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/* BGP Engine pThread -- functions
* Copyright (C) 2009 Chris Hall (GMCH), Highwayman
*
* This file is part of GNU Zebra.
*
* GNU Zebra is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* GNU Zebra is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Zebra; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include <zebra.h>
#include "bgpd/bgp_engine.h"
#include "lib/memory.h"
#include "lib/symtab.h"
/*==============================================================================
* The BGP Engine pThread contains:
*
* * the BGP Finite State Machine (FSM) for BGP Sessions
* * the encoding and decoding of BGP protocol messages
* * all related socket handling and I/O
* * all related timers
*
* The BGP Engine communicates with the BGP Routeing pthread(s) via two Message
* Queues.
*
* There are also shared pools of data:
*
* * the BGP session structures, which ...
* * the Attributes Store
* * the Prefixes Store
* ...
*
* Other pthread-safe facilities used:
*
* * logging
* * privilege raising/lowering
* ...
*
* At the heart of the BGP Engine pthread is a select for the socket I/O, a
* Message Queue reader and a timer handler. The Message Queue uses SIGUSR2 to
* kick the pthread into action if it is stopped on the select.
*
*/
/*==============================================================================
* The qpnexus for the BGP Engine.
*
*
*/
/*==============================================================================
* Start the BGP Engine Thread.
*
* Initialise the Engine Thread qpnexus
*
*/
/* BGP Engine side of bgp_engine_start() must call bgp_open_listeners()
* for which it needs the port and address from command line.
*
* Implemented in bgp_main.c
*/
/*==============================================================================
* Stop the BGP Engine Thread.
*
*/
/* BGP Engine side of bgp_engine_stop() must call bgp_close_listeners()
*
* Implemented in bgp_main.c
*/
/*==============================================================================
* The BGP Engine Thread main loop
*
* Processes:
*
* 1) connections with pending work -- local queue.
*
* When a connection fills its output buffers, any further messages
* requiring output are placed on the connection's pending queue.
*
* When the output buffers empty sufficiently, some of those messages
* can (finally) be processed.
*
* So this is done first.
*
* [This is also where stopped connections are finally reaped.]
*
* 2) messages coming from the Routeing Engine -- mqueue_queue.
*
* These will mostly be BGP UPDATE messages, which will either be
* processed into the relevant connection's output buffers, or end up
* on its pending queue.
*
* There is a flow control mechanism to prevent the Routeing Engine from
* flooding the BGP Engine with UPDATE messages.
*
* Other messages start/stop sessions and so on.
*
* 3) I/O -- qpselect
*
* This deals with all active sockets for read/write/connect/accept.
*
* Each time a socket is readable, one message is read and dispatched to
* the Routeing Engine (or otherwise dealt with by the FSM).
*
* Each time a socket is writable, as much as possible is written to it
* from the connection's write buffer. When the write buffer is drained,
* the connection goes back onto the local queue.
*
* 4) Timers -- qtimers
*
* Which generate FSM events.
*
* Implemented in qpnexus.c
*
*/
/*==============================================================================
* The write queue for the BGP Engine
*
* Each connection has a single message buffer. When that has yet to be
*
*
*/
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