Allow `::` in lighthouse.dns.host config (#1115)

dns_server.go

@@ -129,7 +129,12 @@ func dnsMain(l *logrus.Logger, hostMap *HostMap, c *config.C) func() {
 }
 
 func getDnsServerAddr(c *config.C) string {
-	return c.GetString("lighthouse.dns.host", "") + ":" + strconv.Itoa(c.GetInt("lighthouse.dns.port", 53))
+	dnsHost := strings.TrimSpace(c.GetString("lighthouse.dns.host", ""))
+	// Old guidance was to provide the literal `[::]` in `lighthouse.dns.host` but that won't resolve.
+	if dnsHost == "[::]" {
+		dnsHost = "::"
+	}
+	return net.JoinHostPort(dnsHost, strconv.Itoa(c.GetInt("lighthouse.dns.port", 53)))
 }
 
 func startDns(l *logrus.Logger, c *config.C) {

dns_server_test.go

@@ -4,6 +4,8 @@ import (
 	"testing"
 
 	"github.com/miekg/dns"
+	"github.com/slackhq/nebula/config"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestParsequery(t *testing.T) {
@@ -17,3 +19,40 @@ func TestParsequery(t *testing.T) {
 
 	//parseQuery(m)
 }
+
+func Test_getDnsServerAddr(t *testing.T) {
+	c := config.NewC(nil)
+
+	c.Settings["lighthouse"] = map[interface{}]interface{}{
+		"dns": map[interface{}]interface{}{
+			"host": "0.0.0.0",
+			"port": "1",
+		},
+	}
+	assert.Equal(t, "0.0.0.0:1", getDnsServerAddr(c))
+
+	c.Settings["lighthouse"] = map[interface{}]interface{}{
+		"dns": map[interface{}]interface{}{
+			"host": "::",
+			"port": "1",
+		},
+	}
+	assert.Equal(t, "[::]:1", getDnsServerAddr(c))
+
+	c.Settings["lighthouse"] = map[interface{}]interface{}{
+		"dns": map[interface{}]interface{}{
+			"host": "[::]",
+			"port": "1",
+		},
+	}
+	assert.Equal(t, "[::]:1", getDnsServerAddr(c))
+
+	// Make sure whitespace doesn't mess us up
+	c.Settings["lighthouse"] = map[interface{}]interface{}{
+		"dns": map[interface{}]interface{}{
+			"host": "[::] ",
+			"port": "1",
+		},
+	}
+	assert.Equal(t, "[::]:1", getDnsServerAddr(c))
+}