Date: Wed, 11 Sep 2002 16:09:31 -0400 (EDT) From: Mike Silbersack <silby@silby.com> To: kfl <kfl@xiphos.ca> Cc: freebsd - net <freebsd-net@FreeBSD.org> Subject: Re: T/TCP and FreeBSD 4.5 Message-ID: <Pine.BSF.4.44.0209111604450.42163-100000@niwun.pair.com> In-Reply-To: <JCEDLMKGMLLELHAJNIHJCEBJDGAA.kfl@xiphos.ca>
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On Wed, 11 Sep 2002, kfl wrote: > Hi, > > I'm having a problem using TCP for transaction in FreeBSd 4.5. Here's a > trace from tcpdump and the code I'm using. > Also, from the dump you can see that rfc1644 is on ;) > > Problem: (At 12:41:05.626586, the ack should also ack the data sent with the > SYN.) > > Any hints on what could be wrong? > > Regards, > > Karim Fodil-Lemelin > Xiphos Technologies Inc. > > uname -a: > cartman.xiphos.ca 4.5-RELEASE FreeBSD 4.5-RELEASE #0: Mon Jan 28 14:31:56 I think it needs more cheesy poofs. Ho ho, ok, now to the real answer. In order to make the syn cache more resistant to denial of service attacks, one of its features is that it will not accept any data in the initial SYN packet. In 99.9% of the cases, this is fine, as TCP stacks don't tend to send data along with a SYN. I guess T/TCP differs, though... It would certainly be possible to rewrite the syn cache to be more friendly to T/TCP, but I don't think that anyone has plans to do so. If you have the time and need, you might wish to take a stab at it. If not, you'll have to run 4.4-release (or 4.4-stable before the syncache import) in order to get the old behavior. Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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