l2tp: Enable checksum unnecessary conversions for l2tp/UDP sockets

Signed-off-by: NTom Herbert <therbert@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/l2tp/l2tp_core.c

@@ -1392,6 +1392,8 @@ static int l2tp_tunnel_sock_create(struct net *net,
 		if (err < 0)
 			goto out;
 
+		udp_set_convert_csum(sock->sk, true);
+
 		break;
 
 	case L2TP_ENCAPTYPE_IP: