1 /* $NetBSD: mail_flow.c,v 1.1.1.2 2013/01/02 18:59:01 tron Exp $ */
2
3 /*++
4 /* NAME
5 /* mail_flow 3
6 /* SUMMARY
7 /* global mail flow control
8 /* SYNOPSIS
9 /* #include <mail_flow.h>
10 /*
11 /* ssize_t mail_flow_get(count)
12 /* ssize_t count;
13 /*
14 /* ssize_t mail_flow_put(count)
15 /* ssize_t count;
16 /*
17 /* ssize_t mail_flow_count()
18 /* DESCRIPTION
19 /* This module implements a simple flow control mechanism that
20 /* is based on tokens that are consumed by mail receiving processes
21 /* and that are produced by mail sending processes.
22 /*
23 /* mail_flow_get() attempts to read specified number of tokens. The
24 /* result is > 0 for success, < 0 for failure. In the latter case,
25 /* the process is expected to slow down a little.
26 /*
27 /* mail_flow_put() produces the specified number of tokens. The
28 /* token producing process is expected to produce new tokens
29 /* whenever it falls idle and no more tokens are available.
30 /*
31 /* mail_flow_count() returns the number of available tokens.
32 /* BUGS
33 /* The producer needs to wake up periodically to ensure that
34 /* tokens are not lost due to leakage.
35 /* LICENSE
36 /* .ad
37 /* .fi
38 /* The Secure Mailer license must be distributed with this software.
39 /* AUTHOR(S)
40 /* Wietse Venema
41 /* IBM T.J. Watson Research
42 /* P.O. Box 704
43 /* Yorktown Heights, NY 10598, USA
44 /*--*/
45
46 /* System library. */
47
48 #include <sys_defs.h>
49 #include <sys/stat.h>
50 #include <unistd.h>
51 #include <stdlib.h>
52 #include <string.h>
53
54 /* Utility library. */
55
56 #include <msg.h>
57 #include <iostuff.h>
58 #include <warn_stat.h>
59
60 /* Global library. */
61
62 #include <mail_flow.h>
63
64 /* Master library. */
65
66 #include <master_proto.h>
67
68 #define BUFFER_SIZE 1024
69
70 /* mail_flow_get - read N tokens */
71
mail_flow_get(ssize_t len)72 ssize_t mail_flow_get(ssize_t len)
73 {
74 const char *myname = "mail_flow_get";
75 char buf[BUFFER_SIZE];
76 struct stat st;
77 ssize_t count;
78 ssize_t n = 0;
79
80 /*
81 * Sanity check.
82 */
83 if (len <= 0)
84 msg_panic("%s: bad length %ld", myname, (long) len);
85
86 /*
87 * Silence some wild claims.
88 */
89 if (fstat(MASTER_FLOW_WRITE, &st) < 0)
90 msg_fatal("fstat flow pipe write descriptor: %m");
91
92 /*
93 * Read and discard N bytes. XXX AIX read() can return 0 when an open
94 * pipe is empty.
95 */
96 for (count = len; count > 0; count -= n)
97 if ((n = read(MASTER_FLOW_READ, buf, count > BUFFER_SIZE ?
98 BUFFER_SIZE : count)) <= 0)
99 return (-1);
100 if (msg_verbose)
101 msg_info("%s: %ld %ld", myname, (long) len, (long) (len - count));
102 return (len - count);
103 }
104
105 /* mail_flow_put - put N tokens */
106
mail_flow_put(ssize_t len)107 ssize_t mail_flow_put(ssize_t len)
108 {
109 const char *myname = "mail_flow_put";
110 char buf[BUFFER_SIZE];
111 ssize_t count;
112 ssize_t n = 0;
113
114 /*
115 * Sanity check.
116 */
117 if (len <= 0)
118 msg_panic("%s: bad length %ld", myname, (long) len);
119
120 /*
121 * Write or discard N bytes.
122 */
123 memset(buf, 0, len > BUFFER_SIZE ? BUFFER_SIZE : len);
124
125 for (count = len; count > 0; count -= n)
126 if ((n = write(MASTER_FLOW_WRITE, buf, count > BUFFER_SIZE ?
127 BUFFER_SIZE : count)) < 0)
128 return (-1);
129 if (msg_verbose)
130 msg_info("%s: %ld %ld", myname, (long) len, (long) (len - count));
131 return (len - count);
132 }
133
134 /* mail_flow_count - return number of available tokens */
135
mail_flow_count(void)136 ssize_t mail_flow_count(void)
137 {
138 const char *myname = "mail_flow_count";
139 ssize_t count;
140
141 if ((count = peekfd(MASTER_FLOW_READ)) < 0)
142 msg_warn("%s: %m", myname);
143 return (count);
144 }
145