/* Copyright (c) 2014 Red Hat, Inc. All rights reserved.

* This copyrighted material is made available to anyone wishing
* to use, modify, copy, or redistribute it subject to the terms
* and conditions of the GNU General Public License version 2.

* This program 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 General Public License for more details.

* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/

/* Filesystem basic sanity check, tests all (almost) fops. */

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/xattr.h>
#include <errno.h>
#include <string.h>
#include <dirent.h>
#include <sys/sysmacros.h>

#ifndef linux
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/un.h>
#endif

/* for fd based fops after unlink */
int
fd_based_fops_1(char *filename);
/* for fd based fops before unlink */
int
fd_based_fops_2(char *filename);
/* fops based on fd after dup */
int
dup_fd_based_fops(char *filename);
/* for fops based on path */
int
path_based_fops(char *filename);
/* for fops which operate on directory */
int
dir_based_fops(char *filename);
/* for fops which operate in link files (symlinks) */
int
link_based_fops(char *filename);
/* to test open syscall with open modes available. */
int
test_open_modes(char *filename);
/* generic function which does open write and read. */
int
generic_open_read_write(char *filename, int flag, mode_t mode);

#define OPEN_MODE 0666

int
main(int argc, char *argv[])
{
    int ret = -1;
    int result = 0;
    char filename[255] = {
        0,
    };

    if (argc > 1)
        strcpy(filename, argv[1]);
    else
        strcpy(filename, "temp-xattr-test-file");

    ret = fd_based_fops_1(strcat(filename, "_1"));
    if (ret < 0) {
        fprintf(stderr, "fd based file operation 1 failed\n");
        result |= ret;
    } else {
        fprintf(stdout, "fd based file operation 1 passed\n");
    }

    ret = fd_based_fops_2(strcat(filename, "_2"));
    if (ret < 0) {
        result |= ret;
        fprintf(stderr, "fd based file operation 2 failed\n");
    } else {
        fprintf(stdout, "fd based file operation 2 passed\n");
    }

    ret = dup_fd_based_fops(strcat(filename, "_3"));
    if (ret < 0) {
        result |= ret;
        fprintf(stderr, "dup fd based file operation failed\n");
    } else {
        fprintf(stdout, "dup fd based file operation passed\n");
    }

    ret = path_based_fops(strcat(filename, "_4"));
    if (ret < 0) {
        result |= ret;
        fprintf(stderr, "path based file operation failed\n");
    } else {
        fprintf(stdout, "path based file operation passed\n");
    }

    ret = dir_based_fops(strcat(filename, "_5"));
    if (ret < 0) {
        result |= ret;
        fprintf(stderr, "directory based file operation failed\n");
    } else {
        fprintf(stdout, "directory based file operation passed\n");
    }

    ret = link_based_fops(strcat(filename, "_5"));
    if (ret < 0) {
        result |= ret;
        fprintf(stderr, "link based file operation failed\n");
    } else {
        fprintf(stdout, "link based file operation passed\n");
    }

    ret = test_open_modes(strcat(filename, "_5"));
    if (ret < 0) {
        result |= ret;
        fprintf(stderr, "testing modes of `open' call failed\n");
    } else {
        fprintf(stdout, "testing modes of `open' call passed\n");
    }
    return result;
}

/* Execute all possible fops on a fd which is unlinked */
int
fd_based_fops_1(char *filename)
{
    int fd = 0;
    int ret = -1;
    int result = 0;
    struct stat stbuf = {
        0,
    };
    char wstr[50] = {
        0,
    };
    char rstr[50] = {
        0,
    };

    fd = open(filename, O_RDWR | O_CREAT, OPEN_MODE);
    if (fd < 0) {
        fprintf(stderr, "open failed : %s\n", strerror(errno));
        return ret;
    }

    ret = unlink(filename);
    if (ret < 0) {
        fprintf(stderr, "unlink failed : %s\n", strerror(errno));
        result |= ret;
    }

    strcpy(wstr, "This is my string\n");
    ret = write(fd, wstr, strlen(wstr));
    if (ret <= 0) {
        fprintf(stderr, "write failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lseek(fd, 0, SEEK_SET);
    if (ret < 0) {
        fprintf(stderr, "lseek failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = read(fd, rstr, strlen(wstr));
    if (ret <= 0) {
        fprintf(stderr, "read failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = memcmp(rstr, wstr, strlen(wstr));
    if (ret != 0) {
        fprintf(stderr, "read returning junk\n");
        result |= ret;
    }

