160 lines
3.4 KiB
C
160 lines
3.4 KiB
C
/*++
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/* NAME
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/* dot_lockfile 3
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/* SUMMARY
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/* dotlock file management
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/* SYNOPSIS
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/* #include <dot_lockfile.h>
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/*
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/* int dot_lockfile(path, why)
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/* const char *path;
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/* VSTRING *why;
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/*
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/* void dot_unlockfile(path)
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/* const char *path;
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/* DESCRIPTION
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/* dot_lockfile() constructs a lock file name by appending ".lock" to
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/* \fIpath\fR and creates the named file exclusively. It tries several
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/* times and attempts to break stale locks. A negative result value
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/* means no lock file could be created.
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/*
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/* dot_unlockfile() attempts to remove the lock file created by
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/* dot_lockfile().
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/*
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/* Arguments:
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/* .IP path
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/* Name of the file to be locked or unlocked.
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/* .IP why
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/* A null pointer, or storage for the reason why a lock file could
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/* not be created.
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/* CONFIGURATION PARAMETERS
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/* deliver_lock_attempts, how many times to try to create a lock
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/* deliver_lock_delay, how long to wait between attempts
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/* stale_lock_time, when to break a stale lock
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/* LICENSE
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/* .ad
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/* .fi
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/* The Secure Mailer license must be distributed with this software.
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/* AUTHOR(S)
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/* Wietse Venema
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/* IBM T.J. Watson Research
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/* P.O. Box 704
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/* Yorktown Heights, NY 10598, USA
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/*--*/
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/* System library. */
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#include "sys_defs.h"
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#include <sys/stat.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <time.h>
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/* Utility library. */
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#include <vstring.h>
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#include <stringops.h>
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#include <mymalloc.h>
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/* Global library. */
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#include "mail_params.h"
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#include "dot_lockfile.h"
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/* dot_lockfile - create user.lock file */
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int dot_lockfile(const char *path, VSTRING *why)
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{
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char *lock_file;
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int count;
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struct stat st;
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int fd;
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int status = -1;
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lock_file = concatenate(path, ".lock", (char *) 0);
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for (count = 0; /* void */ ; count++) {
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if (count >= var_flock_tries)
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break;
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if (count > 0)
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sleep(var_flock_delay);
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/*
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* Attempt to create the lock. This code relies on O_EXCL | O_CREAT
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* to not follow symlinks.
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*/
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if ((fd = open(lock_file, O_WRONLY | O_EXCL | O_CREAT, 0)) >= 0) {
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close(fd);
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status = 0;
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break;
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}
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/*
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* We can deal only with "file exists" errors. Any other error means
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* we better give up trying.
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*/
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if (errno != EEXIST)
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break;
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/*
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* Break the lock when it is too old. Give up when we are unable to
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* remove a stale lock.
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*/
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if (stat(lock_file, &st) == 0)
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if (time((time_t *) 0) > st.st_ctime + var_flock_stale)
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if (unlink(lock_file) < 0)
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if (errno != ENOENT)
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break;
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errno = EEXIST;
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}
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if (status && why)
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vstring_sprintf(why, "unable to create lock file %s: %m", lock_file);
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myfree(lock_file);
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return (status);
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}
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/* dot_unlockfile - remove .lock file */
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void dot_unlockfile(const char *path)
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{
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char *lock_file;
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lock_file = concatenate(path, ".lock", (char *) 0);
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(void) unlink(lock_file);
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myfree(lock_file);
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}
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#ifdef TEST
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/*
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* Test program for setting a .lock file.
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*
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* Usage: dot_lockfile filename
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*
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* Creates filename.lock and removes it.
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*/
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#include <msg.h>
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#include <vstream.h>
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#include <msg_vstream.h>
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#include <mail_conf.h>
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main(int argc, char **argv)
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{
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VSTRING *why = vstring_alloc(100);
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msg_vstream_init(argv[0], VSTREAM_ERR);
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if (argc != 2)
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msg_fatal("usage: %s file-to-be-locked", argv[0]);
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mail_conf_read();
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if (dot_lockfile(argv[1], why) < 0)
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msg_fatal("%s", vstring_str(why));
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dot_unlockfile(argv[1]);
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vstring_free(why);
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return (0);
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}
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#endif
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