<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE appref SYSTEM "appref.dtd">

<appref>
  <header>
    <copyright>
      <year>1997</year><year>2020</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>SNMP</title>
    <prepared></prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date></date>
    <rev></rev>
    <file>snmp.xml</file>
  </header>
  <app>SNMP</app>
  <appsummary>The SNMP Application</appsummary>
  <description>
    <p>This chapter describes the <c>snmp</c>
    application in OTP.  The SNMP application provides the following
    services:</p>
    <list type="bulleted">
      <item>
        <p>a multilingual extensible SNMP agent</p>
      </item>
      <item>
        <p>a SNMP manager</p>
      </item>
      <item>
        <p>a MIB compiler</p>
      </item>
    </list>

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  </description>

  <section>
    <marker id="configuration_params"></marker>
    <title>Configuration</title>
    <p>The following configuration parameters are defined for the SNMP
      application. Refer to application(3) for more information about
      configuration parameters.
      </p>

    <p>The snmp part of the config file specifying the configuration 
      parameters is basically the following tuple:</p>
    <pre>
      {snmp, snmp_components_config()}
    </pre>

    <p>A minimal config file for starting a node with both a manager 
      and an agent:</p>
    <pre>
      [{snmp, 
        [{agent, [{db_dir, "/tmp/snmp/agent/db"},
                  {config, [{dir, "/tmp/snmp/agent/conf"}]}]},
         {manager, [{config, [{dir, "/tmp/snmp/manager/conf"},
                              {db_dir, "/tmp/snmp/manager/db"}]}]}]}
        ]
       }
      ].
    </pre>


    <!-- 
	 ********************************************************

	 The info below is also found in the snmp_config.xml file 

	 ********************************************************
    -->


    <p>Each snmp component has its own set of configuration parameters,
      even though some of the types are common to both components. </p>

    <pre>
      snmp_components_config() -> [snmp_component_config()]
      snmp_component_config() -> {agent, agent_options()} | {manager, manager_options()}
      agent_options() = [agent_option()]
      agent_option() = {restart_type,     restart_type()}     | 
                       {agent_type,       agent_type()}       |  
                       {agent_verbosity,  verbosity()}        |  
                       {discovery,        agent_discovery()}  |  
                       {versions,         versions()}         |  
                       {gb_max_vbs,       gb_max_vbs()}       |  
                       {priority,         priority()}         |  
                       {multi_threaded,   multi_threaded()}   |  
                       {db_dir,           db_dir()}           |  
                       {db_init_error,    db_init_error()}    |  
                       {local_db,         local_db()}         |  
                       {net_if,           agent_net_if()}     |  
                       {mibs,             mibs()}             |  
                       {mib_storage,      mib_storage()}      |  
                       {mib_server,       mib_server()}       |  
                       {audit_trail_log,  audit_trail_log()}  |  
                       {error_report_mod, error_report_mod()} |  
                       {note_store,       note_store()}       |  
                       {symbolic_store,   symbolic_store()}   |  
                       {target_cache,     target_cache()}     |  
                       {config,           agent_config()}
      manager_options() = [manager_option()]
      manager_option() = {restart_type,             restart_type()}    | 
                         {net_if,                   manager_net_if()}  |  
                         {server,                   server()}          | 
                         {note_store,               note_store()}      | 
                         {config,                   manager_config()}  |  
                         {inform_request_behaviour, manager_irb()}     | 
                         {mibs,                     manager_mibs()}    | 
                         {priority,                 priority()}        |  
                         {audit_trail_log,          audit_trail_log()} | 
                         {versions,                 versions()}        | 
                         {def_user_mod,             def_user_module()  | 
                         {def_user_data,            def_user_data()}
    </pre>

    <marker id="agent_opts_and_types"></marker>
    <p>Agent specific config options and types:</p>
    <taglist>
      <tag><marker id="agent_type"></marker>
        <c><![CDATA[agent_type() = master | sub <optional>]]></c></tag>
      <item>
        <p>If <c>master</c>, one master agent is
          started. Otherwise, no agents are started. </p>
        <p>Default is <c>master</c>.</p>
      </item>

      <tag><marker id="agent_disco"></marker>
        <c><![CDATA[agent_discovery() = [agent_discovery_opt()] <optional>]]></c></tag>
      <item>
        <p><c>agent_discovery_opt() = 
          {terminating, agent_terminating_discovery_opts()} | 
          {originating, agent_originating_discovery_opts()}</c></p>
        <p>The <c>terminating</c> options effects discovery initiated by 
          a manager. </p>
        <p>The <c>originating</c> options effects discovery initiated 
          by this agent. </p>
        <p>For defaults see the options in <c>agent_discovery_opt()</c>.</p>
      </item>

      <tag><marker id="agent_term_disco_opts"></marker>
        <c><![CDATA[agent_terminating_discovery_opts() = [agent_terminating_discovery_opt()] <optional>]]></c></tag>
      <item>
        <p><c>agent_terminating_discovery_opt() = 
          {enable, boolean()} | 
          {stage2, discovery | plain} | 
          {trigger_username, string()}</c></p>
        <p>These are options effecting discovery <c>terminating</c> in this
          agent (i.e. initiated by a manager). </p>
        <p>The default values for the <c>terminating</c> 
          discovery options are: </p>
        <list type="bulleted">
          <item>enable: <c>true</c></item>
          <item>stage2: <c>discovery</c></item>
          <item>trigger_username: <c>""</c></item>
        </list>
      </item>

