On Mon, Mar 22, 2021 at 01:48:07PM +0800, Bin Meng wrote: > Hi David, > > On Mon, Mar 22, 2021 at 1:24 PM David Gibson > <da...@gibson.dropbear.id.au> wrote: > > > > 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 > > > <da...@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? > > I've never used it like that before. What's the command line to test that? > > > > > > > > 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? > > In QEMU packets are transmitted without CRC between network backends, > and when a NIC receives a packet, the minimum required payload length > is 60 bytes without a CRC.
Ok, I see what you're saying, and indeed it already pads to 60 bytes,
rather than 64 on the Rx side.
--
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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