virtio_net: Fix IP alignment on non-mergeable RX path

We need to enforce the IP alignment on the non-mergeable RX path just
like the other RX path.  Not doing so results in misaligned IP
headers.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -283,10 +283,11 @@ static void try_fill_recv_maxbufs(struct virtnet_info *vi)
 	for (;;) {
 		struct virtio_net_hdr *hdr;
 
-		skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN);
+		skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN);
 		if (unlikely(!skb))
 			break;
 
+		skb_reserve(skb, NET_IP_ALIGN);
 		skb_put(skb, MAX_PACKET_LEN);
 
 		hdr = skb_vnet_hdr(skb);