[PATCH net-next v4 08/16] net: ethernet: oa_tc6: Remove FCS size in RX frame

[Selvamani Rajagopal via B4 Relay <devnull+Selvamani.Rajagopal.onsemi.com@kernel.org>]

From: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>

OA TC6 MAC-PHY appends FCS to the incoming frame.
It is removed from the frame before being passed to the stack.

Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@onsemi.com>
---
 drivers/net/ethernet/oa_tc6/oa_tc6.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/oa_tc6/oa_tc6.c b/drivers/net/ethernet/oa_tc6/oa_tc6.c
index 2f9ace655e81..26033373f16f 100644
--- a/drivers/net/ethernet/oa_tc6/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6/oa_tc6.c
@@ -782,12 +782,22 @@ static void oa_tc6_submit_rx_skb(struct oa_tc6 *tc6)
 {
 	oa_tc6_update_ts_in_rx_skb(tc6);
 
+	/* MAC-PHY delivers each frame with its Ethernet FCS attached.
+	 * Strip it before handing over to the stack, unless the user
+	 * has asked to keep it via NETIF_F_RXFCS. Keeping the FCS
+	 * in the frame is harmless for IP traffic, but is parsed as
+	 * a (malformed) suffix TLV by PTP, which makes ptp4l reject
+	 * every message with "bad message" error.
+	 */
+	if (!(tc6->netdev->features & NETIF_F_RXFCS) &&
+			tc6->rx_skb->len > ETH_FCS_LEN)
+		skb_trim(tc6->rx_skb, tc6->rx_skb->len - ETH_FCS_LEN);
+
 	tc6->rx_skb->protocol = eth_type_trans(tc6->rx_skb, tc6->netdev);
 	tc6->netdev->stats.rx_packets++;
 	tc6->netdev->stats.rx_bytes += tc6->rx_skb->len;
 
 	netif_rx(tc6->rx_skb);
-
 	tc6->rx_skb = NULL;
 }
 

-- 
2.43.0