notes for BGP support

[adferguson]

to add BGP support to our L3external.flg program, we should connect it to Quagga via the remote table functionality. there are two ways to do this:

1. (probably simpler) Integrate with RouteFlow by implementing a proxy application which connects RouteFlow's messages to Flowlog's equivalent thrift events. Here are two examples of the integrated RFProxy application for Pox: https://github.com/CPqD/RouteFlow/tree/master/pox/ext and Ryu: https://github.com/routeflow/ryu-rfproxy
2. Integrate with Quagga directly. Quagga's zebra daemon has a "FIB Push Manager" (FPM) [1] developed by the Cumulous folks which sends the routing decisions via the Linux kernel's Netlink protocol (http://man7.org/linux/man-pages/man7/rtnetlink.7.html and linux/rtnetlink.h). We would write a proxy application which reads Netlink and transforms to appropriate Thrift messages for Flowlog

[1] http://www.nongnu.org/quagga/docs/docs-info.html#zebra-FIB-push-interface