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Simple Network Management Protocol (SNMP)
Reference Manual
Version 4.18

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# snmpa_mpd

### MODULE

snmpa_mpd

### MODULE SUMMARY

Message Processing and Dispatch module for the SNMP agent

### DESCRIPTION

The module snmpa_mpd 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 (Definition of Agent Net if).

### EXPORTS

init(Vsns) -> mpd_state()

Types:

Vsns = [Vsn]
Vsn = v1 | v2 | v3

This function can be called from the net_if process at start-up. The options list defines which versions to use.

It also initializes some SNMP counters.

process_packet(Packet, TDomain, TAddress, State, NoteStore, Log) -> {ok, Vsn, Pdu, PduMS, ACMData} | {discarded, Reason} | {discovery, DiscoPacket}
process_packet(Packet, TDomain, TAddress, LocalEngineID, State, NoteStore, Log) -> {ok, Vsn, Pdu, PduMS, ACMData} | {discarded, Reason} | {discovery, DiscoPacket}

Types:

Packet = binary()
TDomain = snmpUDPDomain
TAddress = {Ip, Udp}
LocalEngineID = string()
Ip = {integer(), integer(), integer(), integer()}
Udp = integer()
State = mpd_state()
NoteStore = pid()
Log = snmp_log()
Vsn = 'version-1' | 'version-2' | 'version-3'
Pdu = #pdu
PduMs = integer()
ACMData = acm_data()
Reason = term()
DiscoPacket = binary()

Processes an incoming packet. Performs authentication and decryption as necessary. The return values should be passed the agent.

Note

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 SnmpEngineID (see SNMP-FRAMEWORK-MIB).

generate_response_msg(Vsn, RePdu, Type, ACMData, Log) -> {ok, Packet} | {discarded, Reason}
generate_response_msg(Vsn, RePdu, Type, ACMData, LocalEngineID, Log) -> {ok, Packet} | {discarded, Reason}

Types:

Vsn = 'version-1' | 'version-2' | 'version-3'
RePdu = #pdu
Type = atom()
ACMData = acm_data()
LocalEngineID = string()
Packet = binary()

Generates a possibly encrypted response packet to be sent to the network. Type is the #pdu.type of the original request.

Note

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 SnmpEngineID (see SNMP-FRAMEWORK-MIB).

generate_msg(Vsn, NoteStore, Pdu, MsgData, To) -> {ok, PacketsAndAddresses} | {discarded, Reason}
generate_msg(Vsn, NoteStore, Pdu, MsgData, LocalEngineID, To) -> {ok, PacketsAndAddresses} | {discarded, Reason}

Types:

Vsn = 'version-1' | 'version-2' | 'version-3'
NoteStore = pid()
Pdu = #pdu
MsgData = msg_data()
LocalEngineID = string()
To = [dest_addrs()]
PacketsAndAddresses = [{TDomain, TAddress, Packet}]
TDomain = snmpUDPDomain
TAddress = {Ip, Udp}
Ip = {integer(), integer(), integer(), integer()}
Udp = integer()
Packet = binary()

Generates a possibly encrypted request packet to be sent to the network.

MsgData is the message specific data used in the SNMP message. This value is received in a send_pdu or send_pdu_req message from the agent. In SNMPv1 and SNMPv2c, this message data is the community string. In SNMPv3, it is the context information. To is a list of the destination addresses and their corresponding security parameters. This value is also received from the requests mentioned above.

Note

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 SnmpEngineID (see SNMP-FRAMEWORK-MIB).

discarded_pdu(Variable) -> void()

Types:

Variable = atom()

Increments the variable associated with a discarded pdu. This function can be used when the net_if process receives a discarded_pdu message from the agent.