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+/*
+ * libEtPan! -- a mail stuff library
+ *
+ * Copyright (C) 2001, 2002 - DINH Viet Hoa
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the libEtPan! project nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * $Id $
+ */
+
+#include "maillock.h"
+
+#include "libetpan-config.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <time.h>
+#include <string.h>
+
+/* ********************************************************************** */
+
+/* lock primitives */
+
+/* the lock code is modified from the dot lock file code from mail.local.c */
+
+/*
+ SENDMAIL LICENSE
+
+The following license terms and conditions apply, unless a different
+license is obtained from Sendmail, Inc., 6425 Christie Ave, Fourth Floor,
+Emeryville, CA 94608, or by electronic mail at license@sendmail.com.
+
+License Terms:
+
+Use, Modification and Redistribution (including distribution of any
+modified or derived work) in source and binary forms is permitted only if
+each of the following conditions is met:
+
+1. Redistributions qualify as "freeware" or "Open Source Software" under
+ one of the following terms:
+
+ (a) Redistributions are made at no charge beyond the reasonable cost of
+ materials and delivery.
+
+ (b) Redistributions are accompanied by a copy of the Source Code or by an
+ irrevocable offer to provide a copy of the Source Code for up to three
+ years at the cost of materials and delivery. Such redistributions
+ must allow further use, modification, and redistribution of the Source
+ Code under substantially the same terms as this license. For the
+ purposes of redistribution "Source Code" means the complete compilable
+ and linkable source code of sendmail including all modifications.
+
+2. Redistributions of source code must retain the copyright notices as they
+ appear in each source code file, these license terms, and the
+ disclaimer/limitation of liability set forth as paragraph 6 below.
+
+3. Redistributions in binary form must reproduce the Copyright Notice,
+ these license terms, and the disclaimer/limitation of liability set
+ forth as paragraph 6 below, in the documentation and/or other materials
+ provided with the distribution. For the purposes of binary distribution
+ the "Copyright Notice" refers to the following language:
+ "Copyright (c) 1998-2002 Sendmail, Inc. All rights reserved."
+
+4. Neither the name of Sendmail, Inc. nor the University of California nor
+ the names of their contributors may be used to endorse or promote
+ products derived from this software without specific prior written
+ permission. The name "sendmail" is a trademark of Sendmail, Inc.
+
+5. All redistributions must comply with the conditions imposed by the
+ University of California on certain embedded code, whose copyright
+ notice and conditions for redistribution are as follows:
+
+ (a) Copyright (c) 1988, 1993 The Regents of the University of
+ California. All rights reserved.
+
+ (b) Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ (i) Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+
+ (ii) Redistributions in binary form must reproduce the above
+ copyright notice, this list of conditions and the following
+ disclaimer in the documentation and/or other materials provided
+ with the distribution.
+
+ (iii) Neither the name of the University nor the names of its
+ contributors may be used to endorse or promote products derived
+ from this software without specific prior written permission.
+
+6. Disclaimer/Limitation of Liability: THIS SOFTWARE IS PROVIDED BY
+ SENDMAIL, INC. AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
+ WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
+ NO EVENT SHALL SENDMAIL, INC., THE REGENTS OF THE UNIVERSITY OF
+ CALIFORNIA OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+*/
+
+/*
+ TODO : lock, prefer fcntl() over flock()
+ AND use dotlock code above
+*/
+
+#define LOCKTO_RM 300 /* timeout for stale lockfile removal */
+#define LOCKTO_GLOB 400 /* global timeout for lockfile creation */
+
+static int lock_common(const char * filename, int fd, short locktype)
+{
+ char lockfilename[PATH_MAX];
+ struct flock lock;
+ /* dot lock file */
+ int statfailed = 0;
+ time_t start;
+ int r;
+ int res;
+
+ lock.l_start = 0;
+ lock.l_len = 0;
+ lock.l_pid = getpid();
+ lock.l_type = locktype;
+ lock.l_whence = SEEK_SET;
+
+ r = fcntl(fd, F_SETLKW, &lock);
+ if (r < 0) {
+ /* WARNING POSIX lock could not be applied */
+ }
+
+ /* dot lock file */
+
+ if (strlen(filename) + 6 > PATH_MAX) {
+ res = -1;
+ goto unlock;
+ }
+
+ snprintf(lockfilename, PATH_MAX, "%s.lock", filename);
+
+ time(&start);
+ while (1) {
+ int fd;
+ struct stat st;
+ time_t now;
+
+ /* global timeout */
+ time(&now);
+ if (now > start + LOCKTO_GLOB) {
+ res = -1;
+ goto unlock;
+ }
+
+ fd = open(lockfilename, O_WRONLY|O_EXCL|O_CREAT, 0);
+ if (fd >= 0) {
+ /* defeat lock checking programs which test pid */
+ write(fd, "0", 2);
+ close(fd);
+ break;
+ }
+
+ /* libEtPan! - adds a delay of 5 seconds between each tries */
+ sleep(5);
+
+ if (stat(lockfilename, &st) < 0) {
+ if (statfailed++ > 5) {
+ res = -1;
+ goto unlock;
+ }
+ continue;
+ }
+ statfailed = 0;
+ time(&now);
+
+ if (now < st.st_ctime + LOCKTO_RM)
+ continue;
+
+ /* try to remove stale lockfile */
+ if (unlink(lockfilename) < 0) {
+ res = -1;
+ goto unlock;
+ }
+
+ /*
+ libEtPan! - removes this delay of 5 seconds,
+ maybe it was misplaced ?
+ */
+#if 0
+ sleep(5);
+#endif
+ }
+
+ return 0;
+
+ unlock:
+ lock.l_start = 0;
+ lock.l_len = 0;
+ lock.l_pid = getpid();
+ lock.l_type = F_UNLCK;
+ lock.l_whence = SEEK_SET;
+
+ r = fcntl(fd, F_SETLK, &lock);
+ if (r < 0) {
+ /* WARNING POSIX lock could not be applied */
+ }
+ err:
+ return res;
+}
+
+static int unlock_common(const char * filename, int fd)
+{
+ char lockfilename[PATH_MAX];
+ struct flock lock;
+ int r;
+
+ if (strlen(filename) + 6 > PATH_MAX)
+ return -1;
+
+ snprintf(lockfilename, PATH_MAX, "%s.lock", filename);
+
+ unlink(lockfilename);
+
+ lock.l_start = 0;
+ lock.l_len = 0;
+ lock.l_pid = getpid();
+ lock.l_type = F_UNLCK;
+ lock.l_whence = SEEK_SET;
+
+ r = fcntl(fd, F_SETLK, &lock);
+ if (r < 0) {
+ /* WARNING POSIX lock could not be applied */
+ }
+
+ return 0;
+}
+
+int maillock_read_lock(const char * filename, int fd)
+{
+ return lock_common(filename, fd, F_RDLCK);
+}
+
+int maillock_read_unlock(const char * filename, int fd)
+{
+ return unlock_common(filename, fd);
+}
+
+int maillock_write_lock(const char * filename, int fd)
+{
+ return lock_common(filename, fd, F_WRLCK);
+}
+
+int maillock_write_unlock(const char * filename, int fd)
+{
+ return unlock_common(filename, fd);
+}