Commit fe7f4052 authored by Dave Stevenson's avatar Dave Stevenson Committed by Phil Elwell
Browse files

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: default avatarDave Stevenson <dave.stevenson@raspberrypi.org>
parent b26ec5dc

drivers/net/usb/lan78xx.c

+5 −1
Original line number Diff line number Diff line
@@ -2973,8 +2973,12 @@ static void lan78xx_rx_csum_offload(struct lan78xx_net *dev, 
				    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_));