netdevsim: pass packets thru GRO on Rx

To replace veth in software GRO testing with netdevsim we need
GRO support in netdevsim. Luckily we already have NAPI support
so this change is trivial (compared to veth).

Reviewed-by: Petr Machata <[e-mail]>
Reviewed-by: Willem de Bruijn <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/netdevsim/netdev.c

···
 		}
 
 		/* skb might be discard at netif_receive_skb, save the len */
-		skblen = skb->len;
-		skb_mark_napi_id(skb, &rq->napi);
-		ret = netif_receive_skb(skb);
-		if (ret == NET_RX_SUCCESS)
-			dev_dstats_rx_add(dev, skblen);
-		else
-			dev_dstats_rx_dropped(dev);
+		dev_dstats_rx_add(dev, skb->len);
+		napi_gro_receive(&rq->napi, skb);
 	}
 
 	nsim_start_peer_tx_queue(dev, rq);