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Date:      Thu, 10 Oct 2002 15:18:58 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        abe <abe@informationwave.net>
Cc:        hackers@freebsd.org
Subject:   Re: fatal trap 12 kernel panic
Message-ID:  <3DA5FCD2.B23CD912@mindspring.com>
References:  <20021010212954.GA67855@dipole.informationwave.net> <3DA5F3BC.CD0154CF@mindspring.com> <20021010214518.GB71656@dipole.informationwave.net>

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abe wrote:
>     This started out as a sudden panic on a machine that was in a
> datacenter for more than 8 months without issue.  Then I installed
> on fresh machines, compiled in ipfw support, and also tried this as
> a module.  The result is the same regardless.

You have a traceback; do you have a system dump?

[ ... ]
> > >  Stopped at    add_dyn_rule+0172:   movl   0(%edx,%ebx,4)x%eax


Knowing the line of C code involved would be much more useful.

Are you suddenly running an application that you did not formerly
run?  The creation of a dynamic rule as a result of a ip_output()
call to ip_fw_chk() to install_state() to add_dyn_rule() implies
that the flow ID passed down to add_dyn_rule() with the value of
dyn_type == DYN_KEEP_STATE is valid.

One possibility that occurs to me is that you end up with a
parent count going over 65535 (it's a u_int16_t).  When it is
counted yet again, it goes to 0, then again, to 1.  Then the
next reference deletion causes it to go 1->0, at which point,
the parent is deleted, even though it's still referenced.

If this is the case, you can work around it by ensuring that a
dynamic limit of 65534 or less is set.

Another workaround would be to change the "count" member of the
"struct ipfw_dyn_rule" to b a u_int32_t, and recompile everything.


Without knowing the source code involved, you are unlikely to get
an answer that's more than a guess.  8-(.

-- Terry

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