/* $NetBSD: mtab_file.c,v 1.1.1.3 2015/01/17 16:34:16 christos Exp $ */
/*
* Copyright (c) 1997-2014 Erez Zadok
* Copyright (c) 1990 Jan-Simon Pendry
* Copyright (c) 1990 Imperial College of Science, Technology & Medicine
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jan-Simon Pendry at Imperial College, London.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*
* File: am-utils/conf/mtab/mtab_file.c
*
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif /* HAVE_CONFIG_H */
#include <am_defs.h>
#include <amu.h>
#define NFILE_RETRIES 10 /* number of retries (seconds) */
#ifdef MOUNT_TABLE_ON_FILE
static FILE *mnt_file;
/*
* If the system is being trashed by something, then
* opening mtab may fail with ENFILE. So, go to sleep
* for a second and try again. (Yes - this has happened to me.)
*
* Note that this *may* block the automounter, oh well.
* If we get to this state then things are badly wrong anyway...
*
* Give the system 10 seconds to recover but then give up.
* Hopefully something else will exit and free up some file
* table slots in that time.
*/
# ifdef HAVE_FLOCK
# define lock(fd) (flock((fd), LOCK_EX))
# else /* not HAVE_FLOCK */
static int
lock(int fd)
{
int rc;
struct flock lk;
lk.l_type = F_WRLCK;
lk.l_whence = 0;
lk.l_start = 0;
lk.l_len = 0;
again:
rc = fcntl(fd, F_SETLKW, (caddr_t) & lk);
if (rc < 0 && (errno == EACCES || errno == EAGAIN)) {
# ifdef DEBUG
dlog("Blocked, trying to obtain exclusive mtab lock");
# endif /* DEBUG */
sleep(1);
goto again;
}
return rc;
}
# endif /* not HAVE_FLOCK */
static FILE *
open_locked_mtab(const char *mnttabname, char *mode, char *fs)
{
FILE *mfp = NULL;
/*
* There is a possible race condition if two processes enter
* this routine at the same time. One will be blocked by the
* exclusive lock below (or by the shared lock in setmntent)
* and by the time the second process has the exclusive lock
* it will be on the wrong underlying object. To check for this
* the mtab file is stat'ed before and after all the locking
* sequence, and if it is a different file then we assume that
* it may be the wrong file (only "may", since there is another
* race between the initial stat and the setmntent).
*
* Simpler solutions to this problem are invited...
*/
int racing = 2;
int rc;
int retries = 0;
struct stat st_before, st_after;
if (mnt_file) {
# ifdef DEBUG
dlog("Forced close on %s in read_mtab", mnttabname);
# endif /* DEBUG */
endmntent(mnt_file);
mnt_file = NULL;
}
again:
if (mfp) {
endmntent(mfp);
mfp = NULL;
}
if (stat(mnttabname, &st_before) < 0) {
plog(XLOG_ERROR, "%s: stat: %m", mnttabname);
if (errno == ESTALE) {
/* happens occasionally */
sleep(1);
goto again;
}
/*
* If 'mnttabname' file does not exist give setmntent() a
* chance to create it (depending on the mode).
* Otherwise, bail out.
*/
else if (errno != ENOENT) {
return 0;
}
}
eacces:
mfp = setmntent((char *)mnttabname, mode);
if (!mfp) {
/*
* Since setmntent locks the descriptor, it
* is possible it can fail... so retry if
* needed.
*/
if (errno == EACCES || errno == EAGAIN) {
# ifdef DEBUG
dlog("Blocked, trying to obtain exclusive mtab lock");
# endif /* DEBUG */
goto eacces;
} else if (errno == ENFILE && retries++ < NFILE_RETRIES) {
sleep(1);
goto eacces;
}
plog(XLOG_ERROR, "setmntent(\"%s\", \"%s\"): %m", mnttabname, mode);
return 0;
}
/*
* At this point we have an exclusive lock on the mount list,
* but it may be the wrong one so...
