net: stmmac: Fix incorrect IP-csum status report

Currently the IP checksum verification status is incorrectly set to
CHECKSUM_UNNECESSARY for all IPv4/IPv6 packets as per the
stmmac_has_ip_ethertype() method implementation. It's wrong since the Rx
COE embedded into the DW *MAC IP-cores supports the TCP/UDP/ICMP protocols
only [1,2,3,4]. From that perspective the commit c2945c435c99 ("net:
stmmac: Prevent DSA tags from breaking COE") was close to solving the
denoted problem, but didn't provide a comprehensive solution.

Since all the low-level driver sub-modules now support reporting the CSUM
verification status from Rx DMA-descriptor let's use it to correctly set
the IP-sum status in the Rx-frames SKB.

[1] DesignWare Cores Ethernet MAC Universal Databook, Revision 3.50a,
    February 2009, p. 114.
[2] DesignWare Cores Ethernet MAC Universal Databook, Revision 3.73a,
    October 2013, p. 189.
[3] DesignWare Cores Ethernet Quality-of-Service Databook, Revision 5.20a,
    April 2020, pp. 368.
[4] DesignWare Cores XGMAC - 10G Ethernet MAC Databook, Revision 3.20a,
    September 2022, p.253.
[n] ...

Fixes: c2945c435c99 ("net: stmmac: Prevent DSA tags from breaking COE")
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>

1 files changed, 40 insertions, 13 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 446439f5dbfd..d74927fbf148 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4986,6 +4986,42 @@ static void stmmac_rx_vlan(struct net_device *dev, struct sk_buff *skb)
 }
 
 /**
+ * stmmac_get_rx_csum - Retrieve Rx CSUM status
+ * @priv:   driver private structure
+ * @status: frame Rx-status
+ * @skb :   the socket buffer
+ * Description :
+ * This function will initialize the SKB IP summed based on the Rx COE
+ * outcomes.
+ */
+static void stmmac_get_rx_csum(struct stmmac_priv *priv, int status,
+			       struct sk_buff *skb)
+{
+	bool coe = priv->dev->features & NETIF_F_RXCSUM;
+
+	/* If Rx COE wasn't synthesized into the IP-core the status may never
+	 * have the csum_none flag. Skip the status check then to be on a safe
+	 * side.
+	 */
+	if (!coe || (status & csum_none)) {
+		skb_checksum_none_assert(skb);
+		return;
+	}
+
+	/* Rx COE feature is relatively similar on the late DW GMAC IP-cores
+	 * (v3.30a and newer) and on the DW QoS Ether and DW XGMAC/XLGMAC/etc
+	 * IP-cores except that the later ones support double tagged
+	 * IP-packets:
+	 * Rx COE type 2:   C-(S-)VLAN + IPv4/IPv6 + TCP/UDP/ICMP
+	 * Rx COE enh:    2xC-(S-)VLAN + IPv4/IPv6 + TCP/UDP/ICMP
+	 *
+	 * In any way the outcomes of the Rx COE work must be retrieved from
+	 * the Rx DMA-descriptor.
+	 */
+	__skb_incr_checksum_unnecessary(skb);
+}
+
+/**
  * stmmac_rx_refill - refill used skb preallocated buffers
  * @priv: driver private structure
  * @queue: RX queue index
@@ -5357,11 +5393,10 @@ 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)
+				   int status, struct xdp_buff *xdp)
 {
 	struct stmmac_rxq_stats *rxq_stats = &priv->xstats.rxq_stats[queue];
 	struct stmmac_channel *ch = &priv->channel[queue];
-	int coe = priv->dev->features & NETIF_F_RXCSUM;
 	unsigned int len = xdp->data_end - xdp->data;
 	enum pkt_hash_types hash_type;
 	struct sk_buff *skb;
@@ -5382,10 +5417,7 @@ 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))
-		skb_checksum_none_assert(skb);
-	else
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
+	stmmac_get_rx_csum(priv, status, skb);
 
 	if (!stmmac_get_rx_hash(priv, p, &hash, &hash_type))
 		skb_set_hash(skb, hash, hash_type);
@@ -5598,7 +5630,7 @@ read_again:
 
 		switch (res) {
 		case STMMAC_XDP_PASS:
-			stmmac_dispatch_skb_zc(priv, queue, p, np, buf->xdp);
+			stmmac_dispatch_skb_zc(priv, queue, p, np, status, buf->xdp);
 			xsk_buff_free(buf->xdp);
 			break;
 		case STMMAC_XDP_CONSUMED:
@@ -5659,7 +5691,6 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 	struct stmmac_rxq_stats *rxq_stats = &priv->xstats.rxq_stats[queue];
 	struct stmmac_rx_queue *rx_q = &priv->dma_conf.rx_queue[queue];
 	struct stmmac_channel *ch = &priv->channel[queue];
-	int coe = priv->dev->features & NETIF_F_RXCSUM;
 	unsigned int count = 0, error = 0, len = 0;
 	unsigned int next_entry = rx_q->cur_rx;
 	enum dma_data_direction dma_dir;
@@ -5892,11 +5923,7 @@ drain_data:
 
 		skb->protocol = eth_type_trans(skb, priv->dev);
 
-		if (unlikely(!coe) || !stmmac_has_ip_ethertype(skb) ||
-		    (status & csum_none))
-			skb_checksum_none_assert(skb);
-		else
-			skb->ip_summed = CHECKSUM_UNNECESSARY;
+		stmmac_get_rx_csum(priv, status, skb);
 
 		if (!stmmac_get_rx_hash(priv, p, &hash, &hash_type))
 			skb_set_hash(skb, hash, hash_type);