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Simple Network Management Protocol (SNMP)
Reference Manual
Version 4.16

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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) -> {ok, Vsn, Pdu, PduMS, ACMData} | {discarded, Reason} | {discovery, DiscoPacket}

Types:

Packet = binary()
TDomain = snmpUDPDomain
TAddress = {Ip, Udp}
Ip = {integer(), integer(), integer(), integer()}
Udp = integer()
State = mpd_state()
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.

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

Types:

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

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

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

Types:

Vsn = 'version-1' | 'version-2' | 'version-3'
Pdu = #pdu
MsgData = msg_data()
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.

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.