Refactor multicast so that it creates a new TCP listener for each interface with LL addresses (so that it will not break if Listen is not set with a wildcard address)

src/yggdrasil/link.go

@@ -119,7 +119,8 @@ func (l *link) listen(uri string) error {
 	}
 	switch u.Scheme {
 	case "tcp":
-		return l.tcp.listen(u.Host)
+		_, err := l.tcp.listen(u.Host)
+		return err
 	default:
 		return errors.New("unknown listen scheme: " + u.Scheme)
 	}

src/yggdrasil/multicast.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"net"
 	"regexp"
-	"sync"
 	"time"
 
 	"golang.org/x/net/ipv6"
@@ -16,19 +15,16 @@ type multicast struct {
 	reconfigure chan chan error
 	sock        *ipv6.PacketConn
 	groupAddr   string
-	myAddr      *net.TCPAddr
-	myAddrMutex sync.RWMutex
+	listeners   map[string]*tcpListener
 }
 
 func (m *multicast) init(core *Core) {
 	m.core = core
 	m.reconfigure = make(chan chan error, 1)
+	m.listeners = make(map[string]*tcpListener)
 	go func() {
 		for {
 			e := <-m.reconfigure
-			m.myAddrMutex.Lock()
-			m.myAddr = m.core.link.tcp.getAddr()
-			m.myAddrMutex.Unlock()
 			e <- nil
 		}
 	}()
@@ -94,10 +90,12 @@ func (m *multicast) interfaces() []net.Interface {
 			continue
 		}
 		for _, expr := range exprs {
+			// Compile each regular expression
 			e, err := regexp.Compile(expr)
 			if err != nil {
 				panic(err)
 			}
+			// Does the interface match the regular expression? Store it if so
 			if e.MatchString(iface.Name) {
 				interfaces = append(interfaces, iface)
 			}
@@ -107,10 +105,6 @@ func (m *multicast) interfaces() []net.Interface {
 }
 
 func (m *multicast) announce() {
-	var anAddr net.TCPAddr
-	m.myAddrMutex.Lock()
-	m.myAddr = m.core.link.tcp.getAddr()
-	m.myAddrMutex.Unlock()
 	groupAddr, err := net.ResolveUDPAddr("udp6", m.groupAddr)
 	if err != nil {
 		panic(err)
@@ -121,27 +115,47 @@ func (m *multicast) announce() {
 	}
 	for {
 		for _, iface := range m.interfaces() {
-			m.sock.JoinGroup(&iface, groupAddr)
+			// Find interface addresses
 			addrs, err := iface.Addrs()
 			if err != nil {
 				panic(err)
 			}
-			m.myAddrMutex.RLock()
-			anAddr.Port = m.myAddr.Port
-			m.myAddrMutex.RUnlock()
 			for _, addr := range addrs {
 				addrIP, _, _ := net.ParseCIDR(addr.String())
+				// Ignore IPv4 addresses
 				if addrIP.To4() != nil {
 					continue
-				} // IPv6 only
+				}
+				// Ignore non-link-local addresses
 				if !addrIP.IsLinkLocalUnicast() {
 					continue
 				}
-				anAddr.IP = addrIP
-				anAddr.Zone = iface.Name
-				destAddr.Zone = iface.Name
-				msg := []byte(anAddr.String())
-				m.sock.WriteTo(msg, nil, destAddr)
+				// Join the multicast group
+				m.sock.JoinGroup(&iface, groupAddr)
+				// Try and see if we already have a TCP listener for this interface
+				var listener *tcpListener
+				if _, ok := m.listeners[iface.Name]; !ok {
+					// No listener was found - let's create one
+					listenaddr := fmt.Sprintf("[%s%%%s]:0", addrIP, iface.Name)
+					if l, err := m.core.link.tcp.listen(listenaddr); err == nil {
+						// Store the listener so that we can stop it later if needed
+						listener = &tcpListener{
+							listener: l,
+							stop:     make(chan bool),
+						}
+						m.listeners[iface.Name] = listener
+					}
+				} else {
+					// An existing listener was found
+					listener = m.listeners[iface.Name]
+				}
+				// Get the listener details and construct the multicast beacon
+				lladdr := (*listener.listener).Addr().String()
+				if a, err := net.ResolveTCPAddr("tcp6", lladdr); err == nil {
+					destAddr.Zone = iface.Name
+					msg := []byte(a.String())
+					m.sock.WriteTo(msg, nil, destAddr)
+				}
 				break
 			}
 			time.Sleep(time.Second)

src/yggdrasil/tcp.go

@@ -33,13 +33,17 @@ const tcp_ping_interval = (default_timeout * 2 / 3)
 