      <tag><marker id="agent_orig_disco_opts"></marker>
        <c><![CDATA[agent_originating_discovery_opts() = [agent_originating_discovery_opt()] <optional>]]></c></tag>
      <item>
	<p><c>agent_originating_discovery_opt() = {enable, boolean()}</c></p>
	<p>These are options effecting discovery <c>originating</c> in this
	agent. </p>
	<p>The default values for the <c>originating</c>
	discovery options are: </p>
	<list type="bulleted">
	  <item>enable: <c>true</c></item>
        </list>
      </item>

      <tag><marker id="agent_mt"></marker>
        <c><![CDATA[multi_threaded() = bool() | extended <optional>]]></c></tag>
      <item>
	<p>If <c>true</c> (or <c>extended</c>), the agent is multi-threaded,
	with one thread for each get request.</p>
	<p>The value <c>extended</c> means that a special 'process'
	is also created intended to handle <em>all</em> notifications. </p>
        <list>
	  <item>
	    <p><c>true</c> - One worker dedicated to 'set-requests' and one
	    (main) worker for all other requests ('get-request' and
	    notifications).</p>
	    <p>If the 'main' worker is busy, a temporary process is
	    spawned to handle that job ('get-request' or notification). </p>
	  </item>
	  <item>
	    <p><c>extended</c> - One worker dedicated to 'set-requests',
	    one worker dedicated to notifications and one
	    (main) worker for all 'get-requests'. </p>
	    <p>If the 'main' worker is busy, a temporary process is
	    spawned to handle that 'get-request'. </p>
	  </item>
	</list>
	<note>
	  <p>Even with multi-threaded set to <c>extended</c>
	  there is still a risk for 'reorder' when sending inform-requsts,
	  which require a response (and may therefor require resending). </p>
	  <p>Also, there is of  course no way to guarantee order once the
	  package is on the network. </p>
	</note>
        <p>Default is <c>false</c>.</p>
      </item>

      <tag><marker id="agent_data_dir"></marker>
        <c><![CDATA[db_dir() = string() <mandatory>]]></c></tag>
      <item>
        <p>Defines where the SNMP agent internal db files are stored.</p>
      </item>

      
      <tag><marker id="agent_gb_max_vbs"></marker>
        <c><![CDATA[gb_max_vbs() = pos_integer() | infinity <optional>]]></c></tag>
      <item>
        <p>Defines the maximum number of varbinds allowed 
	in a Get-BULK response.</p>
        <p>Default is <c>1000</c>.</p>
      </item>

      <tag><marker id="agent_local_db"></marker>
        <c><![CDATA[local_db() = [local_db_opt()] <optional>]]></c></tag>
      <item>
        <p><c>local_db_opt() = {repair, agent_repair()} | {auto_save, agent_auto_save()} |   {verbosity, verbosity()}</c></p>
        <p>Defines options specific for the SNMP agent local database.</p>
        <p>For defaults see the options in <c>local_db_opt()</c>.</p>
      </item>

      <tag><marker id="agent_ldb_repair"></marker>
        <c><![CDATA[agent_repair() = false | true | force <optional>]]></c></tag>
      <item>
        <p>When starting snmpa_local_db it always tries to open an
          existing database. If <c>false</c>, and some errors occur, a new
          database is created instead. If <c>true</c>, an existing file
          will be repaired. If <c>force</c>, the table will be repaired
          even if it was properly closed. </p>
        <p>Default is <c>true</c>.</p>
      </item>

      <tag><marker id="agent_ldb_auto_save"></marker>
        <c><![CDATA[agent_auto_save() = integer() | infinity <optional>]]></c></tag>
      <item>
        <p>The auto save interval. The table is flushed to disk
          whenever not accessed for this amount of time.</p>
        <p>Default is <c>5000</c>.</p>
      </item>

      <tag><marker id="agent_net_if"></marker>
        <c><![CDATA[agent_net_if() = [agent_net_if_opt()] <optional>]]></c></tag>
      <item>
        <p><c>agent_net_if_opt() = {module, agent_net_if_module()} |  {verbosity, verbosity()} |  {options, agent_net_if_options()}</c></p>
        <p>Defines options specific for the SNMP agent network interface 
          entity. </p>
        <p>For defaults see the options in <c>agent_net_if_opt()</c>.</p>
      </item>

      <tag><marker id="agent_ni_module"></marker>
        <c><![CDATA[agent_net_if_module() = atom() <optional>]]></c></tag>
      <item>
        <p>Module which handles the network interface part for the
          SNMP agent. Must implement the 
          <seeerl marker="snmpa_network_interface">snmpa_network_interface</seeerl> behaviour.</p>
        <p>Default is <c>snmpa_net_if</c>.</p>
      </item>

      <tag><marker id="agent_ni_opts"></marker>
        <c><![CDATA[agent_net_if_options() = [agent_net_if_option()] <optional>]]></c></tag>
      <item>
        <p><c>agent_net_if_option() = {bind_to, bind_to()} |  
	{sndbuf,          sndbuf()} |  
	{recbuf,          recbuf()} |  
	{no_reuse,        no_reuse()} |  
	{req_limit,       req_limit()} |
	{filter,          agent_net_if_filter_options()} |
	{extra_sock_opts, extra_socket_options()}</c></p>
	<p>These options are actually specific to the used module.
	The ones shown here are applicable to the default 
	<c>agent_net_if_module()</c>.</p>
	<note>
	  <p>If the user has configured transports <em>with</em> options
	  then those will take precedence over these options.
	  See
	  <seeguide marker="snmp_agent_config_files#agent_information">agent information</seeguide>
	  for more info. </p>
	</note>
	<p>For defaults see the options in <c>agent_net_if_option()</c>.</p>
      </item>

