wgengine/tsdns: skip test that requires local IPv6 when IPv6 unavailable

Fixes #1292

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/tsdns/tsdns_server_test.go

@@ -5,6 +5,9 @@
 package tsdns
 
 import (
+	"log"
+	"testing"
+
 	"github.com/miekg/dns"
 	"inet.af/netaddr"
 )
@@ -71,7 +74,7 @@ func resolveToNXDOMAIN(w dns.ResponseWriter, req *dns.Msg) {
 	w.WriteMsg(m)
 }
 
-func serveDNS(addr string) (*dns.Server, chan error) {
+func serveDNS(tb testing.TB, addr string) (*dns.Server, chan error) {
 	server := &dns.Server{Addr: addr, Net: "udp"}
 
 	waitch := make(chan struct{})
@@ -79,7 +82,11 @@ func serveDNS(addr string) (*dns.Server, chan error) {
 
 	errch := make(chan error, 1)
 	go func() {
-		errch <- server.ListenAndServe()
+		err := server.ListenAndServe()
+		if err != nil {
+			log.Printf("ListenAndServe(%q): %v", addr, err)
+		}
+		errch <- err
 		close(errch)
 	}()
 

wgengine/tsdns/tsdns_test.go

@@ -274,14 +274,27 @@ func TestResolveReverse(t *testing.T) {
 	}
 }
 
+func ipv6Works() bool {
+	c, err := net.Listen("tcp", "[::1]:0")
+	if err != nil {
+		return false
+	}
+	c.Close()
+	return true
+}
+
 func TestDelegate(t *testing.T) {
 	tstest.ResourceCheck(t)
 
+	if !ipv6Works() {
+		t.Skip("skipping test that requires localhost IPv6")
+	}
+
 	dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
 	dnsHandleFunc("nxdomain.site.", resolveToNXDOMAIN)
 
-	v4server, v4errch := serveDNS("127.0.0.1:0")
-	v6server, v6errch := serveDNS("[::1]:0")
+	v4server, v4errch := serveDNS(t, "127.0.0.1:0")
+	v6server, v6errch := serveDNS(t, "[::1]:0")
 
 	defer func() {
 		if err := <-v4errch; err != nil {
@@ -371,7 +384,7 @@ func TestDelegate(t *testing.T) {
 func TestDelegateCollision(t *testing.T) {
 	dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
 
-	server, errch := serveDNS("127.0.0.1:0")
+	server, errch := serveDNS(t, "127.0.0.1:0")
 	defer func() {
 		if err := <-errch; err != nil {
 			t.Errorf("server error: %v", err)
@@ -473,7 +486,7 @@ func TestConcurrentSetMap(t *testing.T) {
 func TestConcurrentSetUpstreams(t *testing.T) {
 	dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
 
-	server, errch := serveDNS("127.0.0.1:0")
+	server, errch := serveDNS(t, "127.0.0.1:0")
 	defer func() {
 		if err := <-errch; err != nil {
 			t.Errorf("server error: %v", err)
@@ -752,7 +765,7 @@ func TestTrimRDNSBonjourPrefix(t *testing.T) {
 func BenchmarkFull(b *testing.B) {
 	dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6, "dns.test.site."))
 
-	server, errch := serveDNS("127.0.0.1:0")
+	server, errch := serveDNS(b, "127.0.0.1:0")
 	defer func() {
 		if err := <-errch; err != nil {
 			b.Errorf("server error: %v", err)