From c254933688ee2c9518cdcdb1c434f20fb9929f3d Mon Sep 17 00:00:00 2001
From: amrut-asm <amrutrn1@gmail.com>
Date: Mon, 2 Oct 2023 19:00:54 +0530
Subject: [PATCH] Allow custom cgroup2 path

---
 felix/bpf/bpfdefs/defs.go              | 14 ++++++++++++--
 felix/bpf/utils/utils.go               | 17 +++++++++--------
 node/pkg/nodeinit/calico-init_linux.go | 11 ++++++-----
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/felix/bpf/bpfdefs/defs.go b/felix/bpf/bpfdefs/defs.go
index fbcc0731c4b..f9127a8899f 100644
--- a/felix/bpf/bpfdefs/defs.go
+++ b/felix/bpf/bpfdefs/defs.go
@@ -14,10 +14,20 @@
 
 package bpfdefs
 
+import "os"
+
 const (
-	DefaultBPFfsPath = "/sys/fs/bpf"
-	CgroupV2Path     = "/run/calico/cgroup"
+	DefaultBPFfsPath    = "/sys/fs/bpf"
+	DefaultCgroupV2Path = "/run/calico/cgroup"
 
 	GlobalPinDir = DefaultBPFfsPath + "/tc/globals/"
 	ObjectDir    = "/usr/lib/calico/bpf"
 )
+
+func GetCgroupV2Path() string {
+	cgroupV2CustomPath := os.Getenv("CALICO_CGROUP_PATH")
+	if cgroupV2CustomPath == "" {
+		return DefaultCgroupV2Path
+	}
+	return cgroupV2CustomPath
+}
diff --git a/felix/bpf/utils/utils.go b/felix/bpf/utils/utils.go
index f3e1179423b..71a1e10db8b 100644
--- a/felix/bpf/utils/utils.go
+++ b/felix/bpf/utils/utils.go
@@ -74,27 +74,28 @@ func MaybeMountBPFfs() (string, error) {
 
 func MaybeMountCgroupV2() (string, error) {
 	var err error
-	if err := os.MkdirAll(bpfdefs.CgroupV2Path, 0700); err != nil {
+	cgroupV2Path := bpfdefs.GetCgroupV2Path()
+	if err := os.MkdirAll(cgroupV2Path, 0700); err != nil {
 		return "", err
 	}
 
-	mnt, err := isMount(bpfdefs.CgroupV2Path)
+	mnt, err := isMount(cgroupV2Path)
 	if err != nil {
-		return "", fmt.Errorf("error checking if %s is a mount: %v", bpfdefs.CgroupV2Path, err)
+		return "", fmt.Errorf("error checking if %s is a mount: %v", cgroupV2Path, err)
 	}
 
-	fsCgroup, err := isCgroupV2(bpfdefs.CgroupV2Path)
+	fsCgroup, err := isCgroupV2(cgroupV2Path)
 	if err != nil {
-		return "", fmt.Errorf("error checking if %s is CgroupV2: %v", bpfdefs.CgroupV2Path, err)
+		return "", fmt.Errorf("error checking if %s is CgroupV2: %v", cgroupV2Path, err)
 	}
 
 	if !mnt {
-		err = mountCgroupV2(bpfdefs.CgroupV2Path)
+		err = mountCgroupV2(cgroupV2Path)
 	} else if !fsCgroup {
-		err = fmt.Errorf("something that's not cgroup v2 is already mounted in %s", bpfdefs.CgroupV2Path)
+		err = fmt.Errorf("something that's not cgroup v2 is already mounted in %s", cgroupV2Path)
 	}
 
-	return bpfdefs.CgroupV2Path, err
+	return cgroupV2Path, err
 }
 
 func mountCgroupV2(path string) error {
diff --git a/node/pkg/nodeinit/calico-init_linux.go b/node/pkg/nodeinit/calico-init_linux.go
index 60af851b202..4c7a72611dc 100644
--- a/node/pkg/nodeinit/calico-init_linux.go
+++ b/node/pkg/nodeinit/calico-init_linux.go
@@ -96,6 +96,7 @@ func ensureCgroupV2Filesystem() error {
 		return fmt.Errorf("failed to open %s. err: %w", mountInfoFile, err)
 	}
 	scanner := bufio.NewScanner(mounts)
+	cgroupV2Path := bpfdefs.GetCgroupV2Path()
 	for scanner.Scan() {
 		// An example line in mountinfo file:
 		// 35 24 0:30 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime shared:9 - cgroup2 cgroup2 rw,nsdelegate,memory_recursiveprot
@@ -106,7 +107,7 @@ func ensureCgroupV2Filesystem() error {
 		if len(extraInfo) > 1 {
 			fsType := strings.Split(extraInfo[1], " ")[0] // fsType is the first string after -
 
-			if mountPoint == bpfdefs.CgroupV2Path && fsType == "cgroup2" {
+			if mountPoint == cgroupV2Path && fsType == "cgroup2" {
 				logrus.Info("Cgroup2 filesystem is mounted.")
 				return nil
 			}
@@ -119,13 +120,13 @@ func ensureCgroupV2Filesystem() error {
 	// If we get here, the Cgroup2 filesystem is not mounted.  Try to mount it.
 	logrus.Info("Cgroup2 filesystem is not mounted. Trying to mount it...")
 
-	err = os.MkdirAll(bpfdefs.CgroupV2Path, 0700)
+	err = os.MkdirAll(cgroupV2Path, 0700)
 	if err != nil {
-		return fmt.Errorf("failed to prepare mount point: %v. err: %w.", bpfdefs.CgroupV2Path, err)
+		return fmt.Errorf("failed to prepare mount point: %v. err: %w", cgroupV2Path, err)
 	}
-	logrus.Infof("Mount point %s is ready for mounting root cgroup2 fs.", bpfdefs.CgroupV2Path)
+	logrus.Infof("Mount point %s is ready for mounting root cgroup2 fs", cgroupV2Path)
 
-	mountCmd := exec.Command("mountns", bpfdefs.CgroupV2Path)
+	mountCmd := exec.Command("mountns", cgroupV2Path)
 	out, err := mountCmd.Output()
 	logrus.Debugf("Executed %v. err:%v out:\n%s", mountCmd, err, out)
 	if err != nil {