snmp_agent: Implement SNMP Agent plugin.

Makefile.am

@@ -1456,6 +1456,14 @@ snmp_la_LDFLAGS = $(PLUGIN_LDFLAGS) $(BUILD_WITH_LIBNETSNMP_LDFLAGS)
 snmp_la_LIBADD = $(BUILD_WITH_LIBNETSNMP_LIBS)
 endif
 
+if BUILD_PLUGIN_SNMP_AGENT
+pkglib_LTLIBRARIES += snmp_agent.la
+snmp_agent_la_SOURCES = src/snmp_agent.c
+snmp_agent_la_CPPFLAGS = $(AM_CPPFLAGS) $(BUILD_WITH_LIBNETSNMP_CPPFLAGS)
+snmp_agent_la_LDFLAGS = $(PLUGIN_LDFLAGS) $(BUILD_WITH_LIBNETSNMP_LDFLAGS)
+snmp_agent_la_LIBADD = $(BUILD_WITH_LIBNETSNMP_LIBS)
+endif
+
 if BUILD_PLUGIN_STATSD
 pkglib_LTLIBRARIES += statsd.la
 statsd_la_SOURCES = src/statsd.c

README

@@ -490,6 +490,13 @@ Features
       updates to the files and write a bunch of updates at once, which lessens
       system load a lot.
 
+    - snmp_agent
+      Receives and handles queries from SNMP master agent and returns the data
+      collected by read plugins. Handles requests only for OIDs specified in
+      configuration file. To handle SNMP queries the plugin gets data from
+      collectd and translates requested values from collectd's internal format
+      to SNMP format.
+
     - unixsock
       One can query the values from the unixsock plugin whenever they're
       needed. Please read collectd-unixsock(5) for a description on how that's
@@ -817,7 +824,11 @@ Prerequisites
     This library is part of the “Manage ONTAP SDK” published by NetApp.
 
   * libnetsnmp (optional)
-    For the `snmp' plugin.
+    For the `snmp' and 'snmp_agent' plugins.
+    <http://www.net-snmp.org/>
+
+  * libnetsnmpagent (optional)
+    Required for the 'snmp_agent' plugin.
     <http://www.net-snmp.org/>
 
   * libnotify (optional)

configure.ac

@@ -3643,6 +3643,7 @@ AC_SUBST([LIBNETAPP_LIBS])
 # }}}
 
 # --with-libnetsnmp {{{
+with_libnetsnmpagent="no"
 AC_ARG_WITH(libnetsnmp, [AS_HELP_STRING([--with-libnetsnmp@<:@=PREFIX@:>@], [Path to the Net-SNMPD library.])],
 [
 	if test "x$withval" = "xno"
@@ -3655,6 +3656,7 @@ AC_ARG_WITH(libnetsnmp, [AS_HELP_STRING([--with-libnetsnmp@<:@=PREFIX@:>@], [Pat
 		with_libnetsnmp_cppflags="-I$withval/include"
 		with_libnetsnmp_ldflags="-I$withval/lib"
 		with_libnetsnmp="yes"
+		with_libnetsnmpagent="yes"
 	fi; fi
 ],
 [with_libnetsnmp="yes"])
@@ -3667,6 +3669,10 @@ then
       [with_libnetsnmp="yes"],
       [with_libnetsnmp="no (net-snmp/net-snmp-config.h not found)"]
     )
+    AC_CHECK_HEADERS(net-snmp/agent/agent_module_config.h,
+      [],
+      [with_libnetsnmpagent="no (net-snmp/agent/agent_module_config.h not found)"]
+    )
 
 	CPPFLAGS="$SAVE_CPPFLAGS"
 fi
@@ -3680,6 +3686,11 @@ then
 		[with_libnetsnmp="no (libnetsnmp not found)"],
 		[$with_snmp_libs])
 
