Begin adding support for multiple OCI runtimes

Allow Podman containers to request to use a specific OCI runtime
if multiple runtimes are configured. This is the first step to
properly supporting containers in a multi-runtime environment.

The biggest changes are that all OCI runtimes are now initialized
when Podman creates its runtime, and containers now use the
runtime requested in their configuration (instead of always the
default runtime).

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 82 insertions, 92 deletions

diff --git a/libpod/runtime.go b/libpod/runtime.go
index 2c50fce85..caeabbe9a 100644
--- a/libpod/runtime.go
+++ b/libpod/runtime.go
@@ -91,18 +91,18 @@ type RuntimeOption func(*Runtime) error
 type Runtime struct {
 	config *RuntimeConfig
 
-	state           State
-	store           storage.Store
-	storageService  *storageService
-	imageContext    *types.SystemContext
-	ociRuntime      *OCIRuntime
-	netPlugin       ocicni.CNIPlugin
-	ociRuntimePath  OCIRuntimePath
-	conmonPath      string
-	imageRuntime    *image.Runtime
-	firewallBackend firewall.FirewallBackend
-	lockManager     lock.Manager
-	configuredFrom  *runtimeConfiguredFrom
+	state             State
+	store             storage.Store
+	storageService    *storageService
+	imageContext      *types.SystemContext
+	defaultOCIRuntime *OCIRuntime
+	ociRuntimes       map[string]*OCIRuntime
+	netPlugin         ocicni.CNIPlugin
+	conmonPath        string
+	imageRuntime      *image.Runtime
+	firewallBackend   firewall.FirewallBackend
+	lockManager       lock.Manager
+	configuredFrom    *runtimeConfiguredFrom
 
 	// doRenumber indicates that the runtime should perform a lock renumber
 	// during initialization.
@@ -123,14 +123,6 @@ type Runtime struct {
 	eventer events.Eventer
 }
 
-// OCIRuntimePath contains information about an OCI runtime.
-type OCIRuntimePath struct {
-	// Name of the runtime to refer to by the --runtime flag
-	Name string `toml:"name"`
-	// Paths to check for this executable
-	Paths []string `toml:"paths"`
-}
-
 // RuntimeConfig contains configuration options used to set up the runtime
 type RuntimeConfig struct {
 	// StorageConfig is the configuration used by containers/storage
@@ -588,63 +580,6 @@ func newRuntimeFromConfig(ctx context.Context, userConfigPath string, options ..
 // Make a new runtime based on the given configuration
 // Sets up containers/storage, state store, OCI runtime
 func makeRuntime(ctx context.Context, runtime *Runtime) (err error) {
-	// Backward compatibility for `runtime_path`
-	if runtime.config.RuntimePath != nil {
-		// Don't print twice in rootless mode.
-		if os.Geteuid() == 0 {
-			logrus.Warningf("The configuration is using `runtime_path`, which is deprecated and will be removed in future.  Please use `runtimes` and `runtime`")
-			logrus.Warningf("If you are using both `runtime_path` and `runtime`, the configuration from `runtime_path` is used")
-		}
-
-		// Transform `runtime_path` into `runtimes` and `runtime`.
-		name := filepath.Base(runtime.config.RuntimePath[0])
-		runtime.config.OCIRuntime = name
-		runtime.config.OCIRuntimes = map[string][]string{name: runtime.config.RuntimePath}
-	}
-
-	// Find a working OCI runtime binary
-	foundRuntime := false
-	// If runtime is an absolute path, then use it as it is.
-	if runtime.config.OCIRuntime != "" && runtime.config.OCIRuntime[0] == '/' {
-		foundRuntime = true
-		runtime.ociRuntimePath = OCIRuntimePath{Name: filepath.Base(runtime.config.OCIRuntime), Paths: []string{runtime.config.OCIRuntime}}
-		stat, err := os.Stat(runtime.config.OCIRuntime)
-		if err != nil {
-			if os.IsNotExist(err) {
-				return errors.Wrapf(err, "the specified OCI runtime %s does not exist", runtime.config.OCIRuntime)
-			}
-			return errors.Wrapf(err, "cannot stat the OCI runtime path %s", runtime.config.OCIRuntime)
-		}
-		if !stat.Mode().IsRegular() {
-			return fmt.Errorf("the specified OCI runtime %s is not a valid file", runtime.config.OCIRuntime)
-		}
-	} else {
-		// If not, look it up in the configuration.
-		paths := runtime.config.OCIRuntimes[runtime.config.OCIRuntime]
-		if paths != nil {
-			for _, path := range paths {
-				stat, err := os.Stat(path)
-				if err != nil {
-					if os.IsNotExist(err) {
-						continue
-					}
-					return errors.Wrapf(err, "cannot stat %s", path)
-				}
-				if !stat.Mode().IsRegular() {
-					continue
-				}
-				foundRuntime = true
-				runtime.ociRuntimePath = OCIRuntimePath{Name: runtime.config.OCIRuntime, Paths: []string{path}}
-				break
-			}
-		}
-	}
-	if !foundRuntime {
-		return errors.Wrapf(ErrInvalidArg,
-			"could not find a working binary (configured options: %v)",
-			runtime.config.OCIRuntimes)
-	}
-
 	// Find a working conmon binary
 	foundConmon := false
 	for _, path := range runtime.config.ConmonPath {
@@ -841,25 +776,80 @@ func makeRuntime(ctx context.Context, runtime *Runtime) (err error) {
 		}
 	}
 
