Merge branch 'stmmac-stop-silently-dropping-bad-checksum-packets'

Oleksij Rempel says:

====================
stmmac: stop silently dropping bad checksum packets

this series reworks how stmmac handles receive checksum offload
(CoE) errors on dwmac4.

At present, when CoE is enabled, the hardware silently discards any
frame that fails checksum validation. These packets never reach the
driver and are not accounted in the generic drop statistics. They are
only visible in the stmmac-specific counters as "payload error" or
"header error" packets, which makes it harder to debug or monitor
network issues.

Following discussion [1], the driver is reworked to propagate checksum
error information up to the stack. With these changes, CoE stays
enabled, but frames that fail hardware validation are no longer dropped
in hardware. Instead, the driver marks them with CHECKSUM_NONE so the
network stack can validate, drop, and properly account them in the
standard drop statistics.

[1] https://lore.kernel.org/all/20250625132117.1b3264e8@kernel.org/
====================

Link: https://patch.msgid.link/20250818090217.2789521-1-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 11 insertions, 3 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
index f4694fd576f5..3dec1a264cf6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
@@ -341,6 +341,7 @@ static inline u32 mtl_chanx_base_addr(const struct dwmac4_addrs *addrs,
 #define MTL_OP_MODE_RFA_SHIFT		8
 
 #define MTL_OP_MODE_EHFC		BIT(7)
+#define MTL_OP_MODE_DIS_TCP_EF		BIT(6)
 
 #define MTL_OP_MODE_RTC_MASK		GENMASK(1, 0)
 #define MTL_OP_MODE_RTC_SHIFT		0
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
index a5fb31eb0192..aac68dc28dc1 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
@@ -110,16 +110,20 @@ static int dwmac4_wrback_get_rx_status(struct stmmac_extra_stats *x,
 
 	message_type = (rdes1 & ERDES4_MSG_TYPE_MASK) >> 8;
 
-	if (rdes1 & RDES1_IP_HDR_ERROR)
+	if (rdes1 & RDES1_IP_HDR_ERROR) {
 		x->ip_hdr_err++;
+		ret |= csum_none;
+	}
 	if (rdes1 & RDES1_IP_CSUM_BYPASSED)
 		x->ip_csum_bypassed++;
 	if (rdes1 & RDES1_IPV4_HEADER)
 		x->ipv4_pkt_rcvd++;
 	if (rdes1 & RDES1_IPV6_HEADER)
 		x->ipv6_pkt_rcvd++;
-	if (rdes1 & RDES1_IP_PAYLOAD_ERROR)
+	if (rdes1 & RDES1_IP_PAYLOAD_ERROR) {
 		x->ip_payload_err++;
+		ret |= csum_none;
+	}
 
 	if (message_type == RDES_EXT_NO_PTP)
 		x->no_ptp_rx_msg_type_ext++;
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
index 0cb84a0041a4..d87a8b595e6a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
@@ -268,6 +268,8 @@ static void dwmac4_dma_rx_chan_op_mode(struct stmmac_priv *priv,
 
 	mtl_rx_op = readl(ioaddr + MTL_CHAN_RX_OP_MODE(dwmac4_addrs, channel));
 
+	mtl_rx_op |= MTL_OP_MODE_DIS_TCP_EF;
+
 	if (mode == SF_DMA_MODE) {
 		pr_debug("GMAC: enable RX store and forward mode\n");
 		mtl_rx_op |= MTL_OP_MODE_RSF;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 0bbdc1f1a691..a55e43804670 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5737,7 +5737,8 @@ drain_data:
 
 		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;