Only set L2TP_ATTR_UDP_CSUM in l2tp_nl_tunnel_send()
when it's running over IPv4.
This prepares the code to also have IPv6 specific attributes.
Signed-off-by: Asbjoern Sloth Toennesen <asbjorn@asbjorn.st>
Signed-off-by: David S. Miller <davem@davemloft.net>
 
        switch (tunnel->encap) {
        case L2TP_ENCAPTYPE_UDP:
+               switch (sk->sk_family) {
+               case AF_INET:
+                       if (nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx))
+                               goto nla_put_failure;
+                       break;
+               }
                if (nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
-                   nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)) ||
-                   nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx))
+                   nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
                        goto nla_put_failure;
                /* NOBREAK */
        case L2TP_ENCAPTYPE_IP: