lib: Remove smux option for snmp

The smux.c code has not been able to compile for 2+ years
and no-one has noticed. Additionally net-snmp has marked
smux integration as deprecated for quite some time as well.

Since no-one has noticed and it's been broken and smux integration
is deprecated let's just remove this from the code base.

From looking at the code, it sure looks like SNMP could use
a decent cleanup.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>

configure.ac

@@ -382,7 +382,7 @@ AC_ARG_ENABLE(bgp-vnc,
 AC_ARG_WITH(rfp-path,
   AS_HELP_STRING([--with-rfp-path[=DIR]],[path to replaced stub RFP used with BGP VNC]))
 AC_ARG_ENABLE(snmp,
-  AS_HELP_STRING([--enable-snmp=ARG], [enable SNMP support (smux or agentx)]))
+  AS_HELP_STRING([--enable-snmp], [enable SNMP support for agentx]))
 AC_ARG_ENABLE(zeromq,
   AS_HELP_STRING([--enable-zeromq], [enable ZeroMQ handler (libfrrzmq)]))
 AC_ARG_WITH(libpam,
@@ -1496,14 +1496,13 @@ int main(void);
      yes)
       SNMP_METHOD=agentx
       ;;
-     smux|agentx)
+     agentx)
       SNMP_METHOD="${enable_snmp}"
       ;;
      *)
-      AC_MSG_ERROR([--enable-snmp given with an unknown method (${enable_snmp}). Use smux or agentx])
+      AC_MSG_ERROR([--enable-snmp given with an unknown method (${enable_snmp}). Use yes or agentx])
       ;;
    esac
-   AH_TEMPLATE([SNMP_SMUX], [Use SNMP SMUX to interface with snmpd])
    AH_TEMPLATE([SNMP_AGENTX], [Use SNMP AgentX to interface with snmpd])
    AC_DEFINE_UNQUOTED(AS_TR_CPP(SNMP_${SNMP_METHOD}),,SNMP method to interface with snmpd)
 fi

doc/user/snmp.rst

@@ -7,8 +7,8 @@ SNMP Support
 :abbr:`SNMP (Simple Network Managing Protocol)` is a widely implemented feature
 for collecting network information from router and/or host. FRR itself does
 not support SNMP agent (server daemon) functionality but is able to connect to
-a SNMP agent using the SMUX protocol (:rfc:`1227`) or the AgentX protocol
-(:rfc:`2741`) and make the routing protocol MIBs available through it.
+a SNMP agent using the the AgentX protocol (:rfc:`2741`) and make the
+routing protocol MIBs available through it.
 
 Note that SNMP Support needs to be enabled at compile-time and loaded as module
 on daemon startup. Refer to :ref:`loadable-module-support` on the latter.
@@ -18,16 +18,10 @@ on daemon startup. Refer to :ref:`loadable-module-support` on the latter.
 Getting and installing an SNMP agent
 ====================================
 
-There are several SNMP agent which support SMUX or AgentX. We recommend to use
+The supported SNMP agent is AgentX. We recommend to use
 the latest version of `net-snmp` which was formerly known as `ucd-snmp`. It is
 free and open software and available at `http://www.net-snmp.org/ <http://www.net-snmp.org/>`_
-and as binary package for most Linux distributions. `net-snmp` has to be
-compiled with `--with-mib-modules=agentx` to be able to accept connections from
-FRR using AgentX protocol or with `--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.
+and as binary package for most Linux distributions.
 
 .. _agentx-configuration:
 
@@ -42,7 +36,7 @@ master SNMP agent (snmpd) and each of the FRR daemons must be configured. In
 :file:`/etc/snmp/snmpd.conf`, the ``master agentx`` directive should be added.
 In each of the FRR daemons, ``agentx`` command will enable AgentX support.
 
-:file:`/etc/snmp/snmpd.conf`:
+:file:`/etc/snmp/zebra.conf`:
 
 ::
 
@@ -97,105 +91,6 @@ need to configure FRR to use another transport, you can configure it through
    agentXSocket tcp:192.168.15.12:705
 
 
-.. _smux-configuration:
-
-SMUX configuration
-==================
-
-To enable SMUX protocol support, FRR must have been build with the
-:option:`--enable-snmp` option.
-
-A separate connection has then to be established between the SNMP agent (snmpd)
-and each of the FRR 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 used for the intercommunication of the
-daemons.
-
-In the following example the ospfd daemon will be connected to the snmpd daemon
-using the password "frr_ospfd". For testing it is recommending to take exactly
-the below snmpd.conf as wrong access restrictions can be hard to debug.
-
-:file:`/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
-   #
-   # the following line is relevant for FRR
-   #
-   smuxpeer .1.3.6.1.4.1.3317.1.2.5 frr_ospfd
-
-:file:`/etc/frr/ospf`:
-
-::
-
-   ! ... the rest of ospfd.conf has been omitted for clarity ...
-   !
-   smux peer .1.3.6.1.4.1.3317.1.2.5 frr_ospfd
-   !
-
-
-After restarting snmpd and frr, a successful connection can be verified in the
-syslog and by querying the SNMP daemon:
-
-::
-
-   snmpd[12300]: [smux_accept] accepted fd 12 from 127.0.0.1:36255
-   snmpd[12300]: accepted smux peer: \\
-      oid GNOME-PRODUCT-ZEBRA-MIB::ospfd, frr-0.96.5
-
-   # snmpwalk -c public -v1 localhost .1.3.6.1.2.1.14.1.1
-   OSPF-MIB::ospfRouterId.0 = IpAddress: 192.168.42.109
-
-
-Be warned that the current version (5.1.1) of the Net-SNMP daemon writes a line
-for every SNMP connect to the syslog which can lead to enormous log file sizes.
-If that is a problem you should consider to patch snmpd and comment out the
-troublesome `snmp_log()` line in the function `netsnmp_agent_check_packet()` in
-`agent/snmp_agent.c`.
-
-MIB and command reference
-=========================
-
-The following OID numbers are used for the interprocess communication of snmpd and
-the FRR daemons with SMUX only.::
-
-  .    (OIDs below .iso.org.dod.internet.private.enterprises)
-  zebra	.1.3.6.1.4.1.3317.1.2.1 .gnome.gnomeProducts.zebra.zserv
-  bgpd	.1.3.6.1.4.1.3317.1.2.2 .gnome.gnomeProducts.zebra.bgpd
-  ripd	.1.3.6.1.4.1.3317.1.2.3 .gnome.gnomeProducts.zebra.ripd
-  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
-
-
-Sadly, SNMP has not been implemented in all daemons yet. The following
-OID numbers are used for querying the SNMP daemon by a client:::
-
-  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
-  bgpd	.1.3.6.1.2.1.15	    .iso.org.dot.internet.mgmt.mib-2.bgp
-  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
-
-
-The following syntax is understood by the FRR daemons for configuring SNMP
-using SMUX:
-
-.. index:: smux peer OID
-.. clicmd:: smux peer OID
-.. index:: no smux peer OID
-.. clicmd:: no smux peer OID
-.. index:: smux peer OID PASSWORD
-.. clicmd:: smux peer OID PASSWORD
-.. index:: no smux peer OID PASSWORD
-.. clicmd:: no smux peer OID PASSWORD
-
 Here is the syntax for using AgentX:
 
 .. index:: agentx