Re: [E1000-devel] e1000 driver is sending jumbo frames exceeding mtu

[Brandeburg, J. <jes...@in...>]

Vik Heyndrickx wrote:
> I'm having a big problem with e1000. It sends out packets that are
> larger than the MTU. This causes tc (linux traffic control) to get
> confused: the data is going out the interface roughly three times
> faster than the configured rate. This problem does not exist with
> another nic installed in the same system.   =20
>=20
> It's a Fedora Core 5 system upgraded to the latest packages. These
> are the relevant bits of information of my systems:=20
>=20
> # uname -a
> Linux alexandria.edch 2.6.18-1.2200.fc5 #1 SMP Sat Oct 14 16:59:56
> EDT 2006 x86_64 x86_64 x86_64 GNU/Linux=20
<snip>

> If there a way to configure the driver not to do this? I want my
> packets limited to 1500 standard sized ethernet frames.=20

Those are TSO frames.  Ethereal shows them as huge frames because before
they get to the driver they are.  The frames are then segmented to MTU
size by the hardware.   you can disable it by disabling TSO using
ethtool, it will however cost you some CPU, but at 100Mb/s that probably
won't be a big deal.  The command is:
ethtool -K eth0 tso off

seems like tc should be using byte counts instead of frame counts,
sounds like a bug in tc :-(

Let us know if you have more issues
 Jesse