rc.d: Add ipfw_netflow

[manu]

Summary

Add an rc.d script to setup a netflow export via ng_netflow
The default is to export netflow data on localhost on the netflow port.
ngtee is used to have the lowest overhead possible.
The ipfw ng hook is the netflow port (it can only be numeric)
Default is netflow version 5.

Sponsored-By: Gandi.net

Test Plan

Tested on router that nat etc ...

[olivier]

I like it: It's work :-)
Some potential improvement:

• allowing to configure just the rule number (01000) in place of having to declaring the full rule line
• Cosmetic: Setting a name to the ksocket, like export-flow or something like that (it just help to describe a little-better the graphiz).

[manu]

Add checks on hook and rule params.
Rule now is only the rule number, easier to customize existing ipfw setup.
Name the ksocket so graph generated by ngctl dot is prettier.

[manu]

Add checks and status command

[manu]

Commited as r320944