xref: /illumos-gate/usr/src/cmd/backup/dump/lftw.c (revision 4870e0a7)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*	Copyright (c) 1988 AT&T	*/
/*	  All Rights Reserved	*/

/* LINTLIBRARY */
/*
 *	ftw - file tree walk
 *
 *	int ftw (path, fn, depth)  char *path; int (*fn)(); int depth;
 *
 *	Given a path name, ftw starts from the file given by that path
 *	name and visits each file and directory in the tree beneath
 *	that file.  If a single file has multiple links within the
 *	structure, it will be visited once for each such link.
 *	For each object visited, fn is called with three arguments.
 *	The first contains the path name of the object, the second
 *	contains a pointer to a stat buffer which will usually hold
 *	appropriate information for the object and the third will
 *	contain an integer value giving additional information:
 *
 *		FTW_F	The object is a file for which stat was
 *			successful.  It does not guarantee that the
 *			file can actually be read.
 *
 *		FTW_D	The object is a directory for which stat and
 *			open for read were both successful.
 *
 *		FTW_DNR	The object is a directory for which stat
 *			succeeded, but which cannot be read.  Because
 *			the directory cannot be read, fn will not be
 *			called for any descendants of this directory.
 *
 *		FTW_NS	Stat failed on the object because of lack of
 *			appropriate permission.  This indication will
 *			be given, for example, for each file in a
 *			directory with read but no execute permission.
 *			Because stat failed, it is not possible to
 *			determine whether this object is a file or a
 *			directory.  The stat buffer passed to fn will
 *			contain garbage.  Stat failure for any reason
 *			other than lack of permission will be
 *			considered an error and will cause ftw to stop
 *			and return -1 to its caller.
 *
 *	If fn returns nonzero, ftw stops and returns the same value
 *	to its caller.  If ftw gets into other trouble along the way,
 *	it returns -1 and leaves an indication of the cause in errno.
 *
 *	The third argument to ftw does not limit the depth to which
 *	ftw will go.  Rather, it limits the depth to which ftw will
 *	go before it starts recycling file descriptors.  In general,
 *	it is necessary to use a file descriptor for each level of the
 *	tree, but they can be recycled for deep trees by saving the
 *	position, closing, re-opening, and seeking.  It is possible
 *	to start recycling file descriptors by sensing when we have
 *	run out, but in general this will not be terribly useful if
 *	fn expects to be able to open files.  We could also figure out
 *	how many file descriptors are available and guarantee a certain
 *	number to fn, but we would not know how many to guarantee,
 *	and we do not want to impose the extra overhead on a caller who
 *	knows how many are available without having to figure it out.
 *
 *	It is possible for ftw to die with a memory fault in the event
 *	of a file system so deeply nested that the stack overflows.
 */

#include <sys/fs/ufs_inode.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <malloc.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <ftw.h>

static int pwdfd;

static int lf_xftw(
	const char *,
	int (*)(const char *, const struct stat64 *, int),
	int,
	int (*)(const char *, struct stat64 *));

int
lf_lftw(
	const char *path,
	int (*fn)(const char *, const struct stat64 *, int),
	int depth)
{
	int rc;

	if ((pwdfd = open(".", O_RDONLY)) < 0) {
		return (-1);
	} else {
		rc = (lf_xftw(path, fn, depth, lstat64));
		(void) close(pwdfd);
		return (rc);
	}
}

static int
#ifdef __STDC__
lf_xftw(
	const char *path,
	int (*fn)(const char *, const struct stat64 *, int),
	int depth,
	int (*statfn)(const char *, struct stat64 *))
#else
lf_xftw(char *path, int (*fn)(), int depth, int (*statfn)())
#endif
{
	int n;
	int rc, sublen, saverr, attrfd;
	DIR *dirp;
	char *subpath, *component;
	struct stat64 sb;
	struct dirent *dp;
	extern dev_t partial_dev;

