From: Dave Stevenson <dave.stevenson@raspberrypi.org>
Date: Mon, 25 Jun 2018 14:07:15 +0000 (+0100)
Subject: net: lan78xx: Use s/w csum check on VLANs without tag stripping
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=9343ac87f2a4e09bf6e27b5f31e72e9e3a82abff;p=linux.git

net: lan78xx: Use s/w csum check on VLANs without tag stripping

Observations of VLANs dropping packets due to invalid
checksums when not offloading VLAN tag receive.
With VLAN tag stripping enabled no issue is observed.

Drop back to s/w checksums if VLAN offload is disabled.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 28da296f8cf7c..2e4130746c40c 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3052,8 +3052,13 @@ static void lan78xx_rx_csum_offload(struct lan78xx_net *dev,
 				    struct sk_buff *skb,
 				    u32 rx_cmd_a, u32 rx_cmd_b)
 {
+	/* HW Checksum offload appears to be flawed if used when not stripping
+	 * VLAN headers. Drop back to S/W checksums under these conditions.
+	 */
 	if (!(dev->net->features & NETIF_F_RXCSUM) ||
-	    unlikely(rx_cmd_a & RX_CMD_A_ICSM_)) {
+	    unlikely(rx_cmd_a & RX_CMD_A_ICSM_) ||
+	    ((rx_cmd_a & RX_CMD_A_FVTG_) &&
+	     !(dev->net->features & NETIF_F_HW_VLAN_CTAG_RX))) {
 		skb->ip_summed = CHECKSUM_NONE;
 	} else {
 		skb->csum = ntohs((u16)(rx_cmd_b >> RX_CMD_B_CSUM_SHIFT_));