IPv6 tethering

[Mygod]

Currently AOSP only has support for IPv6 tethering when using mobile networks under supported carriers since Android 7.0.

It's unclear how to do this for IPv6-capable VPN or even Wi-Fi. The main issue is configuring a valid IPv6 address for clients. This is further complicated by the fact that sometimes dnsmasq (actually I'm not 100% sure yet) will configure another valid IPv6 address using Router Advertisement.

Update: It might be possible to create a bridge. [1, 2]

[githuborer]

Looks like a prob here too. My Xiaomi Mi6 has mobile IPv6 support. If I connect to IPv6 vpn-server my Android has the new default v6 route through tunnel. But all clients have an IPv6 leak even if "Disable IPv6 tethering" option is enabled. I 'll show all routes / routing tables if I 've more time.

[Mygod]

@githuborer That would certainly be helpful. You should check if your clients have an IPv6 address after checking "Disable IPv6 tethering". If you want to do a follow-up, feel free to open another issue as this one is reserved for handling IPv6 tethering better.

[githuborer]

You should check if your clients have an IPv6 address after checking "Disable IPv6 tethering".

Yes that's the point. Real IPv6 is leaking to connected clients. "Disable IPv6 tethering" option does nothing for my phone.

[glennbutler]

Hey I have a OnePlus6 on TMobile which prefers IPv6 by default. I noticed some interesting things recently:

1. I always used Disable IPv6 and if you do whatismyip.com -- laptop only detects IPv4
2. USB DNS has issue when Is this app unable to transfer udp? #1 is turned on, so I turned it off and USB Tethering works.
3. With a VPN (I sometimes use my home/vacation home using OpenVPN and have NordVPN -- both IPv4), if Disable IPv6 is turned off, turning on the VPN does nothing (causes all traffic to go around the VPN), whereas if Disable IPv6 is turned on, all traffic goes through the VPN. You can turn the VPN on and off and traffic will switch to going over the VPN or native at will. So on my phone, re-enabling the IPv6 totally defeats VPN's purpose -- all traffic goes around the VPN.

I am using rooted OnePlus Oxygen, but I think it is pretty close to vanilla Android -- the phone was bought unlocked...the TMobile version may have different tethering system.

I could contribute and look into fixing this -- assume most of this is implemented through iptables and ip6tables, right? Would also love to add a TTL (IPv4) hop limit (IPv6) option to help people using the app to get around tethering restrictions...

[Mygod]

@glennbutler It would be great if you can look into this! I think this might be more than messing with ip6tables as for some VPNs, a simple IPv6 forwarding rule may be enough, but for others some kind of IPv6 NAT might be required (I'm not sure if Android kernel supports this).

[Mygod]

I took an additional look at this and here are my thoughts.

For now, I do not plan to support any kind of IPv6 NAT (because I think IPv4-only NAT should cover all the use cases). However, using a neighbor discovery proxy might be useful for local-only interfaces (portier might be useful but still in development) for advantages of IPv6 networks.

No plan on implementing this any time soon yet.

[androidacy-user]

Verizon support IPv6 natively as well, but none of the wifi networks I use (college, library) do (mind you I only tether on data).

For whatever reason if I set up block IPv6 in VPN hotspot Firefox Nightly on my PC fails to connect to any website (getting an IPv6 address from DNS looks like, and it thinks it can connect but it can't).

[Mygod]

@linuxandria Sounds like the browser cannot do IPv4 fallback gracefully. Try disabling and reenabling your WiFi on your laptop so that it no longer holds a global IPv6 address.

[androidacy-user]

@Mygod you have any idea how many times I tried that? Lol