V 9.18.1 not listen on port 853 after rndc reload

[MAYER Hans]

Dear All, 

now BIND 9.18 is supporting DoT directly I tried to go away from a solution with stunnel4 and therefore I compiled 9.18.1 and modified named.conf
So far everything is working fine. All the tests with dig , openssl and lsof is showing it’s working. 
The problem: when I run a „rndc reload“ the named process is not listen on 853/tcp anymore. All tests with TLS fail. And this on IPv4 as well on IPv6.
The rest of BIND is working well. Still listening on port 53 on UDP and TCP 
When I restart the service so that named stops and a new process is started and running then DoT is working again. 
I run this on Debian 10 buster. 
The interesting story is I run the same version 9.18.1 on a different Debian 10 buster server. On this server the process „named" survives a „rndc reload“  on port 853 

Looking at the log I see: 
network: error: creating TLS socket: permission denied

Why doesn’t named have the permissions after a „rndc reload“ but it has the permissions after a start ? And why on one server but not on another ? 
In both cases the daemon is running as user „bind“ with UID below 128 but not as root. 

Any ideas where to look ? 

Kind regards 
Hans 

— 


maybe the important part of the config

        listen-on {
                   my.ipv4.hiding.here  ;
                   127.0.0.1 ;
        };
        listen-on port 853 tls iiasaatls { any; }; 
        listen-on-v6 { any ; } ;
        listen-on-v6 port 853 tls iiasaatls { any; };