Re: [PATCH net v2] net: dsa: tag_rtl4_a: Bump min packet size

[Vladimir Oltean]

On Mon, Oct 30, 2023 at 10:50:31PM +0100, Linus Walleij wrote:
> > you said that what increments is Dot1dTpPortInDiscards
> No this was a coincidence, we can rule this out.

I see commit 86dd9868b878 ("net: dsa: tag_rtl4_a: Support also egress tags")
also mentions: "Qingfang came up with the solution: we need to pad the
ethernet frame to 60 bytes using eth_skb_pad(), then the switch will
happily accept frames with custom tags.". So the __skb_put_padto() was
something very empirical in the first place.

Since it's all problematic, would you mind removing the __skb_put_padto()
altogether from rtl4a_tag_xmit(), and let me know what is the output for
the following sweep through packet sizes? I truly wonder if it's just
for small and large packets that we see packet drops, or if it's something
repetitive throughout the range as well.

for size in $(seq 0 1476); do if ping 10.0.0.56 -s $size -W 1 -c 1 -q >/dev/null; then echo "$((size + 42)): OK"; else echo "$((size + 42)): NOK"; fi; done