match only cgroup2 and use dummy initcontainerid in tests

statsd/container_linux.go

@@ -36,6 +36,11 @@ const (
 	// Currently, host namespace inode number are hardcoded, which can be used to detect
 	// if we're running in host namespace or not (does not work when running in DinD)
 	hostCgroupNamespaceInode = 0xEFFFFFFB
+
+	// From https://github.com/torvalds/linux/blob/5859a2b1991101d6b978f3feb5325dad39421f29/include/linux/proc_ns.h#L41-L49
+	// Currently, host namespace inode number are hardcoded, which can be used to detect
+	// if we're running in host namespace or not (does not work when running in DinD)
+	hostMntNamespaceInode = 0xEFFFFFFB
 )
 
 var (
@@ -46,6 +51,9 @@ var (
 	expContainerID = regexp.MustCompile(fmt.Sprintf(`(%s|%s|%s)(?:.scope)?$`, uuidSource, containerSource, taskSource))
 
 	cIDMountInfoRegexp = regexp.MustCompile(cIDRegexpStr)
+
+	// initContainerID initializes the container ID.
+	initContainerID = internalInitContainerID
 )
 
 // parseContainerID finds the first container ID reading from r and returns it.
@@ -135,7 +143,7 @@ func parseCgroupMountPath(r io.Reader) string {
 		tokens := strings.Fields(line)
 		if len(tokens) >= 3 {
 			fsType := tokens[2]
-			if strings.HasPrefix(fsType, "cgroup") {
+			if fsType == "cgroup2" {
 				return tokens[1] // line is formatted as "cgroup /sys/fs/cgroup/... cgroup...""
 			}
 		}
@@ -156,7 +164,7 @@ func parseCgroupNodePath(r io.Reader) string {
 
 // getCgroupInode returns the cgroup inode prefixed by "in-" and is used by the agent to retrieve the container ID
 func getCgroupInode(mountsPath, cgroupPath string) string {
-	// Retrieve a cgroup mount point from /proc/self/mounts
+	// Retrieve a cgroup mount point from /proc/mounts
 	f, err := os.Open(mountsPath)
 	if err != nil {
 		return ""
@@ -199,9 +207,20 @@ func isHostCgroupNamespace() bool {
 	return inode == hostCgroupNamespaceInode
 }
 
-// initContainerID initializes the container ID.
+func isHostMountNamespace() bool {
+	fi, err := os.Stat("/proc/self/ns/mnt")
+	if err != nil {
+		return false
+	}
+
+	inode := fi.Sys().(*syscall.Stat_t).Ino
+
+	return inode == hostMntNamespaceInode
+}
+
+// internalInitContainerID initializes the container ID.
 // It can either be provided by the user or read from cgroups.
-func initContainerID(userProvidedID string, cgroupFallback bool) {
+func internalInitContainerID(userProvidedID string, cgroupFallback bool) {
 	initOnce.Do(func() {
 		if userProvidedID != "" {
 			containerID = userProvidedID

statsd/container_stub.go

@@ -3,7 +3,7 @@
 
 package statsd
 
-func initContainerID(userProvidedID string, cgroupFallback bool) {
+var initContainerID = func(userProvidedID string, cgroupFallback bool) {
 	initOnce.Do(func() {
 		if userProvidedID != "" {
 			containerID = userProvidedID

statsd/container_test.go

@@ -17,6 +17,21 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+// initContainerID initializes the container ID.
+func init() {
+	initContainerID = dummyInitContainerId
+}
+
+// dummyInitContainerId initializes the container ID if provided
+func dummyInitContainerId(userProvidedID string, _ bool) {
+	initOnce.Do(func() {
+		if userProvidedID != "" {
+			containerID = userProvidedID
+			return
+		}
+	})
+}
+
 func TestParseContainerID(t *testing.T) {
 	for input, expectedResult := range map[string]string{
 		`other_line
@@ -478,14 +493,21 @@ func TestGetCgroupInode(t *testing.T) {
 			expectedResult:        "in-%d", // Will be formatted with inode number
 		},
 		{
-			description: "hybrid cgroup - should match the first which does not exist",
+			description:           "should not match cgroup",
+			procMountsContent:     "cgroup %s cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct 0 0\n",
+			cgroupNodeDir:         "system.slice/docker-abcdef0123456789abcdef0123456789.scope",
+			procSelfCgroupContent: "0::/system.slice/docker-abcdef0123456789abcdef0123456789.scope\n",
+			expectedResult:        "",
+		},
+		{
+			description: "hybrid cgroup - should match only cgroup2",
 			procMountsContent: `other_line
 cgroup /sys/fs/cgroup/memory cgroup foo,bar 0 0
 cgroup2 %s cgroup2 rw,nosuid,nodev,noexec,relatime,cpu,cpuacct 0 0
 `,
 			cgroupNodeDir:         "system.slice/docker-abcdef0123456789abcdef0123456789.scope",
 			procSelfCgroupContent: "0::/system.slice/docker-abcdef0123456789abcdef0123456789.scope\n",
-			expectedResult:        "", // Will be formatted with inode number
+			expectedResult:        "in-%d", // Will be formatted with inode number
 		},
 		{
 			description:           "Non-matching entry in /proc/self/cgroup",