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, 40 insertions, 12 deletions

diff --git a/libpod/oci.go b/libpod/oci.go
index dcb72fc1b..36c1dea84 100644
--- a/libpod/oci.go
+++ b/libpod/oci.go
@@ -75,25 +75,53 @@ type ociError struct {
 	Msg   string `json:"msg,omitempty"`
 }
 
-// Make a new OCI runtime with provided options
-func newOCIRuntime(oruntime OCIRuntimePath, conmonPath string, conmonEnv []string, cgroupManager string, tmpDir string, logSizeMax int64, noPivotRoot bool, reservePorts bool, supportsJSON bool) (*OCIRuntime, error) {
+// Make a new OCI runtime with provided options.
+// The first path that points to a valid executable will be used.
+func newOCIRuntime(name string, paths []string, conmonPath string, runtimeCfg *RuntimeConfig, supportsJSON bool) (*OCIRuntime, error) {
+	if name == "" {
+		return nil, errors.Wrapf(ErrInvalidArg, "the OCI runtime must be provided a non-empty name")
+	}
+
 	runtime := new(OCIRuntime)
-	runtime.name = oruntime.Name
-	runtime.path = oruntime.Paths[0]
+	runtime.name = name
 	runtime.conmonPath = conmonPath
-	runtime.conmonEnv = conmonEnv
-	runtime.cgroupManager = cgroupManager
-	runtime.tmpDir = tmpDir
-	runtime.logSizeMax = logSizeMax
-	runtime.noPivot = noPivotRoot
-	runtime.reservePorts = reservePorts
+
+	runtime.conmonEnv = runtimeCfg.ConmonEnvVars
+	runtime.cgroupManager = runtimeCfg.CgroupManager
+	runtime.tmpDir = runtimeCfg.TmpDir
+	runtime.logSizeMax = runtimeCfg.MaxLogSize
+	runtime.noPivot = runtimeCfg.NoPivotRoot
+	runtime.reservePorts = runtimeCfg.EnablePortReservation
+
+	// TODO: probe OCI runtime for feature and enable automatically if
+	// available.
 	runtime.supportsJSON = supportsJSON
 
+	foundPath := false
+	for _, path := range paths {
+		stat, err := os.Stat(path)
+		if err != nil {
+			if os.IsNotExist(err) {
+				continue
+			}
+			return nil, errors.Wrapf(err, "cannot stat %s", path)
+		}
+		if !stat.Mode().IsRegular() {
+			continue
+		}
+		foundPath = true
+		runtime.path = path
+		break
+	}
+	if !foundPath {
+		return nil, errors.Wrapf(ErrInvalidArg, "no valid executable found for OCI runtime %s", name)
+	}
+
 	runtime.exitsDir = filepath.Join(runtime.tmpDir, "exits")
 	runtime.socketsDir = filepath.Join(runtime.tmpDir, "socket")
 
-	if cgroupManager != CgroupfsCgroupsManager && cgroupManager != SystemdCgroupsManager {
-		return nil, errors.Wrapf(ErrInvalidArg, "invalid cgroup manager specified: %s", cgroupManager)
+	if runtime.cgroupManager != CgroupfsCgroupsManager && runtime.cgroupManager != SystemdCgroupsManager {
+		return nil, errors.Wrapf(ErrInvalidArg, "invalid cgroup manager specified: %s", runtime.cgroupManager)
 	}
 
 	// Create the exit files and attach sockets directories