[Fix] only replace default api host with docker host (#879)

- move docker-machine lookup into general GetHost function
- only use GetHost result if API host is default (0.0.0.0) to not override user-provided value
- when looking up IP for host value (e.g. localhost), only use IPv4 to prevent errors

cmd/registry/registryCreate.go

@@ -41,9 +41,9 @@ type regCreatePreProcessedFlags struct {
 }
 
 type regCreateFlags struct {
-	Image          string
+	Image   string
 	Network string
-	NoHelp         bool
+	NoHelp  bool
 }
 
 var helptext string = `# You can now use the registry like this (example):

cmd/util/ports.go

@@ -26,6 +26,7 @@ import (
 	"net"
 	"regexp"
 	"strconv"
+	"strings"
 
 	"github.com/docker/go-connections/nat"
 	l "github.com/rancher/k3d/v5/pkg/logger"
@@ -61,7 +62,14 @@ func ParsePortExposureSpec(exposedPortSpec, internalPort string) (*k3d.ExposureO
 			return nil, fmt.Errorf("Failed to lookup host '%s' specified for Port Exposure: %+v", submatches["hostname"], err)
 		}
 		api.Host = submatches["hostname"]
-		submatches["hostip"] = addrs[0] // set hostip to the resolved address
+		for _, addr := range addrs {
+			if !strings.Contains(addr, ":") { // lazy IPv6 check :D
+				submatches["hostip"] = addr // set hostip to the resolved address
+			}
+		}
+		if submatches["hostip"] == "" {
+			return nil, fmt.Errorf("Failed to lookup IPv4 address for host '%s'", submatches["hostname"])
+		}
 	}
 
 	realPortString := ""

pkg/client/cluster.go

@@ -34,16 +34,14 @@ import (
 	"strings"
 	"time"
 
-	gort "runtime"
-
 	"github.com/docker/go-connections/nat"
 	"github.com/imdario/mergo"
 	copystruct "github.com/mitchellh/copystructure"
 	"github.com/rancher/k3d/v5/pkg/actions"
 	config "github.com/rancher/k3d/v5/pkg/config/v1alpha3"
 	l "github.com/rancher/k3d/v5/pkg/logger"
+	"github.com/rancher/k3d/v5/pkg/runtimes"
 	k3drt "github.com/rancher/k3d/v5/pkg/runtimes"
-	"github.com/rancher/k3d/v5/pkg/runtimes/docker"
 	runtimeErr "github.com/rancher/k3d/v5/pkg/runtimes/errors"
 	"github.com/rancher/k3d/v5/pkg/types"
 	k3d "github.com/rancher/k3d/v5/pkg/types"
@@ -357,17 +355,13 @@ ClusterCreatOpts:
 	 * Docker Machine Special Configuration
 	 */
 	if cluster.KubeAPI.Host == k3d.DefaultAPIHost && runtime == k3drt.Docker {
-		if gort.GOOS == "windows" || gort.GOOS == "darwin" {
-			l.Log().Tracef("Running on %s: checking if it's using docker-machine", gort.GOOS)
-			machineIP, err := runtime.(docker.Docker).GetDockerMachineIP()
-			if err != nil {
-				l.Log().Warnf("Using docker-machine, but failed to get it's IP: %+v", err)
-			} else if machineIP != "" {
-				l.Log().Infof("Using the docker-machine IP %s to connect to the Kubernetes API", machineIP)
-				cluster.KubeAPI.Host = machineIP
-				cluster.KubeAPI.Binding.HostIP = machineIP
-			} else {
-				l.Log().Traceln("Not using docker-machine")
+		// If the runtime is docker, attempt to use the docker host
+		if runtime == runtimes.Docker {
+			dockerHost := runtime.GetHost()
+			if dockerHost != "" {
+				dockerHost = strings.Split(dockerHost, ":")[0] // remove the port
+				l.Log().Tracef("Using docker host %s", dockerHost)
+				cluster.KubeAPI.Host = dockerHost
 			}
 		}
 	}

pkg/client/node.go

@@ -673,17 +673,6 @@ func patchServerSpec(node *k3d.Node, runtime runtimes.Runtime) error {
 	node.RuntimeLabels[k3d.LabelServerAPIHost] = node.ServerOpts.KubeAPI.Host
 	node.RuntimeLabels[k3d.LabelServerAPIPort] = node.ServerOpts.KubeAPI.Binding.HostPort
 
-	// If the runtime is docker, attempt to use the docker host
-	if runtime == runtimes.Docker {
-		dockerHost := runtime.GetHost()
-		if dockerHost != "" {
-			dockerHost = strings.Split(dockerHost, ":")[0] // remove the port
-			l.Log().Tracef("Using docker host %s", dockerHost)
-			node.RuntimeLabels[k3d.LabelServerAPIHostIP] = dockerHost
-			node.RuntimeLabels[k3d.LabelServerAPIHost] = dockerHost
-		}
-	}
-
 	node.Args = append(node.Args, "--tls-san", node.RuntimeLabels[k3d.LabelServerAPIHost]) // add TLS SAN for non default host name
 
 	return nil

pkg/runtimes/docker/docker.go

@@ -43,7 +43,19 @@ func (d Docker) ID() string {
 
 // GetHost returns the docker daemon host
 func (d Docker) GetHost() string {
-	// a) DOCKER_HOST env var
+
+	// a) docker-machine
+	machineIP, err := d.GetDockerMachineIP()
+	if err != nil {
+		l.Log().Warnf("[Docker] Using docker-machine, but failed to get it's IP: %+v", err)
+	} else if machineIP != "" {
+		l.Log().Infof("[Docker] Using the docker-machine IP %s to connect to the Kubernetes API", machineIP)
+		return machineIP
+	} else {
+		l.Log().Traceln("[Docker] Not using docker-machine")
+	}
+
+	// b) DOCKER_HOST env var
 	dockerHost := os.Getenv("DOCKER_HOST")
 	if dockerHost == "" {
 		l.Log().Traceln("[Docker] GetHost: DOCKER_HOST empty/unset")
@@ -52,9 +64,9 @@ func (d Docker) GetHost() string {
 			l.Log().Errorf("[Docker] error getting runtime information: %v", err)
 			return ""
 		}
-		// b) Docker for Desktop (Win/Mac) and it's a local connection
+		// c) Docker for Desktop (Win/Mac) and it's a local connection
 		if IsDockerDesktop(info.OS) && IsLocalConnection(info.Endpoint) {
-			// b.1) local DfD connection, but inside WSL, where host.docker.internal resolves to an IP, but it's not reachable
+			// c.1) local DfD connection, but inside WSL, where host.docker.internal resolves to an IP, but it's not reachable
 			if _, ok := os.LookupEnv("WSL_DISTRO_NAME"); ok {
 				l.Log().Debugln("[Docker] wanted to use 'host.docker.internal' as docker host, but it's not reachable in WSL2")
 				return ""