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+/*++
+/* NAME
+/* master_proto 3
+/* SUMMARY
+/* Postfix master - status notification protocol
+/* SYNOPSIS
+/* #include <master_proto.h>
+/*
+/* int master_notify(pid, generation, status)
+/* int pid;
+/* unsigned generation;
+/* int status;
+/* DESCRIPTION
+/* The master process provides a standard environment for its
+/* child processes. Part of this environment is a pair of file
+/* descriptors that the master process shares with all child
+/* processes that provide the same service.
+/* .IP MASTER_LISTEN_FD
+/* The shared file descriptor for accepting client connection
+/* requests. The master process listens on this socket or FIFO
+/* when all child processes are busy.
+/* .IP MASTER_STATUS_FD
+/* The shared file descriptor for sending child status updates to
+/* the master process.
+/* .PP
+/* A child process uses master_notify() to send a status notification
+/* message to the master process.
+/* .IP MASTER_STAT_AVAIL
+/* The child process is ready to accept client connections.
+/* .IP MASTER_STAT_TAKEN
+/* Until further notice, the child process is unavailable for
+/* accepting client connections.
+/* .PP
+/* When a child process terminates without sending a status update,
+/* the master process will figure out that the child is no longer
+/* available.
+/* DIAGNOSTICS
+/* The result is -1 in case of problems. This usually means that
+/* the parent disconnected after a reload request, in order to
+/* force children to commit suicide.
+/* 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 <unistd.h>
+
+/* Utility library. */
+
+#include <msg.h>
+
+/* Global library. */
+
+#include "master_proto.h"
+
+int master_notify(int pid, unsigned generation, int status)
+{
+ const char *myname = "master_notify";
+ MASTER_STATUS stat;
+
+ /*
+ * We use a simple binary protocol to minimize security risks. Since this
+ * is local IPC, there are no byte order or word length issues. The
+ * server treats this information as gossip, so sending a bad PID or a
+ * bad status code will only have amusement value.
+ */
+ stat.pid = pid;
+ stat.gen = generation;
+ stat.avail = status;
+
+ if (write(MASTER_STATUS_FD, (void *) &stat, sizeof(stat)) != sizeof(stat)) {
+ if (msg_verbose)
+ msg_info("%s: status %d: %m", myname, status);
+ return (-1);
+ } else {
+ if (msg_verbose)
+ msg_info("%s: status %d", myname, status);
+ return (0);
+ }
+}