tcp: move mdev_us init to tcp_disconnect()

If we make sure a listener always has its mdev_us
field set to TCP_TIMEOUT_INIT, we do not need to rewrite
this field after a new clone is created.

tcp_disconnect() is very seldom used in real applications.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -2572,6 +2572,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	sk->sk_shutdown = 0;
 	sock_reset_flag(sk, SOCK_DONE);
 	tp->srtt_us = 0;
+	tp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
 	tp->rcv_rtt_last_tsecr = 0;
 	tp->write_seq += tp->max_window + 2;
 	if (tp->write_seq == 0)

net/ipv4/tcp_minisocks.c

@@ -479,7 +479,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 
 	tcp_init_wl(newtp, treq->rcv_isn);
 
-	newtp->mdev_us = jiffies_to_usecs(TCP_TIMEOUT_INIT);
 	minmax_reset(&newtp->rtt_min, tcp_jiffies32, ~0U);
 	newicsk->icsk_ack.lrcvtime = tcp_jiffies32;