      <tag><marker id="agent_ni_req_limit"></marker>
        <c><![CDATA[req_limit() = integer() | infinity <optional>]]></c></tag>
      <item>
        <p>Max number of simultaneous requests handled by the agent.</p>
        <p>Default is <c>infinity</c>.</p>
      </item>

      <tag><marker id="agent_ni_filter_opts"></marker>
        <c><![CDATA[agent_net_if_filter_options() = [agent_net_if_filter_option()] <optional>]]></c></tag>
      <item>
	<p><c>agent_net_if_filter_option() = {module, agent_net_if_filter_module()}</c></p>
	<p>These options are actually specific to the used module.
	  The ones shown here are applicable to the default 
	  <c><![CDATA[agent_net_if_filter_module()]]></c>.</p>
	<p>For defaults see the options in 
          <c>agent_net_if_filter_option()</c>.</p>
      </item>

      <tag><marker id="agent_ni_filter_module"></marker>
        <c><![CDATA[agent_net_if_filter_module() = atom() <optional>]]></c></tag>
      <item>
	<p>Module which handles the network interface filter part for the
	  SNMP agent. Must implement the 
	  <seeerl marker="snmpa_network_interface_filter">snmpa_network_interface_filter</seeerl> behaviour.</p>
	<p>Default is <c>snmpa_net_if_filter</c>.</p>
      </item>

      <tag><marker id="agent_mibs"></marker>
        <c><![CDATA[agent_mibs() = [string()] <optional>]]></c></tag>
      <item>
        <p>Specifies a list of MIBs (including path) that defines which MIBs
          are initially loaded into the SNMP master agent. </p>
        <p>Note that the following mibs will always be loaded:</p>
        <list type="bulleted">
          <item>version v1: <c>STANDARD-MIB</c></item>
          <item>version v2: <c>SNMPv2</c></item>
          <item>version v3: <c>SNMPv2</c>, <c>SNMP-FRAMEWORK-MIB</c> 
           and <c>SNMP-MPD-MIB</c></item>
        </list>
        <p>Default is <c>[]</c>.</p>
      </item>

      <tag><marker id="agent_mib_storage"></marker>
        <c><![CDATA[mib_storage() = [mib_storage_opt()] <optional>]]></c></tag>
      <item>
        <p><c>mib_storage_opt() = {module, mib_storage_module()} |  {options, mib_storage_options()}</c></p>
        <p>This option specifies how basic mib data is stored. 
	This option is used by two parts of the snmp agent: 
	The mib-server and the symbolic-store. </p>
        <p>Default is <c>[{module, snmpa_mib_storage_ets}]</c>. </p>
      </item>

      <tag><marker id="agent_mst_module"></marker>
        <c><![CDATA[mib_storage_module() = snmpa_mib_data_ets | snmpa_mib_data_dets | snmpa_mib_data_mnesia | module()]]></c></tag>
      <item>
        <p>Defines the mib storage module of the SNMP agent as defined by the 
	<seeerl marker="snmpa_mib_storage">snmpa_mib_storage</seeerl> 
	behaviour. </p>
	<p>Several entities (<c>mib-server</c> via the its data module and 
	the <c>symbolic-store</c>) of the snmp agent uses this for storage 
	of miscelaneous mib related data retrieved while loading a mib. </p>
	<p>There are several implementations provided with the agent: 
	<c>snmpa_mib_storage_ets</c>, <c>snmpa_mib_storage_dets</c> and 
	<c>snmpa_mib_storage_mnesia</c>. </p>
        <p>Default module is <c>snmpa_mib_storage_ets</c>. </p>
      </item>

      <tag><marker id="agent_mst_options"></marker>
        <c><![CDATA[mib_storage_options() = list() <optional>]]></c></tag>
      <item>
        <p>This is implementattion depended. That is, it depends on the 
	module. For each module a specific set of options are valid. 
	For the module provided with the app, these options are supported: </p>
        <list type="bulleted">
          <item>
	    <p><c>snmpa_mib_storage_ets</c>: <c>{dir, filename()} | {action, keep | clear}, {checksum, boolean()}</c></p>
	    <list>
	      <item>
		<p><c>dir</c> - If present, points to a directory where a file 
		to which all data in the ets table is "synced". </p>
		<p>Also, when a table is opened this file is read, 
		if it exists. </p>
		<p>By default, this will <em>not</em> be used. </p> 
	      </item>
	      <item>
		<p><c>action</c> - Specifies the behaviour when a non-empty 
		file is found: Keep its content or clear it out. </p>
		<p>Default is <c>keep</c>. </p> 
	      </item>
	      <item>
		<p><c>checksum</c> - Defines if the file is checksummed 
		or not. </p>
		<p>Default is <c>false</c>. </p> 
	      </item>
	    </list>
	  </item>
          <item>
	    <p><c>snmpa_mib_storage_dets</c>: <c>{dir, filename()} | {action, keep | clear}, {auto_save, default | pos_integer()} | {repair, force | boolean()}</c></p>
	    <list>
	      <item>
		<p><c>dir</c> - This <em>mandatory</em> option points to a 
		directory where to place the file of a dets table. </p>
	      </item>
	      <item>
		<p><c>action</c> - Specifies the behaviour when a non-empty 
		file is found: Keep its content or clear it out. </p>
		<p>Default is <c>keep</c>. </p> 
	      </item>
	      <item>
		<p><c>auto_save</c> - Defines the dets auto-save frequency. </p>
		<p>Default is <c>default</c>. </p> 
	      </item>
	      <item>
		<p><c>repair</c> - Defines the dets repair behaviour. </p>
		<p>Default is <c>false</c>. </p> 
	      </item>
	    </list>
	  </item>
          <item>
	    <p><c>snmpa_mib_storage_mnesia</c>: <c>{action, keep | clear}, {nodes, [node()]}</c></p>
	    <list>
	      <item>
		<p><c>action</c> - Specifies the behaviour when a non-empty, 
		already existing, table: Keep its content or clear it out. </p>
		<p>Default is <c>keep</c>. </p>
	      </item>
	      <item>
		<p><c>nodes</c> - A list of node names (or an atom 
		describing a list of nodes) defining where to open the table. 
		Its up to the user to ensure that mnesia is actually running 
		on the specified nodes. </p>
		<p>The following distinct values are recognised: </p>
		<list>
		  <item>
		    <p><c>[]</c> - Translated into a list of the own node: <c>[node()]</c></p>
		  </item>
		  <item>
		    <p><c>all</c> - <c>erlang:nodes()</c></p>
		  </item>
		  <item>
		    <p><c>visible</c> - <c>erlang:nodes(visible)</c></p>
		  </item>
		  <item>
		    <p><c>connected</c> - <c>erlang:nodes(connected)</c></p>
		  </item>
		  <item>
		    <p><c>db_nodes</c> - <c>mnesia:system_info(db_nodes)</c></p>
		  </item>
		</list>
		
