bridge: Use random for test service to avoid clashes

Go test runs tests from different packages in different binaries
and these run in parallel. It's possible that the test bridge
service in different tests execute at the same time, which would
cause failures ("bind address already in use") if the port was
not random.

bridge/net/config.go

@@ -75,13 +75,10 @@ func validateExternalAddress(addr string) (externalAddressPort, error) {
 	if host == "" {
 		return externalAddressPort{}, fmt.Errorf("invalid externalAddress: host cannot be empty")
 	}
-	port, err := strconv.ParseUint(portStr, 10, 16)
+	_, err = strconv.ParseUint(portStr, 10, 16)
 	if err != nil {
 		return externalAddressPort{}, fmt.Errorf("invalid externalAddress: %w", err)
 	}
-	if port == 0 {
-		return externalAddressPort{}, fmt.Errorf("invalid externalAddress: port cannot be 0")
-	}
 
 	_, errIpv4 := gonet.ResolveUDPAddr(UDP4, addr)
 	_, errIpv6 := gonet.ResolveUDPAddr(UDP6, addr)

bridge/net/config_internal_test.go

@@ -105,11 +105,6 @@ func TestConfigValidate(t *testing.T) {
 			config:  &Config{ExternalAddresses: []string{":12345"}},
 			wantErr: true,
 		},
-		{
-			name:    "ZeroPortInExternalAddress",
-			config:  &Config{ExternalAddresses: []string{"localhost:0"}},
-			wantErr: true,
-		},
 		{
 			name:    "InvalidPortInExternalAddress",
 			config:  &Config{ExternalAddresses: []string{"localhost:invalid"}},

bridge/net/network.go

@@ -242,11 +242,24 @@ func (s coAPServers) Close() error {
 	return errors.ErrorOrNil()
 }
 
-func newServers(cfg Config, m *mux.Router) (coAPServers, bool, bool, error) {
+func getPortFromAddress(addr gonet.Addr) (string, error) {
+	udpAddr, ok := addr.(*gonet.UDPAddr)
+	if ok {
+		return fmt.Sprintf("%d", udpAddr.Port), nil
+	}
+	addrStr := addr.String()
+	_, port, err := gonet.SplitHostPort(addrStr)
+	if err != nil {
+		return "", err
+	}
+	return port, nil
+}
+
+func newServers(cfg *Config, m *mux.Router) (coAPServers, bool, bool, error) {
 	servers := make(coAPServers, 0, len(cfg.externalAddressesPort))
 	hasIPv4 := false
 	hasIPv6 := false
-	for _, addr := range cfg.externalAddressesPort {
+	for i, addr := range cfg.externalAddressesPort {
 		var conn *net.UDPConn
 		var err error
 		if addr.network == UDP4 {
@@ -261,6 +274,15 @@ func newServers(cfg Config, m *mux.Router) (coAPServers, bool, bool, error) {
 			_ = servers.Close()
 			return nil, false, false, err
 		}
+		if addr.port == "0" {
+			port, err := getPortFromAddress(conn.LocalAddr())
+			if err != nil {
+				_ = servers.Close()
+				return nil, false, false, err
+			}
+			cfg.externalAddressesPort[i].port = port
+		}
+
 		if conn != nil {
 			servers = append(servers, coAPServer{
 				s: udp.NewServer(
@@ -304,7 +326,7 @@ func New(cfg Config, handler RequestHandler) (*Net, error) {
 		return nil, err
 	}
 	m := mux.NewRouter()
-	servers, hasIPv4, hasIPv6, err := newServers(cfg, m)
+	servers, hasIPv4, hasIPv6, err := newServers(&cfg, m)
 	if err != nil {
 		return nil, err
 	}

bridge/test/test.go

@@ -29,8 +29,8 @@ import (
 
 const (
 	BRIDGE_SERVICE_PIID     = "f47ac10b-58cc-4372-a567-0e02b2c3d479"
-	BRIDGE_DEVICE_HOST      = "127.0.0.1:15000"
-	BRIDGE_DEVICE_HOST_IPv6 = "[::1]:15001"
+	BRIDGE_DEVICE_HOST      = "127.0.0.1:0" // 0 means random port
+	BRIDGE_DEVICE_HOST_IPv6 = "[::1]:0"     // 0 means random port
 )
 
 func MakeConfig(t *testing.T) service.Config {