HowTo: Setting Up NginxProxyManager (SSL) via 6tunnel

[herusalim]

Hi,
I am having a Dual Stack Lite internet provider (https://www.elektronik-kompendium.de/sites/net/2010211.htm).
Therefore, I have a virtual server to provide a tunnel to my local private servers.
Until now it works well to connect to my nginx proxy manager in my local server using this command line in my VPS

/usr/bin/6tunnel

When I am using non-SSL port (480 in this case), it works as expected.

After setting up certificate in my NPM, I wanted the 6tunnel to tunnel the request into the NPM SSL port (4443).

Unfortunately, in this setup, I got the following error:

400 Bad Request

The plain HTTP request was sent to HTTPS port

openresty

Here is the proxy host configuration

map $scheme $hsts_header {
    https   "max-age=63072000; preload";
}

server {
  set $forward_scheme http;
#  set $server         "nextcloud";
  set $port           80;

  listen 80;
listen [::]:80;

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

  server_name <server-name>;

  # Let's Encrypt SSL
  include conf.d/include/letsencrypt-acme-challenge.conf;
  include conf.d/include/ssl-ciphers.conf;
  ssl_certificate /etc/letsencrypt/live/npm-2/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/npm-2/privkey.pem;

  access_log /data/logs/proxy-host-5_access.log proxy;
  error_log /data/logs/proxy-host-5_error.log warn;

  location / {
    # Proxy!
    include conf.d/include/proxy.conf;
  }


  # Custom
  include /data/nginx/custom/server_proxy[.]conf;
}

Could anybody give some insight how could I ensure that the connection between my virtual server and my local server to use HTTPS? Or at least, how to debug this?

I am not sure that this is dependent to my proxy host config. Because I got the same issue even when I disabled my proxy host. But the browser shows 502 Bad Gateway when the NPM docker was shut down. So the issue must be caused somewhere in NPM.

Thanks and best regards,
Heru

PS:

• Access to the same server via HTTP (80) works as expected
• I have a similar setup with 6tunnel and an apache based wordpress server via HTTPS port, and it works. Therefore, I am wondering how to find the root cause of this issue.