Date: Sat, 9 Sep 2006 08:07:09 +1000 From: Peter Jeremy <peterjeremy@optushome.com.au> To: Andre Oppermann <andre@freebsd.org> Cc: freebsd-net@freebsd.org, yar@comp.chem.msu.su, glebius@freebsd.org, freebsd-arch@freebsd.org Subject: Re: Moving ethernet VLAN tags into the mbuf packet header (from mtags) Message-ID: <20060908220709.GA759@turion.vk2pj.dyndns.org> In-Reply-To: <450035AD.3040600@freebsd.org> References: <450035AD.3040600@freebsd.org>
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--azLHFNyN32YCQGCU Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, 2006-Sep-07 17:07:25 +0200, Andre Oppermann wrote: >With the recent addition of a 16bit field for TSO into the mbuf packet >header we've got 16bits left over. I've reserved these bits for the >ethernet VLAN tagging of packet to do away with the allocated mbuf mtag. Sounds reasonable. My only comment is that there doesn't appear to be any way for bpf(4) to filter/capture VLAN information. Before hardware tagging, you could run tcpdump on the vlan parent device and filter on the VLAN tag as well as see the VLAN associated with each packet. I found this very useful for monitoring routed data as well as finding cases where packets were appearing in the wrong VLAN. With hardware tagging (with or without this patch), bpf doesn't have access to the tag information. This is a PITA. --=20 Peter Jeremy --azLHFNyN32YCQGCU Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQFFAemM/opHv/APuIcRArkBAJ9852B/iR8hYOI7MadjjLF8agOe8QCggGDt yqMeEEkto8RSebNvfYMF1WA= =5Yab -----END PGP SIGNATURE----- --azLHFNyN32YCQGCU--
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