IPv4 mapping doesn't work

[nerdius]

Subject of the issue

I'm using Podman and directly fetching the image from docker.io/vaultwarden/server:latest. I'm trying to deploy it using the following command:
podman run -d --userns=keep-id --name vaultwarden -e SIGNUPS_ALLOWED=false -e ROCKET_PORT=3020 -v /home/USERNAME/apps/vaultwarden/vw-data/:/data/:Z -p 3020:3020 vaultwarden/server:latest

The output indicates a successful deployment:

Resolved "vaultwarden/server" as an alias (/home/USERNAME/.cache/containers/short-name-aliases.conf)
Trying to pull docker.io/vaultwarden/server:latest...
Getting image source signatures
Copying blob 8fdbf8c74aad skipped: already exists  
Copying blob 3953aa1aac1b skipped: already exists  
Copying blob ffbb094f4f9e skipped: already exists  
Copying blob f94ad8d4973a skipped: already exists  
Copying blob e436b51dcd0d skipped: already exists  
Copying blob 31d34e7d15a6 skipped: already exists  
Copying blob c79b268f4fca done  
Copying config a0e0193b46 done  
Writing manifest to image destination
Storing signatures
e8712edb5d0703b6376fa41174ba3822822b1ede188feb7e016de9962901ae4a

podman ps indicates that it's running:

CONTAINER ID  IMAGE                                COMMAND     CREATED        STATUS            PORTS                   NAMES
e8712edb5d07  docker.io/vaultwarden/server:latest  /start.sh   5 minutes ago  Up 5 minutes ago  0.0.0.0:3020->3020/tcp  vaultwarden

But when I try to access localhost:3020, nothing loads. Furthermore, the output of netstat -tulpn | grep 3020 indicates that there's an issue with port mapping as only IPv6 gets mapped:

(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
tcp6       0      0 :::3020                 :::*                    LISTEN      641312/containers-r

I since I'm running it in a rootless environment, I tried to add a sysctl rule to enable IPv4 forwarding on the host system by following this tutorial, but to no avail. I also tried different ports and command line parameters, rebooting the server, and setting SELinux to permissive. Nothing worked and the result was identical.

Deployment environment

• vaultwarden version: Latest from vaultwarden/server:latest.
• Install method: Docker image, via Podman.
• Clients used: N/A.
• Reverse proxy and version: Didn't get to it.
• MySQL/MariaDB or PostgreSQL version: N/A.
• Other relevant details: I'm running Rocky Linux 8 on the server. It's fully updated.

Steps to reproduce

1. Install the following packages on Rocky Linux 8: podman, podman-compose.
2. Install Vaultwarden using the following command:
   podman run -d --userns=keep-id --name vaultwarden -e SIGNUPS_ALLOWED=false -e ROCKET_PORT=3020 -v /home/USERNAME/apps/vaultwarden/vw-data/:/data/:Z -p 3020:3020 vaultwarden/server:latest
3. Try to connect to localhost:3020; check if localhost:3020 is listening.

Expected behaviour

IPv4 port should be exposed and I should be able to connect to it.

Actual behaviour

IPv4 mapping doesn't work and you can't connect to it.

Troubleshooting data

N/A.

[nerdius]

I don't know why, but it started working after some time and I can access the interface via Nginx proxy without issues.