master_proto.c

[詳解]

/*++
/* 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);
    }
}