Re: [PATCH] hw/net: fsl_etsec: Tx padding length should exclude CRC

[David Gibson]

On Mon, Mar 22, 2021 at 12:33:06PM +0800, Bin Meng wrote:
> Hi David,
> 
> On Mon, Mar 22, 2021 at 12:11 PM David Gibson
> <david@gibson.dropbear.id.au> wrote:
> >
> > On Tue, Mar 16, 2021 at 04:15:05PM +0800, Bin Meng wrote:
> > > As the comment of tx_padding_and_crc() says: "Never add CRC in QEMU",
> > > min_frame_len should excluce CRC, so it should be 60 instead of 64.
> >
> > Sorry, your reasoning still isn't clear to me.  If qemu is not adding
> > the CRC, what is?
> 
> No one is padding CRC in QEMU. QEMU network backends pass payload
> without CRC in between.

Ok, but the CRCs must be added if the packets are bridged onto a real
device, yes?  Where does that happen?
> 
> > Will it always append a CRC after this padding is complete?
> 
> No.

If that's true, then won't the packets still be shorter than expected
if we only pad to 60 bytes?

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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