e1000e: Minimum packet size must be 17 bytes

This is a HW requirement. Although a buffer as short as 1 byte is allowed,
the total length of packet before, padding and CRC insertion, must be at
least 17 bytes.  So pad all small packets manually up to 17 bytes before
delivering them to HW.

Signed-off-by: Tushar Dave <[email protected]>
Tested-by: Jeff Pieper <[email protected]>
Signed-off-by: Jeff Kirsher <[email protected]>

Author: Tushar Dave

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -5067,6 +5067,17 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb,
 		return NETDEV_TX_OK;
 	}
 
+	/*
+	 * The minimum packet size with TCTL.PSP set is 17 bytes so
+	 * pad skb in order to meet this minimum size requirement
+	 */
+	if (unlikely(skb->len < 17)) {
+		if (skb_pad(skb, 17 - skb->len))
+			return NETDEV_TX_OK;
+		skb->len = 17;
+		skb_set_tail_pointer(skb, 17);
+	}
+
 	mss = skb_shinfo(skb)->gso_size;
 	if (mss) {
 		u8 hdr_len;