[net-next PATCH 2/2] net: dsa: tag_rtl8_4: set KEEP flag

Luiz Angelo Daros de Luca
2026-04-08T20:31:28Z

KEEP=1 is needed because we should respect the format of the packet as
the kernel sends it to us. Unless tx forward offloading is used, the
kernel is giving us the packet exactly as it should leave the specified
port on the wire. Until now this was not needed because the ports were
always functioning in a standalone mode in a VLAN-unaware way, so the
switch would not tag or untag frames anyway. But arguably it should have
been KEEP=1 all along.

Co-developed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
---
net/dsa/tag_rtl8_4.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/dsa/tag_rtl8_4.c b/net/dsa/tag_rtl8_4.c
index b7ed39c5419f..852c6b88079a 100644
--- a/net/dsa/tag_rtl8_4.c
+++ b/net/dsa/tag_rtl8_4.c
@@ -99,6 +99,7 @@
#define RTL8_4_REASON_TRAP 80

#define RTL8_4_LEARN_DIS BIT(5)
+#define RTL8_4_KEEP BIT(7)

#define RTL8_4_TX GENMASK(3, 0)
#define RTL8_4_RX GENMASK(10, 0)
@@ -114,8 +115,9 @@ static void rtl8_4_write_tag(struct sk_buff *skb, struct net_device *dev,
/* Set Protocol; zero REASON */
tag16[1] = htons(FIELD_PREP(RTL8_4_PROTOCOL, RTL8_4_PROTOCOL_RTL8365MB));

- /* Zero EFID_EN, EFID, PRI_EN, PRI, VSEL, VIDX, KEEP; set LEARN_DIS */
- tag16[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1));
+ /* Zero EFID_EN, EFID, PRI_EN, PRI, VSEL, VIDX; set KEEP, LEARN_DIS */
+ tag16[2] = htons(FIELD_PREP(RTL8_4_LEARN_DIS, 1) |
+ FIELD_PREP(RTL8_4_KEEP, 1));

/* Zero ALLOW; set RX (CPU->switch) forwarding port mask */
tag16[3] = htons(FIELD_PREP(RTL8_4_RX, dsa_xmit_port_mask(skb, dev)));

--
2.53.0