	/*
	 * Try to get file status.
	 * If unsuccessful, errno will say why.
	 */
	if ((*statfn)(path, &sb) < 0)
		return (errno == EACCES? (*fn)(path, &sb, FTW_NS): -1);
	/*
	 *	The stat succeeded, so we know the object exists.
	 *	Make sure it is not a mount point for another filesystem.
	 *	The following check must be made here because:
	 *
	 *		+ namefs can be mounted on anything, but a directory
	 *		+ all other filesystems must be mounted on a directory
	 */
	if (sb.st_dev != partial_dev) {
		return (0);
	}
	/*
	 *	Check for presence of attributes on file
	 */
	if (pathconf(path, _PC_XATTR_EXISTS) == 1) {
		attrfd = attropen64(path, ".", O_RDONLY|O_NONBLOCK);
	} else {
		attrfd = -1;
	}
	/*
	 *	If not a directory, call the user function and return.
	 */
	if ((sb.st_mode & S_IFMT) != S_IFDIR &&
	    (sb.st_mode & IFMT) != IFATTRDIR) {
		rc = (*fn)(path, &sb, FTW_F);
		if (rc == 0 && attrfd != -1) {
			(void) fchdir(attrfd);
			rc = lf_xftw(".", fn, depth-1, statfn);
			(void) fchdir(pwdfd);
			(void) close(attrfd);
		}
		return (rc);
	}
	/*
	 *	The object was a directory and not a mount point.
	 *
	 *	Open a file to read the directory
	 */
	dirp = opendir(path);

	/*
	 *	Call the user function, telling it whether
	 *	the directory can be read.  If it can't be read
	 *	call the user function or indicate an error,
	 *	depending on the reason it couldn't be read.
	 */
	if (dirp == NULL)
		rc = (errno == EACCES? (*fn)(path, &sb, FTW_DNR): -1);
	else
		rc = (*fn)(path, &sb, FTW_D);
	/*
	 *	If the directory has attributes, process the
	 *	attributes before processing the directory contents.
	 */
	if (rc == 0 && attrfd != -1) {
		(void) fchdir(attrfd);
		rc = lf_xftw(".", fn, depth-1, statfn);
		(void) fchdir(pwdfd);
		(void) close(attrfd);
	}
	if (rc != 0 || dirp == NULL)
		return (rc);

	/* Allocate a buffer to hold generated pathnames. */
	/* LINTED: the length will fit into a signed integer */
	n = (int)strlen(path);
	sublen = n + MAXNAMLEN + 1; /* +1 for appended / */
	subpath = malloc((unsigned)(sublen+1));	/* +1 for NUL */
	if (subpath == NULL) {
		saverr = errno;
		(void) closedir(dirp);
		errno = saverr;
		return (-1);
	}

	/* Create a prefix to which we will append component names */
	(void) strcpy(subpath, path);
	if (subpath[0] != '\0' && subpath[n-1] != '/')
		subpath[n++] = '/';
	component = &subpath[n];
	/* LINTED: result will fit into a 32-bit int */
	sublen -= component - subpath;

	/*
	 *	Read the directory one component at a time.
	 *	We must ignore "." and "..", but other than that,
	 *	just create a path name and call self to check it out.
	 */
	while ((dp = readdir(dirp)) != NULL) {
		if (strcmp(dp->d_name, ".") != 0 &&
		    strcmp(dp->d_name, "..") != 0) {
			long here;

			/* Append component name to the working path */
			(void) strncpy(component, dp->d_name, sublen);
			component[sublen - 1] = '\0';

			/*
			 *	If we are about to exceed our depth,
			 *	remember where we are and close a file.
			 */
			if (depth <= 1) {
				here = telldir(dirp);
				(void) closedir(dirp);
			}

			/*
			 *	Do a recursive call to process the file.
			 *	(watch this, sports fans)
			 */
			rc = lf_xftw(subpath, fn, depth-1, statfn);
			if (rc != 0) {
				free(subpath);
				if (depth > 1)
					(void) closedir(dirp);
				return (rc);
			}

			/*
			 *	If we closed the file, try to reopen it.
			 */
			if (depth <= 1) {
				dirp = opendir(path);
				if (dirp == NULL) {
					free(subpath);
					return (-1);
				}
				seekdir(dirp, here);
			}
		}
	}

	/*
	 *	We got out of the subdirectory loop.  The return from
	 *	the final readdir is in dp.  Clean up.
	 */
	free(subpath);
	(void) closedir(dirp);
	return (0);
}