tcp: move synflood_warned into struct request_sock_queue

long term plan is to remove struct listen_sock when its hash
table is no longer there.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/request_sock.h

@@ -123,7 +123,6 @@ extern int sysctl_max_syn_backlog;
  */
 struct listen_sock {
 	u32			max_qlen_log;
-	u32			synflood_warned;
 	u32			hash_rnd;
 	u32			nr_table_entries;
 	struct request_sock	*syn_table[0];
@@ -171,6 +170,7 @@ struct fastopen_queue {
 struct request_sock_queue {
 	spinlock_t		rskq_lock;
 	u8			rskq_defer_accept;
+	u32			synflood_warned;
 
 	atomic_t		qlen;
 	atomic_t		young;

net/ipv4/tcp_input.c

@@ -6068,9 +6068,9 @@ static bool tcp_syn_flood_action(const struct sock *sk,
 				 const struct sk_buff *skb,
 				 const char *proto)
 {
+	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 	const char *msg = "Dropping request";
 	bool want_cookie = false;
-	struct listen_sock *lopt;
 
 #ifdef CONFIG_SYN_COOKIES
 	if (sysctl_tcp_syncookies) {
@@ -6081,10 +6081,9 @@ static bool tcp_syn_flood_action(const struct sock *sk,
 #endif
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
 
-	lopt = inet_csk(sk)->icsk_accept_queue.listen_opt;
-	if (!lopt->synflood_warned &&
+	if (!queue->synflood_warned &&
 	    sysctl_tcp_syncookies != 2 &&
-	    xchg(&lopt->synflood_warned, 1) == 0)
+	    xchg(&queue->synflood_warned, 1) == 0)
 		pr_info("%s: Possible SYN flooding on port %d. %s.  Check SNMP counters.\n",
 			proto, ntohs(tcp_hdr(skb)->dest), msg);