netdev - Re: RFC: Support send-to-self over external interfaces (and veths).

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Date:	Mon, 11 Jun 2007 08:52:50 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Patrick McHardy <kaber@...sh.net>
CC:	NetDev <netdev@...r.kernel.org>
Subject: Re: RFC:  Support send-to-self over external interfaces (and veths).

Patrick McHardy wrote:
> Ben Greear wrote:
>   
>> This should also be useful with the pending 'veth' driver, as it
>> emulates two ethernet ports connected with a cross-over cable.
>>
>> To make this work, you have to enable the sysctl (look Dave,
>> no IOCTLS, there might be hope for me yet!! :)), and in your
>> application you will need to use SO_BINDTODEVICE (and probably bind to
>> the local IP as well).  Some applications such as traceroute already
>> support this binding..others such as ping do not.
>>
>> You most likely will also have to set up routing tables using
>> source IPs as a rule to direct these connections to a particular
>> routing table.
>>
>> Comments welcome.
>>     
>
>
> I would really prefer to simply make the prio 0 "lookup local"
> rule deletable so you can rules with higher priority. That
> allows to do send to self without any further code changes
> and avoids the need to bind applications to a device.
>   
I am not against making that change as well, but it is often easier to 
just bind-to-device
than to set up specific host routes for every possible combination..as 
it appears your
method requires.  (I could have mis-understood the routing requirements, 
but it seemed to
if you wanted any 100 interfaces to send to any other, your method would 
required 100 * 100
routes.)

A decent set of programs already support bind-to-device, and others are 
easily patched
if they need the behaviour.

Thanks,
Ben


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-- 
Ben Greear <greearb@...delatech.com> 
Candela Technologies Inc  http://www.candelatech.com


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