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Re: [Xen-users] Use of "ethtool - K eth0 tx off"

To: Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Use of "ethtool - K eth0 tx off"
From: Goetz Bock <bock@xxxxxxxxxxx>
Date: Sun, 28 May 2006 14:15:25 +0200
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On Sun, May 28 '06 at 09:39, Leonardo Pinto wrote:
> I am with problems using method NAT and having that to make use of
> "ethtool - K eth0 tx off"

we all have (well, at last with 3.0.1, I'm not 100% sure if this has
been fixed with 3.0.2)

> - Why is being necessary the indiscriminate use of "tx off"?

EPARSE

> - That is one bug or resource? It will be corrected?

It's a bug. And shortly before 3.0.2 was relesed there were some
attempts to fix it.

It is intended as an optimisztion, but it failed for some (or IMHO most
real world) setups.

> Another fact is, if the use of "tx off", we would not be compromising
> the security?

EPARSE

But disableing TX checksum offloading (that's what ethtool -K tx off
does) does not affect security at all. The CPU only has to compute
the checksum off all outgoing packages, even if the package is intended
for another domU or the Dom0 where not computing the checksum could save
some CPU cycles (as coruption of the package is VERY unlikely).
--  
/"\ Goetz Bock at blacknet dot de  --  secure mobile Linux everNETting
\ /       (c) 2006 Creative Commons, Attribution-ShareAlike 2.0 de
 X   [ 1. Use descriptive subjects - 2. Edit a reply for brevity -  ]
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