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Date:      Tue, 19 May 1998 18:18:22 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        eivind@yes.no (Eivind Eklund)
Cc:        dg@FreeBSD.ORG, current@FreeBSD.ORG
Subject:   Re: cvs commit: src/sys/conf files src/sys/net if_ethersubr.c if_fddisubr.c if_ppp.c src/sys/netinet ip_flow.c in.h in_var.h ip_OR
Message-ID:  <199805191618.SAA09928@labinfo.iet.unipi.it>
In-Reply-To: <19980519163734.18175@follo.net> from "Eivind Eklund" at May 19, 98 04:37:15 pm

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> >   Log:
> >   Added fast IP forwarding code by Matt Thomas <matt@3am-software.com> via
> >   NetBSD, ported to FreeBSD by Pierre Beyssac <pb@fasterix.freenix.org> and
> >   minorly tweaked by me.
> >   This is a standard part of FreeBSD, but must be enabled with:
> >   "sysctl -w net.inet.ip.fastforwarding=1" ...and of course forwarding must
> 
> Why is this?  What are the downsides - just that it is temporary code?

not just that. It completely bypasses the ipfw code.
It is also missing some checks on forwarded packets (e.g. IP header
checksum is not tested, although i don't know if it is mandatory, and
in any case this is easier to fix).

It contains lots of nice ideas though. I was wondering if we could put
at least some into the standard path as well.

E.g. when forwarding a packet, there is a call to ip_output() with the
IP_FORWARDING flag set. We could easily use this info to skip some
checks and work in ip_output (e.g. avoid recomputing the checksum).

Also flow through the firewall code can be optimized since the packet
has been already classified.

	cheers
	luigi
-----------------------------+--------------------------------------
Luigi Rizzo                  |  Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it    |  Universita' di Pisa
tel: +39-50-568533           |  via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522           |  http://www.iet.unipi.it/~luigi/
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