net/packet: fix packet drop as of virtio gso

When we use raw socket as the vhost backend, a packet from virito with
gso offloading information, cannot be sent out in later validaton at
xmit path, as we did not set correct skb->protocol which is further used
for looking up the gso function.

To fix this, we set this field according to virito hdr information.

Fixes: e858fae2b0b8f4 ("virtio_net: use common code for virtio_net_hdr and skb GSO conversion")
Signed-off-by: Jianfeng Tan <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/virtio_net.h

···
 #include <linux/if_vlan.h>
 #include <uapi/linux/virtio_net.h>
 
+static inline int virtio_net_hdr_set_proto(struct sk_buff *skb,
+					   const struct virtio_net_hdr *hdr)
+{
+	switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
+	case VIRTIO_NET_HDR_GSO_TCPV4:
+	case VIRTIO_NET_HDR_GSO_UDP:
+		skb->protocol = cpu_to_be16(ETH_P_IP);
+		break;
+	case VIRTIO_NET_HDR_GSO_TCPV6:
+		skb->protocol = cpu_to_be16(ETH_P_IPV6);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
 					const struct virtio_net_hdr *hdr,
 					bool little_endian)

net/packet/af_packet.c

···
 			}
 		}
 
-		if (po->has_vnet_hdr && virtio_net_hdr_to_skb(skb, vnet_hdr,
-							      vio_le())) {
-			tp_len = -EINVAL;
-			goto tpacket_error;
+		if (po->has_vnet_hdr) {
+			if (virtio_net_hdr_to_skb(skb, vnet_hdr, vio_le())) {
+				tp_len = -EINVAL;
+				goto tpacket_error;
+			}
+			virtio_net_hdr_set_proto(skb, vnet_hdr);
 		}
 
 		skb->destructor = tpacket_destruct_skb;
···
 		if (err)
 			goto out_free;
 		len += sizeof(vnet_hdr);
+		virtio_net_hdr_set_proto(skb, &vnet_hdr);
 	}
 
 	skb_probe_transport_header(skb, reserve);