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Date:      Mon, 29 Mar 2004 21:38:54 +0300
From:      Ruslan Ermilov <ru@freebsd.org>
To:        David Gilbert <dgilbert@dclg.ca>
Cc:        freebsd-net@freebsd.org
Subject:   Re: Disabling VLAN_HWTAGGING
Message-ID:  <20040329183854.GC73842@ip.net.ua>
In-Reply-To: <16488.26976.314273.752771@canoe.dclg.ca>
References:  <200403251118.40718.jbarrett@amduat.net> <20040325234527.GC85417@ip.net.ua> <200403251650.35714.jbarrett@amduat.net> <16488.26976.314273.752771@canoe.dclg.ca>

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On Mon, Mar 29, 2004 at 01:22:24PM -0500, David Gilbert wrote:
> >>>>> "Jacob" =3D=3D Jacob S Barrett <jbarrett@amduat.net> writes:
>=20
> Jacob> On Thursday 25 March 2004 03:45 pm, you wrote:
> >> > Can you disable VLAN_HWTAGGING?
> >>=20
> >> Not without modifying if_nge.c, but it should be pretty trivial.
>=20
> Jacob> As trivial as setting chaning:
> ifp-> if_capabilities =3D IFCAP_HWCSUM | IFCAP_VLAN_HWTAGGING;
> Jacob> to:
> ifp-> if_capabilities =3D 0;
>=20
> Jacob> This didn't solve the problem completely though.  On the remote
> Jacob> host I can now see tagged frames from the if_nge host, but the
> Jacob> reply frames from the if_em host or not visible at all on the
> Jacob> if_nge host (via tcpdump).
>=20
> Are you dumping all packets?  We've found that you can dump a specific
> vlan on nge's, but you can't get good data by dumping the raw port
> itself.  No matter how it's set, in both Linux and FreeBSD, many nge
> chipsets will not show vlan packets from the driver with a tcpdump.
>=20
Hmm, you can't probably see it because the hardware is configured to
do VLAN tag insertion/removal, and stores VLAN data decoupled from the
frame's mbuf chain.  And BPF is very unlikely to reconstruct the
ETHERTYPE_VLAN packet using this information...


Cheers,
--=20
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer

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