Large refactoring/feature commit

1. Change listen addresses to URIs
2. Break out connectionSvc to support listeners and dialers based on schema
3. Add relay announcement and lookups part of discovery service

lib/discover/client_udp.go

@@ -137,11 +137,13 @@ func (d *UDPClient) broadcast(pkt []byte) {
 
 				time.Sleep(1 * time.Second)
 
-				res := d.Lookup(d.id)
-				if debug {
-					l.Debugf("discover %s: broadcast: Self-lookup returned: %v", d.url, res)
+				pkt, err := d.Lookup(d.id)
+				if err != nil && debug {
+					l.Debugf("discover %s: broadcast: Self-lookup failed: %v", d.url, err)
+				} else if debug {
+					l.Debugf("discover %s: broadcast: Self-lookup returned: %v", d.url, pkt.This.Addresses)
 				}
-				ok = len(res) > 0
+				ok = len(pkt.This.Addresses) > 0
 			}
 
 			d.mut.Lock()
@@ -157,13 +159,13 @@ func (d *UDPClient) broadcast(pkt []byte) {
 	}
 }
 
-func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
+func (d *UDPClient) Lookup(device protocol.DeviceID) (Announce, error) {
 	extIP, err := net.ResolveUDPAddr(d.url.Scheme, d.url.Host)
 	if err != nil {
 		if debug {
 			l.Debugf("discover %s: Lookup(%s): %s", d.url, device, err)
 		}
-		return nil
+		return Announce{}, err
 	}
 
 	conn, err := net.DialUDP(d.url.Scheme, d.listenAddress, extIP)
@@ -171,7 +173,7 @@ func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
 		if debug {
 			l.Debugf("discover %s: Lookup(%s): %s", d.url, device, err)
 		}
-		return nil
+		return Announce{}, err
 	}
 	defer conn.Close()
 
@@ -180,7 +182,7 @@ func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
 		if debug {
 			l.Debugf("discover %s: Lookup(%s): %s", d.url, device, err)
 		}
-		return nil
+		return Announce{}, err
 	}
 
 	buf := Query{QueryMagic, device[:]}.MustMarshalXDR()
@@ -189,7 +191,7 @@ func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
 		if debug {
 			l.Debugf("discover %s: Lookup(%s): %s", d.url, device, err)
 		}
-		return nil
+		return Announce{}, err
 	}
 
 	buf = make([]byte, 2048)
@@ -197,12 +199,12 @@ func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
 	if err != nil {
 		if err, ok := err.(net.Error); ok && err.Timeout() {
 			// Expected if the server doesn't know about requested device ID
-			return nil
+			return Announce{}, err
 		}
 		if debug {
 			l.Debugf("discover %s: Lookup(%s): %s", d.url, device, err)
 		}
-		return nil
+		return Announce{}, err
 	}
 
 	var pkt Announce
@@ -211,18 +213,13 @@ func (d *UDPClient) Lookup(device protocol.DeviceID) []string {
 		if debug {
 			l.Debugf("discover %s: Lookup(%s): %s\n%s", d.url, device, err, hex.Dump(buf[:n]))
 		}
-		return nil
+		return Announce{}, err
 	}
 
-	var addrs []string
-	for _, a := range pkt.This.Addresses {
-		deviceAddr := net.JoinHostPort(net.IP(a.IP).String(), strconv.Itoa(int(a.Port)))
-		addrs = append(addrs, deviceAddr)
-	}
 	if debug {
-		l.Debugf("discover %s: Lookup(%s) result: %v", d.url, device, addrs)
+		l.Debugf("discover %s: Lookup(%s) result: %v relays: %v", d.url, device, pkt.This.Addresses, pkt.This.Relays)
 	}
-	return addrs
+	return pkt, nil
 }
 
 func (d *UDPClient) Stop() {