From b5057d60adcbd438b5db80cde812e2c419e22140 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Thu, 24 May 2018 15:05:12 +0100
Subject: [PATCH] Fix enabling/disabling multicast

---
 src/yggdrasil/multicast.go | 4 ++++
 yggdrasil.go               | 4 +++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/yggdrasil/multicast.go b/src/yggdrasil/multicast.go
index d20a0b82..f3355916 100644
--- a/src/yggdrasil/multicast.go
+++ b/src/yggdrasil/multicast.go
@@ -16,6 +16,10 @@ type multicast struct {
 func (m *multicast) init(core *Core) {
 	m.core = core
 	m.groupAddr = "[ff02::114]:9001"
+  // Check if we've been given any expressions
+  if len(m.core.ifceExpr) == 0 {
+    return
+  }
 	// Ask the system for network interfaces
 	allifaces, err := net.Interfaces()
 	if err != nil {
diff --git a/yggdrasil.go b/yggdrasil.go
index 385878a5..4f98b6a8 100644
--- a/yggdrasil.go
+++ b/yggdrasil.go
@@ -48,9 +48,11 @@ func generateConfig(isAutoconf bool) *nodeConfig {
 	cfg := nodeConfig{}
 	if isAutoconf {
 		cfg.Listen = "[::]:0"
+		cfg.MulticastInterfaces = []string{".*"}
 	} else {
 		r1 := rand.New(rand.NewSource(time.Now().UnixNano()))
 		cfg.Listen = fmt.Sprintf("[::]:%d", r1.Intn(65534-32768)+32768)
+		cfg.MulticastInterfaces = []string{}
 	}
 	cfg.AdminListen = "[::1]:9001"
 	cfg.EncryptionPublicKey = hex.EncodeToString(bpub[:])
@@ -59,7 +61,6 @@ func generateConfig(isAutoconf bool) *nodeConfig {
 	cfg.SigningPrivateKey = hex.EncodeToString(spriv[:])
 	cfg.Peers = []string{}
 	cfg.AllowedEncryptionPublicKeys = []string{}
-	cfg.MulticastInterfaces = []string{".*"}
 	cfg.IfName = core.GetTUNDefaultIfName()
 	cfg.IfMTU = core.GetTUNDefaultIfMTU()
 	cfg.IfTAPMode = core.GetTUNDefaultIfTAPMode()
@@ -71,6 +72,7 @@ func generateConfig(isAutoconf bool) *nodeConfig {
 // with -genconf.
 func doGenconf() string {
 	cfg := generateConfig(false)
+	cfg.MulticastInterfaces = append(cfg.MulticastInterfaces, ".*")
 	bs, err := hjson.Marshal(cfg)
 	if err != nil {
 		panic(err)