Date: Wed, 19 Dec 2001 20:54:50 +0300 (MSK) From: Maxim Konovalov <maxim@macomnet.ru> To: Yar Tikhiy <yar@FreeBSD.ORG> Cc: net@FreeBSD.ORG, <hackers@FreeBSD.ORG> Subject: Re: Processing IP options reveals IPSTEALH router Message-ID: <20011219195659.G25693-100000@news1.macomnet.ru> In-Reply-To: <20011219194903.D21732@comp.chem.msu.su>
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On 19:49+0300, Dec 19, 2001, Yar Tikhiy wrote: > On Wed, Dec 19, 2001 at 07:23:55PM +0300, Maxim Konovalov wrote: > > > > > I ran into an absolutely clear, but year-old PR pointing out that > > > a router in the IPSTEALTH mode will reveal itself when processing > > > IP options: kern/23123. > > > > > > The fix proposed seems clean and right to me: don't do IP options > > > at all when in the IPSTEALTH mode. Does anyone have objections? > > > If no, I'll commit the fix. > > > > First of all we should decide what IPSTEALTH is for. Is it just a > > Ruslan's net.inet.ip.decttl or it should really stealth the fact of > > the routing? If the latter how do we behave in source routing case? > > Are there any reasons for a router not to decrement IP TTL besides > trying to stay invisible to a third party? imho there are not. I've asked because ru's net.inet.ip.decttl means "do not decrement TTL" but not "hide the fact of the routing". > As for source routing, I believe a stealthy router should just drop > such packets as though it were a host. Of course, source-routed > packets destined for the router itself should be accepted. So there are three IPSTEALTH cases: 1/ the dst address is not ours, net.inet.ip.sourceroute=0, net.inet.ip.forwarding=1: process ip options by ip_dooptions(). 2/ the dst address is ours: process ip options by ip_dooptions(), 3/ in other cases do not process ip options. By the way, is it correct to forward the packet with incorrect ip options? Now we do not. -- Maxim Konovalov, MAcomnet, Internet-Intranet Dept., system engineer phone: +7 (095) 796-9079, mailto: maxim@macomnet.ru To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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