machine: Add file sharing support

This commit adds file sharing support to `crc start`.
This uses the GetSharedDirs API from libmachine, and only supports
virtiofs for now.
File sharing is meant to be used together for podman support to support
`podman-remote -v somedir:/some-dir-in-container registry.example.com/container-image`
This is currently implemented similarly to what podman does: $HOME is
shared with the VM and mounted at the $HOME mountpoint. This way one can
use podman-remote $HOME/hostdir on the host, and the podman instance
running in the VM can also access $HOME/hostdir which is mounted in the
VM, and share it with the container.

We currently need to hardcode a selinux context on $HOME mounted in the
VM, mainly to overcome limitations in the macOS virtiofs implementation
which vfkit uses.

This fixes #3204

pkg/crc/machine/config/config.go

@@ -15,6 +15,7 @@ type MachineConfig struct {
 	ImageFormat     string
 	SSHKeyPath      string
 	KubeConfig      string
+	SharedDirs      []string
 
 	// macOS specific configuration
 	KernelCmdLine string

pkg/crc/machine/config/driver.go

@@ -1,6 +1,8 @@
 package config
 
 import (
+	"fmt"
+
 	"github.com/code-ready/machine/libmachine/drivers"
 )
 
@@ -15,4 +17,13 @@ func InitVMDriverFromMachineConfig(machineConfig MachineConfig, driver *drivers.
 	driver.BundleName = machineConfig.BundleName
 	driver.ImageSourcePath = machineConfig.ImageSourcePath
 	driver.ImageFormat = machineConfig.ImageFormat
+
+	for i, dir := range machineConfig.SharedDirs {
+		sharedDir := drivers.SharedDir{
+			Source: dir,
+			Target: dir,
+			Tag:    fmt.Sprintf("dir%d", i),
+		}
+		driver.SharedDirs = append(driver.SharedDirs, sharedDir)
+	}
 }

pkg/crc/machine/start.go

@@ -133,6 +133,40 @@ func growRootFileSystem(sshRunner *crcssh.Runner) error {
 
 	return nil
 }
+
+func configureSharedDirs(vm *virtualMachine, sshRunner *crcssh.Runner) error {
+	logging.Debugf("Configuring shared directories")
+	sharedDirs, err := vm.Driver.GetSharedDirs()
+	if err != nil {
+		return err
+	}
+	for _, mount := range sharedDirs {
+		// CoreOS makes / immutable, we need to handle this if we need to create a directory outside of /home and /mnt
+		isHomeOrMnt := strings.HasPrefix(mount.Target, "/home") || strings.HasPrefix(mount.Target, "/mnt")
+		if !isHomeOrMnt {
+			if _, _, err := sshRunner.RunPrivileged("Making / mutable", "chattr", "-i", "/"); err != nil {
+				return err
+			}
+		}
+		if _, _, err := sshRunner.RunPrivileged(fmt.Sprintf("Creating %s", mount.Target), "mkdir", "-p", mount.Target); err != nil {
+			return err
+		}
+		if !isHomeOrMnt {
+			if _, _, err := sshRunner.RunPrivileged("Making / immutable again", "chattr", "+i", "/"); err != nil {
+				return err
+			}
+		}
+		logging.Debugf("Mounting tag %s at %s", mount.Tag, mount.Target)
+		//FIXME: do not hardcode this
+		mount.Type = "virtiofs"
+		if _, _, err := sshRunner.RunPrivileged(fmt.Sprintf("Mounting %s", mount.Target), "mount", "-o", "context=\"system_u:object_r:container_file_t:s0\"", "-t", mount.Type, mount.Tag, mount.Target); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func (client *client) Start(ctx context.Context, startConfig types.StartConfig) (*types.StartResult, error) {
 	telemetry.SetCPUs(ctx, startConfig.CPUs)
 	telemetry.SetMemory(ctx, uint64(startConfig.Memory)*1024*1024)
@@ -174,6 +208,11 @@ func (client *client) Start(ctx context.Context, startConfig types.StartConfig)
 			logging.Infof("Creating CRC VM for Podman %s...", crcBundleMetadata.GetPodmanVersion())
 		}
 
+		sharedDirs := []string{}
+		if homeDir, err := os.UserHomeDir(); err == nil {
+			sharedDirs = append(sharedDirs, homeDir)
+		}
+
 		machineConfig := config.MachineConfig{
 			Name:            client.name,
 			BundleName:      bundleName,
@@ -187,6 +226,7 @@ func (client *client) Start(ctx context.Context, startConfig types.StartConfig)
 			KernelCmdLine:   crcBundleMetadata.GetKernelCommandLine(),
 			Initramfs:       crcBundleMetadata.GetInitramfsPath(),
 			Kernel:          crcBundleMetadata.GetKernelPath(),
+			SharedDirs:      sharedDirs,
 		}
 		if crcBundleMetadata.IsOpenShift() {
 			machineConfig.KubeConfig = crcBundleMetadata.GetKubeConfigPath()
@@ -316,6 +356,10 @@ func (client *client) Start(ctx context.Context, startConfig types.StartConfig)
 		}
 	}
 
+	if err := configureSharedDirs(vm, sshRunner); err != nil {
+		return nil, err
+	}
+
 	if _, _, err := sshRunner.RunPrivileged("make root Podman socket accessible", "chmod 777 /run/podman/ /run/podman/podman.sock"); err != nil {
 		return nil, errors.Wrap(err, "Failed to change permissions to root podman socket")
 	}