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To: Pat_Barron@transarc.com
cc: hackers@freebsd.org
Subject: Re: Why am I getting these SLIP crashes? 
In-reply-to: Your message of "Tue, 27 Dec 94 02:56:27 EST."
             <sizwWfaSMV1bI7WkQx@transarc.com> 
From: David Greenman <davidg@Root.COM>
Reply-To: davidg@Root.COM
Date: Tue, 27 Dec 1994 00:10:13 -0800
Sender: hackers-owner@freebsd.org
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>OK, I have some more data about these SLIP related crashes that I've been
>happening.  Here is what I've been doing to start SLIP sessions:
>
>   1)  "cu -l /dev/cua01 -s 19200"
>   2)  Dial up to Cisco terminal server, start SLIP; the terminal
>       server gives me an IP address (chosen based on what line I've
>       gotten in my hunt group).
>   3)  Use "~^Z" to suspend cu.
>   4)  "slattach -h -s 19200 /dev/cua01"
>   5)  "ifconfig sl0 <my-ip-address>"
>   6)  "route add default <my-default-router-address>"
>   7)  "telnet <some-host>"
>
>At this point, the machine spontaneously reboots.  No panic or anything,
>just a reboot - as if the CPU has taken a double-fault or something else
>that would shut it down.
>
>This even happens if I do "telnet localhost" in step #7 (but this may be
>because a DNS lookup is being attempted across the SLIP interface).
>
>Now, I *can* get this to work; between step #5 and step #6, I have to
>do "route add <my-network-number> <my-slip-address> 0"; I get a warning
>message that says "old usage of trailing 0; assuming route to if", but
>that was what I wanted anyway.  *Then* I can use the network, and th
>machine does not crash.
>
>What changed to make this happen?  I am using the -current version of 2.0,
>which I am sup'ing from freefall.  I first noticed this behavior in a kernel
>I sup'ped some time around the first or second week of December.

   The route cloning code was enabled. I've seen the same symptom here, but
all I had to do was a 'route add default w.x.y.z' after a default route had
been previously added - no telnet or anything, just add the route. The reboot
without panic is most likely caused by a recursion loop occurring between two
or more subroutines until the kernel stack overflows.

-DG