Add support for --host flag

cmd/thv/app/config.go

@@ -13,6 +13,7 @@ import (
 	"github.com/stacklok/toolhive/pkg/labels"
 	"github.com/stacklok/toolhive/pkg/logger"
 	"github.com/stacklok/toolhive/pkg/secrets"
+	"github.com/stacklok/toolhive/pkg/transport"
 )
 
 var configCmd = &cobra.Command{
@@ -262,7 +263,7 @@ func addRunningMCPsToClient(ctx context.Context, clientName string) error {
 		}
 
 		// Generate URL for the MCP server
-		url := client.GenerateMCPServerURL("localhost", port, name)
+		url := client.GenerateMCPServerURL(transport.LocalhostIPv4, port, name)
 
 		// Update each configuration file
 		for _, clientConfig := range clientConfigs {

cmd/thv/app/list.go

@@ -13,6 +13,7 @@ import (
 	"github.com/stacklok/toolhive/pkg/labels"
 	"github.com/stacklok/toolhive/pkg/lifecycle"
 	"github.com/stacklok/toolhive/pkg/logger"
+	"github.com/stacklok/toolhive/pkg/transport"
 )
 
 var listCmd = &cobra.Command{
@@ -28,10 +29,7 @@ var (
 )
 
 // Constants for list command
-const (
-	defaultHost      = "localhost"
-	unknownTransport = "unknown"
-)
+const unknownTransport = "unknown"
 
 // ContainerOutput represents container information for JSON output
 type ContainerOutput struct {
@@ -100,9 +98,9 @@ func printJSONOutput(containers []rt.ContainerInfo) error {
 		}
 
 		// Get transport type from labels
-		transport := labels.GetTransportType(c.Labels)
-		if transport == "" {
-			transport = unknownTransport
+		t := labels.GetTransportType(c.Labels)
+		if t == "" {
+			t = unknownTransport
 		}
 
 		// Get tool type from labels
@@ -117,15 +115,15 @@ func printJSONOutput(containers []rt.ContainerInfo) error {
 		// Generate URL for the MCP server
 		url := ""
 		if port > 0 {
-			url = client.GenerateMCPServerURL(defaultHost, port, name)
+			url = client.GenerateMCPServerURL(transport.LocalhostIPv4, port, name)
 		}
 
 		output = append(output, ContainerOutput{
 			ID:        truncatedID,
 			Name:      name,
 			Image:     c.Image,
 			State:     c.State,
-			Transport: transport,
+			Transport: t,
 			ToolType:  toolType,
 			Port:      port,
 			URL:       url,
@@ -173,7 +171,7 @@ func printMCPServersOutput(containers []rt.ContainerInfo) error {
 		// Generate URL for the MCP server
 		url := ""
 		if port > 0 {
-			url = client.GenerateMCPServerURL(defaultHost, port, name)
+			url = client.GenerateMCPServerURL(transport.LocalhostIPv4, port, name)
 		}
 
 		// Add the MCP server to the map
@@ -216,9 +214,9 @@ func printTextOutput(containers []rt.ContainerInfo) {
 		}
 
 		// Get transport type from labels
-		transport := labels.GetTransportType(c.Labels)
-		if transport == "" {
-			transport = unknownTransport
+		t := labels.GetTransportType(c.Labels)
+		if t == "" {
+			t = unknownTransport
 		}
 
 		// Get port from labels
@@ -230,7 +228,7 @@ func printTextOutput(containers []rt.ContainerInfo) {
 		// Generate URL for the MCP server
 		url := ""
 		if port > 0 {
-			url = client.GenerateMCPServerURL(defaultHost, port, name)
+			url = client.GenerateMCPServerURL(transport.LocalhostIPv4, port, name)
 		}
 
 		// Print container information
@@ -239,7 +237,7 @@ func printTextOutput(containers []rt.ContainerInfo) {
 			name,
 			c.Image,
 			c.State,
-			transport,
+			t,
 			port,
 			url,
 		)

cmd/thv/app/proxy.go

@@ -11,6 +11,7 @@ import (
 	"github.com/stacklok/toolhive/pkg/auth"
 	"github.com/stacklok/toolhive/pkg/logger"
 	"github.com/stacklok/toolhive/pkg/networking"
+	"github.com/stacklok/toolhive/pkg/transport"
 	"github.com/stacklok/toolhive/pkg/transport/proxy/transparent"
 	"github.com/stacklok/toolhive/pkg/transport/types"
 )
@@ -25,11 +26,13 @@ This command creates a standalone proxy without starting a container.`,
 }
 
 var (
+	proxyHost      string
 	proxyPort      int
 	proxyTargetURI string
 )
 
 func init() {
+	proxyCmd.Flags().StringVar(&proxyHost, "host", transport.LocalhostIPv4, "Host for the HTTP proxy to listen on (IP or hostname)")
 	proxyCmd.Flags().IntVar(&proxyPort, "port", 0, "Port for the HTTP proxy to listen on (host port)")
 	proxyCmd.Flags().StringVar(
 		&proxyTargetURI,
@@ -52,6 +55,13 @@ func proxyCmdFunc(cmd *cobra.Command, args []string) error {
 	// Get the server name
 	serverName := args[0]
 
