Re: [PATCH 2/2] [e1000 VLAN] Disable vlan hw accel when promiscuous mode

2007/11/13, Willy Tarreau [off-list ref]:

On Mon, Nov 12, 2007 at 02:57:16PM -0800, David Miller wrote:

quoted

From: "Chris Friesen" <redacted>
Date: Mon, 12 Nov 2007 16:43:24 -0600

quoted

David Miller wrote:

quoted

When you select VLAN, you by definition are asking for non-VLAN
traffic to be elided.  It is like plugging the ethernet cable
into one switch or another.

For max functionality it seems like the raw eth device should show
everything on the wire in promiscuous mode.

If we want to sniff only the traffic for a specific vlan, we can sniff
the vlan device.

VLAN settings are a filter of sorts, much like plugging into
one switch or another filters traffic physically.

If you don't want that filter, turn the VLAN settings off.

I don't really agree with that view. Having spent a lot of time with
tcpdump on production systems, I can say that sometimes you'd like to
be aware that one of your VLANs is wrong and you'd simply like to
sniff the wire to guess the correct tag. And on production, you simply
cannot remove other VLANs, otherwise you disrupt the service.

I agree.
If I had a mis-plugged cable, I can guess it with tcpdump.
Because I cannot see the packets. It means no such packets on the wire 100%.
But if I had a incorrect vlan configuration, it's hard to sure.
In a case both of mis-plugged and mis-configured situation, I cannot
see anything.
Moreover, if I am configuring a machine via vlan interface which is
mis-configured partially, I cannot disable vlan hw acceleration
feature.

Thanks.
Joonwoo