Drop connections to nginx which don't match any server block

drop-unknown-hosts.conf

server {
	listen 80 default_server;
	listen [::]:80 default_server;

	listen 443 ssl default_server;
	listen [::]:443 ssl default_server;

	## For nginx >= 1.19.4:
	## If also using openssl >= 1.1.1j, the certificate directives can be removed.
	## Even if present, the cert is never sent, it's just a workaround for an openssl bug.
	#ssl_reject_handshake on;
	#ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem;		# Generated by ssl-cert package
	#ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;	# Generated by ssl-cert package
	#ssl_stapling off;
	
	## For nginx < 1.19.4:
	## Due to the limitations of this version, the cert will be sent to a client when using TLS1.3.
	## The only other option would be to disable TLS1.3 for the whole nginx instance, which would be silly.
	## The connection will still be dropped after the TLS handshake.
	#ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem;		# Generated by ssl-cert package
	#ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;	# Generated by ssl-cert package
	#ssl_stapling off;
	#ssl_ciphers aNULL;

	return 444;
	error_page 400 =444 /;
}