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/* dotlock.c - dotfile locking
* Copyright (C) 1998 Free Software Foundation, Inc.
*
* This file is part of GNUPG.
*
* GNUPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GNUPG 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include <config.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <errno.h>
#include <unistd.h>
#include <sys/utsname.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "types.h"
#include "util.h"
#include "memory.h"
static int read_lockfile( const char *name );
/****************
* Create a lockfile with the given name. A TIMEOUT of 0
* returns immediately, -1 waits forever (hopefully not), other
* values are timeouts in milliseconds.
* Returns: a char pointer used as handle for release lock
* or NULL in case of an error.
*
* Notes: This function creates a lock file in the same directory
* as file_to_lock with the name "file_to_lock.lock"
* A temporary file ".#lk.<hostname>.pid[.threadid] is used.
* This function does nothing for Windoze.
*/
const char *
make_dotlock( const char *file_to_lock, long timeout )
{
int fd=-1, pid;
char pidstr[16];
const char *handle = NULL;
char *lockname = NULL;
char *tname = NULL;
int have_tfile = 0;
struct utsname uts;
const char *dirpart;
int dirpartlen;
sprintf( pidstr, "%10d\n", getpid() );
/* fixme: add the hostname to the second line (FQDN or IP addr?) */
/* create a temporary file */
#if SYS_NMLN < 8
#error Aiiih
#endif
if( uname( &uts ) )
strcpy( uts.nodename, "unknown" );
if( !(dirpart = strrchr( file_to_lock, '/' )) ) {
dirpart = ".";
dirpartlen = 1;
}
else {
dirpartlen = dirpart - file_to_lock;
dirpart = file_to_lock;
}
#ifdef _THREAD_SAFE
tname = m_alloc( dirpartlen + 6 + strlen(uts.nodename) + 11+ 20 );
sprintf( tname, "%.*s/.#lk.%s.%d.%p",
dirpartlen, dirpart, uts.nodename, getpid(), &pid );
#else
tname = m_alloc( dirpartlen + 6 + strlen(uts.nodename) + 11 );
sprintf( tname, "%.*s/.#lk.%s.%d",
dirpartlen, dirpart, uts.nodename, getpid() );
#endif
do {
errno = 0;
fd = open( tname, O_WRONLY|O_CREAT|O_EXCL,
S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
} while( fd == -1 && errno == EINTR );
if( fd == -1 ) {
log_error( "failed to create temporary file '%s': %s\n",
tname, strerror(errno));
goto leave;
}
have_tfile = 1;
if( write(fd, pidstr, 11 ) != 11 ) {
log_fatal( "error writing to '%s': %s\n", tname, strerror(errno) );
goto leave;
}
if( close(fd) ) {
log_error( "error closing '%s': %s\n", tname, strerror(errno));
goto leave;
}
fd = -1;
lockname = m_alloc( strlen(file_to_lock) + 6 );
strcpy(stpcpy(lockname, file_to_lock), ".lock");
retry:
if( !link(tname, lockname) ) {/* fixme: better use stat to check the link count */
handle = lockname;
lockname = NULL;
}
else if( errno == EEXIST ) {
if( (pid = read_lockfile(lockname)) == -1 ) {
if( errno == ENOENT ) {
log_info( "lockfile disappeared\n");
goto retry;
}
log_info("cannot read lockfile\n");
}
else if( pid == getpid() ) {
log_info( "Oops: lock already hold by us\n");
handle = lockname;
lockname = NULL;
}
#if 0 /* we should not do this without checking the permissions */
/* and the hostname */
else if( kill(pid, 0) && errno == ESRCH ) {
log_info( "removing stale lockfile (created by %d)", pid );
remove( lockname );
goto retry;
}
#endif
if( timeout == -1 ) {
struct timeval tv;
log_info( "waiting for lock (hold by %d) ...\n", pid );
/* can't use sleep, cause signals may be blocked */
tv.tv_sec = 1;
tv.tv_usec = 0;
select(0, NULL, NULL, NULL, &tv);
goto retry;
}
/* fixme: implement timeouts */
}
else
log_error( "lock not made: link() failed: %s\n", strerror(errno) );
leave:
if( fd != -1 )
close(fd);
if( have_tfile )
remove(tname);
m_free(tname);
m_free(lockname);
return handle;
}
/****************
* Create a lockfile for a existing file
* Returns: a char pointer used as handle for release lock
* or NULL in case of an error.
*
* Notes: This function creates a lock file in the same directory
* as file_to_lock with the name "lock.<inode-no>"
*
* int
* make_inodelock( const char *file_to_lock )
*
*/
/****************
* release a lock
* Returns: 0 := success
*/
int
release_dotlock( const char *lockfile )
{
int pid = read_lockfile( lockfile );
if( pid == -1 ) {
log_error( "release_dotlock: lockfile error");
return -1;
}
if( pid != getpid() ) {
log_error( "release_dotlock: not our lock (pid=%d)", pid);
return -1;
}
if( remove( lockfile ) ) {
log_error( "release_dotlock: error removing lockfile '%s'",
lockfile);
return -1;
}
m_free( (char*)lockfile );
return 0;
}
/****************
* Read the lock file and return the pid, returns -1 on error.
*/
static int
read_lockfile( const char *name )
{
int fd, pid;
char pidstr[16];
if( (fd = open(name, O_RDONLY)) == -1 ) {
int e = errno;
log_debug("error opening lockfile '%s': %s\n", name, strerror(errno) );
errno = e;
return -1;
}
if( read(fd, pidstr, 10 ) != 10 ) {
log_debug("error reading lockfile '%s'", name );
close(fd);
errno = 0;
return -1;
}
close(fd);
pid = atoi(pidstr);
if( !pid || pid == -1 ) {
log_error("invalid pid %d in lockfile '%s'", pid, name );
errno = 0;
return -1;
}
return pid;
}
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