This is the [B]ag [O]f [N]etgraph [E]xtensions. An evolving set of extra
netgraph(4) kernel modules.

At present this module provides the following additional nodes:
* ng_pcap(4) provides a way to get pcap information from the netgraph(4)
  system.
* ng_wormhole(4) provides a way to connect vnet enabled jails using netgraph(4).
* ng_ula4tag(4) provides a way to VLAN tag traffic that is either (or both) IPv4
  or IPv6 unique local addresses (ULA).

See manpages for more details and example usage.
net/bone-utils has utilities that simplify using the nodes in this pkg.

If you are on CURRENT you likely need the @invariants flavor.