    ret = ftruncate(fd, 0);
    if (ret < 0) {
        fprintf(stderr, "ftruncate failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fstat(fd, &stbuf);
    if (ret < 0) {
        fprintf(stderr, "fstat failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fsync(fd);
    if (ret < 0) {
        fprintf(stderr, "fsync failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fdatasync(fd);
    if (ret < 0) {
        fprintf(stderr, "fdatasync failed : %s\n", strerror(errno));
        result |= ret;
    }

    /*
     *      These metadata operations fail at the moment because kernel doesn't
     *      pass the client fd in the operation.
     *      The following bug tracks this change.
     *      https://bugzilla.redhat.com/show_bug.cgi?id=1084422
     *      ret = fchmod (fd, 0640);
     *      if (ret < 0) {
     *              fprintf (stderr, "fchmod failed : %s\n", strerror (errno));
     *              result |= ret;
     *      }

     *      ret = fchown (fd, 10001, 10001);
     *      if (ret < 0) {
     *              fprintf (stderr, "fchown failed : %s\n", strerror (errno));
     *              result |= ret;
     *      }

     *      ret = fsetxattr (fd, "trusted.xattr-test", "working", 8, 0);
     *      if (ret < 0) {
     *              fprintf (stderr, "fsetxattr failed : %s\n", strerror
     (errno));
     *              result |= ret;
     *      }

     *      ret = flistxattr (fd, NULL, 0);
     *      if (ret <= 0) {
     *              fprintf (stderr, "flistxattr failed : %s\n", strerror
     (errno));
     *              result |= ret;
     *      }

     *      ret = fgetxattr (fd, "trusted.xattr-test", NULL, 0);
     *      if (ret <= 0) {
     *              fprintf (stderr, "fgetxattr failed : %s\n", strerror
     (errno));
     *              result |= ret;
     *      }

     *      ret = fremovexattr (fd, "trusted.xattr-test");
     *      if (ret < 0) {
     *              fprintf (stderr, "fremovexattr failed : %s\n", strerror
     (errno));
     *              result |= ret;
     *      }
     */

    if (fd)
        close(fd);
    return result;
}

int
fd_based_fops_2(char *filename)
{
    int fd = 0;
    int ret = -1;
    int result = 0;
    struct stat stbuf = {
        0,
    };
    char wstr[50] = {
        0,
    };
    char rstr[50] = {
        0,
    };

    fd = open(filename, O_RDWR | O_CREAT, OPEN_MODE);
    if (fd < 0) {
        fprintf(stderr, "open failed : %s\n", strerror(errno));
        return ret;
    }

    ret = ftruncate(fd, 0);
    if (ret < 0) {
        fprintf(stderr, "ftruncate failed : %s\n", strerror(errno));
        result |= ret;
    }

    strcpy(wstr, "This is my second string\n");
    ret = write(fd, wstr, strlen(wstr));
    if (ret < 0) {
        fprintf(stderr, "write failed: %s\n", strerror(errno));
        result |= ret;
    }

    lseek(fd, 0, SEEK_SET);
    if (ret < 0) {
        fprintf(stderr, "lseek failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = read(fd, rstr, strlen(wstr));
    if (ret <= 0) {
        fprintf(stderr, "read failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = memcmp(rstr, wstr, strlen(wstr));
    if (ret != 0) {
        fprintf(stderr, "read returning junk\n");
        result |= ret;
    }

