basic ranged auto listener (#779)

agent/agent.go

@@ -19,6 +19,7 @@ import (
 
 type Agent struct {
 	cfg          *AgentConfig
+	httpEndpoint string
 	root         env_core.Root
 	agentSocket  string
 	shares       map[string]*share
@@ -109,7 +110,13 @@ func (a *Agent) gateway(cfg *AgentConfig) {
 		logrus.Fatalf("unable to register gateway: %v", err)
 	}
 
-	if err := http.ListenAndServe(cfg.ConsoleEndpoint, agentUi.Middleware(mux)); err != nil {
+	listener, err := AutoListener(cfg.ConsoleAddress, cfg.ConsoleStartPort, cfg.ConsoleEndPort)
+	if err != nil {
+		logrus.Fatalf("unable to create a listener: %v", err)
+	}
+	a.httpEndpoint = listener.Addr().String()
+
+	if err := http.Serve(listener, agentUi.Middleware(mux)); err != nil {
 		logrus.Error(err)
 	}
 }

agent/autoListener.go

@@ -0,0 +1,17 @@
+package agent
+
+import (
+	"fmt"
+	"net"
+)
+
+func AutoListener(address string, startPort, endPort uint16) (net.Listener, error) {
+	for i := startPort; i <= endPort; i++ {
+		l, err := net.Listen("tcp", fmt.Sprintf("%s:%d", address, i))
+		if err != nil {
+			continue
+		}
+		return l, nil
+	}
+	return nil, fmt.Errorf("no listener found in range")
+}

agent/config.go

@@ -1,11 +1,15 @@
 package agent
 
 type AgentConfig struct {
-	ConsoleEndpoint string
+	ConsoleAddress   string
+	ConsoleStartPort uint16
+	ConsoleEndPort   uint16
 }
 
-func DefaultAgentConfig() *AgentConfig {
+func DefaultConfig() *AgentConfig {
 	return &AgentConfig{
-		ConsoleEndpoint: "127.0.0.1:8888",
+		ConsoleAddress:   "127.0.0.1",
+		ConsoleStartPort: 8080,
+		ConsoleEndPort:   8181,
 	}
 }

agent/version.go

@@ -12,6 +12,6 @@ func (i *agentGrpcImpl) Version(_ context.Context, _ *agentGrpc.VersionRequest)
 	logrus.Debugf("responding to version inquiry with '%v'", v)
 	return &agentGrpc.VersionResponse{
 		V:               v,
-		ConsoleEndpoint: i.agent.Config().ConsoleEndpoint,
+		ConsoleEndpoint: i.agent.httpEndpoint,
 	}, nil
 }

cmd/zrok/agentStart.go

@@ -16,7 +16,9 @@ func init() {
 
 type agentStartCommand struct {
 	cmd              *cobra.Command
-	consoleEndpoint string
+	consoleAddress   string
+	consoleStartPort uint16
+	consoleEndPort   uint16
 }
 
 func newAgentStartCommand() *agentStartCommand {
@@ -27,7 +29,9 @@ func newAgentStartCommand() *agentStartCommand {
 	}
 	command := &agentStartCommand{cmd: cmd}
 	cmd.Run = command.run
-	cmd.Flags().StringVar(&command.consoleEndpoint, "console-endpoint", "127.0.0.1:8888", "gRPC gateway endpoint")
+	cmd.Flags().StringVar(&command.consoleAddress, "console-endpoint", "127.0.0.1", "gRPC gateway address")
+	cmd.Flags().Uint16Var(&command.consoleStartPort, "console-start-port", 8080, "gRPC gateway starting port")
+	cmd.Flags().Uint16Var(&command.consoleEndPort, "console-end-port", 8181, "gRPC gateway ending port")
 	return command
 }
 
@@ -41,8 +45,10 @@ func (cmd *agentStartCommand) run(_ *cobra.Command, _ []string) {
 		tui.Error("unable to load environment; did you 'zrok enable'?", nil)
 	}
 
-	cfg := agent.DefaultAgentConfig()
+	cfg := agent.DefaultConfig()
-	cfg.ConsoleEndpoint = cmd.consoleEndpoint
+	cfg.ConsoleAddress = cmd.consoleAddress
+	cfg.ConsoleStartPort = cmd.consoleStartPort
+	cfg.ConsoleEndPort = cmd.consoleEndPort
 	a, err := agent.NewAgent(cfg, root)
 	if err != nil {
 		tui.Error("error creating agent", err)