r8169: fix rx checksum offload

While porting GRO to r8169, I found this driver has a bug in its rx
path.

All skbs given to network stack had their ip_summed set to
CHECKSUM_NONE, while hardware said they had correct TCP/UDP checksums.

The reason is driver sets skb->ip_summed on the original skb before the
copy eventually done by copybreak. The fresh skb gets the ip_summed =
CHECKSUM_NONE value, forcing network stack to recompute checksum, and
preventing my GRO patch to work.

Fix is to make the ip_summed setting after skb copy.

Note : rx_copybreak current value is 16383, so all frames are copied...
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/r8169.c

@@ -4450,9 +4450,8 @@ static inline int rtl8169_fragmented_frame(u32 status)
 	return (status & (FirstFrag | LastFrag)) != (FirstFrag | LastFrag);
 }
 
-static inline void rtl8169_rx_csum(struct sk_buff *skb, struct RxDesc *desc)
+static inline void rtl8169_rx_csum(struct sk_buff *skb, u32 opts1)
 {
-	u32 opts1 = le32_to_cpu(desc->opts1);
 	u32 status = opts1 & RxProtoMask;
 
 	if (((status == RxProtoTCP) && !(opts1 & TCPFail)) ||
@@ -4546,8 +4545,6 @@ static int rtl8169_rx_interrupt(struct net_device *dev,
 				continue;
 			}
 
-			rtl8169_rx_csum(skb, desc);
-
 			if (rtl8169_try_rx_copy(&skb, tp, pkt_size, addr)) {
 				pci_dma_sync_single_for_device(pdev, addr,
 					pkt_size, PCI_DMA_FROMDEVICE);
@@ -4558,6 +4555,7 @@ static int rtl8169_rx_interrupt(struct net_device *dev,
 				tp->Rx_skbuff[entry] = NULL;
 			}
 
+			rtl8169_rx_csum(skb, status);
 			skb_put(skb, pkt_size);
 			skb->protocol = eth_type_trans(skb, dev);