		<p>Default is the result of the call: <c>erlang:nodes()</c>. </p>
	      </item>
	    </list>
	  </item>
        </list>
      </item>

      <tag><marker id="agent_mib_server"></marker>
        <c><![CDATA[mib_server() = [mib_server_opt()] <optional>]]></c></tag>
      <item>
        <p><c>mib_server_opt() = {mibentry_override, mibentry_override()} |  {trapentry_override, trapentry_override()} |  {verbosity, verbosity()} | {cache, mibs_cache()} | {data_module, mib_server_data_module()}</c></p>
        <p>Defines options specific for the SNMP agent mib server. </p>
        <p>For defaults see the options in <c>mib_server_opt()</c>.</p>
      </item>

      <tag><marker id="agent_ms_meo"></marker>
        <c><![CDATA[mibentry_override() = bool() <optional>]]></c></tag>
      <item>
        <p>If this value is false, then when loading a mib each mib-
          entry is checked prior to installation of the mib. 
          The purpose of the check is to prevent that the same symbolic 
          mibentry name is used for different oid's.</p>
        <p>Default is <c>false</c>.</p>
      </item>

      <tag><marker id="agent_ms_teo"></marker>
        <c><![CDATA[trapentry_override() = bool() <optional>]]></c></tag>
      <item>
        <p>If this value is false, then when loading a mib each trap
          is checked prior to installation of the mib. 
          The purpose of the check is to prevent that the same symbolic 
          trap name is used for different trap's.</p>
        <p>Default is <c>false</c>.</p>
      </item>

<!--
      <tag><marker id="agent_ms_data_module"></marker>
        <c><![CDATA[mib_server_data_module() = snmpa_mib_data_tttn | snmpa_mib_data_ttln | module() <optional>]]></c></tag>
-->
      <tag><marker id="agent_ms_data_module"></marker>
        <c><![CDATA[mib_server_data_module() = snmpa_mib_data_tttn | module() <optional>]]></c></tag>
      <item>
        <p>Defines the backend data module of the SNMP agent mib-server as 
	defined by the 
	<seeerl marker="snmpa_mib_data">snmpa_mib_data</seeerl> 
	behaviour. </p>
	<p>At present only the default module is provided with the agent,  
	<c>snmpa_mib_data_tttn</c>. </p>
<!--
	<p>Two modules is provided with the agent 
	<c>snmpa_mib_data_tttn</c> (this is the old implementation) and 
	<c>snmpa_mib_data_ttln</c> (for a mib tree with many holes, 
	this algorithm can be more price efficient). </p>
-->
        <p>Default module is <c>snmpa_mib_data_tttn</c>. </p>
      </item>

      <tag><marker id="agent_ms_cache"></marker>
        <c><![CDATA[mibs_cache() = bool() | mibs_cache_opts() <optional>]]></c></tag>
      <item>
        <p>Shall the agent utilize the mib server lookup cache or not.</p>
        <p>Default is <c>true</c> (in which case the <c>mibs_cache_opts()</c> 
          default values apply).</p>
      </item>

      <tag><marker id="agent_ms_cache_opts"></marker>
        <c><![CDATA[mibs_cache_opts() = [mibs_cache_opt()] <optional>]]></c></tag>
      <item>
        <p><c>mibs_cache_opt() = {autogc, mibs_cache_autogc()} | {gclimit, mibs_cache_gclimit()} | {age, mibs_cache_age()}</c></p>
        <p>Defines options specific for the SNMP agent mib server cache. </p>
        <p>For defaults see the options in <c>mibs_cache_opt()</c>.</p>
      </item>

      <tag><marker id="agent_ms_cache_autogc"></marker>
        <c><![CDATA[mibs_cache_autogc() = bool() <optional>]]></c></tag>
      <item>
        <p>Defines if the mib server shall perform cache gc automatically or 
	leave it to the user (see 
	<seeerl marker="snmpa#gc_mibs_cache">gc_mibs_cache/0,1,2,3</seeerl>). </p>
        <p>Default is <c>true</c>.</p>
      </item>

