[PATCH net 1/3] net: stmmac: honour Rx checksum errors in the AF_XDP zero-copy path

[Grische <opensource@grische.xyz>]

Commit ee0aace5f844 ("net: stmmac: Correctly handle Rx checksum offload
errors") taught stmmac_rx() to honour the csum_none status, but
stmmac_dispatch_skb_zc() still ignores it and sets CHECKSUM_UNNECESSARY
for every IP frame whenever the checksum offload engine (CoE) is
enabled.

Since commit fe4042797651 ("net: stmmac: dwmac4: stop hardware from
dropping checksum-error packets") dwmac4 delivers such frames instead of
dropping them, so this path receives them.

Mark the skb CHECKSUM_NONE when csum_none is set, as stmmac_rx() does.

Fixes: bba2556efad6 ("net: stmmac: Enable RX via AF_XDP zero-copy")
Cc: <stable@vger.kernel.org>
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Grische <opensource@grische.xyz>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 9741f97fa37a..32810f949245 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5463,7 +5463,7 @@ static struct sk_buff *stmmac_construct_skb_zc(struct stmmac_channel *ch,
 
 static void stmmac_dispatch_skb_zc(struct stmmac_priv *priv, u32 queue,
 				   struct dma_desc *p, struct dma_desc *np,
-				   struct xdp_buff *xdp)
+				   struct xdp_buff *xdp, int status)
 {
 	struct stmmac_rxq_stats *rxq_stats = &priv->xstats.rxq_stats[queue];
 	struct stmmac_channel *ch = &priv->channel[queue];
@@ -5488,7 +5488,8 @@ static void stmmac_dispatch_skb_zc(struct stmmac_priv *priv, u32 queue,
 		stmmac_rx_vlan(priv->dev, skb);
 	skb->protocol = eth_type_trans(skb, priv->dev);
 
-	if (unlikely(!coe) || !stmmac_has_ip_ethertype(skb))
+	if (unlikely(!coe) || !stmmac_has_ip_ethertype(skb) ||
+	    (status & csum_none))
 		skb_checksum_none_assert(skb);
 	else
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
@@ -5698,7 +5699,8 @@ static int stmmac_rx_zc(struct stmmac_priv *priv, int limit, u32 queue)
 
 		switch (res) {
 		case STMMAC_XDP_PASS:
-			stmmac_dispatch_skb_zc(priv, queue, p, np, buf->xdp);
+			stmmac_dispatch_skb_zc(priv, queue, p, np, buf->xdp,
+					       status);
 			xsk_buff_free(buf->xdp);
 			break;
 		case STMMAC_XDP_CONSUMED:
-- 
2.54.0