r8169: Support RX-FCS flag.

This allows the NIC to receive the Ethernet FCS
and pass it up the stack, allowing sniffers and
other interested programs to inspect the FCS.

Signed-off-by: Ben Greear <greearb@candelatech.com>

drivers/net/ethernet/realtek/r8169.c

@@ -4186,6 +4186,7 @@ rtl8169_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 		dev->hw_features &= ~NETIF_F_HW_VLAN_RX;
 
 	dev->hw_features |= NETIF_F_RXALL;
+	dev->hw_features |= NETIF_F_RXFCS;
 
 	tp->hw_start = cfg->hw_start;
 	tp->event_slow = cfg->event_slow;
@@ -5773,7 +5774,10 @@ static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, u32 budget
 
 process_pkt:
 			addr = le64_to_cpu(desc->addr);
-			pkt_size = (status & 0x00003fff) - 4;
+			if (likely(!(dev->features & NETIF_F_RXFCS)))
+				pkt_size = (status & 0x00003fff) - 4;
+			else
+				pkt_size = status & 0x00003fff;
 
 			/*
 			 * The driver does not support incoming fragmented