      <tag><marker id="agent_ms_cache_age"></marker>
        <c><![CDATA[mibs_cache_age() = integer() > 0 <optional>]]></c></tag>
      <item>
        <p>Defines how old the entries in the cache will be allowed 
	to become before they are GC'ed (assuming GC is performed). 
	Each entry in the cache is "touched" whenever it is accessed. </p>
	<p>The age is defined in milliseconds. </p>
	<p>Default is <c>10 timutes</c>.</p>
      </item>

      <tag><marker id="agent_ms_cache_gclimit"></marker>
        <c><![CDATA[mibs_cache_gclimit() = infinity | integer() > 0 <optional>]]></c></tag>
      <item>
        <p>When performing a GC, this is the max number of cache entries 
	that will be deleted from the cache. </p>

	<p>The reason why its possible to set a limit, is that if the cache is 
	large, the GC can potentially take a long time, during which 
	the agent is "busy".
	<em>But</em> on a heavily loaded system, we also risk not removing
	enough elements in the cache, instead causing it to grow over time.
	This is the reason the default value is <c>infinity</c>, which will
	ensure that <em>all</em> candidates are removed as soon as possible. </p>

	<p>Default is <c>infinity</c>.</p>
      </item>

      <tag><marker id="agent_error_report_mod"></marker>
        <c><![CDATA[error_report_mod() = atom() <optional>]]></c></tag>
      <item>
        <p>Defines an error report module, implementing the 
          <seeerl marker="snmpa_error_report">snmpa_error_report</seeerl> 
          behaviour. Two modules are provided with the toolkit: 
          <c>snmpa_error_logger</c> and <c>snmpa_error_io</c>.</p>
        <p>Default is <c>snmpa_error_logger</c>.</p>
      </item>

      <tag><marker id="agent_symbolic_store"></marker>
        <c>symbolic_store() = [symbolic_store_opt()]</c></tag>
      <item>
        <p><c>symbolic_store_opt() = {verbosity, verbosity()}</c></p>
        <p>Defines options specific for the SNMP agent symbolic store. </p>
        <p>For defaults see the options in <c>symbolic_store_opt()</c>.</p>
      </item>

      <tag><marker id="agent_target_cache"></marker>
        <c>target_cache() = [target_cache_opt()]</c></tag>
      <item>
        <p><c>target_cache_opt() = {verbosity, verbosity()}</c></p>
        <p>Defines options specific for the SNMP agent target cache. </p>
        <p>For defaults see the options in <c>target_cache_opt()</c>.</p>
      </item>

      <tag><marker id="agent_config"></marker>
        <c><![CDATA[agent_config() = [agent_config_opt()] <mandatory>]]></c></tag>
      <item>
        <p><c>agent_config_opt() = {dir, agent_config_dir()} |  {force_load, force_load()} | {verbosity, verbosity()}</c></p>
        <p>Defines specific config related options for the SNMP agent. </p>
        <p>For defaults see the options in <c>agent_config_opt()</c>.</p>
      </item>

      <tag><marker id="agent_config_dir"></marker>
        <c><![CDATA[agent_config_dir = dir() <mandatory>]]></c></tag>
      <item>
        <p>Defines where the SNMP agent configuration files are stored.</p>
      </item>

      <tag><marker id="agent_force_load"></marker>
        <c><![CDATA[force_load() = bool() <optional>]]></c></tag>
      <item>
        <p>If <c>true</c> the configuration files are re-read
          during start-up, and the contents of the configuration 
          database ignored.  Thus, if <c>true</c>, changes to 
          the configuration database are lost upon reboot of the 
          agent. </p>
        <p>Default is <c>false</c>.</p>
      </item>
    </taglist>

    <marker id="manager_opts_and_types"></marker>
    <p>Manager specific config options and types:</p>
    <taglist>
      <tag><marker id="manager_server"></marker>
        <c><![CDATA[server() = [server_opt()] <optional>]]></c></tag>
      <item>
        <p><c>server_opt() = {timeout, server_timeout()} | {verbosity, verbosity()} | {cbproxy, server_cbproxy()} | {netif_sup, server_nis()}</c></p>
        <p>Specifies the options for the manager server process.</p>
        <p>Default is <c>silence</c>.</p>
      </item>

      <tag><marker id="manager_server_timeout"></marker>
        <c><![CDATA[server_timeout() = integer() <optional>]]></c></tag>
      <item>
        <p>Asynchronous request cleanup time. For every requests,
          some info is stored internally, in order to be able to 
          deliver the reply (when it arrives) to the proper destination.
          If the reply arrives, this info will be deleted. But if
          there is no reply (in time), the info has to be deleted
          after the <em>best before</em> time has been passed.
          This cleanup will be performed at regular intervals, defined 
          by the <c>server_timeout()</c> time.
          The information will have an <em>best before</em> time,
          defined by the <c>Expire</c> time given when calling the
          request function (see 
          <seeerl marker="snmpm#async_get2">async_get</seeerl>,
          <seeerl marker="snmpm#async_get_next2">async_get_next</seeerl> and 
          <seeerl marker="snmpm#async_set2">async_set</seeerl>).</p>
        <p>Time in milli-seconds.</p>
        <p>Default is <c>30000</c>.</p>
      </item>

      <tag><marker id="manager_server_cbproxy"></marker>
        <c><![CDATA[server_cbproxy() = temporary (default) | permanent <optional>]]></c></tag>
      <item>
        <p>This option specifies how the server will handle callback calls.</p>
	<taglist>
	  <tag><marker id="manager_server_cbproxy_temporary"></marker>
	  <c><![CDATA[temporary (default)]]></c></tag>
	  <item>
	    <p>A temporary process will be created for each callback call. </p>
	  </item>
	  
