net: l2tp: only set L2TP_ATTR_UDP_CSUM if AF_INET

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: NAsbjoern Sloth Toennesen <asbjorn@asbjorn.st>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/l2tp/l2tp_netlink.c

@@ -379,9 +379,14 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int fla
 
 	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: