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      1 /*	$NetBSD: deliver_flock.c,v 1.1.1.1 2009/06/23 10:08:45 tron Exp $	*/
      2 
      3 /*++
      4 /* NAME
      5 /*	deliver_flock 3
      6 /* SUMMARY
      7 /*	lock open file for mail delivery
      8 /* SYNOPSIS
      9 /*	#include <deliver_flock.h>
     10 /*
     11 /*	int	deliver_flock(fd, lock_style, why)
     12 /*	int	fd;
     13 /*	int	lock_style;
     14 /*	VSTRING	*why;
     15 /* DESCRIPTION
     16 /*	deliver_flock() sets one exclusive kernel lock on an open file,
     17 /*	for example in order to deliver mail.
     18 /*	It performs several non-blocking attempts to acquire an exclusive
     19 /*	lock before giving up.
     20 /*
     21 /*	Arguments:
     22 /* .IP fd
     23 /*	A file descriptor that is associated with an open file.
     24 /* .IP lock_style
     25 /*	A locking style defined in myflock(3).
     26 /* .IP why
     27 /*	A null pointer, or storage for diagnostics.
     28 /* DIAGNOSTICS
     29 /*	deliver_flock() returns -1 in case of problems, 0 in case
     30 /*	of success. The reason for failure is returned via the \fIwhy\fR
     31 /*	parameter.
     32 /* CONFIGURATION PARAMETERS
     33 /*	deliver_lock_attempts, number of locking attempts
     34 /*	deliver_lock_delay, time in seconds between attempts
     35 /*	sun_mailtool_compatibility, disable kernel locking
     36 /* LICENSE
     37 /* .ad
     38 /* .fi
     39 /*	The Secure Mailer license must be distributed with this software.
     40 /* AUTHOR(S)
     41 /*	Wietse Venema
     42 /*	IBM T.J. Watson Research
     43 /*	P.O. Box 704
     44 /*	Yorktown Heights, NY 10598, USA
     45 /*--*/
     46 
     47 /* System library. */
     48 
     49 #include "sys_defs.h"
     50 #include <unistd.h>
     51 
     52 /* Utility library. */
     53 
     54 #include <vstring.h>
     55 #include <myflock.h>
     56 #include <iostuff.h>
     57 
     58 /* Global library. */
     59 
     60 #include "mail_params.h"
     61 #include "deliver_flock.h"
     62 
     63 /* Application-specific. */
     64 
     65 #define MILLION	1000000
     66 
     67 /* deliver_flock - lock open file for mail delivery */
     68 
     69 int     deliver_flock(int fd, int lock_style, VSTRING *why)
     70 {
     71     int     i;
     72 
     73     for (i = 1; /* void */ ; i++) {
     74 	if (myflock(fd, lock_style,
     75 		    MYFLOCK_OP_EXCLUSIVE | MYFLOCK_OP_NOWAIT) == 0)
     76 	    return (0);
     77 	if (i >= var_flock_tries)
     78 	    break;
     79 	rand_sleep(var_flock_delay * MILLION, var_flock_delay * MILLION / 2);
     80     }
     81     if (why)
     82 	vstring_sprintf(why, "unable to lock for exclusive access: %m");
     83     return (-1);
     84 }
     85