+	// Validate the host flag and default resolving to IP in case hostname is provided
+	validatedHost, err := ValidateAndNormaliseHostFlag(proxyHost)
+	if err != nil {
+		return fmt.Errorf("invalid host: %s", proxyHost)
+	}
+	proxyHost = validatedHost
+
 	// Select a port for the HTTP proxy (host port)
 	port, err := networking.FindOrUsePort(proxyPort)
 	if err != nil {
@@ -94,7 +104,7 @@ func proxyCmdFunc(cmd *cobra.Command, args []string) error {
 		port, proxyTargetURI)
 
 	// Create the transparent proxy with middlewares
-	proxy := transparent.NewTransparentProxy(port, serverName, proxyTargetURI, middlewares...)
+	proxy := transparent.NewTransparentProxy(proxyHost, port, serverName, proxyTargetURI, middlewares...)
 	if err := proxy.Start(ctx); err != nil {
 		return fmt.Errorf("failed to start proxy: %v", err)
 	}

cmd/thv/app/run.go

@@ -3,6 +3,7 @@ package app
 import (
 	"context"
 	"fmt"
+	"net"
 	"os"
 	"strings"
 
@@ -17,6 +18,7 @@ import (
 	"github.com/stacklok/toolhive/pkg/permissions"
 	"github.com/stacklok/toolhive/pkg/registry"
 	"github.com/stacklok/toolhive/pkg/runner"
+	"github.com/stacklok/toolhive/pkg/transport"
 )
 
 var runCmd = &cobra.Command{
@@ -56,6 +58,7 @@ permission profile. Additional configuration can be provided via flags.`,
 var (
 	runTransport         string
 	runName              string
+	runHost              string
 	runPort              int
 	runTargetPort        int
 	runTargetHost        string
@@ -72,12 +75,13 @@ var (
 func init() {
 	runCmd.Flags().StringVar(&runTransport, "transport", "stdio", "Transport mode (sse or stdio)")
 	runCmd.Flags().StringVar(&runName, "name", "", "Name of the MCP server (auto-generated from image if not provided)")
+	runCmd.Flags().StringVar(&runHost, "host", transport.LocalhostIPv4, "Host for the HTTP proxy to listen on (IP or hostname)")
 	runCmd.Flags().IntVar(&runPort, "port", 0, "Port for the HTTP proxy to listen on (host port)")
 	runCmd.Flags().IntVar(&runTargetPort, "target-port", 0, "Port for the container to expose (only applicable to SSE transport)")
 	runCmd.Flags().StringVar(
 		&runTargetHost,
 		"target-host",
-		"localhost",
+		transport.LocalhostIPv4,
 		"Host to forward traffic to (only applicable to SSE transport)")
 	runCmd.Flags().StringVar(
 		&runPermissionProfile,
@@ -131,6 +135,14 @@ func init() {
 
 func runCmdFunc(cmd *cobra.Command, args []string) error {
 	ctx := cmd.Context()
+
+	// Validate the host flag and default resolving to IP in case hostname is provided
+	validatedHost, err := ValidateAndNormaliseHostFlag(runHost)
+	if err != nil {
+		return fmt.Errorf("invalid host: %s", runHost)
+	}
+	runHost = validatedHost
+
 	// Get the server name or image
 	serverOrImage := args[0]
 
@@ -173,6 +185,7 @@ func runCmdFunc(cmd *cobra.Command, args []string) error {
 		rt,
 		cmdArgs,
 		runName,
+		runHost,
 		debugMode,
 		runVolumes,
 		runSecrets,
@@ -437,3 +450,31 @@ func parseCommandArguments(args []string) []string {
 	}
 	return cmdArgs
 }
+
+// ValidateAndNormaliseHostFlag validates and normalizes the host flag resolving it to an IP address if hostname is provided
+func ValidateAndNormaliseHostFlag(host string) (string, error) {
+	// Check if the host is a valid IP address
+	ip := net.ParseIP(host)
+	if ip != nil {
+		if ip.To4() == nil {
+			return "", fmt.Errorf("IPv6 addresses are not supported: %s", host)
+		}
+		return host, nil
+	}
+
+	// If not an IP address, resolve the hostname to an IP address
+	addrs, err := net.LookupHost(host)
+	if err != nil {
+		return "", fmt.Errorf("invalid host: %s", host)
+	}
+
+	// Use the first IPv4 address found
+	for _, addr := range addrs {
+		ip := net.ParseIP(addr)
+		if ip != nil && ip.To4() != nil {
+			return ip.String(), nil
+		}
+	}
+
+	return "", fmt.Errorf("could not resolve host: %s", host)
+}

pkg/api/v1/servers.go

@@ -13,6 +13,7 @@ import (
 	"github.com/stacklok/toolhive/pkg/permissions"
 	"github.com/stacklok/toolhive/pkg/runner"
 	"github.com/stacklok/toolhive/pkg/secrets"
+	"github.com/stacklok/toolhive/pkg/transport"
 )
 
