init.go: move logger setup to StartInitialization

Currently, logrus is used from the Go part of runc init, mostly for a
few debug messages (see setns_init_linux.go and standard_init_linux.go),
and a single warning (see rootfs_linux.go).

This means logrus is part of init implementation, and thus, its setup
belongs to StartInitialization().

Move the code there. As a nice side effect, now we don't have to convert
_LIBCONTAINER_LOGPIPE twice.

Note that since this initialization is now also called from libct/int
tests, which do not set _LIBCONTAINER_LOGLEVEL, let's make
_LIBCONTAINER_LOGLEVEL optional.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

init.go

@@ -3,11 +3,9 @@ package main
 import (
 	"os"
 	"runtime"
-	"strconv"
 
 	"github.com/opencontainers/runc/libcontainer"
 	_ "github.com/opencontainers/runc/libcontainer/nsenter"
-	"github.com/sirupsen/logrus"
 )
 
 func init() {
@@ -17,21 +15,6 @@ func init() {
 		runtime.GOMAXPROCS(1)
 		runtime.LockOSThread()
 
-		level, err := strconv.Atoi(os.Getenv("_LIBCONTAINER_LOGLEVEL"))
-		if err != nil {
-			panic(err)
-		}
-
-		logPipeFd, err := strconv.Atoi(os.Getenv("_LIBCONTAINER_LOGPIPE"))
-		if err != nil {
-			panic(err)
-		}
-
-		logrus.SetLevel(logrus.Level(level))
-		logrus.SetOutput(os.NewFile(uintptr(logPipeFd), "logpipe"))
-		logrus.SetFormatter(new(logrus.JSONFormatter))
-		logrus.Debug("child process in init()")
-
 		if err := libcontainer.StartInitialization(); err != nil {
 			// as the error is sent back to the parent there is no need to log
 			// or write it to stderr because the parent process will handle this

libcontainer/container_linux.go

@@ -501,9 +501,10 @@ func (c *Container) commandTemplate(p *Process, childInitPipe *os.File, childLog
 
 	cmd.ExtraFiles = append(cmd.ExtraFiles, childLogPipe)
 	cmd.Env = append(cmd.Env,
-		"_LIBCONTAINER_LOGPIPE="+strconv.Itoa(stdioFdCount+len(cmd.ExtraFiles)-1),
-		"_LIBCONTAINER_LOGLEVEL="+p.LogLevel,
-	)
+		"_LIBCONTAINER_LOGPIPE="+strconv.Itoa(stdioFdCount+len(cmd.ExtraFiles)-1))
+	if p.LogLevel != "" {
+		cmd.Env = append(cmd.Env, "_LIBCONTAINER_LOGLEVEL="+p.LogLevel)
+	}
 
 	// NOTE: when running a container with no PID namespace and the parent process spawning the container is
 	// PID1 the pdeathsig is being delivered to the container's init process by the kernel for some reason

libcontainer/init_linux.go

@@ -92,9 +92,7 @@ func StartInitialization() (retErr error) {
 	envInitPipe := os.Getenv("_LIBCONTAINER_INITPIPE")
 	pipefd, err := strconv.Atoi(envInitPipe)
 	if err != nil {
-		err = fmt.Errorf("unable to convert _LIBCONTAINER_INITPIPE: %w", err)
-		logrus.Error(err)
-		return err
+		return fmt.Errorf("unable to convert _LIBCONTAINER_INITPIPE: %w", err)
 	}
 	pipe := os.NewFile(uintptr(pipefd), "pipe")
 	defer pipe.Close()
@@ -112,6 +110,26 @@ func StartInitialization() (retErr error) {
 		}
 	}()
 
+	// Set up logging. This is used rarely, and mostly for init debugging.
+
+	// Passing log level is optional; currently libcontainer/integration does not do it.
+	if levelStr := os.Getenv("_LIBCONTAINER_LOGLEVEL"); levelStr != "" {
+		logLevel, err := strconv.Atoi(levelStr)
+		if err != nil {
+			return fmt.Errorf("unable to convert _LIBCONTAINER_LOGLEVEL: %w", err)
+		}
+		logrus.SetLevel(logrus.Level(logLevel))
+	}
+
+	logFD, err := strconv.Atoi(os.Getenv("_LIBCONTAINER_LOGPIPE"))
+	if err != nil {
+		return fmt.Errorf("unable to convert _LIBCONTAINER_LOGPIPE: %w", err)
+	}
+
+	logrus.SetOutput(os.NewFile(uintptr(logFD), "logpipe"))
+	logrus.SetFormatter(new(logrus.JSONFormatter))
+	logrus.Debug("child process in init()")
+
 	// Only init processes have FIFOFD.
 	fifofd := -1
 	envInitType := os.Getenv("_LIBCONTAINER_INITTYPE")
@@ -133,12 +151,6 @@ func StartInitialization() (retErr error) {
 		defer consoleSocket.Close()
 	}
 
-	logPipeFdStr := os.Getenv("_LIBCONTAINER_LOGPIPE")
-	logPipeFd, err := strconv.Atoi(logPipeFdStr)
-	if err != nil {
-		return fmt.Errorf("unable to convert _LIBCONTAINER_LOGPIPE: %w", err)
-	}
-
 	// Get mount files (O_PATH).
 	mountSrcFds, err := parseFdsFromEnv("_LIBCONTAINER_MOUNT_FDS")
 	if err != nil {
@@ -166,7 +178,7 @@ func StartInitialization() (retErr error) {
 	}()
 
 	// If init succeeds, it will not return, hence none of the defers will be called.
-	return containerInit(it, pipe, consoleSocket, fifofd, logPipeFd, mountFds{sourceFds: mountSrcFds, idmapFds: idmapFds})
+	return containerInit(it, pipe, consoleSocket, fifofd, logFD, mountFds{sourceFds: mountSrcFds, idmapFds: idmapFds})
 }
 
 func containerInit(t initType, pipe *os.File, consoleSocket *os.File, fifoFd, logFd int, mountFds mountFds) error {