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Date: Sat, 19 Jul 1997 16:28:26 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199707190628.QAA29484@godzilla.zeta.org.au>
To: bde@zeta.org.au, davidn@labs.usn.blaze.net.au
Subject: Re: cvs commit: src/lib/libutil login_auth.c
Cc: cvs-all@FreeBSD.ORG, cvs-committers@FreeBSD.ORG, cvs-lib@FreeBSD.ORG,
        davidn@FreeBSD.ORG
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>>  >  Modified files:
>>  >    lib/libutil          login_auth.c 
>>  >  Log:
>>  >  sleep() after sending 'nologin' file to ensure output is drained before
>>  >  disconnect.
>>  
>>  This should use tcdrain(3).
>
>Well, no, it doesn't appear to be an operating system issue. The
>sleep() is done after the close(). The problem occurs when DCD
>on a serial port is lowered before the *modem* has sent all of
>its data, and I can easily reproduce the problem on a telnet

What modem?  Output might be connected to the console, and then an
unnecessary sleep is very annoying.

>connection as well (due to telnet's usual misfeature of quitting
>early). tcdrain() before the close() has no effect - I tried that
>before I understood the problem.

This might be caused by driver bugs.  Draining didn't work right in
sio before rev.1.152 (1996/11/30), and corresponding fixes haven't
been made in any other serial drivers :-(.

Telnet seems to work right here.  I tried a 75K file for /etc/nologin.

It's hard handle the modem hanging up before sending all the data that
has been sent to it.  A naive calculation like

	sleeptime = howmany(filesize, DTEspeed / 10);

is very wrong if the effective line speed is much smaller than the DTE
speed or the file size is much smaller than the modem buffer size.

Bruce