Introduce the flopenat(3) function.

Reviewed by:	des, emaste
Differential Revision:	https://reviews.freebsd.org/D11690

2 files changed, 29 insertions, 8 deletions

diff --git a/libutil/flopen.c b/libutil/flopen.c
index 8929729..bb5d996 100644
--- a/libutil/flopen.c
+++ b/libutil/flopen.c
@@ -45,8 +45,8 @@ __FBSDID("$FreeBSD$");
  * 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
+vflopenat(int dirfd, const char *path, int flags, va_list ap)
 {
 	int fd, operation, serrno, trunc;
 	struct stat sb, fsb;
@@ -58,11 +58,7 @@ flopen(const char *path, int flags, ...)
 
 	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;
@@ -73,7 +69,7 @@ flopen(const char *path, int flags, ...)
 	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 +79,7 @@ flopen(const char *path, int flags, ...)
 			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 +119,27 @@ flopen(const char *path, int flags, ...)
 		return (fd);
 	}
 }
+
+int
+flopen(const char *path, int flags, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, flags);
+	ret = vflopenat(AT_FDCWD, path, flags, ap);
+	va_end(ap);
+	return (ret);
+}
+
+int
+flopenat(int dirfd, const char *path, int flags, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, flags);
+	ret = vflopenat(dirfd, path, flags, ap);
+	va_end(ap);
+	return (ret);
+}
diff --git a/libutil/libutil.h b/libutil/libutil.h
index b20ffa2..fa924db 100644
--- a/libutil/libutil.h
+++ b/libutil/libutil.h
@@ -93,6 +93,7 @@ int	expand_number(const char *_buf, uint64_t *_num);
 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);