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Date:      Tue, 30 May 2000 11:57:58 +0400
From:      Vick <vick@unet.ru>
To:        "C. Stephen Gunn" <csg@waterspout.com>
Cc:        Net <freebsd-net@FreeBSD.ORG>
Subject:   Re: VLAN improvement needed...
Message-ID:  <39337486.2460358A@unet.ru>
References:  <392E754B.BCF8AC96@unet.ru> <20000529163917.A15841@waterspout.com>

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[-- Attachment #1 --]
"C. Stephen Gunn" wrote:

> On Fri, May 26, 2000 at 04:59:56PM +0400, Victor Ponomarev wrote:
>
> > Now VLAN support in stable is bad.
>
> I'm not sure what you mean by now.  if_vlan has always had some
> shortcomings.  I don't think anything has changed recently.

May be I didn't correctly understand the reason for introducing this pseudo
interface, but I've thought it's done for interVLAN connectivity.

By the way does anyone advice a good starting point for phys level network
support in BSD (realization strategy, common order of pseudo interface
applying to packets and so on..)

>
> > When host send a packet about 1514 byte switch trunk port add 4 byte and
> > router trunk port substitute vlan tag to another and send it back to
> > switch. The latter remove vlan header and send packet to appropriate
> > vlan ports.
> >
> > Currently FreeBSD router simply drop large packet on it's interface.
> > That's very bad...
>
> Actually several ethernet cards drop these frames as giants.  There
> are also a few (ti in particular) that do not.
>
> > The existing solution on these problem for Intel card may be found at
> >     http://www.euitt.upm.es/~pjlobo/
>
> I've reviewed this patch carefully before.  I still don't see any
> changes the the FXP driver that allow reception of tagged frames.
>
> I do have some modifications around that allow larger frame sizes on
> 3Com 3c905B-TX cards.  I'll dug that patch up, and put it online:
>
>   http://www.physics.purdue.edu/~csg/xl-vlan.patch
>

Well your patch looks more reasonable, because you really change MTU.

> > But there's another problem with small ip packet. When BSD router strip
> > ethernet header for payload < 46 it strip padding bytes also. But when
> > it reinserted data with another vlan header it don't add padding bytes
> > and we have runts packets on interface.
>
> Do you think this is related to VLANs because of the encapsulation?
>
> Do you have a method to duplicate this behavior?
>

I think it related to VLAN realization. See please tcpdump file attached,
frames 9,10; 35-38; and so on...
    192.168.2.1 is VLAN 4
    spok is VLAN 3
It's clearly than undersized packets didn't put back correctly...

>
>  - Steve

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