*/
/*
* Need to get an exclusive lock on the current
* mount table until we have a new copy written
* out, when the lock is released in free_mntlist.
* flock is good enough since the mount table is
* not shared between machines.
*/
do
rc = lock(fileno(mfp));
while (rc < 0 && errno == EINTR);
if (rc < 0) {
plog(XLOG_ERROR, "Couldn't lock %s: %m", mnttabname);
endmntent(mfp);
return 0;
}
/*
* Now check whether the mtab file has changed under our feet
*/
if (stat(mnttabname, &st_after) < 0) {
plog(XLOG_ERROR, "%s: stat: %m", mnttabname);
goto again;
}
if (st_before.st_dev != st_after.st_dev ||
st_before.st_ino != st_after.st_ino) {
struct timeval tv;
if (racing == 0) {
/* Sometimes print a warning */
plog(XLOG_WARNING,
"Possible mount table race - retrying %s", fs);
}
racing = (racing + 1) & 3;
/*
* Take a nap. From: Doug Kingston <dpk@morgan.com>
*/
tv.tv_sec = 0;
tv.tv_usec = (am_mypid & 0x07) << 17;
if (tv.tv_usec)
if (select(0, (voidp) 0, (voidp) 0, (voidp) 0, &tv) < 0)
plog(XLOG_WARNING, "mtab nap failed: %m");
goto again;
}
return mfp;
}
/*
* Unlock the mount table
*/
void
unlock_mntlist(void)
{
/*
* Release file lock, by closing the file
*/
if (mnt_file) {
dlog("unlock_mntlist: releasing");
endmntent(mnt_file);
mnt_file = NULL;
}
}
/*
* Write out a mount list
*/
void
rewrite_mtab(mntlist *mp, const char *mnttabname)
{
FILE *mfp;
int error = 0;
/*
* Concoct a temporary name in the same directory as the target mount
* table so that rename() will work.
*/
char tmpname[64];
int retries;
int tmpfd;
char *cp;
char mcp[128];
xstrlcpy(mcp, mnttabname, sizeof(mcp));
cp = strrchr(mcp, '/');
if (cp) {
memmove(tmpname, mcp, cp - mcp);
tmpname[cp - mcp] = '\0';
} else {
plog(XLOG_WARNING, "No '/' in mtab (%s), using \".\" as tmp directory", mnttabname);
tmpname[0] = '.';
tmpname[1] = '\0';
}
xstrlcat(tmpname, "/mtabXXXXXX", sizeof(tmpname));
retries = 0;
enfile1:
#ifdef HAVE_MKSTEMP
tmpfd = mkstemp(tmpname);
fchmod(tmpfd, 0644);
#else /* not HAVE_MKSTEMP */
mktemp(tmpname);
tmpfd = open(tmpname, O_RDWR | O_CREAT | O_TRUNC, 0644);
#endif /* not HAVE_MKSTEMP */
if (tmpfd < 0) {
if (errno == ENFILE && retries++ < NFILE_RETRIES) {
sleep(1);
goto enfile1;
}
plog(XLOG_ERROR, "%s: open: %m", tmpname);
return;
}
if (close(tmpfd) < 0)
plog(XLOG_ERROR, "Couldn't close tmp file descriptor: %m");
retries = 0;
enfile2:
mfp = setmntent(tmpname, "w");
if (!mfp) {
if (errno == ENFILE && retries++ < NFILE_RETRIES) {
sleep(1);
goto enfile2;
}
plog(XLOG_ERROR, "setmntent(\"%s\", \"w\"): %m", tmpname);
error = 1;
goto out;
}
while (mp) {
if (mp->mnt) {
if (addmntent(mfp, mp->mnt)) {
plog(XLOG_ERROR, "Can't write entry to %s", tmpname);
error = 1;
goto out;
}
}
mp = mp->mnext;
}
/*
* SunOS 4.1 manuals say that the return code from entmntent()
* is always 1 and to treat as a void. That means we need to
* call fflush() to make sure the new mtab file got written.
