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From: Stefan `Sec` Zehl <sec@42.org>
To: John Baldwin <jhb@freebsd.org>
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Subject: Re: The tale of a TCP bug
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On Wed, Mar 30, 2011 at 08:38 -0400, John Baldwin wrote:
> There is at least one case I know of related to a bug I reported earlier
> where a window probe from a remote connection can cause rcv_nxt to advance
> past rcv_adv by one.  However, I think we want to know about those cases,
> and we should probably be treating rcv_adv - rcv_nxt as if it is zero in 
> that case, not -1 (my patch in my original e-mail does just that in a
> different place in tcp_output() when we calculate the window "for real").

I've been running for about a day now with the committed patch and
adv_neg is still zero:

| ice:~>uptime; sysctl net.inet.tcp.adv_neg
|  1:36AM  up 1 day,  4:52, 1 user, load averages: 0.12, 0.06, 0.05
| net.inet.tcp.adv_neg: 0

I'll of course monitor this value and report back if I ever see it
increase :-)

CU,
    Sec
-- 
Diplomacy is the ability to tell a person to go to hell in such a nice way
that he or she looks forward to the trip.