Date: Thu, 22 Apr 2004 07:58:57 -0700 From: jayanth <jayanth@yahoo-inc.com> To: Don Lewis <truckman@FreeBSD.org> Cc: jayanth@yahoo-inc.com Subject: Re: [Full-Disclosure] IETF Draft - Fix for TCP vulnerability (fwd) Message-ID: <20040422145857.GA75539@yahoo-inc.com> In-Reply-To: <200404212331.i3LNVE7E047907@gw.catspoiler.org> References: <20040421184539.H18583@odysseus.silby.com> <200404212331.i3LNVE7E047907@gw.catspoiler.org>
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Don Lewis (truckman@FreeBSD.org) wrote: > On 21 Apr, Mike Silbersack wrote: > > > > On Wed, 21 Apr 2004, Don Lewis wrote: > > > >> > 1. Accept all RSTs meeting the criteria you just listed above. > >> > >> At this step, it would be better if we used the window size that was > >> advertised it the last packet sent, since that is what the sequence > >> number of the RST packet will be calculated from, while the window size > >> could have increased if data was consumed from the receive queue between > >> the time we sent the last packet and when we received the RST. > >> > >> It doesn't look like we keep the necessary data for this. Probably the > >> easiest thing to do would be to calculate the expected sequence number > >> in tcp_output() and stash it in the pcb. > > > > Do you have access to a system that exhibits the "RST at end of window" > > syndrome so that you could code up and test out this part of the patch? > > Nope. The only report of this that I saw was from jayanth. Judging by > the tcpdump timestamps, it looks like whatever this wierd piece of > hardware was, it was nearby. > if i remember right this was done to handle the Alteons which generate a RST segment that would fall within the window size but not the next expected sequence no. So they would do something crazy like rcv_nxt + rcv_win as the sequence no, for the RST segment rather than rcv_nxt + 1. This was part of the RFC though. If it is a problem we can always revert it back. jayanth
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