laserwriter, MDQS, communication problems

[Susan Richter]

I am having a strange problem with my LaserWriter server under MDQS.
The behavior I see is this:  whenever the daemon is started up during boot
(in /etc/rc.local), my status- and page-accounting stuff fails because
the "listener" child (which is trying to listen on a dup of stdout,
attached to the device) can't hear anything.  When I use the exact same
startup routine but do it myself from a tty, everything works fine.

Now, here is what actually happens (describing the case of starting from boot):

The mdqsdaemon starts and goes through its init procedure, which:
    forks a child and the parent suicides, thereby detaching the daemon;
    closes all file descriptors greater than 2;
    doesn't do anything to fds 0, 1, or 2.

When a request needs to be done, the daemon:
    opens the device (in this case, the laserwriter, which is on a tty line
        and has permissions 666)  *for reading and writing*  (this succeeds);
    dups that to fd 1;
        (I put in an fcntl() call to check the mode of fd 1, and already
        at this point it says it's only open for writing!  How can this be?)
    forks/execs the server, which:
        dups fd 1, for listening to the LaserWriter's status reports;
        forks a child to do the listening:
            child tries to fdopen it for reading, fails, and returns. . .
        the printing goes fine, server returns.
     

Again, when the daemon is killed and restarted by hand, this all works
fine.  The only difference I can see is that when it's started from boot,
it runs not attached to a terminal (ps shows "?"), and when I start it
by hand, it shows attached to my tty.

Here's the fragment of rc.local that starts it up, and I use the same
script to start it by hand, using "sh script" while su'd to root:

-------------------------------------------------------------------------
if [ -d /usr/local/lib/mdqs ]; then
        rm -f /usr/spool/mdqs/qtmp/*
        date >> /usr/spool/mdqs/LOGFILE
        /usr/local/lib/mdqs/mdqsdaemon >> /usr/spool/mdqs/LOGFILE 2>&1 &
        (cd /usr/local/lib/mdqs; \
                netdae -n 4 /usr/local/lib/mdqs/netrecv >> /usr/spool/mdqs/LOGFILE 2>&1) &
        /usr/local/clearlw /dev/lw2
        echo -n ' mdqs'                                         >/dev/console
fi
-------------------------------------------------------------------------
Any help or suggestions will certainly be appreciated!
     
                        - Susan Richter
                        richter at rand-unix.ARPA
                        ...!decvax!philabs!ttidca!randvax!richter
                        ...!ihnp4!wlbr!trwrb!randvax!richter

>From postnews Wed Feb  5 12:07:17 1986
Subject: laserwriter, MDQS, communication problems
Newsgroups: mod.computers.laser-printers,net.unix-wizards
Distribution: net


I am having yet another problem with my LaserWriter server under MDQS.
The behavior I see is this:  whenever the daemon is started up during boot
(in /etc/rc.local), my status- and page-accounting stuff fails because
the "listener" child (which is trying to listen on a dup of stdout,
attached to the device) can't hear anything.  When I use the exact same
startup routine but do it myself from a tty, everything works fine.

Now, here is what actually happens (describing the case of starting from boot):

The mdqsdaemon starts and goes through its init procedure, which:
    forks a child and the parent suicides, thereby detaching the daemon;
    closes all file descriptors greater than 2;
    doesn't do anything to fds 0, 1, or 2.

When a request needs to be done, the daemon:
    opens the device (in this case, the laserwriter, which is on a tty line
        and has permissions 666)  *for reading and writing*  (this succeeds);
    dups that to fd 1;
        (I put in an fcntl() call to check the mode of fd 1, and already
        at this point it says it's only open for writing!  How can this be?)
    forks/execs the server, which:
        dups fd 1, for listening to the LaserWriter's status reports;
        forks a child to do the listening:
            child tries to fdopen it for reading, fails, and returns. . .
        the printing goes fine, server returns.
     

Again, when the daemon is killed and restarted by hand, this all works
fine.  The only difference I can see is that when it's started from boot,
it runs not attached to a terminal (ps shows "?"), and when I start it
by hand, it shows attached to my tty.

Here's the fragment of rc.local that starts it up, and I use the same
script to start it by hand, using "sh script" while su'd to root:

-------------------------------------------------------------------------
if [ -d /usr/local/lib/mdqs ]; then
        rm -f /usr/spool/mdqs/qtmp/*
        date >> /usr/spool/mdqs/LOGFILE
        /usr/local/lib/mdqs/mdqsdaemon >> /usr/spool/mdqs/LOGFILE 2>&1 &
        (cd /usr/local/lib/mdqs; \
                netdae -n 4 /usr/local/lib/mdqs/netrecv >> /usr/spool/mdqs/LOGFILE 2>&1) &
        /usr/local/clearlw /dev/lw2
        echo -n ' mdqs'                                         >/dev/console
fi
-------------------------------------------------------------------------
Any help or suggestions will certainly be appreciated!
     
                        - Susan Richter
                        richter at rand-unix.ARPA
                        ...!decvax!philabs!ttidca!randvax!richter
                        ...!ihnp4!wlbr!trwrb!randvax!richter


--
                        richter at rand-unix.ARPA
                        ...!decvax!philabs!ttidca!randvax!richter
                        ...!ihnp4!wlbr!trwrb!randvax!richter