udp: allow header check for dodgy GSO_UDP_L4 packets.

Allow UDP_L4 for robust packets.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp_offload.c

@@ -387,7 +387,8 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 		goto out;
 
-	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
+	    !skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST))
 		return __udp_gso_segment(skb, features, false);
 
 	mss = skb_shinfo(skb)->gso_size;

net/ipv6/udp_offload.c

@@ -42,7 +42,8 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 			goto out;
 
-		if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
+		    !skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST))
 			return __udp_gso_segment(skb, features, true);
 
 		mss = skb_shinfo(skb)->gso_size;