On Saturday, December 17, 2011 6:21:27 pm Pawel Jakub Dawidek wrote:
> On Mon, Dec 12, 2011 at 11:00:23AM -0500, John Baldwin wrote:
> > An update. I've sent Pawel a testing patch to see if my hypothesis is
> > correct
> > (www.freebsd.org/~jhb/patches/tcp_negwin_test.patch). If it is then I
> > intend
> > to commit www.freebsd.org/~jhb/patches/tcp_negwin2.patch as the fix.
>
> Unfortunately it paniced today. Take a look at:
>
> http://people.freebsd.org/~pjd/misc/tcp_panic.jpg
Ok, the one use case I was worried about is happening regularly before your
panic, so that is good. Can you use gdb to figure out which call to
tcp_output() is actually panic'ing? I wonder if it is this case:
/*
* Return any desired output.
*/
if (needoutput || (tp->t_flags & TF_ACKNOW)) {
(void) tcp_output(tp);
/* XXX: Debug */
KASSERT(SEQ_GEQ(tp->rcv_adv, tp->rcv_nxt),
("tcp_input: negative window after ACK"));
And if 'needoutput' is true, but TF_ACKNOW is not set, and tcp_output() decides
to not do anything. I've updated tcp_negwin_test.patch to not panic if that
call
to tcp_output() doesn't actually send a packet. Please re-test.
--
John Baldwin
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