1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* lib/krb5/os/lock_file.c */
4 * Copyright 1990, 1998 by the Massachusetts Institute of Technology.
7 * Export of this software from the United States of America may
8 * require a specific license from the United States Government.
9 * It is the responsibility of any person or organization contemplating
10 * export to obtain such a license before exporting.
12 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
13 * distribute this software and its documentation for any purpose and
14 * without fee is hereby granted, provided that the above copyright
15 * notice appear in all copies and that both that copyright notice and
16 * this permission notice appear in supporting documentation, and that
17 * the name of M.I.T. not be used in advertising or publicity pertaining
18 * to distribution of the software without specific, written prior
19 * permission. Furthermore if you modify this software you must label
20 * your software as modified software and not distribute it in such a
21 * fashion that it might be confused with the original M.I.T. software.
22 * M.I.T. makes no representations about the suitability of
23 * this software for any purpose. It is provided "as is" without express
24 * or implied warranty.
44 #if defined(HAVE_FCNTL_H) && defined(F_SETLKW) && defined(F_RDLCK)
45 #define POSIX_FILE_LOCKS
62 krb5_lock_file(krb5_context context, int fd, int mode)
65 krb5_error_code retval = 0;
66 #ifdef POSIX_FILE_LOCKS
67 int lock_cmd = F_SETLKW;
68 struct flock lock_arg = { 0 };
71 switch (mode & ~KRB5_LOCKMODE_DONTBLOCK) {
72 case KRB5_LOCKMODE_SHARED:
73 #ifdef POSIX_FILE_LOCKS
74 lock_arg.l_type = F_RDLCK;
78 case KRB5_LOCKMODE_EXCLUSIVE:
79 #ifdef POSIX_FILE_LOCKS
80 lock_arg.l_type = F_WRLCK;
84 case KRB5_LOCKMODE_UNLOCK:
85 #ifdef POSIX_FILE_LOCKS
86 lock_arg.l_type = F_UNLCK;
93 return(KRB5_LIBOS_BADLOCKFLAG);
95 if (mode & KRB5_LOCKMODE_DONTBLOCK) {
96 #ifdef POSIX_FILE_LOCKS
100 lock_flag |= LOCK_NB;
104 #ifdef POSIX_FILE_LOCKS
105 lock_arg.l_whence = 0;
106 lock_arg.l_start = 0;
108 if (fcntl(fd, lock_cmd, &lock_arg) == -1) {
109 if (errno == EACCES || errno == EAGAIN) /* see POSIX/IEEE 1003.1-1988,
112 if (errno != EINVAL) /* Fall back to flock if we get EINVAL */
116 return 0; /* We succeeded. Yay. */
120 if (flock(fd, lock_flag) == -1)
126 #else /* Windows or Macintosh */
129 krb5_lock_file(context, fd, mode)
130 krb5_context context;