OpenBSD-4.6/usr.sbin/amd/config/mtab_file.c
/*
* Copyright (c) 1990 Jan-Simon Pendry
* Copyright (c) 1990 Imperial College of Science, Technology & Medicine
* Copyright (c) 1990, 1993
* 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.
*
* from: @(#)mtab_file.c 8.1 (Berkeley) 6/6/93
* $Id: mtab_file.c,v 1.4 2003/06/02 23:36:52 millert Exp $
*/
#include "am.h"
#ifdef READ_MTAB_FROM_FILE
#ifdef USE_FCNTL
#include <fcntl.h>
#else
#include <sys/file.h>
#endif /* USE_FCNTL */
#ifdef UPDATE_MTAB
/*
* Do strict /etc/mtab locking
*/
#define MTAB_LOCKING
/*
* Firewall mtab entries
*/
#define MTAB_STRIPNL
#include <sys/stat.h>
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.
*/
#define NFILE_RETRIES 10 /* seconds */
#ifdef MTAB_LOCKING
#ifdef LOCK_FCNTL
static int lock(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;
}
#else
#define lock(fd) (flock((fd), LOCK_EX))
#endif /* LOCK_FCNTL */
#endif /* MTAB_LOCKING */
static FILE *open_locked_mtab(mtab_file, mode, fs)
char *mtab_file;
char *mode;
char *fs;
{
FILE *mfp = 0;
#ifdef UPDATE_MTAB
/*
* 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;
#ifdef MTAB_LOCKING
int rc;
int retries = 0;
struct stat st_before, st_after;
#endif /* MTAB_LOCKING */
if (mnt_file) {
#ifdef DEBUG
dlog("Forced close on %s in read_mtab", mtab_file);
#endif /* DEBUG */
endmntent(mnt_file);
mnt_file = 0;
}
#ifdef MTAB_LOCKING
again:
if (mfp) {
endmntent(mfp);
mfp = 0;
}
clock_valid = 0;
if (stat(mtab_file, &st_before) < 0) {
plog(XLOG_ERROR, "%s: stat: %m", mtab_file);
if (errno == ESTALE) {
/* happens occasionally */
sleep(1);
goto again;
}
return 0;
}
#endif /* MTAB_LOCKING */
#endif /* UPDATE_MTAB */
eacces:
mfp = setmntent(mtab_file, 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", mtab_file, mode);
return 0;
}
#ifdef MTAB_LOCKING
#ifdef UPDATE_MTAB
/*
* 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", mtab_file);
endmntent(mfp);
return 0;
}
/*
* Now check whether the mtab file has changed under our feet
*/
if (stat(mtab_file, &st_after) < 0) {
plog(XLOG_ERROR, "%s: stat", mtab_file);
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 = (mypid & 0x07) << 17;
if (tv.tv_usec)
if (select(0, (void *)0, (void *)0, (void *)0, &tv) < 0)
plog(XLOG_WARNING, "mtab nap failed: %m");
goto again;
}
#endif /* UPDATE_MTAB */
#endif /* MTAB_LOCKING */
return mfp;
}
/*
* Unlock the mount table
*/
void unlock_mntlist P((void));
void unlock_mntlist()
{
/*
* Release file lock, by closing the file
*/
if (mnt_file) {
endmntent(mnt_file);
mnt_file = 0;
}
}
/*
* Write out a mount list
*/
void rewrite_mtab(mp)
mntlist *mp;
{
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 = mtab;
cp = strrchr(mcp, '/');
if (cp) {
bcopy(mcp, tmpname, cp - mcp);
tmpname[cp-mcp] = '\0';
} else {
plog(XLOG_WARNING, "No '/' in mtab (%s), using \".\" as tmp directory", mtab);
tmpname[0] = '.'; tmpname[1] = '\0';
}
strlcat(tmpname, "/mtabXXXXXX", sizeof(tmpname));
mktemp(tmpname);
retries = 0;
enfile1:
if ((tmpfd = open(tmpname, O_RDWR|O_CREAT|O_TRUNC, 0644)) < 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, mtab) < 0) {
plog(XLOG_ERROR, "rename %s to %s: %m", tmpname, mtab);
error = 1;
goto out;
}
out:
if (error)
(void) unlink(tmpname);
}
#ifdef MTAB_STRIPNL
static void mtab_stripnl(s)
char *s;
{
do {
s = strchr(s, '\n');
if (s)
*s++ = ' ';
} while (s);
}
#endif /* MTAB_STRIPNL */
/*
* Append a mntent structure to the
* current mount table.
*/
void write_mntent(mp)
struct mntent *mp;
{
int retries = 0;
FILE *mfp;
enfile:
mfp = open_locked_mtab(mtab, "a", mp->mnt_dir);
if (mfp) {
#ifdef MTAB_STRIPNL
mtab_stripnl(mp->mnt_opts);
#endif /* MTAB_STRIPNL */
if (addmntent(mfp, mp))
plog(XLOG_ERROR, "Couldn't write %s: %m", mtab);
if (fflush(mfp))
plog(XLOG_ERROR, "Couldn't flush %s: %m", mtab);
(void) endmntent(mfp);
} else {
if (errno == ENFILE && retries < NFILE_RETRIES) {
sleep(1);
goto enfile;
}
plog(XLOG_ERROR, "setmntent(\"%s\", \"a\"): %m", mtab);
}
}
#endif /* UPDATE_MTAB */
static struct mntent *mnt_dup(mp)
struct mntent *mp;
{
struct mntent *new_mp = ALLOC(mntent);
new_mp->mnt_fsname = strdup(mp->mnt_fsname);
new_mp->mnt_dir = strdup(mp->mnt_dir);
new_mp->mnt_type = strdup(mp->mnt_type);
new_mp->mnt_opts = strdup(mp->mnt_opts);
new_mp->mnt_freq = mp->mnt_freq;
new_mp->mnt_passno = mp->mnt_passno;
#ifdef FIXUP_MNTENT_DUP
/*
* Additional fields get dup'ed here
*/
FIXUP_MNTENT_DUP(new_mp, mp);
#endif
return new_mp;
}
/*
* Read a mount table into memory
*/
mntlist *read_mtab(fs)
char *fs;
{
mntlist **mpp, *mhp;
struct mntent *mep;
FILE *mfp = open_locked_mtab(mtab, "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(mntlist);
/*
* Copy the data returned by getmntent
*/
(*mpp)->mnt = mnt_dup(mep);
/*
* Move to next pointer
*/
mpp = &(*mpp)->mnext;
}
*mpp = 0;
#ifdef UPDATE_MTAB
/*
* 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
endmntent(mfp);
#endif /* UPDATE_MTAB */
return mhp;
}
#endif /* READ_MTAB_FROM_FILE */