Date: Wed, 11 Jul 2007 13:08:15 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Mike Silbersack <silby@silby.com> Cc: Andre Oppermann <andre@freebsd.org>, current@freebsd.org, net@freebsd.org Subject: Re: FreeBSD 7 TCP syncache fix: request for testers Message-ID: <20070711130719.S68820@fledge.watson.org> In-Reply-To: <20070710202028.I34890@odysseus.silby.com> References: <20070709234401.S29353@odysseus.silby.com> <20070710132253.GJ1038@void.codelabs.ru> <20070710202028.I34890@odysseus.silby.com>
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On Tue, 10 Jul 2007, Mike Silbersack wrote: > On Tue, 10 Jul 2007, Eygene Ryabinkin wrote: > >> Can't say that I am pushing much traffic through my box, but after applying >> your patch and rebuilding the kernel I am still seeing the messages like >> ----- TCP: [209.132.176.NNN]:NNN to [144.206.NNN.NNN]:NNN tcpflags >> 0x19<FIN,PUSH,ACK>; syncache_expand: Segment failed SYNCOOKIE >> authentication, segment rejected (probably spoofed) TCP: >> [201.90.65.NNN]:NNN to [144.206.NNN.NNN]:NNN; syncache_timer: Response >> timeout ----- But what had changed is that the lines with the >> 'syncache_timer' started to appear. There were no such lines prior to the >> patch, only the 'failed SYNCOOKIE' ones. > > The "syncache_timer: Response timeout" message means that the syncache sent > a SYN-ACK response four times, but still didn't receive a response. This > probably means that someone tried using a port scanner or was going through > a faulty firewall. We'll definitely have to take that log message out > before 7.0 is released. As I mentioned to Andre before he committed the log message support, there needs to be an administrative twiddle for it, and pretty much all need to either be rate-limited or turned off by default when we get to the release. Otherwise they make very easy DoS opportunities, especially for systems with serial consoles. Robert N M Watson Computer Laboratory University of Cambridge
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