View Source snmpm_user behaviour (snmp v5.18)
Behaviour module for the SNMP manager user.
This module defines the behaviour of the manager user. A snmpm_user compliant
module must export the following functions:
handle_error/3handle_agent/5handle_pdu/4handle_trap/3handle_inform/3handle_report/3handle_invalid_result/2
The semantics of them and their exact signatures are explained below.
Some of the function has no defined return value (void()), they can of course
return anything. But the functions that do have specified return value(s) must
adhere to this. None of the functions can use exit of throw to return.
If the manager is not configured to use any particular transport domain, the
behaviour handle_agent/5 will for backwards copmpatibility reasons be called
with the old IpAddr and PortNumber arguments
Summary
Callbacks
This function is called when a message is received from an unknown agent.
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).
Handle a inform message.
If any of the other callback functions crashes (exit, throw or a plain crash) or return an invalid result (if a valid return has been specified), this function is called. The purpose is to allow the user handle this error (for instance to issue an error report).
Handle the reply to an asynchronous request, such as async_get, async_get_next or async_set.
Handle a report message.
Handle a trap/notification message from an agent.
Types
-type ip_address() :: inet:ip_address().
-type port_number() :: inet:port_number().
-type snmp_gen_info() :: {ErrorStatus :: atom(), ErrorIndex :: pos_integer(), Varbinds :: [snmp:varbind()]}.
General error information (does not have to indicate an error)..
-type snmp_v1_trap_info() :: {Enteprise :: snmp:oid(), Generic :: integer(), Spec :: integer(), Timestamp :: integer(), Varbinds :: [snmp:varbind()]}.
Trap related information.
Callbacks
-callback handle_agent(Domain :: atom(), Address :: term(), Type :: pdu | trap | inform | report, SnmpInfo :: snmp_gen_info() | snmp_v1_trap_info(), UserData :: term()) -> Reply :: ignore | {register, UserId :: term(), RTargetName :: snmpm:target_name(), AgentConfig :: [snmpm:agent_config()]}.
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_config(), see snmpm:register_agent/3.
The arguments Type and SnmpInfo relates in the following way:
pdu-SnmpPduInfo(seehandle_pdu/4for more info).trap-SnmpTrapInfo(seehandle_trap/3for more info).report-SnmpReportInfo(seehandle_report/3for more info).inform-SnmpInformInfo(seehandle_inform/3for more info).
The only user which would return {register, UserId, TargetName, AgentConfig}
is the default user.
-callback handle_error(ReqId :: netif | integer(), Reason :: {unexpected_pdu, SnmpInfo :: snmp_gen_info()} | {invalid_sec_info, SecInfo :: term(), SnmpInfo :: snmp_gen_info()} | {empty_message, TransportDomain :: atom(), {Addr :: ip_address(), Port :: port_number()}} | term(), UserData :: term()) -> snmp:void().
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.
Note that there is a special case when the value of ReqId has the value of the
atom netif. This means that the NetIF process has suffered a "fatal" error and
been restarted. With possible loss of traffic!
-callback handle_inform(TargetName :: snmpm:target_name(), SnmpInform :: snmp_gen_info(), UserData :: term()) -> Reply :: ignore | no_reply | unregister | {register, UserId :: term(), RTargetName :: snmpm:target_name(), AgentConfig :: [snmpm:agent_config()]}.
Handle a inform message.
For more info about the agent_config(), see snmpm:register_agent/3.
The only user which would return {register, UserId, TargetName2, AgentConfig}
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.
-callback handle_invalid_result(In, Out) -> no_return() when In :: {Fun :: atom(), Args :: list()}, Out :: {crash, CrashInfo} | {result, InvalidResult :: term()}, CrashInfo :: {ErrorType :: atom(), Error :: term(), Stacktrace :: erlang:stacktrace()}.
If any of the other callback functions crashes (exit, throw or a plain crash) or return an invalid result (if a valid return has been specified), this function is called. The purpose is to allow the user handle this error (for instance to issue an error report).
IN reprecents the function called (and its arguments). OUT represents the
unexpected/invalid result.
-callback handle_pdu(TargetName :: snmpm:target_name(), ReqId :: term(), SnmpResponse :: snmp_gen_info(), UserData :: term()) -> snmp:void().
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.
-callback handle_report(TargetName :: snmpm:target_name(), SnmpReport :: snmp_gen_info(), UserData :: term()) -> Reply :: ignore | unregister | {register, UserId :: term(), RTargetName :: snmpm:target_name(), AgentConfig :: [snmpm:agent_config()]}.
Handle a report message.
For more info about the agent_config(), see snmpm:register_agent/3.
The only user which would return {register, UserId, TargetName2, AgentConfig}
is the default user.
-callback handle_trap(TargetName :: snmpm:target_name(), SnmpTrapInfo :: snmp_gen_info() | snmp_v1_trap_info(), UserData :: term()) -> Reply :: ignore | unregister | {register, UserId :: term(), RTargetName :: snmpm:target_name(), AgentConfig :: [snmpm:agent_config()]}.
Handle a trap/notification message from an agent.
For more info about the agent_config(), see snmpm:register_agent/3.
The only user which would return {register, UserId, TargetName2, agent_info()}
is the default user.