Date: Fri, 1 Apr 2011 08:32:49 -0400 From: John Baldwin <jhb@freebsd.org> To: "Stefan `Sec` Zehl" <sec@42.org> Cc: freebsd-net@freebsd.org Subject: Re: The tale of a TCP bug Message-ID: <201104010832.49214.jhb@freebsd.org> In-Reply-To: <20110331234017.GC3308@ice.42.org> References: <4D8B99B4.4070404@FreeBSD.org> <201103300838.09608.jhb@freebsd.org> <20110331234017.GC3308@ice.42.org>
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On Thursday, March 31, 2011 7:40:17 pm Stefan `Sec` Zehl wrote: > 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: Well, after thinking some more, rcv_nxt == rcv_adv + 1 will not make adv negative. > | 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 :-) Great, thanks! -- John Baldwin
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