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Simple Network Management Protocol (SNMP)
Reference Manual
Version 4.16

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# snmpm_user

### MODULE

snmpm_user

### MODULE SUMMARY

Behaviour module for the SNMP manager user.

### DESCRIPTION

This module defines the behaviour of the manager user. A snmpm_user compliant module must export the following functions:

- handle_error/3

- handle_agent/4

- handle_pdu/4

- handle_trap/3

- handle_inform/3

- handle_report/3

The semantics of them and their exact signatures are explained below.

Note that if an agent is registered using the old, no longer documented, functions (using Addr and Port), the old variant of the callback functions, handle_pdu, handle_trap, handle_inform and handle_report, will be called.

### EXPORTS

handle_error(ReqId, Reason, UserData) -> Reply

Types:

ReqId = integer()
Reason = {unexpected_pdu, SnmpInfo} | {invalid_sec_info, SecInfo, SnmpInfo} | {empty_message, Addr, Port} | term()
Addr = ip_address()
Port = integer()
UserData = term()
Reply = ignore

This function is called when the manager needs to communicate an "asynchronous" error, to the user: e.g. failure to send an asynchronous message (i.e. encoding error), a received message was discarded due to security error, the manager failed to generate a response message to a received inform-request, or when receiving an unexpected PDU from an agent (could be an expired async request).

If ReqId is less then 0, it means that this information was not available to the manager (that info was never retrieved before the message was discarded).

For SnmpInfo see handle_agent below.

handle_agent(Addr, Port, Type, SnmpInfo, UserData) -> Reply

Types:

Addr = ip_address()
Port = integer()
Type = pdu | trap | report | inform
SnmpInfo = SnmpPduInfo | SnmpTrapInfo | SnmpReportInfo | SnmpInformInfo
ErrorStatus = atom()
ErrorIndex = integer()
Varbinds = [varbind()]
varbind() = #varbind
UserData = term()
Reply = ignore | {register, UserId, TargetName, agent_info()}
UserId = term()
TargetName = target_name()
agent_info() = [{agent_info_item(), agent_info_value()}]

This function is called when a message is received from an unknown agent.

Note that this will always be the default user that is called.

For more info about the agent_info(), see register_agent.

The arguments Type and SnmpInfo relates in the following way:

- pdu - SnmpPduInfo (see handle_pdu for more info).

- trap - SnmpTrapInfo (see handle_trap for more info).

- report - SnmpReportInfo (see handle_report for more info).

- inform - SnmpInformInfo (see handle_inform for more info).

The only user which would return {register, UserId, TargetName, agent_info()} is the default user.

handle_pdu(TargetName, ReqId, SnmpPduInfo, UserData) -> Reply

Types:

TargetName = target_name()
ReqId = term()
SnmpPduInfo = {ErrorStatus, ErrorIndex, Varbinds}
ErrorStatus = atom()
ErrorIndex = integer()
Varbinds = [varbind()]
varbind() = #varbind
UserData = term()
Reply = ignore

Handle the reply to an asynchronous request, such as async_get, async_get_next or async_set.

It could also be a late reply to a synchronous request.

ReqId is returned by the asynchronous request function.

handle_trap(TargetName, SnmpTrapInfo, UserData) -> Reply

Types:

TargetName = TargetName2 = target_name()
SnmpTrapInfo = {Enteprise, Generic, Spec, Timestamp, Varbinds} | {ErrorStatus, ErrorIndex, Varbinds}
Enterprise = oid()
Generic = integer()
Spec = integer()
Timestamp = integer()
ErrorStatus = atom()
ErrorIndex = integer()
Varbinds = [varbind()]
varbind() = #varbind
UserData = term()
Reply = ignore | unregister | {register, UserId, TargetName2, agent_info()}
UserId = term()
agent_info() = [{agent_info_item(), agent_info_value()}]

Handle a trap/notification message from an agent.

For more info about the agent_info(), see register_agent

The only user which would return {register, UserId, TargetName2, agent_info()} is the default user.

handle_inform(TargetName, SnmpInformInfo, UserData) -> Reply

Types:

TargetName = TargetName2 = target_name()
SnmpInformInfo = {ErrorStatus, ErrorIndex, Varbinds}
ErrorStatus = atom()
ErrorIndex = integer()
Varbinds = [varbind()]
varbind() = #varbind
UserData = term()
Reply = ignore | unregister | {register, UserId, TargetName2, agent_info()}
UserId = term()
agent_info() = [{agent_info_item(), agent_info_value()}]

Handle a inform message.

For more info about the agent_info(), see register_agent

The only user which would return {register, UserId, TargetName2, agent_info()} is the default user.

If the inform request behaviour configuration option is set to user or {user, integer()}, the response (acknowledgment) to this inform-request will be sent when this function returns.

handle_report(TargetName, SnmpReportInfo, UserData) -> Reply

Types:

TargetName = TargetName2 = target_name()
Addr = ip_address()
Port = integer()
SnmpReportInfo = {ErrorStatus, ErrorIndex, Varbinds}
ErrorStatus = atom()
ErrorIndex = integer()
Varbinds = [varbind()]
varbind() = #varbind
UserData = term()
Reply = ignore | unregister | {register, UserId, TargetName2, agent_info()}
UserId = term()
agent_info() = [{agent_info_item(), agent_info_value()}]

Handle a report message.

For more info about the agent_info(), see register_agent

The only user which would return {register, UserId, TargetName2, agent_info()} is the default user.