Add external dependency libnftables.
When an hNodeB registers, set up nftables rules to count GTP-U packets
(UDP port 2152) to and from that hNodeB's address -- we are assuming
that it is the same address that Iuh is connecting from.
This is a "workaround" to get performance indicators per hNodeB, without
needing a UPF that supports URR.
This patch reads counters from the nftables response using "manual"
string parsing. See also Id4e7fa017c31945388a010d8581715d71482116b which
modifies this to full JSON parsing.
Tweaked-by: osmith
Related: SYS#6773
Depends: libosmocore I0df84b4bb8cb5d8434b735fa3a38e7f95be43e91
Change-Id: I35b7e97fd039e36633dfde1317170527c82f9f68
Neels Hofmeyr
92bf0e31b0