From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: Question about tcp hash function tcp_hashfn() Date: Thu, 1 Jun 2006 10:30:13 +0400 Message-ID: <20060601063012.GC28087@2ka.mipt.ru> References: <20060531090301.GA26782@2ka.mipt.ru> <20060531035124.B3065@openss7.org> <20060531105814.GB7806@2ka.mipt.ru> <20060531.114127.14356069.davem@davemloft.net> <20060601060424.GA28087@2ka.mipt.ru> <20060601001825.A21730@openss7.org> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Cc: "Brian F. G. Bidulock" Return-path: Received: from relay.2ka.mipt.ru ([194.85.82.65]:44250 "EHLO 2ka.mipt.ru") by vger.kernel.org with ESMTP id S965267AbWFAGa5 (ORCPT ); Thu, 1 Jun 2006 02:30:57 -0400 To: David Miller , draghuram@rocketmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Content-Disposition: inline In-Reply-To: <20060601001825.A21730@openss7.org> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Jun 01, 2006 at 12:18:25AM -0600, Brian F. G. Bidulock (bidulock@openss7.org) wrote: > Evgeniy, > > On Thu, 01 Jun 2006, Evgeniy Polyakov wrote: > > > > for (i=0; i > saddr = num2ip(get_random_byte(), get_random_byte(), get_random_byte(), get_random_byte()); > > sport = get_random_word(); > > You still have a problem: you cannot use a pseudo-random number > generator to generate the sample set as the pseudo-random number > generator function itself can interact with the hash. > > Try iterating through all 2**48 values or at least a sizeable > representative subset. Since pseudo-randomness affects both folded and not folded hash distribution, it can not end up in different results. You are right that having test with 2^48 values is really interesting, but it will take ages on my test machine :) -- Evgeniy Polyakov