netdev - Re: e100 + VLANs?

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Message-ID: <1318091046.5276.22.camel@edumazet-laptop>
Date:	Sat, 08 Oct 2011 18:24:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Michael Tokarev <mjt@....msk.ru>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: e100 + VLANs?

Le samedi 08 octobre 2011 à 14:08 +0400, Michael Tokarev a écrit :
> Yesterday I tried to use 802.1Q VLAN tagging with an (oldish)
> e100-driven network card, identified by lspci like this:
> 
>  00:12.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 02)
> 
> Just to discover that it does not quite work: packets of
> size 1497+ bytes gets lost.
> 
> This appears to be a classical problems in this case -
> something forgot to allocate extra 4 bytes for the
> packets.
> 
> There's at least one bugreport from 2008 (!) about this
> very issue: http://bugs.centos.org/view.php?id=2719
> which is still open.
> 
> The kernel I tried this on was 2.6.32, I checked git log
> for drivers/net/e100.c - there was no changes up to
> current version which may be related to this issue.
> 
> The question: is this a driver problem or hardware? If
> it's the driver, can it be fixed? And if it's hardware,
> can the driver notify the user somehow - like, by refusing
> to enable VLAN (sub)devices maybe?
> 
> Yesterday it was actually a bit more complicated for me,
> since the card in question was used to connect to our
> ISP, and they use fixed MAC address per port, so I had
> to find another NIC which is a) able to work with VLAN
> tags properly, and b) is able to change its mac address.
> Lucky I had a VIA RhineIII which does both :)
> 

Since you have two cards (and probably two machines), maybe you could
try to track if the problem is a bad transmit or a bad receive ?

tcpdump on both machines, and ping -s 2000 from both sides...

e100 driver seems VLAN enabled at a first glance.



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