+	AC_CHECK_LIB(netsnmpagent, init_agent,
+		[with_libnetsnmpagent="yes"],
+		[with_libnetsnmpagent="no (libnetsnmpagent not found)"],
+		[$with_snmp_libs])
+
 	LDFLAGS="$SAVE_LDFLAGS"
 fi
 if test "x$with_libnetsnmp" = "xyes"
@@ -3688,6 +3699,10 @@ then
 	BUILD_WITH_LIBNETSNMP_LDFLAGS="$with_libnetsnmp_ldflags"
 	BUILD_WITH_LIBNETSNMP_LIBS="-lnetsnmp"
 fi
+if test "x$with_libnetsnmpagent" = "xyes"
+then
+	BUILD_WITH_LIBNETSNMP_LIBS+=" -lnetsnmpagent"
+fi
 AC_SUBST(BUILD_WITH_LIBNETSNMP_CPPFLAGS)
 AC_SUBST(BUILD_WITH_LIBNETSNMP_LDFLAGS)
 AC_SUBST(BUILD_WITH_LIBNETSNMP_LIBS)
@@ -5899,6 +5914,7 @@ plugin_processes="no"
 plugin_protocols="no"
 plugin_python="no"
 plugin_serial="no"
+plugin_snmp_agent="no"
 plugin_smart="no"
 plugin_swap="no"
 plugin_tape="no"
@@ -6191,6 +6207,10 @@ if test "x$with_kvm_getswapinfo" = "xyes"; then
   plugin_swap="yes"
 fi
 
+if test "x$with_libnetsnmp" = "xyes" && test "x$with_libnetsnmpagent" = "xyes"; then
+  plugin_snmp_agent="yes"
+fi
+
 if test "x$have_swapctl" = "xyes" && test "x$c_cv_have_swapctl_two_args" = "xyes"; then
   plugin_swap="yes"
 fi
@@ -6350,6 +6370,7 @@ AC_PLUGIN([serial],              [$plugin_serial],          [serial port traffic
 AC_PLUGIN([sigrok],              [$with_libsigrok],         [sigrok acquisition sources])
 AC_PLUGIN([smart],               [$plugin_smart],           [SMART statistics])
 AC_PLUGIN([snmp],                [$with_libnetsnmp],        [SNMP querying plugin])
+AC_PLUGIN([snmp_agent],          [$plugin_snmp_agent],      [SNMP agent plugin])
 AC_PLUGIN([statsd],              [yes],                     [StatsD plugin])
 AC_PLUGIN([swap],                [$plugin_swap],            [Swap usage statistics])
 AC_PLUGIN([syslog],              [$have_syslog],            [Syslog logging plugin])
@@ -6774,6 +6795,7 @@ AC_MSG_RESULT([    serial  . . . . . . . $enable_serial])
 AC_MSG_RESULT([    sigrok  . . . . . . . $enable_sigrok])
 AC_MSG_RESULT([    smart . . . . . . . . $enable_smart])
 AC_MSG_RESULT([    snmp  . . . . . . . . $enable_snmp])
+AC_MSG_RESULT([    snmp_agent  . . . . . $enable_snmp_agent])
 AC_MSG_RESULT([    statsd  . . . . . . . $enable_statsd])
 AC_MSG_RESULT([    swap  . . . . . . . . $enable_swap])
 AC_MSG_RESULT([    syslog  . . . . . . . $enable_syslog])

src/collectd.conf.in

@@ -186,6 +186,7 @@
 #@BUILD_PLUGIN_SIGROK_TRUE@LoadPlugin sigrok
 #@BUILD_PLUGIN_SMART_TRUE@LoadPlugin smart
 #@BUILD_PLUGIN_SNMP_TRUE@LoadPlugin snmp
+#@BUILD_PLUGIN_SNMP_AGENT_TRUE@LoadPlugin snmp_agent
 #@BUILD_PLUGIN_STATSD_TRUE@LoadPlugin statsd
 #@BUILD_PLUGIN_SWAP_TRUE@LoadPlugin swap
 #@BUILD_PLUGIN_TABLE_TRUE@LoadPlugin table
@@ -1228,6 +1229,30 @@
 #   </Host>
 #</Plugin>
 