	  <tag><marker id="manager_server_cbproxy_temporary"></marker>
	  <c><![CDATA[permanent]]></c></tag>
	  <item>
	    <p>With this the server will create a permanent (named) process that
	    in effect serializes all callback calls.</p>
	  </item>
	</taglist>
        <p>Default is <c>temporary</c>.</p>
      </item>

      <tag><marker id="manager_server_nis"></marker>
        <c><![CDATA[server_nis() = none (default) | {PingTO, PongTO} <optional>]]></c></tag>
      <item>
	<p>This option specifies if the server should actively supervise the
	net-if process.
	Note that this will only work if the used net-if process actually supports
	the protocol. See
	<seeerl marker="snmpm_network_interface">snmpm_network_interface</seeerl> behaviour for more info. </p>
	<taglist>
	  <tag><marker id="manager_server_nis_none"></marker>
	  <c><![CDATA[none (default)]]></c></tag>
	  <item>
	    <p>No active supervision of the net-if process. </p>
	  </item>
	  
	  <tag><marker id="manager_server_nis_active"></marker>
	  <c><![CDATA[{PingTO :: pos_integer(), PongTO :: pos_integer()}]]></c></tag>
	  <item>
	    <p>The <c>PingTO</c> time specifies the between a successful ping
	    (or start) and the time when a ping message is to be sent to the net-if
	    process (basically the time between ping). </p>
	    <p>The <c>PongTO</c> time specifies how long time the net-if process
	    has to respond to a ping message, with a <em>pong</em> message.
	    Its starts counting when the ping message has been sent.</p>
	    <p>Both times are in milli seconds.</p>
	  </item>
	</taglist>
	<p>Default is <c>none</c>.</p>
      </item>

      <tag><marker id="manager_config"></marker>
        <c><![CDATA[manager_config() = [manager_config_opt()] <mandatory>]]></c></tag>
      <item>
        <p><c>manager_config_opt() = {dir, manager_config_dir()} |  {db_dir, manager_db_dir()} |  {db_init_error, db_init_error()} |  {repair, manager_repair()} |  {auto_save, manager_auto_save()} |  {verbosity, verbosity()}</c></p>
        <p>Defines specific config related options for the SNMP manager. </p>
        <p>For defaults see the options in <c>manager_config_opt()</c>.</p>
      </item>

      <tag><marker id="manager_config_dir"></marker>
        <c><![CDATA[manager_config_dir = dir() <mandatory>]]></c></tag>
      <item>
        <p>Defines where the SNMP manager configuration files are stored.</p>
      </item>

      <tag><marker id="manager_config_db_dir"></marker>
        <c><![CDATA[manager_db_dir = dir() <mandatory>]]></c></tag>
      <item>
        <p>Defines where the SNMP manager store persistent data.</p>
      </item>

      <tag><marker id="manager_config_repair"></marker>
        <c><![CDATA[manager_repair() = false | true | force <optional>]]></c></tag>
      <item>
        <p>Defines the repair option for the persistent database (if 
          and how the table is repaired when opened). </p>
        <p>Default is <c>true</c>.</p>
      </item>

      <tag><marker id="manager_config_auto_save"></marker>
        <c><![CDATA[manager_auto_save() = integer() | infinity <optional>]]></c></tag>
      <item>
        <p>The auto save interval. The table is flushed to disk
          whenever not accessed for this amount of time.</p>
        <p>Default is <c>5000</c>.</p>
      </item>

      <tag><marker id="manager_irb"></marker>
        <c><![CDATA[manager_irb() = auto | user | {user, integer()} <optional>]]></c></tag>
      <item>
        <p>This option defines how the manager will handle the sending of 
          response (acknowledgment) to received inform-requests. </p>
        <list type="bulleted">
          <item>
            <p><c>auto</c> - The manager will autonomously send response
              (acknowledgment&gt; to inform-request messages.</p>
          </item>
          <item>
            <p><c>{user, integer()}</c> - The manager will send response
              (acknowledgment) to inform-request messages when the 
              <seeerl marker="snmpm_user#handle_inform">handle_inform</seeerl> 
              function completes. The integer is the time, in milli-seconds, 
              that the manager will consider the stored inform-request info 
              valid.</p>
          </item>
          <item>
            <p><c>user</c> - Same as <c>{user, integer()}</c>, except that 
              the default time, 15 seconds (15000), is used.</p>
          </item>
        </list>
        <p>See 
          <seeerl marker="snmpm_network_interface">snmpm_network_interface</seeerl>, 
          <seeerl marker="snmpm_user">handle_inform</seeerl> and 
          <seeguide marker="snmp_manager_netif">definition of the manager net if</seeguide> for more info.</p>
        <p>Default is <c>auto</c>.</p>
      </item>

      <tag><marker id="manager_mibs"></marker>
        <c><![CDATA[manager_mibs() = [string()] <optional>]]></c></tag>
      <item>
        <p>Specifies a list of MIBs (including path) and defines which MIBs
          are initially loaded into the SNMP manager. </p>
        <p>Default is <c>[]</c>.</p>
      </item>

      <tag><marker id="manager_net_if"></marker>
        <c><![CDATA[manager_net_if() = [manager_net_if_opt()] <optional>]]></c></tag>
      <item>
        <p><c>manager_net_if_opt() = {module, manager_net_if_module()} | 
          {verbosity, verbosity()} | 
          {options, manager_net_if_options()}</c></p>
        <p>Defines options specific for the SNMP manager network interface 
          entity. </p>
        <p>For defaults see the options in <c>manager_net_if_opt()</c>.</p>
      </item>

