[PATCH net-next v2 07/14] net: stmmac: move TSO VLAN tag insertion to core code

Russell King (Oracle)
2026-04-01T07:22:03Z

stmmac_tso_xmit() checks whether the skbuff is trying to offload
vlan tag insertion to hardware, which from the comment in the code
appears to be buggy when the TSO feature is used.

Rather than stmmac_tso_xmit() inserting the VLAN tag, handle this
in stmmac_features_check() which will then use core net code to
handle this. See net/core/dev.c::validate_xmit_skb()

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
.../net/ethernet/stmicro/stmmac/stmmac_main.c | 23 ++++++++-----------
1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b4cc34dd0d76..c67f042a90af 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4456,19 +4456,6 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
u8 proto_hdr_len, hdr;
dma_addr_t des;

- /* Always insert VLAN tag to SKB payload for TSO frames.
- *
- * Never insert VLAN tag by HW, since segments split by
- * TSO engine will be un-tagged by mistake.
- */
- if (skb_vlan_tag_present(skb)) {
- skb = __vlan_hwaccel_push_inside(skb);
- if (unlikely(!skb)) {
- priv->xstats.tx_dropped++;
- return NETDEV_TX_OK;
- }
- }
-
nfrags = skb_shinfo(skb)->nr_frags;
queue = skb_get_queue_mapping(skb);

@@ -4969,6 +4956,16 @@ static netdev_features_t stmmac_features_check(struct sk_buff *skb,
if (!stmmac_tso_channel_permitted(netdev_priv(dev), queue) ||
!stmmac_tso_valid_packet(skb))
features &= ~NETIF_F_GSO_MASK;
+
+ /* If we are going to be using hardware TSO, always insert
+ * VLAN tag to SKB payload for TSO frames.
+ *
+ * Never insert VLAN tag by HW, since segments split by
+ * TSO engine will be un-tagged by mistake.
+ */
+ if (features & NETIF_F_GSO_MASK)
+ features &= ~(NETIF_F_HW_VLAN_STAG_TX |
+ NETIF_F_HW_VLAN_CTAG_TX);
}

return vlan_features_check(skb, features);
--
2.47.3