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Message-Id: <20231027-fix-rtl8366rb-v1-1-d565d905535a@linaro.org> Date: Fri, 27 Oct 2023 22:21:39 +0200 From: Linus Walleij <linus.walleij@...aro.org> To: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>, Vladimir Oltean <olteanv@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com> Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org> Subject: [PATCH] dsa: tag_rtl4_a: Bump min packet size It was reported that the "LuCI" web UI was not working properly with a device using the RTL8366RB switch. Disabling the egress port tagging code made the switch work again, but this is not a good solution as we want to be able to direct traffic to a certain port. It turns out that sometimes, but not always, small packets are dropped by the switch for no reason. If we pad the ethernet frames to a minimum of ETH_FRAME_LEN + FCS (1518 bytes) everything starts working fine. As we completely lack datasheet or any insight into how this switch works, this trial-and-error solution is the best we can do. I have tested smaller sizes, ETH_FRAME_LEN doesn't work for example. Fixes: 0e90dfa7a8d8 ("net: dsa: tag_rtl4_a: Fix egress tags") Signed-off-by: Linus Walleij <linus.walleij@...aro.org> --- net/dsa/tag_rtl4_a.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c index c327314b95e3..8b1e81a6377b 100644 --- a/net/dsa/tag_rtl4_a.c +++ b/net/dsa/tag_rtl4_a.c @@ -41,8 +41,11 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, u8 *tag; u16 out; - /* Pad out to at least 60 bytes */ - if (unlikely(__skb_put_padto(skb, ETH_ZLEN, false))) + /* We need to pad out to at least ETH_FRAME_LEN + FCS bytes. This was + * found by trial-and-error. Sometimes smaller frames work, but sadly + * not always. + */ + if (unlikely(__skb_put_padto(skb, ETH_FRAME_LEN + ETH_FCS_LEN, false))) return NULL; netdev_dbg(dev, "add realtek tag to package to port %d\n", --- base-commit: 58720809f52779dc0f08e53e54b014209d13eebb change-id: 20231027-fix-rtl8366rb-e752bd5901ca Best regards, -- Linus Walleij <linus.walleij@...aro.org>
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