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<header>
<copyright>
<year>1999</year><year>2016</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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<title>snmpa_mpd</title>
<prepared></prepared>
<responsible></responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date></date>
<rev></rev>
<file>snmpa_mpd.xml</file>
</header>
<module>snmpa_mpd</module>
<modulesummary>Message Processing and Dispatch module for the SNMP agent</modulesummary>
<description>
<p>The module <c>snmpa_mpd</c> implements the version independent
Message Processing and Dispatch functionality in SNMP for the agent.
It is supposed to be used from a Network Interface process
(<seealso marker="snmp_agent_netif">Definition of Agent Net if</seealso>).
</p>
<marker id="init"></marker>
</description>
<section>
<title>DATA TYPES</title>
<p>See the <seealso marker="snmpa_conf#types">
data types in <c>snmpa_conf</c></seealso>.</p>
</section>
<funcs>
<func>
<name>init(Vsns) -> mpd_state()</name>
<fsummary>Initialize the MPD module</fsummary>
<type>
<v>Vsns = [Vsn]</v>
<v>Vsn = v1 | v2 | v3</v>
</type>
<desc>
<p>This function can be called from the net_if process at start-up.
The options list defines which versions to use.
</p>
<p>It also initializes some SNMP counters.
</p>
<marker id="process_packet"></marker>
</desc>
</func>
<func>
<name>process_packet(Packet, From, State, NoteStore, Log) -> {ok, Vsn, Pdu, PduMS, ACMData} | {discarded, Reason} | {discovery, DiscoPacket}</name>
<name>process_packet(Packet, From, LocalEngineID, State, NoteStore, Log) -> {ok, Vsn, Pdu, PduMS, ACMData} | {discarded, Reason} | {discovery, DiscoPacket}</name>
<fsummary>Process a packet received from the network</fsummary>
<type>
<v>Packet = binary()</v>
<v>From = {TDomain, TAddr}</v>
<v>TDomain = transportDomainUdpIpv4 | transportDomainUdpIpv6</v>
<v>TAddr = {IpAddr, IpPort}</v>
<v>LocalEngineID = string()</v>
<v>IpAddr = <seealso marker="kernel:inet#type-ip_address">inet:ip_address()</seealso></v>
<v>IpPort = inet:port_number()</v>
<v>State = mpd_state()</v>
<v>NoteStore = pid()</v>
<v>Log = snmp_log()</v>
<v>Vsn = 'version-1' | 'version-2' | 'version-3'</v>
<v>Pdu = #pdu</v>
<v>PduMs = integer()</v>
<v>ACMData = acm_data()</v>
<v>Reason = term()</v>
<v>DiscoPacket = binary()</v>
</type>
<desc>
<p>Processes an incoming packet. Performs authentication and
decryption as necessary. The return values should be passed to the
agent.</p>
<note>
<p>Note that the use of the LocalEngineID argument is only intended
for special cases, if the agent is to "emulate" multiple EngineIDs!
By default, the agent uses the value of <c>SnmpEngineID</c>
(see SNMP-FRAMEWORK-MIB). </p>
</note>
<marker id="generate_response_msg"></marker>
</desc>
</func>
<func>
<name>generate_response_msg(Vsn, RePdu, Type, ACMData, Log) -> {ok, Packet} | {discarded, Reason}</name>
<name>generate_response_msg(Vsn, RePdu, Type, ACMData, LocalEngineID, Log) -> {ok, Packet} | {discarded, Reason}</name>
<fsummary>Generate a response packet to be sent to the network</fsummary>
<type>
<v>Vsn = 'version-1' | 'version-2' | 'version-3'</v>
<v>RePdu = #pdu</v>
<v>Type = atom()</v>
<v>ACMData = acm_data()</v>
<v>LocalEngineID = string()</v>
<v>Packet = binary()</v>
</type>
<desc>
<p>Generates a possibly encrypted response packet to be sent to the
network. <c>Type</c> is the <c>#pdu.type</c> of the original
request.</p>
<note>
<p>Note that the use of the LocalEngineID argument is only intended
for special cases, if the agent is to "emulate" multiple EngineIDs!
