From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ulrich Weber Subject: Re: [RFC PATCH] dont create cached routes from ARP requests Date: Fri, 24 Sep 2010 17:38:48 +0200 Message-ID: <4C9CC608.7010401@astaro.com> References: <20100922162209.GA10281@babylon> <20100922.203442.233700254.davem@davemloft.net> <20100923144708.GA8037@babylon> <1285254302.2509.47.camel@edumazet-laptop> <4C9CBCFC.6080300@gmail.com> <1285342083.2503.252.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Ulrich Weber , David Miller , netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from dhost002-56.dex002.intermedia.net ([64.78.21.185]:10859 "EHLO dhost002-56.dex002.intermedia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753572Ab0IXPiz (ORCPT ); Fri, 24 Sep 2010 11:38:55 -0400 In-Reply-To: <1285342083.2503.252.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: Yes, as I wrote before my Cable ISP is flooding me with ARP requests from 10.0.0.0/8, which get a route via the primary PPP link. I know thats not a common setup but why do that kind of routes have to be cached ? :) steps to reproduce: server: ip route add 1.0.0.0/8 dev dummy0 client: ip route add 1.0.0.0/8 dev eth0 nmap --min-rate 500 -sP 1.0.0.0/8 On 09/24/2010 05:28 PM, Eric Dumazet wrote: > Le vendredi 24 septembre 2010 =C3=A0 17:00 +0200, Ulrich Weber a =C3=A9= crit : >> Hi Eric, >> >> please find the output in the attached text file. >> >> Neighbor garbage collection wont't work because all >> neighbor records are bound to cached routes. >> >> Forced route garbaged collections returns without freeing >> any routes, probably because the route threshold is quite high >> with 65536 compared to the small neighbor threshold of 1024, >> resulting in a fixed amount of 1024 cached routes... >> >> Instead of running the garbage collection we could flush the route >> cache completely if the neighbor cache overflows. >> But why do we have to cache that routes in first place ? >> See the previous patch which skips caching for that kind of routes. >=20 > What are the packets you receive ? A flood of ARP answers ? >=20 > a "tcpdump -X" of a few packets would help to understand. >=20 >=20 >=20 --=20 Ulrich Weber | uweber@astaro.com | Software Engineer Astaro GmbH & Co. KG | www.astaro.com | Phone +49-721-25516-0 | Fax =E2= =80=93200 An der RaumFabrik 33a | 76227 Karlsruhe | Germany