reverse proxy with dns control

[arx]

I succeeded, practically the directives

roxy_buffering off;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;

they had to be placed on top location  "if ($host ~ testdns) {

and under
location / {

now I should make an external file with all allowed dns I would like someone
to help me with the syntax

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,293951,293959#msg-293959