From d6d8ce789fd236959c9c0c6df2dbfb017e614bd0 Mon Sep 17 00:00:00 2001
From: MaMe82 <mame8282@googlemail.com>
Date: Mon, 6 Aug 2018 15:38:50 +0200
Subject: [PATCH] Enable multicast on interfaces, to allow mDNS (avahi-daemon)

---
 netlink/netlink_linux.go | 33 +++++++++++++++++++++++++++++++++
 service/network.go       | 24 +++++++++++++++++++++++-
 2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/netlink/netlink_linux.go b/netlink/netlink_linux.go
index 2773e34..f88516a 100644
--- a/netlink/netlink_linux.go
+++ b/netlink/netlink_linux.go
@@ -587,6 +587,38 @@ func NetworkSetMacAddress(iface *net.Interface, macaddr string) error {
 	return s.HandleAck(wb.Seq)
 }
 
+//Added by MaMe82
+// Bring down a particular network interface.
+// This is identical to running: ip link set $name down
+func NetworkSetMulticast(iface *net.Interface, enable bool) error {
+	s, err := getNetlinkSocket()
+	if err != nil {
+		return err
+	}
+	defer s.Close()
+
+	wb := newNetlinkRequest(syscall.RTM_SETLINK, syscall.NLM_F_ACK)
+
+	msg := newIfInfomsg(syscall.AF_UNSPEC)
+	msg.Index = int32(iface.Index)
+	msg.Flags = syscall.NLM_F_REQUEST
+	msg.Change = DEFAULT_CHANGE
+	msg.IfInfomsg.Change |= syscall.IFF_MULTICAST
+	if enable {
+		msg.IfInfomsg.Flags |= syscall.IFF_MULTICAST
+	} else {
+		msg.IfInfomsg.Flags = uint32(int(msg.IfInfomsg.Flags) & ^syscall.IFF_MULTICAST)
+	}
+
+	wb.AddData(msg)
+
+	if err := s.Send(wb); err != nil {
+		return err
+	}
+
+	return s.HandleAck(wb.Seq)
+}
+
 // Set link Maximum Transmission Unit
 // This is identical to running: ip link set dev $name mtu $MTU
 // bridge is a bitch here https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=292088
@@ -616,6 +648,7 @@ func NetworkSetMTU(iface *net.Interface, mtu int) error {
 	return s.HandleAck(wb.Seq)
 }
 
+
 // Set link queue length
 // This is identical to running: ip link set dev $name txqueuelen $QLEN
 func NetworkSetTxQueueLen(iface *net.Interface, txQueueLen int) error {
diff --git a/service/network.go b/service/network.go
index bf51c39..58a2e5b 100644
--- a/service/network.go
+++ b/service/network.go
@@ -136,11 +136,17 @@ func ConfigureInterface(settings *pb.EthernetInterfaceSettings) (err error) {
 		if settings.Enabled {
 			log.Printf("Setting Interface %s to UP\n", iface.Name)
 			err = netlink.NetworkLinkUp(iface)
+			if err != nil { return err }
+			log.Printf("Setting Interface %s to MULTICAST to ON\n", iface.Name)
+			err = netlink.NetworkSetMulticast(iface, true)
+			if err != nil { return err }
+
 		} else {
 			log.Printf("Setting Interface %s to DOWN\n", iface.Name)
 			err = netlink.NetworkLinkDown(iface)
+			if err != nil { return err }
 		}
-		if err != nil { return err }
+
 	case pb.EthernetInterfaceSettings_DHCP_SERVER:
 		//Generate net
 		ipNet, err := IpNetFromIPv4AndNetmask(settings.IpAddress4, settings.Netmask4)
@@ -155,6 +161,11 @@ func ConfigureInterface(settings *pb.EthernetInterfaceSettings) (err error) {
 		if settings.Enabled {
 			log.Printf("Setting Interface %s to UP\n", iface.Name)
 			err = netlink.NetworkLinkUp(iface)
+			if err != nil { return err }
+			log.Printf("Setting Interface %s to MULTICAST to ON\n", iface.Name)
+			err = netlink.NetworkSetMulticast(iface, true)
+			if err != nil { return err }
+
 
 			//check DhcpServerSettings
 			if settings.DhcpServerSettings == nil {
@@ -194,7 +205,18 @@ func ConfigureInterface(settings *pb.EthernetInterfaceSettings) (err error) {
 	case pb.EthernetInterfaceSettings_DHCP_CLIENT:
 		netlink.NetworkLinkFlush(iface)
 		if settings.Enabled {
+			log.Printf("Setting Interface %s to UP\n", iface.Name)
+			err = netlink.NetworkLinkUp(iface)
+			if err != nil { return err }
+			log.Printf("Setting Interface %s to MULTICAST to ON\n", iface.Name)
+			err = netlink.NetworkSetMulticast(iface, true)
+			if err != nil { return err }
+
 			StartDHCPClient(settings.Name)
+		} else {
+			log.Printf("Setting Interface %s to DOWN\n", iface.Name)
+			err = netlink.NetworkLinkDown(iface)
+			if err != nil { return err }
 		}
 
 	}