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2012-11-30fpm: Add public header for Forwarding Plane ManagerAvneesh Sachdev
The Forwarding Plane Manager (FPM) is an optional component that may be used in scenarios where the router has a forwarding path that is distinct from the kernel, commonly a hardware-based fast path. It is responsible for programming forwarding information (such as routes and nexthops) in the fast path. In Quagga, the Routing Information Base is maintained in the 'zebra' infrastructure daemon. Routing protocols communicate their best routes to zebra, and zebra computes the best route across protocols for each prefix. This latter information comprises the bulk of the Forwarding Information Base. The new header file added by this patch, 'fpm/fpm.h', defines a point-to-point interface using which zebra can update the FPM about changes in routes. The communication takes place over a stream socket. The FPM listens on a well-known TCP port, and zebra initiates the connection. All messages sent over the connection start with a short 'FPM header'. In the case of route add/delete messages, the header is followed by a netlink message. Zebra should send a complete copy of the forwarding table(s) to the FPM, including routes that it may have picked up from the kernel. The FPM interface uses replace semantics. That is, if a 'route add' message for a prefix is followed by another 'route add' message, the information in the second message is complete by itself, and replaces the information sent in the first message. If the connection to the FPM goes down for some reason, the client (zebra) should send the FPM a complete copy of the forwarding table(s) when it reconnects. Signed-off-by: Avneesh Sachdev <avneesh@opensourcerouting.org> Signed-off-by: David Lamparter <equinox@opensourcerouting.org>