[PPP]: Fixed hardware RX checksum handling

When we pull the PPP protocol off the skb, we forgot to update the
hardware RX checksum.  This may lead to messages such as

	dsl0: hw csum failure.

Similarly, we need to clear the hardware checksum flag when we use
the existing packet to store the decompressed result.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ppp_generic.c

@@ -1610,6 +1610,8 @@ ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb)
 		}
 		else if (!pskb_may_pull(skb, skb->len))
 			goto err;
+		else
+			skb->ip_summed = CHECKSUM_NONE;
 
 		len = slhc_uncompress(ppp->vj, skb->data + 2, skb->len - 2);
 		if (len <= 0) {
@@ -1690,6 +1692,7 @@ ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb)
 			kfree_skb(skb);
 		} else {
 			skb_pull(skb, 2);	/* chop off protocol */
+			skb_postpull_rcsum(skb, skb->data - 2, 2);
 			skb->dev = ppp->dev;
 			skb->protocol = htons(npindex_to_ethertype[npi]);
 			skb->mac.raw = skb->data;