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
deliver_flock(int fd,int lock_style,VSTRING * why)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