net: skip some interface tests on Dragonfly for now

Skipping tests isn't great, but neither is a wall of red masking other
potential regressions.

Updates golang#34368

Change-Id: I5fdfa54846dd8d648001594c74f059af8af52247
Reviewed-on: https://go-review.googlesource.com/c/go/+/201482
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/net/interface_test.go

@@ -8,6 +8,7 @@ package net
 
 import (
 	"fmt"
+	"internal/testenv"
 	"reflect"
 	"runtime"
 	"testing"
@@ -50,10 +51,20 @@ func ipv6LinkLocalUnicastAddr(ifi *Interface) string {
 	return ""
 }
 
-func TestInterfaces(t *testing.T) {
-	if runtime.GOOS == "darwin" && (runtime.GOARCH == "arm" || runtime.GOARCH == "arm64") {
-		t.Skipf("sysctl is not supported on iOS")
+func condSkipInterfaceTest(t *testing.T) {
+	t.Helper()
+	switch runtime.GOOS {
+	case "darwin":
+		if runtime.GOARCH == "arm" || runtime.GOARCH == "arm64" {
+			t.Skipf("sysctl is not supported on iOS")
+		}
+	case "dragonfly":
+		testenv.SkipFlaky(t, 34368)
 	}
+}
+
+func TestInterfaces(t *testing.T) {
+	condSkipInterfaceTest(t)
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)
@@ -85,9 +96,7 @@ func TestInterfaces(t *testing.T) {
 }
 
 func TestInterfaceAddrs(t *testing.T) {
-	if runtime.GOOS == "darwin" && (runtime.GOARCH == "arm" || runtime.GOARCH == "arm64") {
-		t.Skipf("sysctl is not supported on iOS")
-	}
+	condSkipInterfaceTest(t)
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)
@@ -107,9 +116,7 @@ func TestInterfaceAddrs(t *testing.T) {
 }
 
 func TestInterfaceUnicastAddrs(t *testing.T) {
-	if runtime.GOOS == "darwin" && (runtime.GOARCH == "arm" || runtime.GOARCH == "arm64") {
-		t.Skipf("sysctl is not supported on iOS")
-	}
+	condSkipInterfaceTest(t)
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)
@@ -137,9 +144,7 @@ func TestInterfaceUnicastAddrs(t *testing.T) {
 }
 
 func TestInterfaceMulticastAddrs(t *testing.T) {
-	if runtime.GOOS == "darwin" && (runtime.GOARCH == "arm" || runtime.GOARCH == "arm64") {
-		t.Skipf("sysctl is not supported on iOS")
-	}
+	condSkipInterfaceTest(t)
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)