[PATCH v2] net: dsa: tag_mtk: add padding for tx packets

[Vladimir Oltean]

On Tue, May 10, 2022 at 04:52:16PM +0200, Felix Fietkau wrote:
> 
> On 10.05.22 14:37, Vladimir Oltean wrote:
> > On Tue, May 10, 2022 at 11:40:13AM +0200, Felix Fietkau wrote:
> > > Padding for transmitted packets needs to account for the special tag.
> > > With not enough padding, garbage bytes are inserted by the switch at the
> > > end of small packets.
> > 
> > I don't think padding bytes are guaranteed to be zeroes. Aren't they
> > discarded? What is the issue?
> With the broken padding, ARP requests are silently discarded on the receiver
> side in my test. Adding the padding explicitly fixes the issue.
> 
> - Felix

Ok, I'm not going to complain too much about the patch, but I'm still
curious where are the so-called "broken" packets discarded.
I think the receiving MAC should be passing up to software a buffer
without the extra padding beyond the L2 payload length (at least that's
the behavior I'm familiar with).