runtime: Move the resourcecontrol package one layer up

And try to reduce the number of virtcontainers packages, step by step.

Signed-off-by: Samuel Ortiz <s.ortiz@apple.com>

src/runtime/pkg/resourcecontrol/utils_linux.go

@@ -0,0 +1,131 @@
+// Copyright (c) 2020 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package resourcecontrol
+
+import (
+	"context"
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"github.com/containerd/cgroups"
+	systemdDbus "github.com/coreos/go-systemd/v22/dbus"
+	"github.com/godbus/dbus/v5"
+	"github.com/opencontainers/runc/libcontainer/cgroups/systemd"
+)
+
+// DefaultResourceControllerID runtime-determined location in the cgroups hierarchy.
+const DefaultResourceControllerID = "/vc"
+
+// validCgroupPath returns a valid cgroup path.
+// see https://github.com/opencontainers/runtime-spec/blob/master/config-linux.md#cgroups-path
+func ValidCgroupPath(path string, systemdCgroup bool) (string, error) {
+	if IsSystemdCgroup(path) {
+		return path, nil
+	}
+
+	if systemdCgroup {
+		return "", fmt.Errorf("malformed systemd path '%v': expected to be of form 'slice:prefix:name'", path)
+	}
+
+	// In the case of an absolute path (starting with /), the runtime MUST
+	// take the path to be relative to the cgroups mount point.
+	if filepath.IsAbs(path) {
+		return filepath.Clean(path), nil
+	}
+
+	// In the case of a relative path (not starting with /), the runtime MAY
+	// interpret the path relative to a runtime-determined location in the cgroups hierarchy.
+	// clean up path and return a new path relative to DefaultResourceControllerID
+	return filepath.Join(DefaultResourceControllerID, filepath.Clean("/"+path)), nil
+}
+
+func IsSystemdCgroup(cgroupPath string) bool {
+
+	// If we are utilizing systemd to manage cgroups, we expect to receive a path
+	// in the format slice:scopeprefix:name. A typical example would be:
+	//
+	// system.slice:docker:6b4c4a4d0cc2a12c529dcb13a2b8e438dfb3b2a6af34d548d7d
+	//
+	// Based on this, let's split by the ':' delimiter and verify that the first
+	// section has .slice as a suffix.
+	parts := strings.Split(cgroupPath, ":")
+	if len(parts) == 3 && strings.HasSuffix(parts[0], ".slice") {
+		return true
+	}
+
+	return false
+}
+
+func newProperty(name string, units interface{}) systemdDbus.Property {
+	return systemdDbus.Property{
+		Name:  name,
+		Value: dbus.MakeVariant(units),
+	}
+}
+
+func cgroupHierarchy(path string) (cgroups.Hierarchy, cgroups.Path, error) {
+	if !IsSystemdCgroup(path) {
+		return cgroups.V1, cgroups.StaticPath(path), nil
+	} else {
+		slice, unit, err := getSliceAndUnit(path)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		cgroupSlicePath, _ := systemd.ExpandSlice(slice)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		return cgroups.Systemd, cgroups.Slice(cgroupSlicePath, unit), nil
+	}
+}
+
+func createCgroupsSystemd(slice string, unit string, pid uint32) error {
+	ctx := context.TODO()
+	conn, err := systemdDbus.NewWithContext(ctx)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	properties := []systemdDbus.Property{
+		systemdDbus.PropDescription("cgroup " + unit),
+		newProperty("DefaultDependencies", false),
+		newProperty("MemoryAccounting", true),
+		newProperty("CPUAccounting", true),
+		newProperty("IOAccounting", true),
+	}
+
+	// https://github.com/opencontainers/runc/blob/master/docs/systemd.md
+	if strings.HasSuffix(unit, ".scope") {
+		// It's a scope, which we put into a Slice=.
+		properties = append(properties, systemdDbus.PropSlice(slice))
+		properties = append(properties, newProperty("Delegate", true))
+		properties = append(properties, systemdDbus.PropPids(pid))
+	} else {
+		return fmt.Errorf("Failed to create cgroups with systemd: unit %s is not a scope", unit)
+	}
+
+	ch := make(chan string)
+	// https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/
+	_, err = conn.StartTransientUnitContext(ctx, unit, "replace", properties, ch)
+	if err != nil {
+		return err
+	}
+	<-ch
+	return nil
+}
+
+func getSliceAndUnit(cgroupPath string) (string, string, error) {
+	parts := strings.Split(cgroupPath, ":")
+	if len(parts) == 3 && strings.HasSuffix(parts[0], ".slice") {
+		return parts[0], fmt.Sprintf("%s-%s.scope", parts[1], parts[2]), nil
+	}
+
+	return "", "", fmt.Errorf("Path: %s is not valid systemd's cgroups path", cgroupPath)
+}