Date: Wed, 21 Apr 2004 17:59:51 -0400 From: Gary Corcoran <garycor@comcast.net> To: Tillman Hodgson <tillman@seekingfire.com> Cc: freebsd-security@freebsd.org Subject: Re: Other possible protection against RST/SYN attacks (was Re: TCP RST attack Message-ID: <4086EED7.3070808@comcast.net> In-Reply-To: <20040421214445.GX476@seekingfire.com> References: <6.0.3.0.0.20040420144001.0723ab80@209.112.4.2> <200404201332.40827.dr@kyx.net> <20040421111003.GB19640@lum.celabo.org> <6.0.3.0.0.20040421121715.04547510@209.112.4.2> <20040421165454.GB20049@lum.celabo.org> <6.0.3.0.0.20040421132605.0901bb40@209.112.4.2> <48FCF8AA-93CF-11D8-9C50-000393C94468@sarenet.es> <6.0.3.0.0.20040421161217.05453308@209.112.4.2> <75226E9B-93D3-11D8-90F9-003065ABFD92@mac.com> <4086E522.7090303@comcast.net> <20040421214445.GX476@seekingfire.com>
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Tillman Hodgson wrote: > On Wed, Apr 21, 2004 at 05:18:26PM -0400, Gary Corcoran wrote: > >>Charles Swiger wrote: >> >>>The default TTL gets decremented with every hop, which means that a >>>packet coming in with a TTL of 255 had to be sent by a directly >>>connected system. [ip_ttl is an octet, so it can't hold a larger TTL >>>value.] >> >>Huh? 255-- == 254, not 0. A TTL of 255 just allows the maximum possible >>number of hops, before being declared hopelessly lost. > > > Exactly -- if you see an incoming packet with a TTL of 255, it must've > originated on a directly connected system /or it would've already been > decremented to 254 or lower/. Ah, yes, of course. I thought the original poster was implying that the packet could only exist on a direct connection, and wouldn't be passed along to another hop if it had a TTL of 255. But I guess I just got the wrong impression - sorry for the confusion. In any event, it still seems like 255 is overkill for this application... Gary
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