tcp: avoid spurious SYN flood detection at listen() time

At listen() time, there is a small window where listener is visible with
a zero backlog, triggering a spurious "Possible SYN flooding on port"
message.

Nothing prevents us from setting the correct backlog.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 3 insertions, 3 deletions

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 3208a65d1c28..fd645c49e71e 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -312,7 +312,7 @@ static inline unsigned int inet_csk_listen_poll(const struct sock *sk)
                         (POLLIN | POLLRDNORM) : 0;
 }
 
-int inet_csk_listen_start(struct sock *sk, const int nr_table_entries);
+int inet_csk_listen_start(struct sock *sk, int backlog);
 void inet_csk_listen_stop(struct sock *sk);
 
 void inet_csk_addr2sockaddr(struct sock *sk, struct sockaddr *uaddr);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 514b9e910bd4..ba9ec9a0d0ce 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -727,14 +727,14 @@ void inet_csk_prepare_forced_close(struct sock *sk)
 }
 EXPORT_SYMBOL(inet_csk_prepare_forced_close);
 
-int inet_csk_listen_start(struct sock *sk, const int nr_table_entries)
+int inet_csk_listen_start(struct sock *sk, int backlog)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct inet_sock *inet = inet_sk(sk);
 
         reqsk_queue_alloc(&icsk->icsk_accept_queue);
 
-        sk->sk_max_ack_backlog = 0;
+        sk->sk_max_ack_backlog = backlog;
         sk->sk_ack_backlog = 0;
         inet_csk_delack_init(sk);