fix: do not bind to IPv6 socket if 0.0.0.0 is passed

This fixes an odd default behaviour exhibited by the Go listener.

Author: raphaelcoeffic

config/options.go

@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"net"
 	"os"
 	"path"
 	"reflect"
@@ -77,7 +76,7 @@ type CloudbuildOpts struct {
 	// General options:
 	ConfigPath      string   `mapstructure:"config-path"`
 	LogLevel        LogLevel `mapstructure:"log-level"`
-	HTTPBindAddress net.IP   `mapstructure:"listen-ip"`
+	HTTPBindAddress string   `mapstructure:"listen-ip"`
 	HTTPBindPort    uint16   `mapstructure:"port"`
 	TrustedPlatform string   `mapstructure:"platform"`
 
@@ -177,8 +176,8 @@ func (o *CloudbuildOpts) BindAPIOpts(c *cobra.Command) {
 	c.Flags().Uint16VarP(
 		&o.HTTPBindPort, "port", "p", o.HTTPBindPort, "HTTP listen port",
 	)
-	c.Flags().IPVarP(
-		&o.HTTPBindAddress, "listen-ip", "l", net.IPv4zero, "HTTP listen IP",
+	c.Flags().StringVarP(
+		&o.HTTPBindAddress, "listen-ip", "l", o.HTTPBindAddress, "HTTP listen IP",
 	)
 	c.Flags().StringVar(
 		&o.TargetsDef, "targets", o.TargetsDef, "Targets definition",

server/http.go

@@ -2,6 +2,7 @@ package server
 
 import (
 	"errors"
+	"net"
 	"net/http"
 	"strings"
 
@@ -263,5 +264,22 @@ func (app *Application) Start(listen string, opts *config.CloudbuildOpts) error
 		}
 	})
 
-	return router.Run(listen)
+	var network string
+
+	switch {
+	case strings.HasPrefix(listen, "0.0.0.0"):
+		network = "tcp4" // IPv4 only
+	case listen == "" || strings.HasPrefix(listen, ":"):
+		network = "tcp" // Dual-stack (default Go behavior)
+	default:
+		network = "tcp" // Let Go decide based on the address
+	}
+
+	listener, err := net.Listen(network, listen)
+	if err != nil {
+		return err
+	}
+	defer listener.Close()
+
+	return router.RunListener(listener)
 }