Definition of Manager Configuration Files — snmp v5.18.2

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# Definition of Manager Configuration Files

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Configuration data may be included in configuration files that is located in the configuration directory. The name of this directory is given in the `config_dir` configuration parameter. These files are read at start-up.

The directory where the configuration files are found is given as a parameter to the manager.

The entry format in all files are Erlang terms, separated by a '.' and a newline. In the following sections, the formats of these terms are described. Comments may be specified as ordinary Erlang comments.

If syntax errors are discovered in these files they are reported with the function `config_err/2` of the error report module at start-up.

## Manager Information

The manager information should be stored in a file called `manager.conf`.

Each entry is a tuple of size two:

`{Variable, Value}.`

- `Variable` is one of the following:

  - `transports` - which defines the transport domains and their addresses for the manager. Mandatory

    `Value` is a list of `{Domain, Addr}` tuples or `Domain` atoms.

    - `Domain` is one of `transportDomainUdpIpv4` or `transportDomainUdpIpv6`.

    - `Addr` is for the currently supported domains either an `IpAddr` or an `{IpAddr, IpPort}` tuple.`IpAddr` is either a regular Erlang/OTP `ip_address()` or a traditional SNMP integer list and `IpPort` is an integer.

      When `Addr` does not contain a port number, the value of `port` is used.

      When a `Addr` is not specified i.e by using only a `Domain` atom, the host's name is resolved to find the IP address, and the value of `port` is used.

  - `port` - which defines which UDP port the manager uses for communicating with agents. Mandatory if `transports` does not define a port number for every transport.

  - `engine_id` - The `SnmpEngineID` as defined in SNMP-FRAMEWORK-MIB. Mandatory.

  - `max_message_size` - The `snmpEngineMaxMessageSize` as defined in SNMP-FRAMEWORK-MIB. Mandatory.

- `Value` is the value for the variable.

The legacy and intermediate variables `address` and `domain` are still supported so old configurations will work.

The following example shows a `manager.conf` file:

    {transports,       [{transportDomainUdpIpv4, {{141,213,11,24}, 5000}},
                        {transportDomainUdpIpv6, {{0,0,0,0,0,0,0,1}, 5000}}]}.
    {engine_id,        "mgrEngine"}.
    {max_message_size, 484}.

The value of `engine_id` is a string, which should have a very specific structure. See RFC 2271/2571 for details.

And this is a code (snippet) example of how to generate this file in runtime:

    ManagerDir    = "/tmp",
    Port          = 5000,
    Addr4         = {141,213,11,24},
    Addr6         = {0,0,0,0,0,0,0,1},
    Transports    = [{transportDomainUdpIpv4, {Addr4, Port}},
                     {transportDomainUdpIpv6, {Addr6, Port}}],
    EngineID      = "mgrEngine",
    MMS           = 484,
    ManagerConfig = [snmpm_conf:manager_entry(transports,       Transports),
                     snmpm_conf:manager_entry(engine_id,        EngineID),
                     snmpm_conf:manager_entry(max_message_size, MMS)],
    snmpm_conf:write_manager_config(ManagerDir, ManagerConfig),

## Users

For each manager user, the manager needs some information. This information is either added in the `users.conf` config file or by calling the register_user function in run-time.

Each row defines a manager user of the manager.

Each entry is a tuple of size four:

`{UserId, UserMod, UserData, DefaultAgentConfig}.`

- `UserId` is any term (used to uniquely identify the user).
- `UserMod` is the user callback module (atom).
- `UserData` is any term (passed on to the user when calling the `UserMod`.
- `DefaultAgentConfig` is a list of default agent config's. These values are used as default values when this user registers agents.

And this is a code (snippet) example of how to generate this file in runtime:

    ManagerDir         = "/tmp",
    UserID             = make_ref(),
    UserMod            = my_manager_callback_mod,
    UserData           = self(),
    DefaultAgentConfig = [{version, v1}, {timeout, 2500}, {max_message_size, 484}],
    UsersConfig = [snmpm_conf:users_entry(UserID, UserMod, UserData,
                                          DefaultAgentConfig)],
    snmpm_conf:write_users_config(ManagerDir, UsersConfig),

## Agents

The information needed to handle agents should be stored in a file called `agents.conf`. It is also possible to add agents in run-time by calling the register_agent.

