agentx: add appropriate documentation

doc/overview.texi

@@ -7,7 +7,7 @@ provides TCP/IP based routing services with routing protocols support such
 as RIPv1, RIPv2, RIPng, OSPFv2, OSPFv3, BGP-4, and BGP-4+ (@pxref{Supported
 RFCs}). Quagga also supports special BGP Route Reflector and Route Server
 behavior.  In addition to traditional IPv4 routing protocols, Quagga also
-supports IPv6 routing protocols.  With SNMP daemon which supports SMUX
+supports IPv6 routing protocols.  With SNMP daemon which supports SMUX and AgentX
 protocol, Quagga provides routing protocol MIBs (@pxref{SNMP Support}).
 
   Quagga uses an advanced software architecture to provide you with a high
@@ -238,6 +238,9 @@ J. Chu, Editor. July 1994.}
 @cite{OSPF Version 2 Management Information Base. F. Baker, R. Coltun.
 November 1995.}
 
+@item @asis{RFC2741}
+@cite{Agent Extensibility (AgentX) Protocol. M. Daniele, B. Wijnen. January 2000.}
+
 @end table
 
 @node How to get Quagga

doc/snmp.texi

@@ -5,11 +5,12 @@
 feature for collecting network information from router and/or host.
 Quagga itself does not support SNMP agent (server daemon) functionality
 but is able to connect to a SNMP agent using the SMUX protocol
-(@cite{RFC1227}) and make the routing protocol MIBs available through
-it.
+(@cite{RFC1227}) or the AgentX protocol (@cite{RFC2741}) and make the
+routing protocol MIBs available through it.
 
 @menu
 * Getting and installing an SNMP agent::
+* AgentX configuration::
 * SMUX configuration::
 * MIB and command reference::
 * Handling SNMP Traps::
@@ -18,20 +19,82 @@ it.
 @node Getting and installing an SNMP agent
 @section Getting and installing an SNMP agent
 
-There are several SNMP agent which support SMUX. We recommend to use the latest
+There are several SNMP agent which support SMUX or AgentX. We recommend to use the latest
 version of @code{net-snmp} which was formerly known as @code{ucd-snmp}.
 It is free and open software and available at @uref{http://www.net-snmp.org/}
 and as binary package for most Linux distributions.
-@code{net-snmp} has to be compiled with @code{--with-mib-modules=smux} to
-be able to accept connections from Quagga.
+@code{net-snmp} has to be compiled with @code{--with-mib-modules=agentx} to
+be able to accept connections from Quagga using AgentX protocol or with
+@code{--with-mib-modules=smux} to use SMUX protocol.
+
+Nowadays, SMUX is a legacy protocol. The AgentX protocol should be
+preferred for any new deployment. Both protocols have the same coverage.
+
+@node AgentX configuration
+@section AgentX configuration
+
+To enable AgentX protocol support, Quagga must have been build with the
+@code{--enable-snmp} or @code{--enable-snmp=agentx} option. Both the
+master SNMP agent (snmpd) and each of the Quagga daemons must be
+configured. In @code{/etc/snmp/snmpd.conf}, @code{master agentx}
+directive should be added. In each of the Quagga daemons, @code{agentx}
+command will enable AgentX support.
+
+@example
+/etc/snmp/snmpd.conf:
+	#
+	# example access restrictions setup
+	#
+	com2sec readonly default public
+	group MyROGroup v1 readonly
+	view all included .1 80
+	access MyROGroup "" any noauth exact all none none
+	#
+	# enable master agent for AgentX subagents
+	#
+	master agentx
+
+/etc/quagga/ospfd.conf:
+	! ... the rest of ospfd.conf has been omitted for clarity ...
+	!
+	agentx
+	!
+@end example
+
+Upon successful connection, you should get something like this in the
+log of each Quagga daemons:
+
+@example
+2012/05/25 11:39:08 ZEBRA: snmp[info]: NET-SNMP version 5.4.3 AgentX subagent connected
+@end example
+
+Then, you can use the following command to check everything works as expected:
+
+@example
+# snmpwalk -c public -v1 localhost .1.3.6.1.2.1.14.1.1
+OSPF-MIB::ospfRouterId.0 = IpAddress: 192.168.42.109
+[...]
+@end example
+
+The AgentX protocol can be transported over a Unix socket or using TCP
+or UDP. It usually defaults to a Unix socket and depends on how NetSNMP
+was built. If need to configure Quagga to use another transport, you can
+configure it through @code{/etc/snmp/quagga.conf}:
+
+@example
+/etc/snmp/quagga.conf:
+	[snmpd]
+	# Use a remote master agent
+	agentXSocket tcp:192.168.15.12:705
+@end example
 
 @node SMUX configuration
 @section SMUX configuration
 
 To enable SMUX protocol support, Quagga must have been build with the
-@code{--enable-snmp} option.
+@code{--enable-snmp=smux} option.
 
-A separate connection has then to be established between between the
+A separate connection has then to be established between the
 SNMP agent (snmpd) and each of the Quagga daemons. This connections
 each use different OID numbers and passwords. Be aware that this OID
 number is not the one that is used in queries by clients, it is solely
@@ -85,7 +148,7 @@ troublesome @code{snmp_log()} line in the function
 @section MIB and command reference
 
 The following OID numbers are used for the interprocess communication of snmpd and
-the Quagga daemons. Sadly, SNMP has not been implemented in all daemons yet.
+the Quagga daemons with SMUX only.
 @example
             (OIDs below .iso.org.dod.internet.private.enterprises)
 zebra	.1.3.6.1.4.1.3317.1.2.1 .gnome.gnomeProducts.zebra.zserv
@@ -95,7 +158,8 @@ ospfd	.1.3.6.1.4.1.3317.1.2.5 .gnome.gnomeProducts.zebra.ospfd
 ospf6d	.1.3.6.1.4.1.3317.1.2.6 .gnome.gnomeProducts.zebra.ospf6d
 @end example
 
-The following OID numbers are used for querying the SNMP daemon by a client:
+Sadly, SNMP has not been implemented in all daemons yet. The following
+OID numbers are used for querying the SNMP daemon by a client:
 @example
 zebra	.1.3.6.1.2.1.4.24   .iso.org.dot.internet.mgmt.mib-2.ip.ipForward
 ospfd	.1.3.6.1.2.1.14	    .iso.org.dot.internet.mgmt.mib-2.ospf
@@ -104,7 +168,7 @@ ripd	.1.3.6.1.2.1.23	    .iso.org.dot.internet.mgmt.mib-2.rip2
 ospf6d	.1.3.6.1.3.102	    .iso.org.dod.internet.experimental.ospfv3
 @end example
 
-The following syntax is understood by the Quagga daemons for configuring SNMP:
+The following syntax is understood by the Quagga daemons for configuring SNMP using SMUX:
 @deffn {Command} {smux peer @var{oid}} {}
 @deffnx {Command} {no smux peer @var{oid}} {}
 @end deffn
@@ -113,4 +177,9 @@ The following syntax is understood by the Quagga daemons for configuring SNMP:
 @deffnx {Command} {no smux peer @var{oid} @var{password}} {}
 @end deffn
 
+Here is the syntax for using AgentX:
+@deffn {Command} {agentx} {}
+@deffnx {Command} {no agentx} {}
+@end deffn
+
 @include snmptrap.texi