    ret = fstat(fd, &stbuf);
    if (ret < 0) {
        fprintf(stderr, "fstat failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fchmod(fd, 0640);
    if (ret < 0) {
        fprintf(stderr, "fchmod failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fchown(fd, 10001, 10001);
    if (ret < 0) {
        fprintf(stderr, "fchown failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fsync(fd);
    if (ret < 0) {
        fprintf(stderr, "fsync failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fsetxattr(fd, "trusted.xattr-test", "working", 8, 0);
    if (ret < 0) {
        fprintf(stderr, "fsetxattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fdatasync(fd);
    if (ret < 0) {
        fprintf(stderr, "fdatasync failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = flistxattr(fd, NULL, 0);
    if (ret <= 0) {
        fprintf(stderr, "flistxattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fgetxattr(fd, "trusted.xattr-test", NULL, 0);
    if (ret <= 0) {
        fprintf(stderr, "fgetxattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fremovexattr(fd, "trusted.xattr-test");
    if (ret < 0) {
        fprintf(stderr, "fremovexattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    if (fd)
        close(fd);
    unlink(filename);

    return result;
}

int
path_based_fops(char *filename)
{
    int ret = -1;
    int fd = 0;
    int result = 0;
    struct stat stbuf = {
        0,
    };
    char newfilename[255] = {
        0,
    };
    char *hardlink = "linkfile-hard.txt";
    char *symlnk = "linkfile-soft.txt";
    char buf[1024] = {
        0,
    };

    fd = creat(filename, 0644);
    if (fd < 0) {
        fprintf(stderr, "creat failed: %s\n", strerror(errno));
        return ret;
    }

    ret = truncate(filename, 0);
    if (ret < 0) {
        fprintf(stderr, "truncate failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = stat(filename, &stbuf);
    if (ret < 0) {
        fprintf(stderr, "stat failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = chmod(filename, 0640);
    if (ret < 0) {
        fprintf(stderr, "chmod failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = chown(filename, 10001, 10001);
    if (ret < 0) {
        fprintf(stderr, "chown failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = setxattr(filename, "trusted.xattr-test", "working", 8, 0);
    if (ret < 0) {
        fprintf(stderr, "setxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = listxattr(filename, NULL, 0);
    if (ret <= 0) {
        ret = -1;
        fprintf(stderr, "listxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = getxattr(filename, "trusted.xattr-test", NULL, 0);
    if (ret <= 0) {
        fprintf(stderr, "getxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = removexattr(filename, "trusted.xattr-test");
    if (ret < 0) {
        fprintf(stderr, "removexattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = access(filename, R_OK | W_OK);
    if (ret < 0) {
        fprintf(stderr, "access failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = link(filename, hardlink);
    if (ret < 0) {
        fprintf(stderr, "link failed: %s\n", strerror(errno));
        result |= ret;
    }
    unlink(hardlink);

    ret = symlink(filename, symlnk);
    if (ret < 0) {
        fprintf(stderr, "symlink failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = readlink(symlnk, buf, sizeof(buf));
    if (ret < 0) {
        fprintf(stderr, "readlink failed: %s\n", strerror(errno));
        result |= ret;
    }
    unlink(symlnk);

    /* Create a character special file */
    ret = mknod("cspecial", S_IFCHR | S_IRWXU | S_IRWXG, makedev(2, 3));
    if (ret < 0) {
        fprintf(stderr, "cpsecial mknod failed: %s\n", strerror(errno));
        result |= ret;
    }
    unlink("cspecial");

    ret = mknod("bspecial", S_IFBLK | S_IRWXU | S_IRWXG, makedev(4, 5));
    if (ret < 0) {
        fprintf(stderr, "bspecial mknod failed: %s\n", strerror(errno));
        result |= ret;
    }
    unlink("bspecial");

#ifdef linux
    ret = mknod("fifo", S_IFIFO | S_IRWXU | S_IRWXG, 0);
#else
    ret = mkfifo("fifo", 0);
#endif
    if (ret < 0) {
        fprintf(stderr, "fifo mknod failed: %s\n", strerror(errno));
        result |= ret;
    }
    unlink("fifo");

