Date: Fri, 14 May 1999 22:57:26 +0200 From: Harold Gutch <logix@foobar.franken.de> To: Thamer Al-Herbish <shadows@whitefang.com>, security@FreeBSD.ORG Subject: Re: Forwarded from BUGTRAQ: SYN floods against FreeBSD Message-ID: <19990514225726.B22317@foobar.franken.de> In-Reply-To: <Pine.BSF.4.05.9905141314001.253-100000@rage.whitefang.com>; from Thamer Al-Herbish on Fri, May 14, 1999 at 01:17:26PM -0700 References: <4.2.0.37.19990514133829.0461e220@localhost> <Pine.BSF.4.05.9905141314001.253-100000@rage.whitefang.com>
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On Fri, May 14, 1999 at 01:17:26PM -0700, Thamer Al-Herbish wrote: > On Fri, 14 May 1999, Brett Glass wrote: > > > One question about "the Linux way of doing it" as described > > below. What happens if the secret just happens to be modified > > right after the SYN-ACK? Could be you'd drop a connection or > > two that was legitimate. Seems like you'd need to test against > > an old AND a new secret to avoid the race condition, especially > > in the presence of congestion. > > There were a few "trade offs" with the implementation. I have a copy > of the syn-cookies mailing list archive. Forgot where I originally > got it from: > > http://www.whitefang.com/syn-cookies.txt > I had a look at the archives a few weeks back, just having a quick look at most of the mails. I guess I must have missed those trade offs when reading it not too precisely - I'll check them again. > Oh and here's the obligatory question: has anyone already attempted > to write a cookie mechanism for fbsd? > I considered doing to, but seeing that FreeBSD already takes an (arguable) approach against SYN-floods stopped even thinking of something like that pretty quickly. FreeBSD basically drops sockets in SYN_RCVD state if too many of them are open and another SYN-packet arrives, making place for this new socket. bye, Harold -- <Shabby> Sleep is an abstinence syndrome wich occurs due to lack of caffein. Wed Mar 4 04:53:33 CET 1998 #unix, ircnet To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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