 // ServerRoutes defines the routes for server management.
@@ -144,12 +145,13 @@ func (s *ServerRoutes) createServer(w http.ResponseWriter, r *http.Request) {
 		s.containerRuntime,
 		req.CmdArguments,
 		req.Name,
+		req.Host,
 		s.debugMode,
 		req.Volumes,
 		runSecrets,
 		req.AuthzConfig,
 		req.PermissionProfile,
-		"localhost", // Seems like a reasonable default for now.
+		transport.LocalhostIPv4, // Seems like a reasonable default for now.
 		req.OIDC.Issuer,
 		req.OIDC.Audience,
 		req.OIDC.JwksURL,
@@ -227,6 +229,7 @@ type serverListResponse struct {
 type createRequest struct {
 	Name              string                    `json:"name"`
 	Image             string                    `json:"image"`
+	Host              string                    `json:"host"`
 	CmdArguments      []string                  `json:"cmd_arguments"`
 	TargetPort        int                       `json:"target_port"`
 	EnvVars           []string                  `json:"env_vars"`

pkg/lifecycle/manager.go

@@ -209,9 +209,14 @@ func (*defaultManager) RunContainerDetached(runConfig *runner.RunConfig) error {
 		detachedArgs = append(detachedArgs, "--name", runConfig.ContainerName)
 	}
 
+	if runConfig.Host != "" {
+		detachedArgs = append(detachedArgs, "--host", runConfig.Host)
+	}
+
 	if runConfig.Port != 0 {
 		detachedArgs = append(detachedArgs, "--port", fmt.Sprintf("%d", runConfig.Port))
 	}
+
 	if runConfig.TargetPort != 0 {
 		detachedArgs = append(detachedArgs, "--target-port", fmt.Sprintf("%d", runConfig.TargetPort))
 	}

pkg/runner/config.go

@@ -17,6 +17,7 @@ import (
 	"github.com/stacklok/toolhive/pkg/networking"
 	"github.com/stacklok/toolhive/pkg/permissions"
 	"github.com/stacklok/toolhive/pkg/secrets"
+	"github.com/stacklok/toolhive/pkg/transport"
 	"github.com/stacklok/toolhive/pkg/transport/types"
 )
 
@@ -41,6 +42,9 @@ type RunConfig struct {
 	// Transport is the transport mode (sse or stdio)
 	Transport types.TransportType `json:"transport" yaml:"transport"`
 
+	// Host is the host for the HTTP proxy
+	Host string `json:"host" yaml:"host"`
+
 	// Port is the port for the HTTP proxy to listen on (host port)
 	Port int `json:"port" yaml:"port"`
 
@@ -120,6 +124,7 @@ func NewRunConfigFromFlags(
 	runtime rt.Runtime,
 	cmdArgs []string,
 	name string,
+	host string,
 	debug bool,
 	volumes []string,
 	secretsList []string,
@@ -131,6 +136,13 @@ func NewRunConfigFromFlags(
 	oidcJwksURL string,
 	oidcClientID string,
 ) *RunConfig {
+	// Ensure default values for host and targetHost
+	if host == "" {
+		host = transport.LocalhostIPv4
+	}
+	if targetHost == "" {
+		targetHost = transport.LocalhostIPv4
+	}
 	config := &RunConfig{
 		Runtime:                     runtime,
 		CmdArgs:                     cmdArgs,
@@ -143,6 +155,7 @@ func NewRunConfigFromFlags(
 		TargetHost:                  targetHost,
 		ContainerLabels:             make(map[string]string),
 		EnvVars:                     make(map[string]string),
+		Host:                        host,
 	}
 
 	// Set OIDC config if any values are provided
@@ -165,10 +178,10 @@ func (c *RunConfig) WithAuthz(config *authz.Config) *RunConfig {
 }
 
 // WithTransport parses and sets the transport type
-func (c *RunConfig) WithTransport(transport string) (*RunConfig, error) {
-	transportType, err := types.ParseTransportType(transport)
+func (c *RunConfig) WithTransport(t string) (*RunConfig, error) {
+	transportType, err := types.ParseTransportType(t)
 	if err != nil {
-		return c, fmt.Errorf("invalid transport mode: %s. Valid modes are: sse, stdio", transport)
+		return c, fmt.Errorf("invalid transport mode: %s. Valid modes are: sse, stdio", t)
 	}
 	c.Transport = transportType
 	return c, nil

pkg/runner/config_test.go

@@ -804,6 +804,7 @@ func TestNewRunConfigFromFlags(t *testing.T) {
 	runtime := &mockRuntime{}
 	cmdArgs := []string{"arg1", "arg2"}
 	name := "test-server"
+	host := "localhost"
 	debug := true
 	volumes := []string{"/host:/container"}
 	secretsList := []string{"secret1,target=ENV_VAR1"}
@@ -819,6 +820,7 @@ func TestNewRunConfigFromFlags(t *testing.T) {
 		runtime,
 		cmdArgs,
 		name,
+		host,
 		debug,
 		volumes,
 		secretsList,