#ifdef linux
    ret = mknod("sock", S_IFSOCK | S_IRWXU | S_IRWXG, 0);
    if (ret < 0) {
        fprintf(stderr, "sock mknod failed: %s\n", strerror(errno));
        result |= ret;
    }
#else
    {
        int s;
        const char *pathname = "sock";
        struct sockaddr_un addr;

        s = socket(PF_LOCAL, SOCK_STREAM, 0);
        memset(&addr, 0, sizeof(addr));
        strncpy(addr.sun_path, pathname, sizeof(addr.sun_path));
        ret = bind(s, (const struct sockaddr *)&addr, SUN_LEN(&addr));
        if (ret < 0) {
            fprintf(stderr, "fifo mknod failed: %s\n", strerror(errno));
            result |= ret;
        }
        close(s);
    }
#endif
    unlink("sock");

    strcpy(newfilename, filename);
    strcat(newfilename, "_new");
    ret = rename(filename, newfilename);
    if (ret < 0) {
        fprintf(stderr, "rename failed: %s\n", strerror(errno));
        result |= ret;
    }
    unlink(newfilename);

    if (fd)
        close(fd);

    unlink(filename);
    return result;
}

int
dup_fd_based_fops(char *filename)
{
    int fd = 0;
    int result = 0;
    int newfd = 0;
    int ret = -1;
    struct stat stbuf = {
        0,
    };
    char wstr[50] = {
        0,
    };
    char rstr[50] = {
        0,
    };

    fd = open(filename, O_RDWR | O_CREAT, OPEN_MODE);
    if (fd < 0) {
        fprintf(stderr, "open failed : %s\n", strerror(errno));
        return ret;
    }

    newfd = dup(fd);
    if (newfd < 0) {
        fprintf(stderr, "dup failed: %s\n", strerror(errno));
        result |= ret;
    }

    close(fd);

    strcpy(wstr, "This is my string\n");
    ret = write(newfd, wstr, strlen(wstr));
    if (ret <= 0) {
        fprintf(stderr, "write failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lseek(newfd, 0, SEEK_SET);
    if (ret < 0) {
        fprintf(stderr, "lseek failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = read(newfd, rstr, strlen(wstr));
    if (ret <= 0) {
        fprintf(stderr, "read failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = memcmp(rstr, wstr, strlen(wstr));
    if (ret != 0) {
        fprintf(stderr, "read returning junk\n");
        result |= ret;
    }

    ret = ftruncate(newfd, 0);
    if (ret < 0) {
        fprintf(stderr, "ftruncate failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fstat(newfd, &stbuf);
    if (ret < 0) {
        fprintf(stderr, "fstat failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fchmod(newfd, 0640);
    if (ret < 0) {
        fprintf(stderr, "fchmod failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fchown(newfd, 10001, 10001);
    if (ret < 0) {
        fprintf(stderr, "fchown failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fsync(newfd);
    if (ret < 0) {
        fprintf(stderr, "fsync failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fsetxattr(newfd, "trusted.xattr-test", "working", 8, 0);
    if (ret < 0) {
        fprintf(stderr, "fsetxattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fdatasync(newfd);
    if (ret < 0) {
        fprintf(stderr, "fdatasync failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = flistxattr(newfd, NULL, 0);
    if (ret <= 0) {
        fprintf(stderr, "flistxattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fgetxattr(newfd, "trusted.xattr-test", NULL, 0);
    if (ret <= 0) {
        fprintf(stderr, "fgetxattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    ret = fremovexattr(newfd, "trusted.xattr-test");
    if (ret < 0) {
        fprintf(stderr, "fremovexattr failed : %s\n", strerror(errno));
        result |= ret;
    }

    if (newfd)
        close(newfd);
    ret = unlink(filename);
    if (ret < 0) {
        fprintf(stderr, "unlink failed : %s\n", strerror(errno));
        result |= ret;
    }
    return result;
}

int
dir_based_fops(char *dirname)
{
    int ret = -1;
    int result = 0;
    DIR *dp = NULL;
    char buff[255] = {
        0,
    };
    struct dirent *dbuff = {
        0,
    };
    struct stat stbuff = {
        0,
    };
    char newdname[255] = {
        0,
    };
    char *cwd = NULL;

    ret = mkdir(dirname, 0755);
    if (ret < 0) {
        fprintf(stderr, "mkdir failed: %s\n", strerror(errno));
        return ret;
    }

    dp = opendir(dirname);
    if (dp == NULL) {
        fprintf(stderr, "opendir failed: %s\n", strerror(errno));
        result |= ret;
    }

