Retry direct unix package calls if observing EINTR

Retry Recvfrom, Sendmsg, Readmsg, and Read as they can return EINTR.

Signed-off-by: Evan Phoenix <[email protected]>

Author: evanphx

libcontainer/notify_v2_linux.go

@@ -2,6 +2,7 @@ package libcontainer
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 	"unsafe"
 
@@ -40,7 +41,11 @@ func registerMemoryEventV2(cgDir, evName, cgEvName string) (<-chan struct{}, err
 
 		for {
 			n, err := unix.Read(fd, buffer[:])
+			if err == unix.EINTR { //nolint:errorlint // unix errors are bare
+				continue
+			}
 			if err != nil {
+				err = os.NewSyscallError("read", err)
 				logrus.Warnf("unable to read event data from inotify, got error: %v", err)
 				return
 			}

libcontainer/sync_unix.go

@@ -42,9 +42,20 @@ func (s *syncSocket) WritePacket(b []byte) (int, error) {
 }
 
 func (s *syncSocket) ReadPacket() ([]byte, error) {
-	size, _, err := unix.Recvfrom(int(s.f.Fd()), nil, unix.MSG_TRUNC|unix.MSG_PEEK)
+	var (
+		size int
+		err  error
+	)
+
+	for {
+		size, _, err = unix.Recvfrom(int(s.f.Fd()), nil, unix.MSG_TRUNC|unix.MSG_PEEK)
+		if err != unix.EINTR { //nolint:errorlint // unix errors are bare
+			break
+		}
+	}
+
 	if err != nil {
-		return nil, fmt.Errorf("fetch packet length from socket: %w", err)
+		return nil, fmt.Errorf("fetch packet length from socket: %w", os.NewSyscallError("recvfrom", err))
 	}
 	// We will only get a zero size if the socket has been closed from the
 	// other end (otherwise recvfrom(2) will block until a packet is ready). In

libcontainer/utils/cmsg.go

@@ -42,9 +42,20 @@ func RecvFile(socket *os.File) (_ *os.File, Err error) {
 	oob := make([]byte, oobSpace)
 
 	sockfd := socket.Fd()
-	n, oobn, _, _, err := unix.Recvmsg(int(sockfd), name, oob, unix.MSG_CMSG_CLOEXEC)
+	var (
+		n, oobn int
+		err     error
+	)
+
+	for {
+		n, oobn, _, _, err = unix.Recvmsg(int(sockfd), name, oob, unix.MSG_CMSG_CLOEXEC)
+		if err != unix.EINTR { //nolint:errorlint // unix errors are bare
+			break
+		}
+	}
+
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("recvmsg", err)
 	}
 	if n >= MaxNameLen || oobn != oobSpace {
 		return nil, fmt.Errorf("recvfile: incorrect number of bytes read (n=%d oobn=%d)", n, oobn)
@@ -115,5 +126,10 @@ func SendFile(socket *os.File, file *os.File) error {
 // SendRawFd sends a specific file descriptor over the given AF_UNIX socket.
 func SendRawFd(socket *os.File, msg string, fd uintptr) error {
 	oob := unix.UnixRights(int(fd))
-	return unix.Sendmsg(int(socket.Fd()), []byte(msg), oob, nil, 0)
+	for {
+		err := unix.Sendmsg(int(socket.Fd()), []byte(msg), oob, nil, 0)
+		if err != unix.EINTR { //nolint:errorlint // unix errors are bare
+			return os.NewSyscallError("sendmsg", err)
+		}
+	}
 }