+#<Plugin snmp_agent>
+#  <Data "memAvailReal">
+#    Plugin "memory"
+#    Type "memory"
+#    TypeInstance "free"
+#    OIDs "1.3.6.1.4.1.2021.4.6.0"
+#  </Data>
+#  <Table "ifTable">
+#    IndexOID "IF-MIB::ifIndex"
+#    SizeOID "IF-MIB::ifNumber"
+#    <Data "ifDescr">
+#      Instance true
+#      Plugin "interface"
+#      OIDs "IF-MIB::ifDescr"
+#    </Data>
+#    <Data "ifOctets">
+#      Plugin "interface"
+#      Type "if_octets"
+#      TypeInstance ""
+#      OIDs "IF-MIB::ifInOctets" "IF-MIB::ifOutOctets"
+#    </Data>
+#  </Table>
+#</Plugin>
+
 #<Plugin statsd>
 #  Host "::"
 #  Port "8125"

src/collectd.conf.pod

@@ -6930,6 +6930,115 @@ Since the configuration of the C<snmp plugin> is a little more complicated than
 other plugins, its documentation has been moved to an own manpage,
 L<collectd-snmp(5)>. Please see there for details.
 
+=head2 Plugin C<snmp_agent>
+
+The I<snmp_agent> plugin is an AgentX subagent that receives and handles queries
+from SNMP master agent and returns the data collected by read plugins.
+The I<snmp_agent> plugin handles requests only for OIDs specified in
+configuration file. To handle SNMP queries the plugin gets data from collectd
+and translates requested values from collectd's internal format to SNMP format.
+This plugin is a generic plugin and cannot work without configuration.
+For more details on AgentX subagent see
+<http://www.net-snmp.org/tutorial/tutorial-5/toolkit/demon/>
+
+B<Synopsis:>
+
+  <Plugin snmp_agent>
+    <Data "memAvailReal">
+      Plugin "memory"
+      Type "memory"
+      TypeInstance "free"
+      OIDs "1.3.6.1.4.1.2021.4.6.0"
+    </Data>
+    <Table "ifTable">
+      IndexOID "IF-MIB::ifIndex"
+      SizeOID "IF-MIB::ifNumber"
+      <Data "ifDescr">
+        Instance true
+        Plugin "interface"
+        OIDs "IF-MIB::ifDescr"
+      </Data>
+      <Data "ifOctets">
+        Plugin "interface"
+        Type "if_octets"
+        TypeInstance ""
+        OIDs "IF-MIB::ifInOctets" "IF-MIB::ifOutOctets"
+      </Data>
+    </Table>
+  </Plugin>
+
+There are two types of blocks that can be contained in the
+C<E<lt>PluginE<nbsp> snmp_agentE<gt>> block: B<Data> and B<Table>:
+
+=head3 The B<Data> block
+
+The B<Data> block defines a list OIDs that are to be handled. This block can
+define scalar or table OIDs. If B<Data> block is defined inside of B<Table>
+block it reperesents table OIDs.
+The following options can be set:
+
+=over 4
+
+=item B<Instance> I<true|false>
+
+When B<Instance> is set to B<true>, the value for requested OID is copied from
+plugin instance field of corresponding collectd value. If B<Data> block defines
+scalar data type B<Instance> has no effect and can be omitted.
+
+=item B<Plugin> I<String>
+
+Read plugin name whose collected data will be mapped to specified OIDs.
+
+=item B<Type> I<String>
+
+Collectd's type that is to be used for specified OID, e.E<nbsp>g. "if_octets"
+for example. The types are read from the B<TypesDB> (see L<collectd.conf(5)>).
+
+=item B<TypeInstance> I<String>
+
+Collectd's type-instance that is to be used for specified OID.
+
+=item B<OIDs> I<OID> [I<OID> ...]
+
+Configures the OIDs to be handled by I<snmp_agent> plugin. Values for these OIDs
+are taken from collectd data type specified by B<Plugin>, B<Type>,
+B<TypeInstance> fields of this B<Data> block. Number of the OIDs configured
+should correspond to number of values in specified B<Type>.
+For example two OIDs "IF-MIB::ifInOctets" "IF-MIB::ifOutOctets" can be mapped to
+"rx" and "tx" values of "if_octets" type.
+
+=item B<Scale> I<Value>
+
+The values taken from collectd are multiplied by I<Value>. The field is optional
+and the default is B<1.0>.
+
+=item B<Shift> I<Value>
+
+I<Value> is added to values from collectd after they have been multiplied by
+B<Scale> value. The field is optional and the default value is B<0.0>.
+
+=back
+
+=head3 The B<Table> block
+
+The B<Table> block defines a collection of B<Data> blocks that belong to one
+snmp table. In addition to multiple B<Data> blocks the following options can be
+set:
+
+=over 4
+
+=item B<IndexOID> I<OID>
+
+OID that is handled by the plugin and is mapped to numerical index value that is
+generated by the plugin for each table record.
+
+=item B<SizeOID> I<OID>
+
+OID that is handled by the plugin. Returned value is the number of records in
+the table. The field is optional.
+
+=back
+
 =head2 Plugin C<statsd>
 
