Date: Wed, 20 Aug 2003 17:41:33 +0200
From: Stephan von Krawczynski <skraw@ithnet.com>
To: "David S. Miller" <davem@redhat.com>
Cc: ak@colin2.muc.de, dang@fprintf.net, ak@muc.de, lmb@suse.de,
       linux-kernel@vger.kernel.org, alan@lxorguk.ukuu.org.uk
Subject: Re: [2.4 PATCH] bugfix: ARP respond on all devices
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On Tue, 19 Aug 2003 12:28:47 -0700
"David S. Miller" <davem@redhat.com> wrote:

> On 19 Aug 2003 21:32:35 +0200
> Andi Kleen <ak@colin2.muc.de> wrote:
> 
> > What happens on outgoing active ARPs is a different thing. Reasonable
> > choices would be either the prefered source address of the route or
> > the local interface's address. I must admit I don't have a strong
> > opinion on what the better behaviour of those is, but neither of them would
> > seem particularly wrong to me.
> 
> Andi, we take the source address from the packet we are
> trying to send out that interface.
> 
> Just as it is going to be legal to send out a packet from
> that interface using that source address, it is legal to
> send out an ARP request from that interface using that source
> address.

Aehm, sorry but the logic is bogus. A routed packet will be sent out this
interface with a foreign IP as source, too. Though nobody will want to send an
arp request with a foreign ip as source.
But you say here: Just as I can send out a packet with IP X from that interface
I can send out ARP request with same source.
Obviously you don't want that.
So you cannot step from A to B in your logical chain here.

Again. I'd like to stress I don't want to insult you or anything. The simple
thing is this: there are a lot setups out there that could benefit from your
tolerance in this issue. Can't we simply take the issue to the point: "you are
right, but you show tolerance for boxes that are not completely wrong" ?
I mean the world is full of people that are right and intolerant, so that in
fact doesn't really make them special ...

Please let us keep in mind that joe-average-user cannot handle complex setups
with arpfilter, arp_filter or anything the like. But he can right away enter
IT-superstore XYZ and buy a brand new router box for 20 bucks. If he is unlucky
(and you stay intolerant) he will for sure _not_ blame this box but his desktop
linux if things don't work out as expected.
I think we should at least make a minimum effort to keep things simple (and
explainable to joe-average-user), even if the background is complex.
Everywhere we have a solution for a problem that is overly complex, we will
fail to gain a broad market share, because there may very likely be easier
solutions under <name-some-os> _and_ we attract support problems for all
distributors.

Regards,
Stephan
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