Each entry is a tuple:

`{UserId, TargetName, Comm, Domain, Addr, EngineID, Timeout, MaxMessageSize, Version, SecModel, SecName, SecLevel}.`

- `UserId` is the identity of the manager user responsible for this agent (term).
- `TargetName` is a unique non-empty string.
- `Comm` is the community string (string).
- `Domain` is the transport domain, either `transportDomainUdpIpv4` or `transportDomainUdpIpv6`.
- `Addr` is the address in the transport domain, either an `{IpAddr, IpPort}` tuple or a traditional SNMP integer list containing port number. `IpAddr` is either a regular Erlang/OTP `ip_address()` or a traditional SNMP integer list not containing port number, and `IpPort` is an integer.
- `EngineID` is the engine-id of the agent (string).

- `Timeout` is re-transmission timeout (`infinity` | integer).

- `MaxMessageSize` is the max message size for outgoing messages to this agent (integer).

- `Version` is the version (v1 | v2 | v3).

- `SecModel` is the security model (any | v1 | v2c | usm).

- `SecName` is the security name (string).

- `SecLevel` is security level (noAuthNoPriv | authNoPriv | authPriv).

Legacy configurations using tuples without `Domain` element, as well as with all `TDomain`, `Ip` and `Port` elements still work.

And this is a code (snippet) example of how to generate this file in runtime:

    ManagerDir   = "/tmp",
    UserID       = ...
    AgentsConfig = [snmpm_conf:agents_entry(UserID,
                                            "target 1",
    					"FOOBAR",
    					transportDomainUdpIpv4, {{1,2,3,4},161},
    					"agent Engine 1"
    					1500,
    					484.
    					v1, v1, "sec name 1", noAuthNoPriv),
    		snmpm_conf:agents_entry(UserID,
                                            "target 2",
    					"FOOBAR",
    					transportDomainUdpIpv4, {{5,6,7,8},161},
    					"agent Engine 2"
    					1500,
    					1000.
    					v1, v1, "sec name 2", noAuthNoPriv)],
    snmpm_conf:write_agents_config(ManagerDir, UsersConfig),

## Security data for USM

The information about Security data for USM should be stored in a file called `usm.conf`, which must be present if the manager wishes to use SNMPv3 when communicating with agents. It is also possible to add usm data in run-time by calling the register_usm_user.

The corresponding table is `usmUserTable` in the SNMP-USER-BASED-SM-MIB (adjusted according to SNMP-USM-HMAC-SHA2-MIB).

Each entry is a term:

`{EngineID, UserName, AuthP, AuthKey, PrivP, PrivKey}.`
`{EngineID, UserName, SecName, AuthP, AuthKey, PrivP, PrivKey}.`

The first case is when we have the identity-function (`SecName` = `UserName`).

- `EngineID` is a string.

- `UserName` is a string.

- `SecName` is a string.

- `AuthP` is a `usmNoAuthProtocol`, `usmHMACMD5AuthProtocol`, `usmHMACSHAAuthProtocol`, `usmHMAC128SHA224AuthProtocol`, `usmHMAC192SH256AuthProtocol`, `usmHMAC256SHA384AuthProtocol` or `usmHMAC384SHA512AuthProtocol`.

- `AuthKey` is a list (of integer). This is the User's secret localized authentication key. It is not visible in the MIB. The length (number of octets) of this key needs to be:

  - 16 if `usmHMACMD5AuthProtocol`.
  - 20 if `usmHMACSHAAuthProtocol`.
  - 28 if `usmHMAC128SHA224AuthProtocol`.
  - 32 if `usmHMAC192SHA256AuthProtocol`.
  - 48 if `usmHMAC256SHA384AuthProtocol`.
  - 64 if `usmHMAC384SHA512AuthProtocol`.

- `PrivP` is a `usmNoPrivProtocol`, `usmDESPrivProtocol` or `usmAesCfb128Protocol`.

- `PrivKey` is a list (of integer). This is the User's secret localized encryption key. It is not visible in the MIB. The length of this key needs to be 16 if `usmDESPrivProtocol` or `usmAesCfb128Protocol` is used.

    ManagerDir = "/tmp",
    UsmConfig  = [snmpm_conf:usm_entry("engine",
                                       "user 1",
    	                           usmNoAuthProtocol,
    	 			   [],
    	 			   usmNoPrivProtocol,
    	 			   [])],
    snmpm_conf:write_usm_config(ManagerDir, UsmConfig),

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