Date: Thu, 12 Jul 2007 01:08:41 +0200 From: Andre Oppermann <andre@freebsd.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: current@freebsd.org, net@freebsd.org Subject: Re: FreeBSD 7 TCP syncache fix: request for testers Message-ID: <469562F9.4060700@freebsd.org> In-Reply-To: <20070711130719.S68820@fledge.watson.org> References: <20070709234401.S29353@odysseus.silby.com> <20070710132253.GJ1038@void.codelabs.ru> <20070710202028.I34890@odysseus.silby.com> <20070711130719.S68820@fledge.watson.org>
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Robert Watson wrote: > 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. Yes, I'm aware of that and will provide an appropriate patch shortly. -- Andre
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