Index: lib/libutil/Makefile
===================================================================
--- lib/libutil/Makefile
+++ lib/libutil/Makefile
@@ -35,6 +35,7 @@
 	property.3 pty.3 quotafile.3 realhostname.3 realhostname_sa.3 \
 	_secure_path.3 trimdomain.3 uucplock.3 pw_util.3
 MAN+=	login.conf.5
+MLINKS+=flopen.3 flopenat.3
 MLINKS+=kld.3 kld_isloaded.3 kld.3 kld_load.3
 MLINKS+=login_auth.3 auth_cat.3 login_auth.3 auth_checknologin.3
 MLINKS+=login_cap.3 login_close.3 login_cap.3 login_getcapbool.3 \
Index: lib/libutil/flopen.3
===================================================================
--- lib/libutil/flopen.3
+++ lib/libutil/flopen.3
@@ -25,11 +25,12 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 6, 2009
+.Dd July 25, 2017
 .Dt FLOPEN 3
 .Os
 .Sh NAME
-.Nm flopen
+.Nm flopen ,
+.Nm flopenat
 .Nd "Reliably open and lock a file"
 .Sh LIBRARY
 .Lb libutil
@@ -40,6 +41,10 @@
 .Fn flopen "const char *path" "int flags"
 .Ft int
 .Fn flopen "const char *path" "int flags" "mode_t mode"
+.Ft int
+.Fn flopenat "int fd" "const char *path" "int flags"
+.Ft int
+.Fn flopenat "int fd" "const char *path" "int flags" "mode_t mode"
 .Sh DESCRIPTION
 The
 .Fn flopen
@@ -79,6 +84,18 @@
 .Va flags
 includes
 .Dv O_CREAT .
+.Pp
+The
+.Fn flopenat
+function is equivalent to the
+.Fn flopen
+function except in the case where the
+.Fa path
+specifies a relative path.
+In this case the file to be opened is determined relative to the directory
+associated with the file descriptor
+.Fa fd
+instead of the current working directory.
 .Sh RETURN VALUES
 If successful,
 .Fn flopen
Index: lib/libutil/flopen.c
===================================================================
--- lib/libutil/flopen.c
+++ lib/libutil/flopen.c
@@ -45,26 +45,16 @@
  * code's apparent simplicity; there would be no need for this function if it
  * was easy to get right.
  */
-int
-flopen(const char *path, int flags, ...)
+static int
+flopenatm(int dirfd, const char *path, int flags, mode_t mode)
 {
 	int fd, operation, serrno, trunc;
 	struct stat sb, fsb;
-	mode_t mode;
 
 #ifdef O_EXLOCK
 	flags &= ~O_EXLOCK;
 #endif
 
-	mode = 0;
-	if (flags & O_CREAT) {
-		va_list ap;
-
-		va_start(ap, flags);
-		mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
-		va_end(ap);
-	}
-
         operation = LOCK_EX;
         if (flags & O_NONBLOCK)
                 operation |= LOCK_NB;
@@ -73,7 +63,7 @@
 	flags &= ~O_TRUNC;
 
 	for (;;) {
-		if ((fd = open(path, flags, mode)) == -1)
+		if ((fd = openat(dirfd, path, flags, mode)) == -1)
 			/* non-existent or no access */
 			return (-1);
 		if (flock(fd, operation) == -1) {
@@ -83,7 +73,7 @@
 			errno = serrno;
 			return (-1);
 		}
-		if (stat(path, &sb) == -1) {
+		if (fstatat(dirfd, path, &sb, 0) == -1) {
 			/* disappeared from under our feet */
 			(void)close(fd);
 			continue;
@@ -123,3 +113,37 @@
 		return (fd);
 	}
 }
+
+int
+flopen(const char *path, int flags, ...)
+{
+	mode_t mode;
+
+	mode = 0;
+	if (flags & O_CREAT) {
+		va_list ap;
+
+		va_start(ap, flags);
+		mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
+		va_end(ap);
+	}
+
+	return (flopenatm(AT_FDCWD, path, flags, mode));
+}
+
+int
+flopenat(int dirfd, const char *path, int flags, ...)
+{
+	mode_t mode;
+
+	mode = 0;
+	if (flags & O_CREAT) {
+		va_list ap;
+
+		va_start(ap, flags);
+		mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
+		va_end(ap);
+	}
+
+	return (flopenatm(dirfd, path, flags, mode));
+}
Index: lib/libutil/libutil.h
===================================================================
--- lib/libutil/libutil.h
+++ lib/libutil/libutil.h
@@ -93,6 +93,7 @@
 int	extattr_namespace_to_string(int _attrnamespace, char **_string);
 int	extattr_string_to_namespace(const char *_string, int *_attrnamespace);
 int	flopen(const char *_path, int _flags, ...);
+int	flopenat(int _dirfd, const char *_path, int _flags, ...);
 int	forkpty(int *_amaster, char *_name,
 	    struct termios *_termp, struct winsize *_winp);
 void	hexdump(const void *_ptr, int _length, const char *_hdr, int _flags);