lockfile.c revision 266692 
1/*
2 * Copyright (c) 1998-2001 Proofpoint, Inc. and its suppliers.
3 *	All rights reserved.
4 * Copyright (c) 1983, 1995-1997 Eric P. Allman.  All rights reserved.
5 * Copyright (c) 1988, 1993
6 *	The Regents of the University of California.  All rights reserved.
7 *
8 * By using this file, you agree to the terms and conditions set
9 * forth in the LICENSE file which can be found at the top level of
10 * the sendmail distribution.
11 *
12 */
13
14#include <sendmail.h>
15
16SM_RCSID("@(#)$Id: lockfile.c,v 8.22 2013-11-22 20:51:50 ca Exp $")
17
18
19/*
20**  LOCKFILE -- lock a file using flock or (shudder) fcntl locking
21**
22**	Parameters:
23**		fd -- the file descriptor of the file.
24**		filename -- the file name (for error messages). [unused]
25**		ext -- the filename extension. [unused]
26**		type -- type of the lock.  Bits can be:
27**			LOCK_EX -- exclusive lock.
28**			LOCK_NB -- non-blocking.
29**			LOCK_UN -- unlock.
30**
31**	Returns:
32**		true if the lock was acquired.
33**		false otherwise.
34*/
35
36bool
37lockfile(fd, filename, ext, type)
38	int fd;
39	char *filename;
40	char *ext;
41	int type;
42{
43#if !HASFLOCK
44	int action;
45	struct flock lfd;
46
47	memset(&lfd, '\0', sizeof lfd);
48	if (bitset(LOCK_UN, type))
49		lfd.l_type = F_UNLCK;
50	else if (bitset(LOCK_EX, type))
51		lfd.l_type = F_WRLCK;
52	else
53		lfd.l_type = F_RDLCK;
54	if (bitset(LOCK_NB, type))
55		action = F_SETLK;
56	else
57		action = F_SETLKW;
58
59	if (fcntl(fd, action, &lfd) >= 0)
60		return true;
61
62	/*
63	**  On SunOS, if you are testing using -oQ/tmp/mqueue or
64	**  -oA/tmp/aliases or anything like that, and /tmp is mounted
65	**  as type "tmp" (that is, served from swap space), the
66	**  previous fcntl will fail with "Invalid argument" errors.
67	**  Since this is fairly common during testing, we will assume
68	**  that this indicates that the lock is successfully grabbed.
69	*/
70
71	if (errno == EINVAL)
72		return true;
73
74#else /* !HASFLOCK */
75
76	if (flock(fd, type) >= 0)
77		return true;
78
79#endif /* !HASFLOCK */
80
81	return false;
82}
83