By default, the agent uses the value of <c>SnmpEngineID</c>
(see SNMP-FRAMEWORK-MIB). </p>
</note>
<marker id="generate_msg"></marker>
</desc>
</func>
<func>
<name>generate_msg(Vsn, NoteStore, Pdu, MsgData, To) -> {ok, PacketsAndAddresses} | {discarded, Reason}</name>
<name>generate_msg(Vsn, NoteStore, Pdu, MsgData, LocalEngineID, To) -> {ok, PacketsAndAddresses} | {discarded, Reason}</name>
<fsummary>Generate a request message to be sent to the network</fsummary>
<type>
<v>Vsn = 'version-1' | 'version-2' | 'version-3'</v>
<v>NoteStore = pid()</v>
<v>Pdu = #pdu</v>
<v>MsgData = msg_data()</v>
<v>LocalEngineID = string()</v>
<v>To = [dest_addrs()]</v>
<v>PacketsAndAddresses = [{TDomain, TAddress, Packet}]</v>
<v>TDomain = snmpUDPDomain</v>
<v>TAddress = {Ip, Udp}</v>
<v>Ip = {integer(), integer(), integer(), integer()}</v>
<v>Udp = integer()</v>
<v>Packet = binary()</v>
</type>
<desc>
<p>Generates a possibly encrypted request packet to be sent to the
network.
</p>
<p><c>MsgData</c> is the message specific data used in
the SNMP message. This value is received in a
<seealso marker="snmp_agent_netif#im_send_pdu"><c>send_pdu</c></seealso>
or
<seealso marker="snmp_agent_netif#im_send_pdu_req">
<c>send_pdu_req</c></seealso>
message from the agent. In SNMPv1 and
SNMPv2c, this message data is the community string. In
SNMPv3, it is the context information.</p>
<p>
<c>To</c> is a list of destination addresses and
their corresponding security parameters. This value is
received in the same message from the agent and then transformed
trough <seealso marker="#process_taddrs"><c>process_taddrs</c></seealso>
before passed to this function.</p>
<note>
<p>Note that the use of the LocalEngineID argument is only intended
for special cases, if the agent is to "emulate" multiple EngineIDs!
By default, the agent uses the value of <c>SnmpEngineID</c>
(see SNMP-FRAMEWORK-MIB). </p>
</note>
<marker id="process_taddrs"></marker>
</desc>
</func>
<func>
<name>process_taddrs(TDests) -> Dests</name>
<fsummary>Transform addresses from internal MIB format to a less internal
</fsummary>
<type>
<v>TDests = [TDest]</v>
<v>TDest = {{TDomain, TAddr}, SecData} | {TDomain, TAddr}</v>
<v>TDomain = term() % Not at tuple</v>
<v>TAddr = term()</v>
<v>SecData = term()</v>
<v>Dests = [Dest]</v>
<v>Dest = {{Domain, Addr}, SecData} | {Domain, Addr}</v>
<v>Domain = transportDomain()</v>
<v>Addr = transportAddress() % Depends on Domain</v>
</type>
<desc>
<p>Transforms addresses from internal MIB format to one
more useful to <seealso marker="snmp_agent_netif">Agent Net if</seealso>.
</p>
<p>See also <seealso marker="#generate_msg"><c>generate_msg</c>.</seealso>
</p>
<marker id="discarded_pdu"></marker>
</desc>
</func>
<func>
<name>discarded_pdu(Variable) -> void()</name>
<fsummary>Increment the variable associated with a discarded pdu</fsummary>
<type>
<v>Variable = atom()</v>
</type>
<desc>
<p>Increments the variable associated with a discarded pdu.
This function can be used when the net_if process receives a
<c>discarded_pdu</c> message from the agent.
</p>
</desc>
</func>
</funcs>
</erlref>
