From e4e42e67e35189ab3a10cf1457e409198c618257 Mon Sep 17 00:00:00 2001
From: Daniel J Walsh <dwalsh@redhat.com>
Date: Fri, 13 Sep 2019 14:01:53 -0400
Subject: We need to convert libpod.conf files in user homedir for cgroupv2

If a user upgrades to a machine that defaults to a cgroups V2 machine
and has a libpod.conf file in their homedir that defaults to OCI Runtime runc,
then we want to change it one time to crun.

runc as of this point does not work on cgroupV2 systems.  This patch will
eventually be removed but is needed until runc has support.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>
---
 libpod/runtime.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/libpod/runtime.go b/libpod/runtime.go
index e2b9667be..675c92b7a 100644
--- a/libpod/runtime.go
+++ b/libpod/runtime.go
@@ -23,6 +23,7 @@ import (
 	"github.com/containers/libpod/libpod/events"
 	"github.com/containers/libpod/libpod/image"
 	"github.com/containers/libpod/libpod/lock"
+	"github.com/containers/libpod/pkg/cgroups"
 	sysreg "github.com/containers/libpod/pkg/registries"
 	"github.com/containers/libpod/pkg/rootless"
 	"github.com/containers/libpod/pkg/util"
@@ -254,6 +255,8 @@ type RuntimeConfig struct {
 	// SDNotify tells Libpod to allow containers to notify the host
 	// systemd of readiness using the SD_NOTIFY mechanism
 	SDNotify bool
+	// CgroupCheck verifies if the cgroup check for correct OCI runtime has been done.
+	CgroupCheck bool `toml:"cgroup_check,omitempty"`
 }
 
 // runtimeConfiguredFrom is a struct used during early runtime init to help
@@ -575,6 +578,10 @@ func newRuntimeFromConfig(ctx context.Context, userConfigPath string, options ..
 				configPath)
 		}
 
+		if err := cgroupV2Check(configPath, tmpConfig); err != nil {
+			return nil, err
+		}
+
 		if tmpConfig.StaticDir != "" {
 			runtime.configuredFrom.libpodStaticDirSet = true
 		}
@@ -664,6 +671,14 @@ func newRuntimeFromConfig(ctx context.Context, userConfigPath string, options ..
 				runtime.config.OCIRuntime = tmpConfig.OCIRuntime
 			}
 
+			cgroupsV2, err := cgroups.IsCgroup2UnifiedMode()
+			if err != nil {
+				return nil, err
+			}
+			if cgroupsV2 {
+				runtime.config.CgroupCheck = true
+			}
+
 			break
 		}
 	}
@@ -1451,3 +1466,37 @@ func (r *Runtime) ImageRuntime() *image.Runtime {
 func (r *Runtime) SystemContext() *types.SystemContext {
 	return r.imageContext
 }
+
+// Since runc does not currently support cgroupV2
+// Change to default crun on first running of libpod.conf
+// TODO Once runc has support for cgroups, this function should be removed.
+func cgroupV2Check(configPath string, tmpConfig *RuntimeConfig) error {
+	if !tmpConfig.CgroupCheck && rootless.IsRootless() {
+		cgroupsV2, err := cgroups.IsCgroup2UnifiedMode()
+		if err != nil {
+			return err
+		}
+		if cgroupsV2 {
+			path, err := exec.LookPath("crun")
+			if err != nil {
+				logrus.Warnf("Can not find crun package on the host, containers might fail to run on cgroup V2 systems without crun: %q", err)
+				// Can't find crun path so do nothing
+				return nil
+			}
+			tmpConfig.CgroupCheck = true
+			tmpConfig.OCIRuntime = path
+			file, err := os.OpenFile(configPath, os.O_RDWR|os.O_CREATE, 0666)
+			if err != nil {
+				return errors.Wrapf(err, "cannot open file %s", configPath)
+			}
+			defer file.Close()
+			enc := toml.NewEncoder(file)
+			if err := enc.Encode(tmpConfig); err != nil {
+				if removeErr := os.Remove(configPath); removeErr != nil {
+					logrus.Debugf("unable to remove %s: %q", configPath, err)
+				}
+			}
+		}
+	}
+	return nil
+}
-- 
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