From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Dichtel Subject: Re: [PATCH] ipv4/ipv6: check hop limit field on input Date: Tue, 02 Jun 2009 11:35:03 +0200 Message-ID: <4A24F247.2040406@dev.6wind.com> References: <4A23F027.3060907@dev.6wind.com> <20090601161917.GA29745@Chamillionaire.breakpoint.cc> <4A240681.2010300@6wind.com> <4A242161.3010609@cosmosbay.com> <4A242418.1090804@hp.com> <1243907646.15854.16.camel@merlyn> Reply-To: nicolas.dichtel@6wind.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Brian Haley , Eric Dumazet , Florian Westphal , netdev To: John Dykstra Return-path: Received: from 33.106-14-84.ripe.coltfrance.com ([84.14.106.33]:4812 "EHLO proxy.6wind.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752016AbZFBKDa (ORCPT ); Tue, 2 Jun 2009 06:03:30 -0400 In-Reply-To: <1243907646.15854.16.camel@merlyn> Sender: netdev-owner@vger.kernel.org List-ID: John Dykstra wrote: > On Mon, 2009-06-01 at 14:55 -0400, Brian Haley wrote: >> 'ping6 -t 0 host' does work however. The problem I see is that if you ping a system, >> if it's a host it will respond, if it's a router it won't - the RFCs don't >> explicitly state the host should drop the packet. > > There are two cases--an echo request to an address assigned to a > router's interface, and to an address _beyond_ the router on another > link. > > Any given interface on a router can have forwarding dynamically enabled > or disabled. I don't remember prescribed echo request or hop limit > behavior changing depending on the forwarding enable, so it seems that > if you ping an address assigned to a router's interface, the router is > expected to follow the (apparently unwritten) host rules. Good point. > > Echo requests forwarded by a router should obviously have the hop limit > decremented and checked. > >> I don't know if that difference >> in behavior is desired. Do we know how any other OSes behave? > > FWIW, the random BSD flavors I have on hand all check hop limit when > forwarding, but not when processing local ingress traffic. > > Also FWIW, as I remember, the TAHI tests only check hop limit behavior > on forwarded traffic. Right. > > Nicolas, what's driving your patch? Are you trying to align slow path > behavior with one of the 6WIND fast path implementations? No. I'm just checking RFC conformance ;-) Nicolas > > -- John > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html