    dbuff = readdir(dp);
    if (NULL == dbuff) {
        fprintf(stderr, "readdir failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = closedir(dp);
    if (ret < 0) {
        fprintf(stderr, "closedir failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = stat(dirname, &stbuff);
    if (ret < 0) {
        fprintf(stderr, "stat failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = chmod(dirname, 0744);
    if (ret < 0) {
        fprintf(stderr, "chmod failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = chown(dirname, 10001, 10001);
    if (ret < 0) {
        fprintf(stderr, "chmod failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = setxattr(dirname, "trusted.xattr-test", "working", 8, 0);
    if (ret < 0) {
        fprintf(stderr, "setxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = listxattr(dirname, NULL, 0);
    if (ret <= 0) {
        ret = -1;
        fprintf(stderr, "listxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = getxattr(dirname, "trusted.xattr-test", NULL, 0);
    if (ret <= 0) {
        ret = -1;
        fprintf(stderr, "getxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = removexattr(dirname, "trusted.xattr-test");
    if (ret < 0) {
        fprintf(stderr, "removexattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    strcpy(newdname, dirname);
    strcat(newdname, "/../");
    ret = chdir(newdname);
    if (ret < 0) {
        fprintf(stderr, "chdir failed: %s\n", strerror(errno));
        result |= ret;
    }

    cwd = getcwd(buff, 255);
    if (NULL == cwd) {
        fprintf(stderr, "getcwd failed: %s\n", strerror(errno));
        result |= ret;
    }

    strcpy(newdname, dirname);
    strcat(newdname, "new");
    ret = rename(dirname, newdname);
    if (ret < 0) {
        fprintf(stderr, "rename failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = rmdir(newdname);
    if (ret < 0) {
        fprintf(stderr, "rmdir failed: %s\n", strerror(errno));
        result |= ret;
    }

    rmdir(dirname);
    return result;
}

int
link_based_fops(char *filename)
{
    int ret = -1;
    int result = 0;
    int fd = 0;
    char newname[255] = {
        0,
    };
    char linkname[255] = {
        0,
    };
    struct stat lstbuf = {
        0,
    };

    fd = creat(filename, 0644);
    if (fd < 0) {
        fd = 0;
        fprintf(stderr, "creat failed: %s\n", strerror(errno));
        return ret;
    }

    strcpy(newname, filename);
    strcat(newname, "_hlink");
    ret = link(filename, newname);
    if (ret < 0) {
        fprintf(stderr, "link failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = unlink(filename);
    if (ret < 0) {
        fprintf(stderr, "unlink failed: %s\n", strerror(errno));
        result |= ret;
    }

    strcpy(linkname, filename);
    strcat(linkname, "_slink");
    ret = symlink(newname, linkname);
    if (ret < 0) {
        fprintf(stderr, "symlink failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lstat(linkname, &lstbuf);
    if (ret < 0) {
        fprintf(stderr, "lstbuf failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lchown(linkname, 10001, 10001);
    if (ret < 0) {
        fprintf(stderr, "lchown failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lsetxattr(linkname, "trusted.lxattr-test", "working", 8, 0);
    if (ret < 0) {
        fprintf(stderr, "lsetxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = llistxattr(linkname, NULL, 0);
    if (ret < 0) {
        ret = -1;
        fprintf(stderr, "llistxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lgetxattr(linkname, "trusted.lxattr-test", NULL, 0);
    if (ret < 0) {
        ret = -1;
        fprintf(stderr, "lgetxattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    ret = lremovexattr(linkname, "trusted.lxattr-test");
    if (ret < 0) {
        fprintf(stderr, "lremovexattr failed: %s\n", strerror(errno));
        result |= ret;
    }

    if (fd)
        close(fd);
    unlink(linkname);
    unlink(newname);
    return result;
}

int
test_open_modes(char *filename)
{
    int ret = -1;
    int result = 0;

    ret = generic_open_read_write(filename, O_CREAT | O_WRONLY, OPEN_MODE);
    if (ret != 0) {
        fprintf(stderr, "flag O_CREAT|O_WRONLY failed: \n");
        result |= ret;
    }

    ret = generic_open_read_write(filename, O_CREAT | O_RDWR, OPEN_MODE);
    if (ret != 0) {
        fprintf(stderr, "flag O_CREAT|O_RDWR failed\n");
        result |= ret;
    }