      <tag><marker id="manager_ni_opts"></marker>
        <c><![CDATA[manager_net_if_options() = [manager_net_if_option()] <optional>]]></c></tag>
      <item>
        <p><c>manager_net_if_option() = {bind_to, bind_to()} | 
	{sndbuf,          sndbuf()} |  
	{recbuf,          recbuf()} | 
	{no_reuse,        no_reuse()} |
	{filter,          manager_net_if_filter_options()} |
	{extra_sock_opts, extra_socket_options()}</c></p>
        <p>These options are actually specific to the used module.
	The ones shown here are applicable to the default 
	<c>manager_net_if_module()</c>.</p>
        <p>For defaults see the options in <c>manager_net_if_option()</c>.</p>
      </item>

      <tag><marker id="manager_ni_module"></marker>
        <c><![CDATA[manager_net_if_module() = atom() <optional>]]></c></tag>
      <item>
        <p>The module which handles the network interface part for the
          SNMP manager. It must implement the 
          <seeerl marker="snmpm_network_interface">snmpm_network_interface</seeerl> behaviour.</p>
        <p>Default is <c>snmpm_net_if</c>.</p>
      </item>

      <tag><marker id="manager_ni_filter_opts"></marker>
        <c><![CDATA[manager_net_if_filter_options() = [manager_net_if_filter_option()] <optional>]]></c></tag>
      <item>
	<p><c>manager_net_if_filter_option() = {module, manager_net_if_filter_module()}</c></p>
	<p>These options are actually specific to the used module.
	  The ones shown here are applicable to the default 
	  <c><![CDATA[manager_net_if_filter_module()]]></c>.</p>
	<p>For defaults see the options in 
          <c>manager_net_if_filter_option()</c>.</p>
      </item>

      <tag><marker id="manager_ni_filter_module"></marker>
        <c><![CDATA[manager_net_if_filter_module() = atom() <optional>]]></c></tag>
      <item>
	<p>Module which handles the network interface filter part for the
	  SNMP manager. Must implement the 
	  <seeerl marker="snmpm_network_interface_filter">snmpm_network_interface_filter</seeerl> behaviour.</p>
	<p>Default is <c>snmpm_net_if_filter</c>.</p>
      </item>

      <tag><marker id="manager_def_user_module"></marker>
        <c><![CDATA[def_user_module() = atom() <optional>]]></c></tag>
      <item>
        <p>The module implementing the default user. See the 
          <seeerl marker="snmpm_user">snmpm_user</seeerl> behaviour.</p>
        <p>Default is <c>snmpm_user_default</c>.</p>
      </item>

      <tag><marker id="manager_def_user_data"></marker>
        <c><![CDATA[def_user_data() = term() <optional>]]></c></tag>
      <item>
        <p>Data for the default user. Passed to the user module when 
          calling the callback functions.</p>
        <p>Default is <c>undefined</c>.</p>
      </item>
    </taglist>

    <marker id="common_types"></marker>
    <p>Common config types:</p>
    <taglist>
      <tag><marker id="restart_type"></marker>
        <c>restart_type() = permanent | transient | temporary</c></tag>
      <item>
        <p>See <seeerl marker="stdlib:supervisor#child_spec">supervisor</seeerl> 
          documentation for more info.</p>
        <p>Default is <c>permanent</c> for the agent and <c>transient</c>
          for the manager.</p>
      </item>

      <tag><marker id="db_init_error"></marker>
        <c>db_init_error() = terminate | create | create_db_and_dir</c></tag>
      <item>
        <p>Defines what to do if the agent or manager is unable to open an
          existing database file. <c>terminate</c> means that the
          agent/manager will terminate and <c>create</c> means that the 
          agent/manager will remove the faulty file(s) and create new ones,
          and <c>create_db_and_dir</c> means that the agent/manager will
          create the database file along with any missing parent directories
          for the database file.</p>
        <p>Default is <c>terminate</c>.</p>
      </item>

      <tag><marker id="prio"></marker>
        <c><![CDATA[priority() = atom() <optional>]]></c></tag>
      <item>
        <p>Defines the Erlang priority for all SNMP processes.</p>
        <p>Default is <c>normal</c>.</p>
      </item>

      <tag><marker id="versions"></marker>
        <c><![CDATA[versions() = [version()] <optional>]]></c></tag>
      <item>
        <p><c>version() = v1 | v2 | v3</c></p>
        <p>Which SNMP versions shall be accepted/used.</p>
        <p>Default is <c>[v1,v2,v3]</c>.</p>
      </item>

      <tag><marker id="verbosity"></marker>
        <c><![CDATA[verbosity() = silence | info | log | debug | trace <optional>]]></c></tag>
      <item>
        <p>Verbosity for a SNMP process. This specifies now much debug info
          is printed.</p>
        <p>Default is <c>silence</c>.</p>
      </item>

      <tag><marker id="bind_to"></marker>
        <c><![CDATA[bind_to() = bool() <optional>]]></c></tag>
      <item>
        <p>If <c>true</c>, net_if binds to the IP address.
          If <c>false</c>, net_if listens on any IP address on the host
          where it is running. </p>
        <p>Default is <c>false</c>.</p>
      </item>

