BIND 9.16 incoming TCP connection errors

[Anand Buddhdev]

Hi folks,

I'm running an authoritative server on BIND 9.16. It gets about 3500 
q/s, of which around 200 q/s are over TCP. At least, this is what DSC 
reports (DSC is a libpcap application sniffing traffic independent of BIND).

In my named.conf, I have set:

reserved-sockets 1000;
tcp-clients 900;

Yet, when BIND is running, it is frequently logging:

16-Jun-2020 15:21:58.815 general: Accepting TCP connection failed: 
socket is not connected

What does this log message mean? I don't think it's related to quota, 
because the quota message is different ("TCP connection failed: quota 
reached").

Another question I have is that the "reserved-sockets" option has a note 
saying that it might go away. Does this mean that it's not actually 
necessary? The documentation suggests that I have to increase it if I 
want to increase the value of "tcp-clients".

Regards,
Anand