 // The TCP listener and information about active TCP connections, to avoid duplication.
 type tcp struct {
-	link          *link
-	reconfigure   chan chan error
-	mutex         sync.Mutex // Protecting the below
-	listeners     map[string]net.Listener
-	listenerstops map[string]chan bool
-	calls         map[string]struct{}
-	conns         map[linkInfo](chan struct{})
+	link        *link
+	reconfigure chan chan error
+	mutex       sync.Mutex // Protecting the below
+	listeners   map[string]*tcpListener
+	calls       map[string]struct{}
+	conns       map[linkInfo](chan struct{})
+}
+
+type tcpListener struct {
+	listener *net.Listener
+	stop     chan bool
 }
 
 // Wrapper function to set additional options for specific connection types.
@@ -60,7 +64,7 @@ func (t *tcp) getAddr() *net.TCPAddr {
 	t.mutex.Lock()
 	defer t.mutex.Unlock()
 	for _, listener := range t.listeners {
-		return listener.Addr().(*net.TCPAddr)
+		return (*listener.listener).Addr().(*net.TCPAddr)
 	}
 	return nil
 }
@@ -72,8 +76,7 @@ func (t *tcp) init(l *link) error {
 	t.mutex.Lock()
 	t.calls = make(map[string]struct{})
 	t.conns = make(map[linkInfo](chan struct{}))
-	t.listeners = make(map[string]net.Listener)
-	t.listenerstops = make(map[string]chan bool)
+	t.listeners = make(map[string]*tcpListener)
 	t.mutex.Unlock()
 
 	go func() {
@@ -89,7 +92,7 @@ func (t *tcp) init(l *link) error {
 						e <- errors.New("unknown scheme: " + add)
 						continue
 					}
-					if err := t.listen(add[6:]); err != nil {
+					if _, err := t.listen(add[6:]); err != nil {
 						e <- err
 						continue
 					}
@@ -110,7 +113,7 @@ func (t *tcp) init(l *link) error {
 		if listenaddr[:6] != "tcp://" {
 			continue
 		}
-		if err := t.listen(listenaddr[6:]); err != nil {
+		if _, err := t.listen(listenaddr[6:]); err != nil {
 			return err
 		}
 	}
@@ -118,7 +121,7 @@ func (t *tcp) init(l *link) error {
 	return nil
 }
 
-func (t *tcp) listen(listenaddr string) error {
+func (t *tcp) listen(listenaddr string) (*net.Listener, error) {
 	var err error
 
 	ctx := context.Background()
@@ -127,36 +130,36 @@ func (t *tcp) listen(listenaddr string) error {
 	}
 	listener, err := lc.Listen(ctx, "tcp", listenaddr)
 	if err == nil {
+		l := tcpListener{
+			listener: &listener,
+			stop:     make(chan bool, 1),
+		}
 		t.mutex.Lock()
-		t.listeners[listenaddr] = listener
-		t.listenerstops[listenaddr] = make(chan bool, 1)
+		t.listeners[listenaddr[6:]] = &l
 		t.mutex.Unlock()
-		go t.listener(listenaddr)
-		return nil
+		go t.listener(&l)
+		return &listener, nil
 	}
 
-	return err
+	return nil, err
 }
 
 // Runs the listener, which spawns off goroutines for incoming connections.
-func (t *tcp) listener(listenaddr string) {
-	t.mutex.Lock()
-	listener, ok1 := t.listeners[listenaddr]
-	listenerstop, ok2 := t.listenerstops[listenaddr]
-	t.mutex.Unlock()
-	if !ok1 || !ok2 {
-		t.link.core.log.Errorln("Tried to start TCP listener for", listenaddr, "which doesn't exist")
+func (t *tcp) listener(listener *tcpListener) {
+	if listener == nil {
 		return
 	}
-	reallistenaddr := listener.Addr().String()
-	defer listener.Close()
+	reallistener := *listener.listener
+	reallistenaddr := reallistener.Addr().String()
+	stop := listener.stop
+	defer reallistener.Close()
 	t.link.core.log.Infoln("Listening for TCP on:", reallistenaddr)
 	accepted := make(chan bool)
 	for {
 		var sock net.Conn
 		var err error
 		go func() {
-			sock, err = listener.Accept()
+			sock, err = reallistener.Accept()
 			accepted <- true
 		}()
 		select {
@@ -166,7 +169,7 @@ func (t *tcp) listener(listenaddr string) {
 				return
 			}
 			go t.handler(sock, true)
-		case <-listenerstop:
+		case <-stop:
 			t.link.core.log.Errorln("Stopping TCP listener on:", reallistenaddr)
 			return
 		}