IPv6 (only) support

[sgryphon]

I have asset tracker running on my Thingy:91, connecting to nRFCloud, but only when I have IPv4 or dual stack enabled.

With IPv6 only enabled (setting PDN family / type to IPv6), the application fails to connect.

From the logs, it seems to be trying to use an IPv4 address to connect to:

<dbg> nrf_cloud_transport: nct_connect: IPv4 address: 3.208.62.91
...
<err> nrf_cloud: nRF cloud connect failed -114

Note that with the work IPv4 it actually goes through a carrier NAT44 gateway, i.e. the device is on a private IPv4 network and has to go through NAT44 to get to the server.

On the IPv6 network there is a similar setup; the carrier runs DNS64 and NAT64, which means an IPv6 server is connected directly, but an IPv4 server is still reachable via NAT64 (with the same NAT address as in the IPv4 mode).

Note that I have confirmed this works for a basic HTTPS connection, i.e. on the IPv6 only network I have tested against an IPv4 only server.

[coderbyheart]

Please use {DevZone for questions that are not related to nRF Asset Tracker (there is no nRF Cloud support in nRF Asset Tracker).