1/*
2 * This program is free software; you can redistribute it and/or
3 * modify it under the terms of the GNU General Public License as
4 * published by the Free Software Foundation; either version 2 of
5 * the License, or (at your option) any later version.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
10 * GNU General Public License for more details.
11 *
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
15 * MA 02111-1307 USA
16 */
17/***************************************************************************
18 * LPRng - An Extended Print Spooler System
19 *
20 * Copyright 1988-2003, Patrick Powell, San Diego, CA
21 *     papowell@lprng.com
22 * See LICENSE for conditions of use.
23 *
24 ***************************************************************************/
25
26 static char *const _id =
27"$Id: lockfile.c,v 1.1.1.1 2008/10/15 03:28:27 james26_jang Exp $";
28
29/***************************************************************************
30 * MODULE: lockfile.c
31 * lock file manipulation procedures.
32 ***************************************************************************
33 * File Locking Routines:
34 * int Do_lock( int fd, int block );
35 *     fd - file descriptor
36 *     block - non-zero- block until lock
37 *     Returns: 0 - success
38 *             -1 - fail
39 ***************************************************************************
40 * Lock File Manipulation:
41 * Each active server has a lock file, which it uses to record its
42 * activity.  The lock file is created and then locked;
43 * the deamon will place its PID and an activity in the lock file.
44 *
45 * The struct lockfile{} gives the format of this file.
46 *
47 * Programs wanting to know the server status will read the file.
48 * Note:  only active servers, not status programs, will lock the file.
49 * This prevents a status program from locking out a server.
50 * The information in the lock file may be stale,  as the lock program
51 * may update the file without the knowledge of the checker.
52 * However, by making the file fixed size and small, we can read/write
53 * it with a single operation,  making the window of modification small.
54 ***************************************************************************/
55
56#include "lp.h"
57#include "lockfile.h"
58#include "fileopen.h"
59/**** ENDINCLUDE ****/
60
61#if defined(HAVE_SYS_TTYCOM_H)
62#include <sys/ttycom.h>
63#endif
64#if defined(HAVE_SYS_TTOLD_H) && !defined(IRIX)
65#include <sys/ttold.h>
66#endif
67#if defined(HAVE_SYS_IOCTL_H)
68#include <sys/ioctl.h>
69#endif
70
71
72/***************************************************************************
73 * Do_lock( fd , int block )
74 * does a lock on a file;
75 * if block is nonzero, block until file unlocked
76 * Returns: < 0 if lock fn failed
77 *            0 if successful
78 ***************************************************************************/
79
80int Do_lock( int fd, int block )
81{
82    int code = -2;
83
84	DEBUG3("Do_lock: fd %d, block '%d'", fd, block );
85
86#if defined(HAVE_FLOCK)
87	if( code == -2 ){
88		int err;
89		int how;
90
91		if( block ){
92			how = LOCK_EX;
93		} else {
94			how = LOCK_EX|LOCK_NB;
95		}
96
97		DEBUG3 ("Do_lock: using flock" );
98		code = flock( fd, how );
99		err = errno;
100		if( code < 0 ){
101			DEBUG1( "Do_lock: flock failed '%s'", Errormsg( err ));
102			code = -1;
103		} else {
104			code = 0;
105		}
106		errno = err;
107	}
108#endif
109#if defined(HAVE_LOCKF)
110	if( code == -2 ){
111		int err;
112		int how;
113
114		if( block ){
115			how = F_LOCK;
116		} else {
117			how = F_TLOCK;
118		}
119
120		DEBUG3 ("Do_lock: using lockf" );
121		code = lockf( fd, how, 0);
122		err = errno;
123		if( code < 0 ){
124			DEBUG1( "Do_lock: lockf failed '%s'", Errormsg( err));
