1 files changed, 142 insertions, 0 deletions
diff --git a/src/master/mail_flow.c b/src/master/mail_flow.c
new file mode 100644
index 0000000..2958500
--- /dev/null
+++ b/src/master/mail_flow.c
@@ -0,0 +1,142 @@
+/*++
+/* NAME
+/*	mail_flow 3
+/* SUMMARY
+/*	global mail flow control
+/* SYNOPSIS
+/*	#include <mail_flow.h>
+/*
+/*	ssize_t	mail_flow_get(count)
+/*	ssize_t	count;
+/*
+/*	ssize_t	mail_flow_put(count)
+/*	ssize_t	count;
+/*
+/*	ssize_t	mail_flow_count()
+/* DESCRIPTION
+/*	This module implements a simple flow control mechanism that
+/*	is based on tokens that are consumed by mail receiving processes
+/*	and that are produced by mail sending processes.
+/*
+/*	mail_flow_get() attempts to read specified number of tokens. The
+/*	result is > 0 for success, < 0 for failure. In the latter case,
+/*	the process is expected to slow down a little.
+/*
+/*	mail_flow_put() produces the specified number of tokens. The
+/*	token producing process is expected to produce new tokens
+/*	whenever it falls idle and no more tokens are available.
+/*
+/*	mail_flow_count() returns the number of available tokens.
+/* BUGS
+/*	The producer needs to wake up periodically to ensure that
+/*	tokens are not lost due to leakage.
+/* LICENSE
+/* .ad
+/* .fi
+/*	The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/*	Wietse Venema
+/*	IBM T.J. Watson Research
+/*	P.O. Box 704
+/*	Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <iostuff.h>
+#include <warn_stat.h>
+
+/* Global library. */
+
+#include <mail_flow.h>
+
+/* Master library. */
+
+#include <master_proto.h>
+
+#define BUFFER_SIZE	1024
+
+/* mail_flow_get - read N tokens */
+
+ssize_t mail_flow_get(ssize_t len)
+{
+    const char *myname = "mail_flow_get";
+    char    buf[BUFFER_SIZE];
+    struct stat st;
+    ssize_t count;
+    ssize_t n = 0;
+
+    /*
+     * Sanity check.
+     */
+    if (len <= 0)
+	msg_panic("%s: bad length %ld", myname, (long) len);
+
+    /*
+     * Silence some wild claims.
+     */
+    if (fstat(MASTER_FLOW_WRITE, &st) < 0)
+	msg_fatal("fstat flow pipe write descriptor: %m");
+
+    /*
+     * Read and discard N bytes. XXX AIX read() can return 0 when an open
+     * pipe is empty.
+     */
+    for (count = len; count > 0; count -= n)
+	if ((n = read(MASTER_FLOW_READ, buf, count > BUFFER_SIZE ?
+		      BUFFER_SIZE : count)) <= 0)
+	    return (-1);
+    if (msg_verbose)
+	msg_info("%s: %ld %ld", myname, (long) len, (long) (len - count));
+    return (len - count);
+}
+
+/* mail_flow_put - put N tokens */
+
+ssize_t mail_flow_put(ssize_t len)
+{
+    const char *myname = "mail_flow_put";
+    char    buf[BUFFER_SIZE];
+    ssize_t count;
+    ssize_t n = 0;
+
+    /*
+     * Sanity check.
+     */
+    if (len <= 0)
+	msg_panic("%s: bad length %ld", myname, (long) len);
+
+    /*
+     * Write or discard N bytes.
+     */
+    memset(buf, 0, len > BUFFER_SIZE ? BUFFER_SIZE : len);
+
+    for (count = len; count > 0; count -= n)
+	if ((n = write(MASTER_FLOW_WRITE, buf, count > BUFFER_SIZE ?
+		       BUFFER_SIZE : count)) < 0)
+	    return (-1);
+    if (msg_verbose)
+	msg_info("%s: %ld %ld", myname, (long) len, (long) (len - count));
+    return (len - count);
+}
+
+/* mail_flow_count - return number of available tokens */
+
+ssize_t mail_flow_count(void)
+{
+    const char *myname = "mail_flow_count";
+    ssize_t count;
+
+    if ((count = peekfd(MASTER_FLOW_READ)) < 0)
+	msg_warn("%s: %m", myname);
+    return (count);
+}