1 /*
2  * Copyright (c) 1998-2001 Sendmail, 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 
16 SM_RCSID("@(#)$Id: lockfile.c,v 8.21 2003/11/10 22:57:38 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 
36 bool
37 lockfile(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