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To: asmodai@bart.nl
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Subject: Re: Panic (TCP)
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Date: Mon, 21 Feb 2000 21:26:56 +0900
From: Yoshinobu Inoue <shin@nd.net.fujitsu.co.jp>
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> >Might there be incorrect memory over writing?
> 
> How you mean?

I think one possibility of the problem is that some code is
incorrectly overwriting some part of the memory, and a tcpcb's
tt_persist->c_flags is happen to overwritten.

Now I am very much interested in the value of
tp->tt_persist->c_flags at panic, if CALLOUT_PENDING and
possibly other flags are just set, or completely broken data
is written on it.

And if later, I am also interested in other values around
tp->tt_persist->c_flags, to check what kind of value is
written around there.

> Debugging tips are welcome, since I am not the biggest bulb wrt
> debugging.

I am not also, and you might have already known these things,
but in case they are useful,

  -If DDB is specified in kernel config file, and all src/sys
   tree including sys/compile dir is saved onto another
   machine, it will be very useful at next panic, because remote GDB
   debugging is available by those data.

   (Though if the bug happens at very delicate timing, it
   might prevent the bug from happening again.)
   
  -Adding some printfs in tcp_output.c:tcp_setpersist() panic
   case might be useful.

Thanks,
Yoshinobu Inoue


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