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Date:      Tue, 05 Dec 2000 13:40:54 +1100
From:      Peter Jeremy <peter.jeremy@alcatel.com.au>
To:        David Gilbert <dgilbert@velocet.ca>
Cc:        freebsd-stable@FreeBSD.ORG
Subject:   Re: Full size vlan packets.
Message-ID:  <20001205134053.A95349@gsmx07.alcatel.com.au>
In-Reply-To: <14865.20151.114515.408874@trooper.velocet.net>; from dgilbert@velocet.ca on Tue, Nov 14, 2000 at 09:39:51AM -0500
References:  <14865.20151.114515.408874@trooper.velocet.net>

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[Catching up on old mail]
On 2000-Nov-14 09:39:51 -0500, David Gilbert <dgilbert@velocet.ca> wrote:
>I posted a request here some time ago about getting FreeBSD to do full 
>sized VLAN packets.

I have boxes doing this running both -STABLE and -CURRENT (both somewhat
old, but I'm in the process of upgrading the -STABLE machine).

There are two major issues involved in getting this to work:
1) ifconfig on a vlan will set to the MTU to the MTU of the parent
   device - 4 unless the parent device's header length is the length
   of a VLAN header.  This can be over-ridden by explicitly specifying
   the MTU in the ifconfig command.  The header length (ifi_hdrlen)
   doesn't appear to be used elsewhere so it should also be possible to
   change the header length on the parent device, but my initial
   attempt to do this didn't work correctly.
2) The individual ethernet drivers need to be patched to support the
   larger packets.  This is driver-dependent and varies from just
   changing the receive buffer size to playing with bits that are
   only documented under NDA.

There are also assorted buglets in the general VLAN support:
- kern/20611: VLAN parent device does not count VLAN output bytes
- bin/21880: (libcap/tcpdump don't allow matching on VLAN packets)
- kern/19436 (arp(8) doesn't support VLANs)

At the device level, I have patches for tx (SMC 83c170), fxp
(Intel 82559), xl (3Com 3c905B and later) and tl (TI ThunderLAN).
(The latter two untested).

Peter


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