[NETFILTER]: Fix HW checksum handling in ECN target

Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ipt_ECN.c

@@ -71,6 +71,10 @@ set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward)
 		return 0;
 	tcph = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4;
 
+	if ((*pskb)->ip_summed == CHECKSUM_HW &&
+	    skb_checksum_help(*pskb, inward))
+		return 0;
+
 	diffs[0] = ((u_int16_t *)tcph)[6];
 	if (einfo->operation & IPT_ECN_OP_SET_ECE)
 		tcph->ece = einfo->proto.tcp.ece;
@@ -79,13 +83,10 @@ set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward)
 	diffs[1] = ((u_int16_t *)tcph)[6];
 	diffs[0] = diffs[0] ^ 0xFFFF;
 
-	if ((*pskb)->ip_summed != CHECKSUM_HW)
+	if ((*pskb)->ip_summed != CHECKSUM_UNNECESSARY)
 		tcph->check = csum_fold(csum_partial((char *)diffs,
 						     sizeof(diffs),
 						     tcph->check^0xFFFF));
-	else
-		if (skb_checksum_help(*pskb, inward))
-			return 0;
 	(*pskb)->nfcache |= NFC_ALTERED;
 	return 1;
 }