Date: Thu, 14 Aug 2014 12:44:22 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: "Alexander V. Chernikov" <melifaro@yandex-team.ru> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Luigi Rizzo <luigi@freebsd.org>, "Andrey V. Elsukov" <ae@freebsd.org>, freebsd-ipfw <freebsd-ipfw@freebsd.org> Subject: Re: [CFT] new tables for ipfw Message-ID: <CA%2BhQ2%2BiPPhy47eN0=KaSYBaNMdObY20yko7dRY1MMuP_mfnmOQ@mail.gmail.com> In-Reply-To: <53EC880B.3020903@yandex-team.ru> References: <53EBC687.9050503@yandex-team.ru> <CA%2BhQ2%2Bg=A_rLHCVpBqn0AtFLu_gNGtzbmXvc-7JhpLqPSWw44A@mail.gmail.com> <53EC880B.3020903@yandex-team.ru>
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On Thu, Aug 14, 2014 at 11:57 AM, Alexander V. Chernikov < melifaro@yandex-team.ru> wrote: > On 14.08.2014 13:23, Luigi Rizzo wrote: > > > > > On Wed, Aug 13, 2014 at 10:11 PM, Alexander V. Chernikov < > melifaro@yandex-team.ru> wrote: > >> Hello list. >> >> I've been hacking ipfw for a while and It seems there is something ready >> to test/review in projects/ipfw branch. >> > > =E2=80=8Bthis is a fantastic piece of work, thanks for doing it and for > integrating the feedback. > =E2=80=8B > I have some detailed feedback that will send you privately, > but just a curiosity: > > =E2=80=8B...=E2=80=8B >> >> Some examples (see ipfw(8) manual page for the description): >> >> >> =E2=80=8B... >> >> >> ipfw table mi_test create type cidr algo "cidr:hash masks=3D/30,/64" >> > > =E2=80=8Bwhy do we need to specify mask lengths in the above=E2=80=8B ? > > Well, since we're hashing IP we have to know mask to cut host bits in > advance. > (And the real reason is that I'm too lazy to implement hierarchical > matching (check /32, then /31, then /30) like how, for example, > =E2=80=8Boh well for that we should use cidr:radix Research results have never shown a strong superiority of hierarchical hash tables over good radix implementations, and in those cases one usually adopts partial prefix expansion so you only have, say, masks that are a multiple of 2..8 bits so you only need a small number of hash lookups. =E2=80=8Bcheers luigi=E2=80=8B
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