    ret = generic_open_read_write(filename, O_CREAT | O_RDONLY, OPEN_MODE);
    if (ret != 0) {
        fprintf(stderr, "flag O_CREAT|O_RDONLY failed\n");
        result |= ret;
    }

    ret = creat(filename, 0644);
    close(ret);
    ret = generic_open_read_write(filename, O_WRONLY, 0);
    if (ret != 0) {
        fprintf(stderr, "flag O_WRONLY failed\n");
        result |= ret;
    }

    ret = creat(filename, 0644);
    close(ret);
    ret = generic_open_read_write(filename, O_RDWR, 0);
    if (0 != ret) {
        fprintf(stderr, "flag O_RDWR failed\n");
        result |= ret;
    }

    ret = creat(filename, 0644);
    close(ret);
    ret = generic_open_read_write(filename, O_RDONLY, 0);
    if (0 != ret) {
        fprintf(stderr, "flag O_RDONLY failed\n");
        result |= ret;
    }

    ret = creat(filename, 0644);
    close(ret);
    ret = generic_open_read_write(filename, O_TRUNC | O_WRONLY, 0);
    if (0 != ret) {
        fprintf(stderr, "flag O_TRUNC|O_WRONLY failed\n");
        result |= ret;
    }

#if 0 /* undefined behaviour, unable to reliably test */
        ret = creat (filename, 0644);
        close (ret);
        ret = generic_open_read_write (filename, O_TRUNC|O_RDONLY, 0);
        if (0 != ret) {
               fprintf (stderr, "flag O_TRUNC|O_RDONLY failed\n");
               result |= ret;
        }
#endif

    ret = generic_open_read_write(filename, O_CREAT | O_RDWR | O_SYNC,
                                  OPEN_MODE);
    if (0 != ret) {
        fprintf(stderr, "flag O_CREAT|O_RDWR|O_SYNC failed\n");
        result |= ret;
    }

    ret = creat(filename, 0644);
    close(ret);
    ret = generic_open_read_write(filename, O_CREAT | O_EXCL, OPEN_MODE);
    if (0 != ret) {
        fprintf(stderr, "flag O_CREAT|O_EXCL failed\n");
        result |= ret;
    }

    return result;
}

int
generic_open_read_write(char *filename, int flag, mode_t mode)
{
    int fd = 0;
    int ret = -1;
    char wstring[50] = {
        0,
    };
    char rstring[50] = {
        0,
    };

    fd = open(filename, flag, mode);
    if (fd < 0) {
        if (flag == (O_CREAT | O_EXCL) && errno == EEXIST) {
            unlink(filename);
            return 0;
        } else {
            fprintf(stderr, "open failed: %s\n", strerror(errno));
            return -1;
        }
    }

    strcpy(wstring, "My string to write\n");
    ret = write(fd, wstring, strlen(wstring));
    if (ret <= 0) {
        if (errno != EBADF) {
            fprintf(stderr, "write failed: %s\n", strerror(errno));
            close(fd);
            unlink(filename);
            return ret;
        }
    }

    ret = lseek(fd, 0, SEEK_SET);
    if (ret < 0) {
        close(fd);
        unlink(filename);
        return ret;
    }

    ret = read(fd, rstring, strlen(wstring));
    if (ret < 0 && flag != (O_CREAT | O_WRONLY) && flag != O_WRONLY &&
        flag != (O_TRUNC | O_WRONLY)) {
        close(fd);
        unlink(filename);
        return ret;
    }

    /* Compare the rstring with wstring. But we do not want to return
     * error when the flag is either O_RDONLY, O_CREAT|O_RDONLY or
     * O_TRUNC|O_RDONLY. Because in that case we are not writing
     * anything to the file.*/

    ret = memcmp(wstring, rstring, strlen(wstring));
    if (0 != ret && flag != (O_TRUNC | O_WRONLY) && flag != O_WRONLY &&
        flag != (O_CREAT | O_WRONLY) &&
        !(flag == (O_CREAT | O_RDONLY) || flag == O_RDONLY ||
          flag == (O_TRUNC | O_RDONLY))) {
        fprintf(stderr, "read is returning junk\n");
        close(fd);
        unlink(filename);
        return ret;
    }

    close(fd);
    unlink(filename);
    return 0;
}