[Joe_Cool]

Sadly all real firewalls need root. I was using AFWall+ for a long time it has neat controls for every app to allow or deny Wifi, Cell or LAN (if you have). It is a iptables/nftables frontend so you can customize the rules to your heart's content: https://github.com/ukanth/afwall Works from Android 2+

Without root only VPN solutions like Adguard are available.

EDIT: if you want neat stats: Glasswire has an Android version. I have only used the beta so I have no idea about its current state. Might be worth checking out though.

[ignoramous]

ex-AOSP and rethink dns+firewall dev here

> Sadly all real firewalls need root

What do you mean by a "real" firewall? It is very much possible to build a userspace firewall in Android using the VPN APIs.

On Android, ROMs like GrapheneOS, Lineage, and CalyxOS have firewalls built-in.

> Glasswire has an Android version

Note though, Glasswire was recently acquired by another company: https://archive.is/KW2R3

[yndoendo]

I thought parts of the Android OS can by-pass the VPN so the firewall becomes ineffective against blocking Google, OEMs, and others that have root. Wouldn't the VPN API being used as a firewall also prevent one to use a VPN client at the same time?

[khimaros]

for the latter, Rethink can be configured to work with eg. a wireguard VPN because it has a built-in wireguard client.

[Joe_Cool]

> Note though, Glasswire was recently acquired by another company

Ah that's why the premium stuff is now free. I was wondering. Let's hope it's not the first sign of enshittification.

> What do you mean by a "real" firewall?

In my experience the "block all non VPN traffic" options in Android don't work reliably. iptables does however.

It's a sad state that you cannot even set a static IPv6 on Android without root.

[ignoramous]

> In my experience the "block all non VPN traffic" options in Android don't work reliably. iptables does however.

Both (iptables/nftables and VPN APIs) have to be enforced by the Linux Kernel, which is subject to the same "Androidisms", if that makes sense.

root, in fact, opens up a gaping hole in that, it totally compromises Android's security model. IMO, it isn't worth to root Android just to run iptables (just because it seems like iptables is what makes a firewall).

[Joe_Cool]

IMHO Android's security model is incredibly flawed anyways. I don't even need root to access stuff I shouldn't have access to on my Mediatek based phone because the firmware has tons of gaping security holes anyways.

I think device you don't have root on isn't really yours and should be treated as a lease.

But you are right, when Wifi/Data is on at boot even the -tables might not get updated fast enough so stuff might get through.