From 2f5552c32d01678bfbfdbb8838e1672d62521a6c Mon Sep 17 00:00:00 2001
From: flouthoc <flouthoc.git@gmail.com>
Date: Wed, 19 May 2021 01:19:20 +0530
Subject: Podman info add support for status of cgroup controllers

Signed-off-by: flouthoc <flouthoc.git@gmail.com>
---
 pkg/cgroups/cgroups.go | 106 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 98 insertions(+), 8 deletions(-)

(limited to 'pkg/cgroups')

diff --git a/pkg/cgroups/cgroups.go b/pkg/cgroups/cgroups.go
index aefb5183b..911edeb5b 100644
--- a/pkg/cgroups/cgroups.go
+++ b/pkg/cgroups/cgroups.go
@@ -128,28 +128,118 @@ func init() {
 // getAvailableControllers get the available controllers
 func getAvailableControllers(exclude map[string]controllerHandler, cgroup2 bool) ([]controller, error) {
 	if cgroup2 {
-		return nil, fmt.Errorf("getAvailableControllers not implemented yet for cgroup v2")
+		controllers := []controller{}
+		subtreeControl := cgroupRoot + "/cgroup.subtree_control"
+		// rootless cgroupv2: check available controllers for current user ,systemd or servicescope will inherit
+		if rootless.IsRootless() {
+			userSlice, err := getCgroupPathForCurrentProcess()
+			if err != nil {
+				return controllers, err
+			}
+			//userSlice already contains '/' so not adding here
+			basePath := cgroupRoot + userSlice
+			subtreeControl = fmt.Sprintf("%s/cgroup.subtree_control", basePath)
+		}
+		subtreeControlBytes, err := ioutil.ReadFile(subtreeControl)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed while reading controllers for cgroup v2 from %q", subtreeControl)
+		}
+		for _, controllerName := range strings.Fields(string(subtreeControlBytes)) {
+			c := controller{
+				name:    controllerName,
+				symlink: false,
+			}
+			controllers = append(controllers, c)
+		}
+		return controllers, nil
 	}
 
-	infos, err := ioutil.ReadDir(cgroupRoot)
-	if err != nil {
-		return nil, err
-	}
+	subsystems, _ := cgroupV1GetAllSubsystems()
 	controllers := []controller{}
-	for _, i := range infos {
-		name := i.Name()
+	// cgroupv1 and rootless: No subsystem is available: delegation is unsafe.
+	if rootless.IsRootless() {
+		return controllers, nil
+	}
+
+	for _, name := range subsystems {
 		if _, found := exclude[name]; found {
 			continue
 		}
+		isSymLink := false
+		fileInfo, err := os.Stat(cgroupRoot + "/" + name)
+		if err != nil {
+			isSymLink = !fileInfo.IsDir()
+		}
 		c := controller{
 			name:    name,
-			symlink: !i.IsDir(),
+			symlink: isSymLink,
 		}
 		controllers = append(controllers, c)
 	}
+
 	return controllers, nil
 }
 
+// GetAvailableControllers get string:bool map of all the available controllers
+func GetAvailableControllers(exclude map[string]controllerHandler, cgroup2 bool) ([]string, error) {
+	availableControllers, err := getAvailableControllers(exclude, cgroup2)
+	if err != nil {
+		return nil, err
+	}
+	controllerList := []string{}
+	for _, controller := range availableControllers {
+		controllerList = append(controllerList, controller.name)
+	}
+
+	return controllerList, nil
+}
+
+func cgroupV1GetAllSubsystems() ([]string, error) {
+	f, err := os.Open("/proc/cgroups")
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	subsystems := []string{}
+
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		text := s.Text()
+		if text[0] != '#' {
+			parts := strings.Fields(text)
+			if len(parts) >= 4 && parts[3] != "0" {
+				subsystems = append(subsystems, parts[0])
+			}
+		}
+	}
+	if err := s.Err(); err != nil {
+		return nil, err
+	}
+	return subsystems, nil
+}
+
+func getCgroupPathForCurrentProcess() (string, error) {
+	path := fmt.Sprintf("/proc/%d/cgroup", os.Getpid())
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	cgroupPath := ""
+	s := bufio.NewScanner(f)
+	for s.Scan() {
+		text := s.Text()
+		procEntries := strings.SplitN(text, "::", 2)
+		cgroupPath = procEntries[1]
+	}
+	if err := s.Err(); err != nil {
+		return cgroupPath, err
+	}
+	return cgroupPath, nil
+}
+
 // getCgroupv1Path is a helper function to get the cgroup v1 path
 func (c *CgroupControl) getCgroupv1Path(name string) string {
 	return filepath.Join(cgroupRoot, name, c.path)
-- 
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