Index: include/fts.h
===================================================================
--- include/fts.h
+++ include/fts.h
@@ -61,6 +61,7 @@
 
 #define	FTS_NAMEONLY	0x100		/* (private) child names only */
 #define	FTS_STOP	0x200		/* (private) unrecoverable error */
+#define	FTS_CAPMODE	0x400		/* (private) capability mode */
 	int fts_options;		/* fts_open options, global flags */
 	void *fts_clientptr;		/* thunk for sort function */
 } FTS;
@@ -75,7 +76,7 @@
 	char *fts_accpath;		/* access path */
 	char *fts_path;			/* root path */
 	int fts_errno;			/* errno for this node */
-	int fts_symfd;			/* fd for symlink */
+	int fts_symfd;			/* fd for symlink or capmode */
 	__size_t fts_pathlen;		/* strlen(fts_path) */
 	__size_t fts_namelen;		/* strlen(fts_name) */
 
@@ -124,6 +125,8 @@
 __BEGIN_DECLS
 FTSENT	*fts_children(FTS *, int);
 int	 fts_close(FTS *);
+FTS	*fts_fopen(char * const *, int, int *,
+	    int (*)(const FTSENT * const *, const FTSENT * const *));
 void	*fts_get_clientptr(FTS *);
 #define	 fts_get_clientptr(fts)	((fts)->fts_clientptr)
 FTS	*fts_get_stream(FTSENT *);
Index: lib/libc/gen/Symbol.map
===================================================================
--- lib/libc/gen/Symbol.map
+++ lib/libc/gen/Symbol.map
@@ -403,6 +403,7 @@
 	fts_get_clientptr;
 	fts_get_stream;
 	fts_open;
+	fts_fopen;
 	fts_read;
 	fts_set;
 	fts_set_clientptr;
Index: lib/libc/gen/fts.3
===================================================================
--- lib/libc/gen/fts.3
+++ lib/libc/gen/fts.3
@@ -28,7 +28,7 @@
 .\"     @(#)fts.3	8.5 (Berkeley) 4/16/94
 .\" $FreeBSD$
 .\"
-.Dd January 12, 2014
+.Dd March 21, 2019
 .Dt FTS 3
 .Os
 .Sh NAME
@@ -39,6 +39,8 @@
 .Sh SYNOPSIS
 .In fts.h
 .Ft FTS *
+.Fn fts_fopen "char * const *path_argv" "int options" "int *file_descriptors" "int (*compar)(const FTSENT * const *, const FTSENT * const *)"
+.Ft FTS *
 .Fn fts_open "char * const *path_argv" "int options" "int (*compar)(const FTSENT * const *, const FTSENT * const *)"
 .Ft FTSENT *
 .Fn fts_read "FTS *ftsp"
@@ -62,7 +64,9 @@
 file hierarchies.
 A simple overview is that the
 .Fn fts_open
-function returns a
+and
+.Fn fts_fopen
+functions return a
 .Dq handle
 on a file hierarchy, which is then supplied to
 the other
@@ -521,6 +525,18 @@
 .Fa path_argv
 for the root paths, and in the order listed in the directory for
 everything else.
+.Sh FTS_FOPEN
+The
+.Fn fts_fopen
+function works exactly the same as
+.Fn fts_open .
+It takes an extra array of file descriptors corresponding to each
+path passed in the argument.
+.Fn fts_fopen
+sets the
+.Dv FTS_NOCDHIR
+option automatically.
+It also can be used in capability mode.
 .Sh FTS_READ
 The
 .Fn fts_read
@@ -726,8 +742,10 @@
 function
 returns 0 on success, and \-1 if an error occurs.
 .Sh ERRORS
-The function
+The functions
 .Fn fts_open
+and
+.Fn fts_fopen
 may fail and set
 .Va errno
 for any of the errors specified for the library functions
@@ -790,7 +808,11 @@
 .Fx 5.0 ,
 principally to provide for alternative interfaces to the
 .Nm
-functionality using different data structures.
+functionality using different data structures. The
+.Fn fts_fopen
+function was introduced in
+.Fx 13.0
+to allow the fts interface to be used in capability mode.
 .Sh BUGS
 The
 .Fn fts_open
Index: lib/libc/gen/fts.c
===================================================================
--- lib/libc/gen/fts.c
+++ lib/libc/gen/fts.c
@@ -58,6 +58,8 @@
 static size_t	 fts_maxarglen(char * const *);
 static void	 fts_padjust(FTS *, FTSENT *);
 static int	 fts_palloc(FTS *, size_t);
+static FTS	*fts_private_open(char * const *, int, int *,
+    int (*)(const FTSENT * const *, const FTSENT * const *));
 static FTSENT	*fts_sort(FTS *, FTSENT *, size_t);
 static int	 fts_stat(FTS *, FTSENT *, int, int);
 static int	 fts_safe_changedir(FTS *, FTSENT *, int, char *);
@@ -109,18 +111,40 @@
 fts_open(char * const *argv, int options,
     int (*compar)(const FTSENT * const *, const FTSENT * const *))
 {
-	struct _fts_private *priv;
-	FTS *sp;
-	FTSENT *p, *root;
-	FTSENT *parent, *tmp;
-	size_t len, nitems;
+	/* Options check. */
+	if (options & ~FTS_OPTIONMASK) {
+		errno = EINVAL;
+		return (NULL);
+	}
+
+	return fts_private_open(argv, options, NULL, compar);
+}
 
