For some time now I’ve been using reverse proxy for all my web applications, the only one that wasn’t playing ball was HomeAssistant, it just simply wouldn’t let me login. Now the below has fixed the issue!

dsm-reverse-proxy-websocket

Configuration fix for Synology DSM 6 reverse proxy to handle websocket

BACKUP YOUR portal.mustache BEFORE MODIFYING IT!

You need to edit the file /usr/syno/share/nginx/Portal.mustache to add the followings in the Location section:

proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_read_timeout 86400;

Then restart the httpd with:

sudo synoservicecfg --restart nginx

This will restart ALL http service running, not only reverse proxy, as a single instance of NGinX runs everything.

A modified Portal.mustache is provided in this repo (warning: based on DSM 6.1.6-15266).

Credit: https://github.com/orobardet/dsm-reverse-proxy-websocket