Date: Mon, 12 Aug 2002 12:20:03 -0700 (PDT) From: "G.P. de Boer" <g.p.de.boer@st.hanze.nl> To: freebsd-bugs@FreeBSD.org Subject: kern/41552: TCP timers' sysctl's overflow Message-ID: <200208121920.g7CJK3ms088778@freefall.freebsd.org>
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The following reply was made to PR kern/41552; it has been noted by GNATS. From: "G.P. de Boer" <g.p.de.boer@st.hanze.nl> To: Garrett Wollman <wollman@lcs.mit.edu> Cc: freebsd-gnats-submit@FreeBSD.ORG Subject: kern/41552: TCP timers' sysctl's overflow Date: Mon, 12 Aug 2002 21:21:33 +0200 At 20:40 12-8-2002, you wrote: > > When setting syscontrols like net.inet.tcp.keepidle on a system with > > clocktick-granularity above 1000 Hz, there's an overflow triggered, > > resulting in at least inaccurate, but sometimes negative TCP > > timeouts. > >1 kHz timers are just barely within spec for TCP (using the 32-bit >fields in RFC 1323). Well.. since LINT says 1000Hz is advisable for dummynet use. For polling 1000 or even 2000Hz is advised. IF this is a problem with RFC1323, which strikes me as odd, then there's more to this problem than meets the eye. A setting in LINT shouldn't break anything so fundamental as TCP. Anyway.. it's a integer overflow and it breaks stuff in nasty ways. It's possible to DoS a host with malfunctioning keep-alives: I already had more than 400 hanging connections (in LAST_ACK state) in a few days on a moderately loaded server. The fix is there already, I just think it should be in -RELEASE too. With regards, Pieter To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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