nslcd_systemd: Use go 1.9 syscall.RawConn to implement getpeercred()

Eh.  I'm not really sure how I feel about this change.  I feel better about
the syscalls that the program makes.  But the code is longer.  There's more
boilerplate.  I wish syscall.RawConn let our function return an error that
would bubble up.

1 files changed, 13 insertions, 3 deletions

diff --git a/nslcd_systemd/nslcd_systemd.go b/nslcd_systemd/nslcd_systemd.go
index df6ca71..2ba9899 100644
--- a/nslcd_systemd/nslcd_systemd.go
+++ b/nslcd_systemd/nslcd_systemd.go
@@ -67,12 +67,22 @@ func get_socket() (socket net.Listener, err error) {
 }
 
 func getpeercred(conn *net.UnixConn) (cred unix.Ucred, err error) {
-	file, err := conn.File()
+	rawconn, err := conn.SyscallConn()
 	if err != nil {
 		return
 	}
-	defer file.Close()
-	_cred, err := unix.GetsockoptUcred(int(file.Fd()), unix.SOL_SOCKET, unix.SO_PEERCRED)
+	var _cred *unix.Ucred
+	var _err error
+	err = rawconn.Control(func(fd uintptr) {
+		_cred, _err = unix.GetsockoptUcred(int(fd), unix.SOL_SOCKET, unix.SO_PEERCRED)
+	})
+	if err != nil {
+		return
+	}
+	if _err != nil {
+		err = _err
+		return
+	}
 	cred = *_cred
 	return
 }