mikaela.github.io/n/firewalld.md

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# Quick note on firewalld usage

This is practically [/ufw](/ufw), but fore Firewalld which Fedora comes with.
The blog post also predates me having a /n directory here.

**_After done, run `sudo firewall-cmd --reload`_**

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- [Zones](#zones)
- [Protocols](#protocols)
- [Services](#services)
- [Ports](#ports)

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## Zones

firewalld zones are privilege of NetworkManager users, this tends to be
a systemd-networkd household. Then again I don't believe in absolutely trusted
zones.

Zone would be specified by `--zone=home` in the commands. The other zone I
could imagine using is `public`.

## Protocols

```bash
sudo firewall-cmd --add-protocol=ipv6-icmp --permanent
```

- Tells computers when things go wrong with IPv6 network. See also [Neil Alexander: Understanding ICMP and why you shouldn't just block it outright](https://neilalexander.dev/2017/04/16/understanding-icmp).
  - _Motivation for being here is [20/20 in IPv6-test.com](https://ipv6-test.com)._

## Services

```bash
sudo firewall-cmd --add-service=ssh --permanent
sudo firewall-cmd --add-service=mosh --permanent
sudo firewall-cmd --add-service=ntp --permanent
sudo firewall-cmd --add-service=syncthing --permanent
sudo firewall-cmd --add-service=mdns --permanent
```

- I trust Chrony (ntp) to not allow it to be used from outside of LAN
  as `firewalld` is apparently not designed with limiting source
  addresses in mind.
- `syncthing` is the client, not to be confused with `syncthing-gui`
  or `syncthing-relay`.

## Ports

```bash
sudo firewall-cmd --permanent --add-port=9001/udp
sudo firewall-cmd --permanent --add-port=6771/udp
```

- `9001/udp` is Yggdrasil automatic peering, although link-local and
  unlikely to be recognised by predefined rules.
- `6771/udp` is [Bittorrent Local Peer Discovery](http://bittorrent.org/beps/bep_0014.html)