From owner-freebsd-hackers  Wed Apr 16 07:07:14 1997
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To: hackers@freebsd.org
Subject: 2.2.1-R crash with looped serial gettys
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Date: Wed, 16 Apr 1997 10:07:07 -0400
From: Chris Shenton <cshenton@it.hq.nasa.gov>
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I've built a little box for pppd/mpd and routing out of a 486sx33 and
a whopping 8MB RAM; seems to mostly run fine with 2.2.1-RELEASE. It's
a fairly minimal install (Kernel User option I think) and I rebuilt
the kernel to fit the hardware.  I've added a dual 16550A serial port
card to which I'll connect a pair of modems. I have getty running on
the ports, cuaa1 and cuaa2.

PROBLEM:

If I connect a null-modem cable between the ports, the system crashes
within a couple seconds.  It's repeatable.

It leaves no message in /var/log/messages, or dmesg, and there's no
core file.

I presume looping the serial gettys is causing them to scream at each
other "Login:"; "Invalid Login:"; no *you* login; dammit, `login' is
not a valid login... and consumes too many resources.



Not sure if there's an intelligent way to detect this and prevent it,
but it did seem surprising that simply connecting a cable crashed the
machine.