how to know that wifi supports only ipv6 i.e it is ipv6 only router

How can Wifi router clients can know that router supports ipv6 only and does not support ipv4 ?.

We currently use a faulty logic that if router does not provide ipv4 ip . consider it as ipv6 only router .

but this can cause problem in case of some ipv4 dhcp server issue in router .

can supplicant or other module can know that it is ipv6 only router ?.

is there any android api to know this .

Solution

The clients can't know if the router only provides IPv6 or if router has an ipv4-failure.

Smart clients could check if DNS is DNS64. In that case the probability is high, that the router doesn't provide IPv4.

There is a draft on going to do it via flag in the RAs.