qBittorrent webui slow through Gluetun after enabling ipv6

[Linouxs]

I recently set up ipv6 in Docker so I could use ipv6 through the vpn. Everything works great, I can access ipv6 addresses through the vpn and connect to qBittorrent webui through port 8080 with FIREWALL_INPUT_PORTS, except after enabling ipv6 the webui of qBittorrent became very slow.

When i disconnect my qBittorrent container from the Gluetun container and test it directly to the qbittorrent container, the webgui loads instantly. It's only slow when i access the webui through gluetun since ipv6 was enabled.

I can curl -6 from another container in the same network to gluetun, so ipv6 seems working correctly. I also didn't see any errors in the container logs. Sometimes when I load the webui it gives the loading message: "Checking current auth state...".

Oh and I use Nginx Proxy Manager to access the webgui. Its a container on the same docker network. Its a user defined docker network in bridge mode with ipv4 and ipv6 addresses

[Linouxs]

I did some more testing but it seems that curl -6 in other containers to the webui isn't working anymore, it gives the error "No route to host" or "Could not connect to server" while using curl -4 works just fine. So I suspect a routing issue in the Gluetun container. FIREWALL_OUTBOUND_SUBNETS= to the ipv6 docker network subnet didn't solve the problem either.

Maybe I'm missing something but afaik iptables and the routing table looks alright in the Gluetun container (fd00 subnets/addresses are from the Docker network):

Routing table: