[PATCH] net: stmmac: Disable checksum insertion for XDP frame TX

[PATCH] net: stmmac: Disable checksum insertion for XDP frame TX

[Jisheng Zhang]

stmmac enables TX checksum insertion for XDP frames whenever the queue
supports it. XDP frames carry no TX checksum offload request, so this
can overwrite a checksum already present in the packet.

Pass false to stmmac_prepare_tx_desc() when transmitting an XDP frame
so that the packet is sent with its checksum fields unchanged.

Fixes: be8b38a722e6 ("net: stmmac: Add support for XDP_TX action")
Fixes: 8b278a5b69a2 ("net: stmmac: Add support for XDP_REDIRECT action")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 24656b35350b..8fe75b00974f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5184,7 +5184,6 @@ static int stmmac_xdp_xmit_xdpf(struct stmmac_priv *priv, int queue,
 {
 	struct stmmac_txq_stats *txq_stats = &priv->xstats.txq_stats[queue];
 	struct stmmac_tx_queue *tx_q = &priv->dma_conf.tx_queue[queue];
-	bool csum = !priv->plat->tx_queues_cfg[queue].coe_unsupported;
 	unsigned int entry = tx_q->cur_tx;
 	enum stmmac_txbuf_type buf_type;
 	struct dma_desc *tx_desc;
@@ -5229,7 +5228,7 @@ static int stmmac_xdp_xmit_xdpf(struct stmmac_priv *priv, int queue,
 	stmmac_set_desc_addr(priv, tx_desc, dma_addr);
 
 	stmmac_prepare_tx_desc(priv, tx_desc, 1, xdpf->len,
-			       csum, priv->descriptor_mode, true, true,
+			       false, priv->descriptor_mode, true, true,
 			       xdpf->len);
 
 	tx_q->tx_count_frames++;
-- 
2.53.0

Re: [PATCH] net: stmmac: Disable checksum insertion for XDP frame TX

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

 - Whether the issue was actually triggered, or is only theoretical
   (e.g. found by code inspection). If it was triggered please include
   the symptoms, like the stack trace or error messages.

 - What hardware the change was tested on. For driver fixes please
   mention the device (and if relevant firmware version) used for
   testing, or say that the change was not tested on real hardware.

Please do not repost the series just to address the above. Instead,
reply to this email with the missing information, so that reviewers
can take it into account. If the series needs another revision for
other reasons, please include the information in the commit messages
then.

The evaluation is done by an LLM so it may be wrong, if you think
that is the case please reply and explain.

Re: [PATCH] net: stmmac: Disable checksum insertion for XDP frame TX

[Andrew Lunn]

On Tue, Sep 29, 2026 at 08:10:25PM +0800, Jisheng Zhang wrote:
> stmmac enables TX checksum insertion for XDP frames whenever the queue
> supports it. XDP frames carry no TX checksum offload request, so this
> can overwrite a checksum already present in the packet.
> 
> Pass false to stmmac_prepare_tx_desc() when transmitting an XDP frame
> so that the packet is sent with its checksum fields unchanged.

This seems odd to me.

If the frame contains a checksum, it is either correct, and the
hardware calculated one will come out the same, not an issue.  Or the
checksum in the frame is actually wrong, because the frame has got
mangled by eBPF before sending it out, and you want the hardware to
calculate the correct value.

What an i missing?

	Andrew