cxgb4vf: don't offload Rx checksums for IPv6 fragments

The checksum provided by the device doesn't include the L3 headers,
as IPv6 expects

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4vf/sge.c

@@ -1648,14 +1648,15 @@ int t4vf_ethrx_handler(struct sge_rspq *rspq, const __be64 *rsp,
 
 	if (csum_ok && !pkt->err_vec &&
 	    (be32_to_cpu(pkt->l2info) & (RXF_UDP_F | RXF_TCP_F))) {
-		if (!pkt->ip_frag)
+		if (!pkt->ip_frag) {
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
-		else {
+			rxq->stats.rx_cso++;
+		} else if (pkt->l2info & htonl(RXF_IP_F)) {
 			__sum16 c = (__force __sum16)pkt->csum;
 			skb->csum = csum_unfold(c);
 			skb->ip_summed = CHECKSUM_COMPLETE;
+			rxq->stats.rx_cso++;
 		}
-		rxq->stats.rx_cso++;
 	} else
 		skb_checksum_none_assert(skb);