From b9c24cd23091e817942d4eaab95712e84dbec8aa Mon Sep 17 00:00:00 2001 From: Avneesh Sachdev Date: Tue, 13 Nov 2012 22:49:00 +0000 Subject: doc: add blurbs on zebra FPM interface and commands Update documentation with some text on the zebra interface to the optional Forwarding Path Manager component, and the related cli commands. Signed-off-by: Avneesh Sachdev Signed-off-by: David Lamparter --- doc/main.texi | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) (limited to 'doc/main.texi') diff --git a/doc/main.texi b/doc/main.texi index a5759137..a6bf0d1c 100644 --- a/doc/main.texi +++ b/doc/main.texi @@ -11,6 +11,7 @@ different routing protocols. * Interface Commands:: Commands for zebra interfaces * Static Route Commands:: Commands for adding static routes * zebra Route Filtering:: Commands for zebra route filtering +* zebra FIB push interface:: Interface to optional FPM component * zebra Terminal Mode Commands:: Commands for zebra's VTY @end menu @@ -227,6 +228,54 @@ ip protocol rip route-map RM1 @end group @end example +@node zebra FIB push interface +@section zebra FIB push interface + +Zebra supports a 'FIB push' interface that allows an external +component to learn the forwarding information computed by the Quagga +routing suite. + +In Quagga, the Routing Information Base (RIB) resides inside +zebra. Routing protocols communicate their best routes to zebra, and +zebra computes the best route across protocols for each prefix. This +latter information makes up the Forwarding Information Base +(FIB). Zebra feeds the FIB to the kernel, which allows the IP stack in +the kernel to forward packets according to the routes computed by +Quagga. The kernel FIB is updated in an OS-specific way. For example, +the @code{netlink} interface is used on Linux, and route sockets are +used on FreeBSD. + +The FIB push interface aims to provide a cross-platform mechanism to +support scenarios where the router has a forwarding path that is +distinct from the kernel, commonly a hardware-based fast path. In +these cases, the FIB needs to be maintained reliably in the fast path +as well. We refer to the component that programs the forwarding plane +(directly or indirectly) as the Forwarding Plane Manager or FPM. + +The FIB push interface comprises of a TCP connection between zebra and +the FPM. The connection is initiated by zebra -- that is, the FPM acts +as the TCP server. + +The relevant zebra code kicks in when zebra is configured with the +@code{--enable-fpm} flag. Zebra periodically attempts to connect to +the well-known FPM port. Once the connection is up, zebra starts +sending messages containing routes over the socket to the FPM. Zebra +sends a complete copy of the forwarding table to the FPM, including +routes that it may have picked up from the kernel. The existing +interaction of zebra with the kernel remains unchanged -- that is, the +kernel continues to receive FIB updates as before. + +The format of the messages exchanged with the FPM is defined by the +file @file{fpm/fpm.h} in the quagga tree. + +The zebra 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, zebra sends +the FPM a complete copy of the forwarding table(s) when it reconnects. + @node zebra Terminal Mode Commands @section zebra Terminal Mode Commands @@ -271,3 +320,13 @@ If so, the box can't work as a router. @deffn Command {show ipv6forward} {} Display whether the host's IP v6 forwarding is enabled or not. @end deffn + +@deffn Command {show zebra fpm stats} {} +Display statistics related to the zebra code that interacts with the +optional Forwarding Plane Manager (FPM) component. +@end deffn + +@deffn Command {clear zebra fpm stats} {} +Reset statistics related to the zebra code that interacts with the +optional Forwarding Plane Manager (FPM) component. +@end deffn -- cgit v1.2.1