      <tag><marker id="no_reuse"></marker>
        <c><![CDATA[no_reuse() = bool() <optional>]]></c></tag>
      <item>
        <p>If <c>true</c>, net_if does not specify that the IP
          and port address should be reusable. If <c>false</c>, 
          the address is set to reusable. </p>
        <p>Default is <c>false</c>.</p>
      </item>

      <tag><marker id="recbuf"></marker>
        <c><![CDATA[recbuf() = integer() <optional>]]></c></tag>
      <item>
        <p>Receive buffer size. </p>
        <p>Default value is defined by <c>gen_udp</c>.</p>
      </item>

      <tag><marker id="sndbuf"></marker>
        <c><![CDATA[sndbuf() = integer() <optional>]]></c></tag>
      <item>
        <p>Send buffer size. </p>
        <p>Default value is defined by <c>gen_udp</c>.</p>
      </item>

      <tag><marker id="extra_sock_opts"></marker>
        <c><![CDATA[extra_socket_options() = list() <optional>]]></c></tag>
      <item>
	<p>A list of arbitrary socket options. </p>
	<p>This list is not inspected by snmp (other then checking that
	its a list). Its the users responsibility to ensure that these
	are valid options and does not conflict with the "normal" options. </p>
        <p>Default is <c>[]</c>.</p>
      </item>

      <tag><marker id="note_store"></marker>
        <c><![CDATA[note_store() = [note_store_opt()] <optional>]]></c></tag>
      <item>
        <p><c>note_store_opt() = {timeout, note_store_timeout()} |  {verbosity, verbosity()}</c></p>
        <p>Specifies the start-up verbosity for the SNMP note store.</p>
        <p>For defaults see the options in <c>note_store_opt()</c>.</p>
      </item>

      <tag><marker id="ns_timeout"></marker>
        <c><![CDATA[note_store_timeout() = integer() <optional>]]></c></tag>
      <item>
        <p>Note cleanup time. When storing a note in the note store,
          each note is given lifetime. Every <c>timeout</c> the note_store
          process performs a GC to remove the expired note's. Time in
          milli-seconds.</p>
        <p>Default is <c>30000</c>.</p>

      </item>

      <tag><marker id="audit_trail_log"></marker>
        <c><![CDATA[audit_trail_log() = [audit_trail_log_opt()] <optional>]]></c></tag>
      <item>
        <p><c>audit_trail_log_opt() = {type, atl_type()} | {dir, atl_dir()} |  {size, atl_size()} |  {repair, atl_repair()} | {seqno, atl_seqno()}</c></p>
        <p>If present, this option specifies the options for the 
          audit trail logging. The <c>disk_log</c> module is used 
          to maintain a wrap log. If present, the <c>dir</c> and 
          <c>size</c> options are mandatory.</p>
        <p>If not present, audit trail logging is not used.</p>
      </item>

      <tag><marker id="atl_type"></marker>
        <c><![CDATA[atl_type() = read | write | read_write <optional>]]></c></tag>
      <item>
        <p>Specifies what type of an audit trail log should be used. 
          The effect of the type is actually different for the the agent
          and the manager. </p>
        <p>For the agent:</p>
        <list type="bulleted">
          <item>If <c>write</c> is specified, only set requests are logged.  </item>
          <item>If <c>read</c> is specified, only get requests are logged.  </item>
          <item>If <c>read_write</c>, all requests are logged.  </item>
        </list>
        <p>For the manager:</p>
        <list type="bulleted">
          <item>If <c>write</c> is specified, only sent messages are logged.  </item>
          <item>If <c>read</c> is specified, only received messages are logged.  </item>
          <item>If <c>read_write</c>, both outgoing and incoming messages are 
           logged.  </item>
        </list>
        <p>Default is <c>read_write</c>.</p>
      </item>

      <tag><marker id="atl_dir"></marker>
        <c><![CDATA[atl_dir = dir() <mandatory>]]></c></tag>
      <item>
        <p>Specifies where the audit trail log should be stored.</p>
        <p>If <c>audit_trail_log</c> specifies that logging should take
          place, this parameter <em>must</em> be defined.</p>
      </item>

      <tag><marker id="atl_size"></marker>
        <c><![CDATA[atl_size() = {integer(), integer()} <mandatory>]]></c></tag>
      <item>
        <p>Specifies the size of the audit
          trail log.  This parameter is sent to <c>disk_log</c>.  </p>
        <p>If <c>audit_trail_log</c> specifies that logging should 
          take place, this parameter <em>must</em> be defined.</p>
      </item>

      <tag><marker id="atl_repair"></marker>
        <c><![CDATA[atl_repair() = true | false | truncate | snmp_repair <optional>]]></c></tag>
      <item>
        <p>Specifies if and how the audit trail log shall be repaired
          when opened. Unless this parameter has the value <c>snmp_repair</c>
          it is sent to <c>disk_log</c>. If, on the other hand, the value is
          <c>snmp_repair</c>, snmp attempts to handle certain faults on its
          own. And even if it cannot repair the file, it does not truncate it 
          directly, but instead <em>moves it aside</em> for later off-line 
          analysis.</p>
        <p>Default is <c>true</c>.</p>
      </item>

      <tag><marker id="atl_seqno"></marker>
        <c><![CDATA[atl_seqno() = true | false <optional>]]></c></tag>
      <item>
        <p>Specifies if the audit trail log entries will be (sequence)
          numbered or not. The range of the sequence numbers are according
          to RFC 5424, i.e. 1 through 2147483647. </p>
        <p>Default is <c>false</c>.</p>
      </item>
    </taglist>
  </section>

  <section>
    <title>See Also</title>
    <p>application(3), disk_log(3)</p>
  </section>
  
</appref>

