libvirt/tests/virfilemock.c

/*
 * Copyright (C) 2018 Red Hat, Inc.
 *
 * This library 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.
 *
 * This library 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 this library.  If not, see
 * <http://www.gnu.org/licenses/>.
 */

#include <config.h>

#include <stdio.h>
#include <mntent.h>
#include <sys/vfs.h>
#include <unistd.h>
#ifdef __linux__
# include <linux/magic.h>
#endif

#include "virmock.h"

#define VIR_FROM_THIS VIR_FROM_NONE

static FILE *(*real_setmntent)(const char *filename, const char *type);
static int (*real_statfs)(const char *path, struct statfs *buf);
static char *(*real_realpath)(const char *path, char *resolved);
static int (*real_access)(const char *path, int mode);


static void
init_syms(void)
{
    if (real_setmntent)
        return;

    VIR_MOCK_REAL_INIT(setmntent);
    VIR_MOCK_REAL_INIT(statfs);
    VIR_MOCK_REAL_INIT(realpath);
    VIR_MOCK_REAL_INIT(access);
}


FILE *
setmntent(const char *filename, const char *type)
{
    const char *mtab;

    init_syms();

    if ((mtab = g_getenv("LIBVIRT_MTAB")))
        filename = mtab;

    return real_setmntent(filename, type);
}


#ifndef NFS_SUPER_MAGIC
# define NFS_SUPER_MAGIC 0x6969
#endif
#ifndef OCFS2_SUPER_MAGIC
# define OCFS2_SUPER_MAGIC 0x7461636f
#endif
#ifndef GFS2_MAGIC
# define GFS2_MAGIC 0x01161970
#endif
#ifndef AFS_FS_MAGIC
# define AFS_FS_MAGIC 0x6B414653
#endif
#ifndef SMB_SUPER_MAGIC
# define SMB_SUPER_MAGIC 0x517B
#endif
#ifndef CIFS_SUPER_MAGIC
# define CIFS_SUPER_MAGIC 0xFF534D42
#endif
#ifndef HUGETLBFS_MAGIC
# define HUGETLBFS_MAGIC 0x958458f6
#endif
#ifndef FUSE_SUPER_MAGIC
# define FUSE_SUPER_MAGIC 0x65735546
#endif
#ifndef CEPH_SUPER_MAGIC
# define CEPH_SUPER_MAGIC 0x00c36400
#endif
#ifndef GPFS_SUPER_MAGIC
# define GPFS_SUPER_MAGIC 0x47504653
#endif
#ifndef QB_MAGIC
# define QB_MAGIC 0x51626d6e
#endif


static int
statfs_mock(const char *mtab,
            const char *path,
            struct statfs *buf)
{
    FILE *f;
    struct mntent mb;
    char mntbuf[1024];
    g_autofree char *canonPath = NULL;
    int ret = -1;

    if (!(f = real_setmntent(mtab, "r"))) {
        fprintf(stderr, "Unable to open %s", mtab);
        return -1;
    }

    /* We don't need to do this in callers because real statfs(2)
     * does that for us. However, in mocked implementation we
     * need to do this. */
    if (!(canonPath = realpath(path, NULL)))
        return -1;

    while (getmntent_r(f, &mb, mntbuf, sizeof(mntbuf))) {
        int ftype;

        if (STRNEQ(mb.mnt_dir, canonPath))
            continue;

        if (STREQ(mb.mnt_type, "nfs") ||
            STREQ(mb.mnt_type, "nfs4")) {
            ftype = NFS_SUPER_MAGIC;
        } else if (STREQ(mb.mnt_type, "gfs2")||
                   STREQ(mb.mnt_type, "gfs2meta")) {
            ftype = GFS2_MAGIC;
        } else if (STREQ(mb.mnt_type, "ocfs2")) {
            ftype = OCFS2_SUPER_MAGIC;
        } else if (STREQ(mb.mnt_type, "afs")) {
            ftype = AFS_FS_MAGIC;
        } else if (STREQ(mb.mnt_type, "smb3")) {
            ftype = SMB_SUPER_MAGIC;
        } else if (STREQ(mb.mnt_type, "cifs")) {
            ftype = CIFS_SUPER_MAGIC;
        } else if (STRPREFIX(mb.mnt_type, "fuse")) {
            ftype = FUSE_SUPER_MAGIC;
        } else if (STRPREFIX(mb.mnt_type, "ceph")) {
            ftype = CEPH_SUPER_MAGIC;
        } else if (STRPREFIX(mb.mnt_type, "gpfs")) {
            ftype = GPFS_SUPER_MAGIC;
        } else {
            /* Everything else is EXT4. We don't care really for other paths. */
            ftype = EXT4_SUPER_MAGIC;
        }

        memset(buf, 0, sizeof(*buf));
        /* We only care about f_type so far. */
        buf->f_type = ftype;
        ret = 0;
        break;
    }

    endmntent(f);
    return ret;
}


int
statfs(const char *path, struct statfs *buf)
{
    const char *mtab;

    init_syms();

    if ((mtab = g_getenv("LIBVIRT_MTAB")))
        return statfs_mock(mtab, path, buf);

    return real_statfs(path, buf);
}


char *
realpath(const char *path, char *resolved)
{

    init_syms();

    if (g_getenv("LIBVIRT_MTAB")) {
        const char *p;

        if ((p = STRSKIP(path, "/some/symlink"))) {
            if (resolved)
                g_snprintf(resolved, PATH_MAX, "/gluster%s", p);
            else
                resolved = g_strdup_printf("/gluster%s", p);
        } else {
            if (resolved)
                g_strlcpy(resolved, path, PATH_MAX);
            else
                resolved = g_strdup(path);
        }

        return resolved;
    }

    return real_realpath(path, resolved);
}


int
access(const char *path, int mode)
{
    const char *mtab = g_getenv("LIBVIRT_MTAB");

    init_syms();

    if (mtab && mode == F_OK) {
        struct statfs buf;

        /* The real statfs works on any existing file on a filesystem, while
         * our mocked version only works on the mount point. Thus we have to
         * pretend no files on the filesystem exist to make sure
         * virFileGetExistingParent returns the mount point which can later be
         * checked by statfs. Instead of checking we were called for a mount
         * point by walking through the mtab, we just call our mocked statfs
         * that does it for us.
         */
        return statfs_mock(mtab, path, &buf);
    }

    return real_access(path, mode);
}