snmp(3erl)

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💖 snmp — Erlang Module Definition 💖

okay so this is snmp(3erl), the Erlang module definition page, and it's literally the interface functions to the SNMP toolkit. buckle up bestie, this one is a baddie — it's long, so it's coming in parts.

✨ NAME ✨

snmp — Interface functions to the SNMP toolkit 🫶

🌸 DESCRIPTION 🌸

The module snmp contains interface functions to the SNMP toolkit. that's it, that's the whole vibe. it's the front door to everything SNMP in Erlang and honestly? iconic.

🎀 COMMON DATA TYPES 🎀

These are the data-types used in the functions below, so like, know them before you go anywhere:

  • datetime() = {date(), time()}

See calendar for more info. yes, the calendar module. go look, it's right there 💅

👑 EXPORTS 👑

💜 config() -> ok | {error, Reason}

A simple interactive configuration tool. Simple config files can be generated, but more complex configurations still have to be edited manually — no cap, the tool doesn't do everything for you.

The tool is a textual based tool that asks some questions and generates sys.config and *.conf files. it literally interviews you, bestie.

Note that if the application shall support version 3, then the crypto app must be started before running this function (password generation). so start crypto first, periodt.
Note also that some of the configuration files for the agent and manager share the same names. This means that they have to be stored in different directories! ⚠️ like, same name, different folder — do NOT mix them up.

🦋 start() -> ok | {error, Reason}

🦋 start(Type) -> ok | {error, Reason}

Types:

Type = start_type()

Starts the SNMP application. See application for more info — that's where all the app-starting lore lives.

🌈 start_agent() -> ok | {error, Reason}

🌈 start_agent(Type) -> ok | {error, Reason}

Types:

Type = start_type()

The SNMP application consists of several entities, of which the agent is one. This function starts the agent entity of the application. just the agent. one little guy. 👑

Note that the only way to actually start the agent in this way is to add the agent related config after starting the application (e.g it cannot be part of the normal application config; sys.config). This is done by calling: application:set_env(snmp, agent, Conf).

The default value for Type is normal.

🧚 start_manager() -> ok | {error, Reason}

🧚 start_manager(Type) -> ok | {error, Reason}

Types:

Type = start_type()

The SNMP application consists of several entities, of which the manager is one. This function starts the manager entity of the application. same deal as the agent but make it manager-core 💼

Note that the only way to actually start the manager in this way is to add the manager related config after starting the application (e.g it cannot be part of the normal application config; sys.config). This is done by calling: application:set_env(snmp, manager, Conf).

The default value for Type is normal.

🍓 date_and_time() -> DateAndTime

Types:

DateAndTime = [int()]

Returns current date and time as the data type DateAndTime, as specified in RFC1903. This is an OCTET STRING. slay, timestamps.

⭐ date_and_time_to_universal_time_dst(DateAndTime) -> [utc()]

Types:

DateAndTime = [int()]
utc() = {{Y,Mo,D},{H,M,S}}

Converts a DateAndTime list to a list of possible universal time(s). The universal time value on the same format as defined in calendar(3erl). note the plural — list of possible times, because DST is chaos and we respect that 🙈

💫 date_and_time_to_string(DateAndTime) -> string()

💫 date_and_time_to_string(DateAndTime, Validate) -> string()

Types:

DateAndTime = [int()]
Validate = fun(Kind, Data) -> boolean()

Converts a DateAndTime list to a printable string, according to the DISPLAY-HINT definition in RFC2579. pretty output, we love to see it ✨

The validation fun, Validate, allows for a more "flexible" validation of the DateAndTime argument. Whenever the data is found to not follow RFC2579, the fun is called to allow a more "lax" validation. See the validate_date_and_time/2 function for more info on the Validate fun. lowkey a hall pass for your data.

💫 date_and_time_to_string2(DateAndTime) -> string()

Types:

DateAndTime = [int()]

Converts a DateAndTime list to a printable string, according to the DISPLAY-HINT definition in RFC2579, with the extension that it also allows the values "hours from UTC" = 14 together with "minutes from UTC" = 0. yes, the sequel function. it's giving part two: the reckoning 🔥

🌸 local_time_to_date_and_time_dst(Local) -> [DateAndTime]

Types:

Local = {{Y,Mo,D},{H,M,S}}
DateAndTime = [int()]

Converts a local time value to a list of possible DateAndTime list(s). The local time value on the same format as defined in calendar(3erl). again with the possibilities — because your local time is a suggestion, bestie 💅

🎀 universal_time_to_date_and_time(UTC) -> DateAndTime

Types:

UTC = {{Y,Mo,D},{H,M,S}}
DateAndTime = [int()]

Converts a universal time value to a DateAndTime list. The universal time value on the same format as defined in calendar(3erl). utc said "i'm the standard here" and honestly? correct.