+FTS *
+fts_fopen(char * const *argv, int options, int *fds,
+    int (*compar)(const FTSENT * const *, const FTSENT * const *))
+{
 	/* Options check. */
 	if (options & ~FTS_OPTIONMASK) {
 		errno = EINVAL;
 		return (NULL);
 	}
 
+	options |= FTS_NOCHDIR | FTS_CAPMODE;
+
+	return fts_private_open(argv, options, fds, compar);
+}
+
+static FTS *
+fts_private_open(char * const *argv, int options, int *fds,
+    int (*compar)(const FTSENT * const *, const FTSENT * const *))
+{
+	struct _fts_private *priv;
+	FTS *sp;
+	FTSENT *p, *root;
+	FTSENT *parent, *tmp;
+	size_t len, nitems;
+
 	/* fts_open() requires at least one path */
 	if (*argv == NULL) {
 		errno = EINVAL;
@@ -161,6 +185,10 @@
 		p->fts_level = FTS_ROOTLEVEL;
 		p->fts_parent = parent;
 		p->fts_accpath = p->fts_name;
+		if (fds != NULL) {
+			p->fts_symfd = _dup(*fds);
+			fds++;
+		}
 		p->fts_info = fts_stat(sp, p, ISSET(FTS_COMFOLLOW), -1);
 
 		/* Command-line "." and ".." are real directories. */
@@ -255,6 +283,8 @@
 	if (sp->fts_cur) {
 		for (p = sp->fts_cur; p->fts_level >= FTS_ROOTLEVEL;) {
 			freep = p;
+			if (p->fts_symfd > 0)
+				_close(p->fts_symfd);
 			p = p->fts_link != NULL ? p->fts_link : p->fts_parent;
 			free(freep);
 		}
@@ -647,7 +677,17 @@
 #else
 #define __opendir2(path, flag) opendir(path)
 #endif
-	if ((dirp = __opendir2(cur->fts_accpath, oflag)) == NULL) {
+	if (ISSET(FTS_CAPMODE)) {
+		if (cur->fts_symfd == -1) {
+			cur->fts_symfd = _openat(cur->fts_parent->fts_symfd,
+			    cur->fts_name, O_RDONLY);
+			if (cur->fts_symfd < 0)
+				goto dirfail;
+		}
+		if ((dirp = fdopendir(cur->fts_symfd)) == NULL)
+			goto dirfail;
+	} else if ((dirp = __opendir2(cur->fts_accpath, oflag)) == NULL) {
+dirfail:
 		if (type == BREAD) {
 			cur->fts_info = FTS_DNR;
 			cur->fts_errno = errno;
@@ -819,8 +859,12 @@
 		}
 		++nitems;
 	}
-	if (dirp)
-		(void)closedir(dirp);
+	if (dirp) {
+		if (cur->fts_symfd == -1)
+			(void)closedir(dirp);
+		else
+			(void)fdclosedir(dirp);
+	}
 
 	/*
 	 * If realloc() changed the address of the path, adjust the
@@ -876,10 +920,14 @@
 	int saved_errno;
 	const char *path;
 
-	if (dfd == -1)
-		path = p->fts_accpath, dfd = AT_FDCWD;
-	else
+	if (dfd != -1)
 		path = p->fts_name;
+	else if (p->fts_symfd != -1)
+		path = ".", dfd = p->fts_symfd;
+	else if (p->fts_parent->fts_symfd != -1)
+		path = p->fts_name, dfd = p->fts_parent->fts_symfd;
+	else
+		path = p->fts_accpath, dfd = AT_FDCWD;
 
 	/* If user needs stat info, stat buffer already allocated. */
 	sbp = ISSET(FTS_NOSTAT) ? &sb : p->fts_statp;
@@ -1036,6 +1084,7 @@
 	p->fts_namelen = namelen;
 	p->fts_path = sp->fts_path;
 	p->fts_errno = 0;
+	p->fts_symfd = -1;
 	p->fts_flags = 0;
 	p->fts_instr = FTS_NOINSTR;
 	p->fts_number = 0;