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From 44136672c6043943bcf0772bb0edfb6fc23354dc Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.org>
Date: Mon, 9 Apr 2018 14:31:54 +0100
Subject: [PATCH 269/454] net: lan78xx: Request s/w csum check on VLAN tagged
 packets.

There appears to be some issue in the LAN78xx where the checksum
computed on a VLAN tagged packet is incorrect, or at least not
in the form that the kernel is after. This is most easily shown
by pinging a device via a VLAN tagged interface and it will dump
out the error message and stack trace from netdev_rx_csum_fault.
It has also been seen with standard TCP and UDP packets.

Until this is fully understood, request that the network stack
computes the checksum on packets signalled as having a VLAN tag
applied.

See https://github.com/raspberrypi/linux/issues/2458

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
---
 drivers/net/usb/lan78xx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2956,8 +2956,12 @@ static void lan78xx_rx_csum_offload(stru
                                    struct sk_buff *skb,
                                    u32 rx_cmd_a, u32 rx_cmd_b)
 {
+       /* Checksum offload appears to be flawed if used with VLANs.
+        * Elect for sw checksum check instead.
+        */
        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_)) {
                skb->ip_summed = CHECKSUM_NONE;
        } else {
                skb->csum = ntohs((u16)(rx_cmd_b >> RX_CMD_B_CSUM_SHIFT_));