Changes

gtp_tunnel: Log Tx of ICMPv6 Router Solicitation

Change-Id: I5883a0e399e47b6e169c5adf8446e9d2aeecbe68

Support configuring IPv4v6 tunnels

Change-Id: Ic2da7a761a8df7e006fc02ca6557a48f371e4151

Implement logic to perform IPv6 SLAAC in GTPU tunnel

The IPv6 SLAAC prcoedure is not yet triggered in this patch; it will be
triggered by cups_client's new command in follow-up patch.

Depends: libosmo-netif.git Change-Id I78ec7270c717af0a1b8ffd9398cd69ea7a0dbee2
Change-Id: I837a4d7ec7c134412ab4a2e09909670e81ecbeea

cups_client: Add commands to perform IPv6 SLAAC and obtain GTP tunnel IPv6 global info

Change-Id: I917b5c70f143d48b55b4e270e24594d1a36f71aa

cups_client: SPlit Tx of json str into its own function

This helper can be used in the future to submit a str multiple times
(eg. to multiple cups clients) without having to re-allocate the
content.

Change-Id: I505bf2eeea998a749e55f8f3b05c5013b5761297

cups_client: Log error decoding EUA

Change-Id: I98c7841da0f2662291aab5180f6113cb5fca4867