Systemd/src/basic/stat-util.c

/* SPDX-License-Identifier: LGPL-2.1+ */
/***
  This file is part of systemd.

  Copyright 2010-2012 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/magic.h>
#include <sched.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/types.h>
#include <unistd.h>

#include "dirent-util.h"
#include "fd-util.h"
#include "fs-util.h"
#include "macro.h"
#include "missing.h"
#include "stat-util.h"
#include "string-util.h"

int is_symlink(const char *path) {
        struct stat info;

        assert(path);

        if (lstat(path, &info) < 0)
                return -errno;

        return !!S_ISLNK(info.st_mode);
}

int is_dir(const char* path, bool follow) {
        struct stat st;
        int r;

        assert(path);

        if (follow)
                r = stat(path, &st);
        else
                r = lstat(path, &st);
        if (r < 0)
                return -errno;

        return !!S_ISDIR(st.st_mode);
}

int is_device_node(const char *path) {
        struct stat info;

        assert(path);

        if (lstat(path, &info) < 0)
                return -errno;

        return !!(S_ISBLK(info.st_mode) || S_ISCHR(info.st_mode));
}

int dir_is_empty(const char *path) {
        _cleanup_closedir_ DIR *d;
        struct dirent *de;

        d = opendir(path);
        if (!d)
                return -errno;

        FOREACH_DIRENT(de, d, return -errno)
                return 0;

        return 1;
}

bool null_or_empty(struct stat *st) {
        assert(st);

        if (S_ISREG(st->st_mode) && st->st_size <= 0)
                return true;

        /* We don't want to hardcode the major/minor of /dev/null,
         * hence we do a simpler "is this a device node?" check. */

        if (S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode))
                return true;

        return false;
}

int null_or_empty_path(const char *fn) {
        struct stat st;

        assert(fn);

        if (stat(fn, &st) < 0)
                return -errno;

        return null_or_empty(&st);
}

int null_or_empty_fd(int fd) {
        struct stat st;

        assert(fd >= 0);

        if (fstat(fd, &st) < 0)
                return -errno;

        return null_or_empty(&st);
}

int path_is_read_only_fs(const char *path) {
        struct statvfs st;

        assert(path);

        if (statvfs(path, &st) < 0)
                return -errno;

        if (st.f_flag & ST_RDONLY)
                return true;

        /* On NFS, statvfs() might not reflect whether we can actually
         * write to the remote share. Let's try again with
         * access(W_OK) which is more reliable, at least sometimes. */
        if (access(path, W_OK) < 0 && errno == EROFS)
                return true;

        return false;
}

int path_is_os_tree(const char *path) {
        int r;

        assert(path);

        /* Does the path exist at all? If not, generate an error immediately. This is useful so that a missing root dir
         * always results in -ENOENT, and we can properly distuingish the case where the whole root doesn't exist from
         * the case where just the os-release file is missing. */
        if (laccess(path, F_OK) < 0)
                return -errno;

        /* We use /usr/lib/os-release as flag file if something is an OS */
        r = chase_symlinks("/usr/lib/os-release", path, CHASE_PREFIX_ROOT, NULL);
        if (r == -ENOENT) {

                /* Also check for the old location in /etc, just in case. */
                r = chase_symlinks("/etc/os-release", path, CHASE_PREFIX_ROOT, NULL);
                if (r == -ENOENT)
                        return 0; /* We got nothing */
        }
        if (r < 0)
                return r;

        return 1;
}

int files_same(const char *filea, const char *fileb, int flags) {
        struct stat a, b;

        assert(filea);
        assert(fileb);

        if (fstatat(AT_FDCWD, filea, &a, flags) < 0)
                return -errno;

        if (fstatat(AT_FDCWD, fileb, &b, flags) < 0)
                return -errno;

        return a.st_dev == b.st_dev &&
               a.st_ino == b.st_ino;
}

bool is_fs_type(const struct statfs *s, statfs_f_type_t magic_value) {
        assert(s);
        assert_cc(sizeof(statfs_f_type_t) >= sizeof(s->f_type));

        return F_TYPE_EQUAL(s->f_type, magic_value);
}

int fd_is_fs_type(int fd, statfs_f_type_t magic_value) {
        struct statfs s;

        if (fstatfs(fd, &s) < 0)
                return -errno;

        return is_fs_type(&s, magic_value);
}

int path_is_fs_type(const char *path, statfs_f_type_t magic_value) {
        _cleanup_close_ int fd = -1;

        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
        if (fd < 0)
                return -errno;

        return fd_is_fs_type(fd, magic_value);
}

bool is_temporary_fs(const struct statfs *s) {
    return is_fs_type(s, TMPFS_MAGIC) ||
           is_fs_type(s, RAMFS_MAGIC);
}

int fd_is_temporary_fs(int fd) {
        struct statfs s;

        if (fstatfs(fd, &s) < 0)
                return -errno;

        return is_temporary_fs(&s);
}

int fd_is_network_ns(int fd) {
        int r;

        r = fd_is_fs_type(fd, NSFS_MAGIC);
        if (r <= 0)
                return r;
        r = ioctl(fd, NS_GET_NSTYPE);
        if (r < 0)
                return -errno;
        return r == CLONE_NEWNET;
}

int path_is_temporary_fs(const char *path) {
        _cleanup_close_ int fd = -1;

        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
        if (fd < 0)
                return -errno;

        return fd_is_temporary_fs(fd);
}