.
 // Source-specific multicast is defined in RFC 4607.
 //
+// On Darwin, this package requires OS X Mavericks version 10.9 or
+// above, or equivalent.
+//
 //
 // Unicasting
 //

ipv6/main_test.go

@@ -1,27 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package ipv6_test
-
-import (
-	"flag"
-	"fmt"
-	"os"
-	"os/exec"
-	"runtime"
-	"strings"
-	"testing"
-)
-
-func TestMain(m *testing.M) {
-	flag.Parse()
-	if runtime.GOOS == "darwin" {
-		vers, _ := exec.Command("sw_vers", "-productVersion").Output()
-		if string(vers) == "10.8" || strings.HasPrefix(string(vers), "10.8.") {
-			fmt.Fprintf(os.Stderr, "# skipping tests on OS X 10.8 to avoid kernel panics; golang.org/issue/17015\n")
-			os.Exit(0)
-		}
-	}
-	os.Exit(m.Run())
-}

ipv6/multicast_test.go

@@ -29,15 +29,15 @@ var packetConnReadWriteMulticastUDPTests = []struct {
 
 func TestPacketConnReadWriteMulticastUDP(t *testing.T) {
 	switch runtime.GOOS {
-	case "freebsd": // due to a bug on loopback marking
-		// See http://www.freebsd.org/cgi/query-pr.cgi?pr=180065.
-		t.Skipf("not supported on %s", runtime.GOOS)
 	case "nacl", "plan9", "windows":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}
 	if !supportsIPv6 {
 		t.Skip("ipv6 is not supported")
 	}
+	if !nettest.SupportsIPv6MulticastDeliveryOnLoopback() {
+		t.Skipf("multicast delivery doesn't work correctly on %s", runtime.GOOS)
+	}
 	ifi := nettest.RoutedInterface("ip6", net.FlagUp|net.FlagMulticast|net.FlagLoopback)
 	if ifi == nil {
 		t.Skipf("not available on %s", runtime.GOOS)
@@ -129,15 +129,15 @@ var packetConnReadWriteMulticastICMPTests = []struct {
 
 func TestPacketConnReadWriteMulticastICMP(t *testing.T) {
 	switch runtime.GOOS {
-	case "freebsd": // due to a bug on loopback marking
-		// See http://www.freebsd.org/cgi/query-pr.cgi?pr=180065.
-		t.Skipf("not supported on %s", runtime.GOOS)
 	case "nacl", "plan9", "windows":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}
 	if !supportsIPv6 {
 		t.Skip("ipv6 is not supported")
 	}
+	if !nettest.SupportsIPv6MulticastDeliveryOnLoopback() {
+		t.Skipf("multicast delivery doesn't work correctly on %s", runtime.GOOS)
+	}
 	if m, ok := nettest.SupportsRawIPSocket(); !ok {
 		t.Skip(m)
 	}