-	supportsJSON := false
-	for _, r := range runtime.config.RuntimeSupportsJSON {
-		if r == runtime.config.OCIRuntime {
-			supportsJSON = true
-			break
+	// Get us at least one working OCI runtime.
+	runtime.ociRuntimes = make(map[string]*OCIRuntime)
+
+	// Is the old runtime_path defined?
+	if runtime.config.RuntimePath != nil {
+		// Don't print twice in rootless mode.
+		if os.Geteuid() == 0 {
+			logrus.Warningf("The configuration is using `runtime_path`, which is deprecated and will be removed in future.  Please use `runtimes` and `runtime`")
+			logrus.Warningf("If you are using both `runtime_path` and `runtime`, the configuration from `runtime_path` is used")
 		}
+
+		if len(runtime.config.RuntimePath) == 0 {
+			return errors.Wrapf(ErrInvalidArg, "empty runtime path array passed")
+		}
+
+		name := filepath.Base(runtime.config.RuntimePath[0])
+
+		supportsJSON := false
+		for _, r := range runtime.config.RuntimeSupportsJSON {
+			if r == name {
+				supportsJSON = true
+				break
+			}
+		}
+
+		ociRuntime, err := newOCIRuntime(name, runtime.config.RuntimePath, runtime.conmonPath, runtime.config, supportsJSON)
+		if err != nil {
+			return err
+		}
+
+		runtime.ociRuntimes[name] = ociRuntime
+		runtime.defaultOCIRuntime = ociRuntime
 	}
 
-	// Make an OCI runtime to perform container operations
-	ociRuntime, err := newOCIRuntime(runtime.ociRuntimePath,
-		runtime.conmonPath, runtime.config.ConmonEnvVars,
-		runtime.config.CgroupManager, runtime.config.TmpDir,
-		runtime.config.MaxLogSize, runtime.config.NoPivotRoot,
-		runtime.config.EnablePortReservation,
-		supportsJSON)
-	if err != nil {
-		return err
+	// Initialize remaining OCI runtimes
+	for name, paths := range runtime.config.OCIRuntimes {
+		if len(paths) == 0 {
+			return errors.Wrapf(ErrInvalidArg, "must provide at least 1 path to OCI runtime %s", name)
+		}
+
+		supportsJSON := false
+		for _, r := range runtime.config.RuntimeSupportsJSON {
+			if r == name {
+				supportsJSON = true
+				break
+			}
+		}
+
+		ociRuntime, err := newOCIRuntime(name, paths, runtime.conmonPath, runtime.config, supportsJSON)
+		if err != nil {
+			return err
+		}
+
+		runtime.ociRuntimes[name] = ociRuntime
+	}
+
+	// Set default runtime
+	if runtime.config.OCIRuntime != "" {
+		ociRuntime, ok := runtime.ociRuntimes[runtime.config.OCIRuntime]
+		if !ok {
+			return errors.Wrapf(ErrInvalidArg, "default OCI runtime %q not found", runtime.config.OCIRuntime)
+		}
+		runtime.defaultOCIRuntime = ociRuntime
+	}
+
+	// Do we have at least one valid OCI runtime?
+	if len(runtime.ociRuntimes) == 0 {
+		return errors.Wrapf(ErrInvalidArg, "no OCI runtime has been configured")
+	}
+
+	// Do we have a default runtime?
+	if runtime.defaultOCIRuntime == nil {
+		return errors.Wrapf(ErrInvalidArg, "no default OCI runtime was configured")
 	}
-	runtime.ociRuntime = ociRuntime
 
 	// Make the per-boot files directory if it does not exist
 	if err := os.MkdirAll(runtime.config.TmpDir, 0755); err != nil {