e1000: Small packets may get corrupted during padding by HW

On PCI/PCI-X HW, if packet size is less than ETH_ZLEN,
packets may get corrupted during padding by HW.
To WA this issue, pad all small packets manually.

Signed-off-by: Tushar Dave <tushar.n.dave@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -3149,6 +3149,17 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb,
 		return NETDEV_TX_OK;
 	}
 
+	/* On PCI/PCI-X HW, if packet size is less than ETH_ZLEN,
+	 * packets may get corrupted during padding by HW.
+	 * To WA this issue, pad all small packets manually.
+	 */
+	if (skb->len < ETH_ZLEN) {
+		if (skb_pad(skb, ETH_ZLEN - skb->len))
+			return NETDEV_TX_OK;
+		skb->len = ETH_ZLEN;
+		skb_set_tail_pointer(skb, ETH_ZLEN);
+	}
+
 	mss = skb_shinfo(skb)->gso_size;
 	/* The controller does a simple calculation to
 	 * make sure there is enough room in the FIFO before