clusterCreate: use docker VM IP for API connection (#399)

Try
- `docker-machine ip`
- host lookup for `host.docker.internal`

Fixes #388

pkg/cluster/cluster.go

@@ -31,8 +31,11 @@ import (
 	"strings"
 	"time"
 
+	gort "runtime"
+
 	"github.com/imdario/mergo"
 	k3drt "github.com/rancher/k3d/v3/pkg/runtimes"
+	"github.com/rancher/k3d/v3/pkg/runtimes/docker"
 	"github.com/rancher/k3d/v3/pkg/types"
 	k3d "github.com/rancher/k3d/v3/pkg/types"
 	"github.com/rancher/k3d/v3/pkg/util"
@@ -60,6 +63,21 @@ func ClusterCreate(ctx context.Context, runtime k3drt.Runtime, cluster *k3d.Clus
 	 * Network
 	 */
 
+	if cluster.ExposeAPI.Host == k3d.DefaultAPIHost && runtime == k3drt.Docker {
+		if gort.GOOS == "windows" || gort.GOOS == "darwin" {
+			log.Tracef("Running on %s -> Trying to get IP of the docker machine", gort.GOOS)
+			machineIP, err := runtime.(docker.Docker).GetDockerMachineIP()
+			if err != nil {
+				log.Warnf("Failed to get Docker Machine IP: %+v", err)
+			} else if machineIP != "" {
+				log.Infof("Using the docker machine IP %s to connect to the Kubernetes API", machineIP)
+				cluster.ExposeAPI.Host = machineIP
+				cluster.ExposeAPI.HostIP = machineIP
+			}
+		}
+
+	}
+
 	// error out if external cluster network should be used but no name was set
 	if cluster.Network.Name == "" && cluster.Network.External {
 		return fmt.Errorf("Failed to use external network because no name was specified")

pkg/runtimes/docker/machine.go

@@ -0,0 +1,74 @@
+/*
+Copyright © 2020 The k3d Author(s)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+
+package docker
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"os/exec"
+	"strings"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func (d Docker) GetDockerMachineIP() (string, error) {
+	machine := os.ExpandEnv("$DOCKER_MACHINE_NAME")
+	dockerHostName := "host.docker.internal"
+
+	// Option 1: use the docker-machine executable
+	if machine != "" {
+		dockerMachinePath, err := exec.LookPath("docker-machine")
+		if err != nil {
+			return "", err
+		}
+
+		out, err := exec.Command(dockerMachinePath, "ip", machine).Output()
+		if err != nil {
+			log.Printf("Error executing 'docker-machine ip'")
+
+			if exitError, ok := err.(*exec.ExitError); ok {
+				log.Printf("%s", string(exitError.Stderr))
+			}
+			return "", err
+		}
+		ipStr := strings.TrimSuffix(string(out), "\n")
+		ipStr = strings.TrimSuffix(ipStr, "\r")
+
+		return ipStr, nil
+	}
+
+	// Option 2: Try to lookup "host.docker.internal"
+	log.Debugf("Docker Machine not found, trying to lookup '%s' instead...", dockerHostName)
+	addrs, err := net.LookupHost(dockerHostName)
+	if err != nil {
+		log.Debugf("Lookup of Host %s failed: %+v", dockerHostName, err)
+		return "", fmt.Errorf("Failed to get IP of Docker VM")
+	}
+	if len(addrs) == 0 {
+		log.Debugf("Lookup of Host %s didn't return any addresses", dockerHostName)
+		return "", fmt.Errorf("Failed to get IP of Docker VM")
+	}
+	log.Debugf("Addresses returned for %s: %+v", dockerHostName, addrs)
+	return addrs[0], nil
+}