 The I<statsd plugin> listens to a UDP socket, reads "events" in the statsd

src/daemon/utils_avltree.c

@@ -534,6 +534,8 @@ int c_avl_pick(c_avl_tree_t *t, void **key, void **value) {
   c_avl_node_t *n;
   c_avl_node_t *p;
 
+  assert(t != NULL);
+
   if ((key == NULL) || (value == NULL))
     return (-1);
   if (t->root == NULL)

src/daemon/utils_cache.c

@@ -477,6 +477,75 @@ gauge_t *uc_get_rate(const data_set_t *ds, const value_list_t *vl) {
   return (ret);
 } /* gauge_t *uc_get_rate */
 
+int uc_get_value_by_name(const char *name, value_t **ret_values,
+                         size_t *ret_values_num) {
+  value_t *ret = NULL;
+  size_t ret_num = 0;
+  cache_entry_t *ce = NULL;
+  int status = 0;
+
+  pthread_mutex_lock(&cache_lock);
+
+  if (c_avl_get(cache_tree, name, (void *) &ce) == 0) {
+    assert(ce != NULL);
+
+    /* remove missing values from getval */
+    if (ce->state == STATE_MISSING) {
+      status = -1;
+    } else {
+      ret_num = ce->values_num;
+      ret = malloc(ret_num * sizeof(*ret));
+      if (ret == NULL) {
+        ERROR("utils_cache: uc_get_value_by_name: malloc failed.");
+        status = -1;
+      } else {
+        memcpy(ret, ce->values_raw, ret_num * sizeof(value_t));
+      }
+    }
+  }
+  else {
+    DEBUG("utils_cache: uc_get_value_by_name: No such value: %s", name);
+    status = -1;
+  }
+
+  pthread_mutex_unlock(&cache_lock);
+
+  if (status == 0) {
+    *ret_values = ret;
+    *ret_values_num = ret_num;
+  }
+
+  return (status);
+} /* int uc_get_value_by_name */
+
+value_t *uc_get_value(const data_set_t *ds, const value_list_t *vl) {
+  char name[6 * DATA_MAX_NAME_LEN];
+  value_t *ret = NULL;
+  size_t ret_num = 0;
+  int status;
+
+  if (FORMAT_VL(name, sizeof(name), vl) != 0) {
+    ERROR("utils_cache: uc_get_value: FORMAT_VL failed.");
+    return (NULL);
+  }
+
+  status = uc_get_value_by_name(name, &ret, &ret_num);
+  if (status != 0)
+    return (NULL);
+
+  /* This is important - the caller has no other way of knowing how many
+   * values are returned. */
+  if (ret_num != (size_t) ds->ds_num) {
+    ERROR("utils_cache: uc_get_value: ds[%s] has %zu values, "
+          "but uc_get_value_by_name returned %zu.", ds->type, ds->ds_num,
+          ret_num);
+    sfree(ret);
+    return (NULL);
+  }
+
+  return (ret);
+} /* value_t *uc_get_value */
+
 size_t uc_get_size(void) {
   size_t size_arrays = 0;
 

src/daemon/utils_cache.h

@@ -42,6 +42,8 @@ int uc_update(const data_set_t *ds, const value_list_t *vl);
 int uc_get_rate_by_name(const char *name, gauge_t **ret_values,
                         size_t *ret_values_num);
 gauge_t *uc_get_rate(const data_set_t *ds, const value_list_t *vl);
+int uc_get_value_by_name(const char *name, value_t **ret_values, size_t *ret_values_num);
+value_t *uc_get_value(const data_set_t *ds, const value_list_t *vl);
 
 size_t uc_get_size(void);
 int uc_get_names(char ***ret_names, cdtime_t **ret_times, size_t *ret_number);