vxlan: Add checksum check to the features check function

We need to perform an additional check on the inner headers to determine if
we can offload the checksum for them.  Previously this check didn't occur
so we would generate an invalid frame in the case of an IPv6 header
encapsulated inside of an IPv4 tunnel.  To fix this I added a secondary
check to vxlan_features_check so that we can verify that we can offload the
inner checksum.
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/if_ether.h

@@ -28,6 +28,11 @@ static inline struct ethhdr *eth_hdr(const struct sk_buff *skb)
 	return (struct ethhdr *)skb_mac_header(skb);
 }
 
+static inline struct ethhdr *inner_eth_hdr(const struct sk_buff *skb)
+{
+	return (struct ethhdr *)skb_inner_mac_header(skb);
+}
+
 int eth_header_parse(const struct sk_buff *skb, unsigned char *haddr);
 
 extern ssize_t sysfs_format_mac(char *buf, const unsigned char *addr, int len);

include/net/vxlan.h

@@ -252,7 +252,9 @@ static inline netdev_features_t vxlan_features_check(struct sk_buff *skb,
 	    (skb->inner_protocol_type != ENCAP_TYPE_ETHER ||
 	     skb->inner_protocol != htons(ETH_P_TEB) ||
 	     (skb_inner_mac_header(skb) - skb_transport_header(skb) !=
-	      sizeof(struct udphdr) + sizeof(struct vxlanhdr))))
+	      sizeof(struct udphdr) + sizeof(struct vxlanhdr)) ||
+	     (skb->ip_summed != CHECKSUM_NONE &&
+	      !can_checksum_protocol(features, inner_eth_hdr(skb)->h_proto))))
 		return features & ~(NETIF_F_CSUM_MASK | NETIF_F_GSO_MASK);
 
 	return features;