👑 validate_date_and_time(DateAndTime) -> bool()

👑 validate_date_and_time(DateAndTime, Validate) -> bool()

Types:

DateAndTime = term()
Validate = fun(Kind, Data) -> boolean()

Checks if DateAndTime is a correct DateAndTime value, as specified in RFC2579. This function can be used in instrumentation functions to validate a DateAndTime value. vibe check for timestamps, basically 🕵️‍♀️

The validation fun, Validate, allows for a more "flexible" validation of the DateAndTime argument. Whenever the data is found to not follow RFC2579, the fun is called to allow a more "lax" validation. The input to the validation fun looks like this:

Kind             Data
--------------   ----------------------
year             {Year1, Year2}
month            Month
day              Day
hour             Hour
minute           Minute
seconds          Seconds
deci_seconds     DeciSeconds
diff             [Sign, Hour, Minute]
valid_date       {Year, Month, Day}

memorize that table, it's giving cheat sheet energy 🎀

🔥 passwd2localized_key(Alg, Passwd, EngineID) -> Key

Types:

Alg = algorithm()
algorithm() = md5 | sha | sha224 | sha256 | sha384 | sha512
Passwd = string()
EngineID = string()
Key = list()

Generates a key that can be used as an authentication or privacy key using MD5, SHA, SHA224, SHA256, SHA384 or SHA512. The key is localized for EngineID. so it's your password but make it engine-specific — no reusing keys across engines, we're not messy 💅

🦋 octet_string_to_bits(S) -> Val

Types:

Val = bits()

Utility function for converting a value of type OCTET-STRING to BITS. glow-up but for data types ✨

🦋 bits_to_octet_string(B) -> Val

Types:

Val = octet_string()

Utility function for converting a value of type BITS to OCTET-STRING. the reverse glow-up. they're reversible, it's fine.

💜 read_mib(FileName) -> {ok, mib()} | {error, Reason}

Types:

FileName = string()
mib() = #mib{}
Reason = term()

Read a compiled mib. short, sweet, does exactly what it says on the tin 🫶

🌈 log_to_txt(LogDir, Mibs, OutFile, LogName, LogFile) -> ok | {ok, Cnt} | {error, Reason}

🌈 log_to_txt(LogDir, Mibs, OutFile, LogName, LogFile, Block | Start) -> ok | {ok, Cnt} | {error, Reason}

🌈 log_to_txt(LogDir, Mibs, OutFile, LogName, LogFile, Start, Block | Stop) -> ok | {ok, Cnt} | {error, Reason}

🌈 log_to_txt(LogDir, Mibs, OutFile, LogName, LogFile, Start, Stop, Block) -> ok | {ok, Cnt} | {error, Reason}

Types:

LogDir = string()
Mibs = [MibName]
OutFile = string()
MibName = string()
LogName = string()
LogFile = string()
Start = Stop = null | datetime() | {local_time,datetime()} | {universal_time,datetime()}
Block = boolean()
Cnt = {NumOK, NumERR}
NumOK = non_neg_integer()
NumERR = pos_integer()
Reason = term()

Converts an Audit Trail Log to a readable text file, where each item has a trailing TAB character, and any TAB character in the body of an item has been replaced by ESC TAB. yes, the tabs got escaped — they were being too much 😭

The function can be used on a running system, or by copying the entire log directory and calling this function. SNMP must be running in order to provide MIB information. so like, the vibes must be live.

LogDir is the name of the directory where the audit trail log is stored. Mibs is a list of Mibs to be used. The function uses the information in the Mibs to convert for example object identifiers to their symbolic name. OutFile is the name of the generated text-file. LogName is the name of the log, LogFile is the name of the log file. Start is the start (first) date and time from which log events will be converted and Stop is the stop (last) date and time to which log events will be converted. The Block argument indicates if the log should be blocked during conversion. This could be useful when converting large logs (when otherwise the log could wrap during conversion). Defaults to true.

The format of an audit trail log text item is as follows:

Tag Addr - Community [TimeStamp] Vsn
PDU

where Tag is request, response, report, trap or inform; Addr is IP:Port (or comma space separated list of such); Community is the community parameter (SNMP version v1 and v2), or SecLevel:"AuthEngineID":"UserName" (SNMP v3); TimeStamp is a date and time stamp, and Vsn is the SNMP version. PDU is a textual version of the protocol data unit. There is a new line between Vsn and PDU.

If the entire log is successfully converted, the function will return ok. If one of more entries fail to convert, the function will instead return {ok, {NumOK, NumERR}}, where the counters indicate how many valid and erroneous entries where found. If instead {error, Reason} is returned, the conversion encountered a fatal error and where either never done of aborted midway. yeah — that's the 💀 outcome. fatal error, no conversion, we go home.

