quoted

      case TCP_SYN_SENT:

@@ -1491,8 +1492,10 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
       */
      if (inet_csk_reqsk_queue_is_full(sk) && !isn) {
              want_cookie = tcp_syn_flood_action(sk, skb, "TCP");
-             if (!want_cookie)
+             if (!want_cookie) {
+                     NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
                      goto drop;
+             }

This should be done in tcp_syn_flood_action() for IPv4/IPv6
factorization.

Thanks Eric. In fact, tcp_syn_flood_action() already has
                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);

which is the right thing to do instead of incrementing LISTENOVERFLOWS
since it is syn table that is overflowing and
not accept_queue.

I will send V2 with this fixed.

Vijay