AllowedIPs = ::/0 routes IPv4 - on Android?

[Valentijn Sessink]

Hi Marek,

Do you have any sources for that? AFAIK, ::/0 is a convenient way to 
describe "any IPv6 address".

Still, if you are correct and should ::/0 include IPv4, then the exact 
same setup under Linux operates differently, because here ::/0 only 
routes IPv6, not IPv4. Note the empty result for the ipv4 routing table:

# AllowedIPs = ::/0
v at lnx:~$ ip ro li ta 51820
v at lnx:~$ ip -6 ro li ta 51820
default dev wgip6 metric 1024 pref medium

# AllowedIPs = ::/0, 0.0.0.0/0
v at lnx:~$ ip ro li ta 51820
default dev wgip6 scope link
v at lnx:~$ ip -6 ro li ta 51820
default dev wgip6 metric 1024 pref medium

So the question remains: ::/0 under Android routes all IPv4 traffic to 
the WG interface, while under Linux, it will only route IPv6.
Is this known behaviour?

The wg-quick manpage is ambiguous, saying that "if one of those routes 
is the default route (0.0.0.0/0 or ::/0), then it uses ip-rule(8) to 
handle overriding of the default gateway." No information on routing 
IPv4 or IPv6 differently.

A rephrase could be something like "if one of those routes is 0.0.0.0/0, 
or ::/0, it uses ip-rule(8) to handle overriding the default route for 
IPv4 or IPv6 respectivally."

Best regards,

Valentijn

On 24-10-2023 11:37, Marek Küthe wrote:
> ::/0 does not describe no IPv4 address, but all IP addresses. So when
[...]
> On Tue, 5 Sep 2023 16:04:34 +0200
> Valentijn Sessink <v at sess.ink> wrote:
>> AllowedIPs = ::/0
[...]
>> To my surprise, I found out that this also tries to route IPv4 addresses
>> to the other WG side.
>> Is this a known feature? Android 13, WireGuard for Android
>> v1.0.20230707, (from AOSP).-- 
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