*/
if (fflush(mfp)) {
plog(XLOG_ERROR, "flush new mtab file: %m");
error = 1;
goto out;
}
(void) endmntent(mfp);
/*
* Rename temporary mtab to real mtab
*/
if (rename(tmpname, mnttabname) < 0) {
plog(XLOG_ERROR, "rename %s to %s: %m", tmpname, mnttabname);
error = 1;
goto out;
}
out:
if (error)
(void) unlink(tmpname);
}
static void
mtab_stripnl(char *s)
{
do {
s = strchr(s, '\n');
if (s)
*s++ = ' ';
} while (s);
}
/*
* Append a mntent structure to the
* current mount table.
*/
void
write_mntent(mntent_t *mp, const char *mnttabname)
{
int retries = 0;
FILE *mfp;
enfile:
mfp = open_locked_mtab(mnttabname, "a", mp->mnt_dir);
if (mfp) {
mtab_stripnl(mp->mnt_opts);
if (addmntent(mfp, mp))
plog(XLOG_ERROR, "Couldn't write %s: %m", mnttabname);
if (fflush(mfp))
plog(XLOG_ERROR, "Couldn't flush %s: %m", mnttabname);
(void) endmntent(mfp);
} else {
if (errno == ENFILE && retries < NFILE_RETRIES) {
sleep(1);
goto enfile;
}
plog(XLOG_ERROR, "setmntent(\"%s\", \"a\"): %m", mnttabname);
}
}
#endif /* MOUNT_TABLE_ON_FILE */
static mntent_t *
mnt_dup(mntent_t *mp)
{
mntent_t *new_mp = ALLOC(mntent_t);
new_mp->mnt_fsname = xstrdup(mp->mnt_fsname);
new_mp->mnt_dir = xstrdup(mp->mnt_dir);
new_mp->mnt_type = xstrdup(mp->mnt_type);
new_mp->mnt_opts = xstrdup(mp->mnt_opts);
new_mp->mnt_freq = mp->mnt_freq;
new_mp->mnt_passno = mp->mnt_passno;
#ifdef HAVE_MNTENT_T_MNT_TIME
# ifdef HAVE_MNTENT_T_MNT_TIME_STRING
new_mp->mnt_time = xstrdup(mp->mnt_time);
# else /* not HAVE_MNTENT_T_MNT_TIME_STRING */
new_mp->mnt_time = mp->mnt_time;
# endif /* not HAVE_MNTENT_T_MNT_TIME_STRING */
#endif /* HAVE_MNTENT_T_MNT_TIME */
#ifdef HAVE_MNTENT_T_MNT_CNODE
new_mp->mnt_cnode = mp->mnt_cnode;
#endif /* HAVE_MNTENT_T_MNT_CNODE */
return new_mp;
}
/*
* Read a mount table into memory
*/
mntlist *
read_mtab(char *fs, const char *mnttabname)
{
mntlist **mpp, *mhp;
mntent_t *mep;
FILE *mfp = open_locked_mtab(mnttabname, "r+", fs);
if (!mfp)
return 0;
mpp = &mhp;
/*
* XXX - In SunOS 4 there is (yet another) memory leak
* which loses 1K the first time getmntent is called.
* (jsp)
*/
while ((mep = getmntent(mfp))) {
/*
* Allocate a new slot
*/
*mpp = ALLOC(struct mntlist);
/*
* Copy the data returned by getmntent
*/
(*mpp)->mnt = mnt_dup(mep);
/*
* Move to next pointer
*/
mpp = &(*mpp)->mnext;
}
*mpp = NULL;
#ifdef MOUNT_TABLE_ON_FILE
/*
* If we are not updating the mount table then we
* can free the resources held here, otherwise they
* must be held until the mount table update is complete
*/
mnt_file = mfp;
#else /* not MOUNT_TABLE_ON_FILE */
endmntent(mfp);
#endif /* not MOUNT_TABLE_ON_FILE */
return mhp;
}