125			code = -1;
126		} else {
127			code = 0;
128		}
129		errno = err;
130	}
131#endif
132#if defined(HAVE_FCNTL)
133	if( code == -2 ){
134		struct flock file_lock;
135		int err;
136		int how;
137		DEBUG3 ("Do_lock: using fcntl with SEEK_SET, block %d", block );
138
139		how = F_SETLK;
140		if( block ) how = F_SETLKW;
141
142		memset( &file_lock, 0, sizeof( file_lock ) );
143		file_lock.l_type = F_WRLCK;
144		file_lock.l_whence = SEEK_SET;
145		code = fcntl( fd, how, &file_lock);
146		err = errno;
147		if( code < 0 ){
148			code = -1;
149		} else {
150			code = 0;
151		}
152		DEBUG3 ("devlock_fcntl: status %d", code );
153		errno = err;
154	}
155#endif
156
157	DEBUG3 ("Do_lock: status %d", code);
158	return( code);
159}
160
161
162
163/***************************************************************************
164 * Do_unlock( fd )
165 * unlocks a lock on a file;
166 * Returns: < 0 if lock fn failed
167 *            0 if successful
168 ***************************************************************************/
169
170int Do_unlock( int fd )
171{
172    int code = -2;
173
174	DEBUG3("Do_unlock: fd %d", fd );
175
176#if defined(HAVE_FLOCK)
177	if( code == -2 ){
178		int err;
179		int how;
180
181		how = LOCK_EX|LOCK_UN;
182		DEBUG3 ("Do_unlock: using flock" );
183		code = flock( fd, how );
184		err = errno;
185		if( code < 0 ){
186			DEBUG1( "Do_unlock: flock failed '%s'", Errormsg( err ));
187			code = -1;
188		} else {
189			code = 0;
190		}
191		errno = err;
192	}
193#endif
194#if defined(HAVE_LOCKF)
195	if( code == -2 ){
196		int err;
197		int how;
198
199		how = F_ULOCK;
200
201		DEBUG3 ("Do_unlock: using lockf" );
202		code = lockf( fd, how, 0);
203		err = errno;
204		if( code < 0 ){
205			DEBUG1( "Do_unlock: lockf failed '%s'", Errormsg( err));
206			code = -1;
207		} else {
208			code = 0;
209		}
210		errno = err;
211	}
212#endif
213#if defined(HAVE_FCNTL)
214	if( code == -2 ){
215		struct flock file_lock;
216		int err;
217		int how;
218		DEBUG3 ("Do_unlock: using fcntl with SEEK_SET" );
219
220		how = F_SETLK;
221		memset( &file_lock, 0, sizeof( file_lock ) );
222		file_lock.l_type = F_UNLCK;
223		file_lock.l_whence = SEEK_SET;
224		code = fcntl( fd, how, &file_lock);
225		err = errno;
226		if( code < 0 ){
227			code = -1;
228		} else {
229			code = 0;
230		}
231		DEBUG3 ("devlock_fcntl: status %d", code );
232		errno = err;
233	}
234#endif
235
236	DEBUG3 ("Do_unlock: status %d", code);
237	return( code);
238}
239
240
241
242
243/***************************************************************************
244 * LockDevice(fd, block)
245 * Tries to lock the device file so that two or more queues can work on
246 * the same print device. First does a non-blocking lock, if this fails,
247 * puts a nice message in the status file and blocks in a second lock.
248 * (contributed by Michael Joosten <joost@cadlab.de>)
249 *
250 * Finally, you can set locking off (:lk@:)
251 *
252 * RETURNS: >= 0 if successful, < 0 if fails
253 ***************************************************************************/
254
255int LockDevice(int fd, int block )
256{
257	int lock = -1;
258	int err = errno;
259
260	DEBUG2 ("LockDevice: locking '%d'", fd );
261
262#if defined(TIOCEXCL) && !defined(HAVE_BROKEN_TIOCEXCL)
263	DEBUG2 ("LockDevice: TIOCEXL on '%d', isatty %d",
264		fd, isatty( fd ) );
265    if( isatty (fd) ){
266        /* use the TIOCEXCL ioctl. See termio(4). */
267		DEBUG2 ("LockDevice: TIOCEXL on '%d'", fd);
268        lock = ioctl( fd, TIOCEXCL, (void *) 0);
269		err = errno;
270        if( lock < 0) {
271			lock = -1;
272			LOGERR(LOG_INFO) "LockDevice: TIOCEXCL failed");
273		} else {
274			lock = 0;
275		}
276    }
277#endif
278	if( lock < 0 ){
279		lock = Do_lock( fd, block );
280	}
281
282	errno = err;
283	return( lock );
284}
285