🌟 log_to_io(LogDir, Mibs, LogName, LogFile) -> ok | {ok, Cnt} | {error, Reason}

🌟 log_to_io(LogDir, Mibs, LogName, LogFile, Block | Start) -> ok | {ok, Cnt} | {error, Reason}

🌟 log_to_io(LogDir, Mibs, LogName, LogFile, Start, Block | Stop) -> ok | {ok, Cnt} | {error, Reason}

🌟 log_to_io(LogDir, Mibs, LogName, LogFile, Start, Stop, Block) -> ok | {ok, Cnt} | {error, Reason}

Types:

LogDir = string()
Mibs = [MibName]
MibName = string()
LogName = string()
LogFile = string()
Start = Stop = null | datetime() | {local_time,datetime()} | {universal_time,datetime()}
Cnt = {NumOK, NumERR}
NumOK = non_neg_integer()
NumERR = pos_integer()
Reason = term()

Okay so the function right above this? It converts an Audit Trail Log to a readable format and prints it on stdio. 💅 For the full tea, see log_to_txt above. Now let’s get into the rest of the exports, bestie. ✨

change_log_size(LogName, NewSize) -> ok | {error, Reason}

Types:

                 LogName = string()
                 NewSize = {MaxBytes, MaxFiles}
                 MaxBytes = integer()
                 MaxFiles = integer()
                 Reason = term()

Changes the log size of the Audit Trail Log. The application must be configured to use the audit trail log function. Please refer to disk_log(3erl) in Kernel Reference Manual for a description of how to change the log size.

The change is permanent, as long as the log is not deleted. That means, the log size is remembered across reboots. 👑

Types:

                 Prefix = string() | integer()

Utility function(s) to produce a formatted printout of the versions info generated by the versions1 function. 🖨️

This is the same as doing, e.g.:

                         {ok, V} = snmp:versions1(),
                         snmp:print_versions(V).

versions1() -> {ok, Info} | {error, Reason} / versions2() -> {ok, Info} | {error, Reason}

Types:

                 Info = [info()]
                 info() = term()
                 Reason = term()

Utility functions used to retrieve some system and application info. 🔍

The difference between the two functions is in how they get the modules to check. versions1 uses the app-file and versions2 uses the function application:get_key. iykyk

Types:

                 VersionInfo = [version_info()]
                 version_info() = term()
                 Prefix = string() | integer()

Utility function to produce a formatted printout of the versions info generated by the versions1 and versions2 functions. 🌸

Example:

                         {ok, V} = snmp:versions1(),
                         snmp:print_versions(V).

enable_trace() -> void()

Starts a dbg tracer that prints trace events to stdout (using plain io:format after a minor formatting). 🔍

disable_trace() -> void()

Stop the tracer. 🛑

set_trace(Targets) -> void()

Types:

                 Targets = target() | targets()
                 target() = module()
                 module() = atom()
                 targets() = [target() | {target(), target_options()}]
                 target_options() = [target_option()]
                 target_option() = {return_trace, boolean()} | {scope, scope()}
                 scope() = all_functions | exported_functions | function_name()
                 | {function_name(), function_arity()}
                 function_name() = atom()
                 function_arity() = integer() >= 0

This function is used to set up default trace on function(s) for the given module or modules. The scope of the trace will be all exported functions (both the call info and the return value). Timestamp info will also be included. ⏱️

reset_trace(Targets) -> void()

Types:

                 Targets = module() | modules()
                 modules() = [module()]
                 module() = atom()

This function is used to reset (disable) trace for the given module(s). 🚫

set_trace(Targets, Opts) -> void()

Types:

                 Targets = target() | targets()
                 target() = module()
                 module() = atom()
                 targets() = [target() | {target(), target_options()}]
                 target_options() = [target_option()]
                 target_option() = {return_trace, boolean()} | {scope, scope()}
                 scope() = all_functions | exported_functions | function_name()
                 | {function_name(), function_arity()}
                 function_name() = atom()
                 function_arity() = integer() >= 0
                 Opts = disable | trace_options()
                 trace_options() = [trace_option()]
                 trace_option() = {timestamp, boolean()} | target_option()

This function is used to set up trace on function(s) for the given module or modules. ✨

The example below sets up trace on the exported functions (default) of module snmp_generic and all functions of module snmp_generic_mnesia. With return values (which is default) and timestamps in both cases (which is also default):

                     snmp:enable_trace(),
                     snmp:set_trace([snmp_generic,
                                        {snmp_generic_mnesia, [{scope, all_functions}]}]),
                     .
                     .
                     .
                        snmp:set_trace(snmp_generic, disable),
                     .
                     .
                     .
                     snmp:disable_trace(),

🌈 SEE ALSO 🌈

calendar(3erl)

And that’s a wrap, bestie! This iconic page is brought to you by Ericsson AB, version snmp 5.13.5, and the man page snmp(3erl). No cap, it’s giving legend status. 💅👑

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