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net-snmp

2.5.5 • Public • Published

net-snmp

This module implements versions 1, 2c and 3 of the Simple Network Management Protocol (SNMP).

This module is installed using node package manager (npm):

npm install net-snmp

It is loaded using the require() function:

var snmp = require ("net-snmp");

Sessions to remote hosts can then be created and used to perform SNMP requests and send SNMP traps or informs:

var session = snmp.createSession ("127.0.0.1", "public");

var oids = ["1.3.6.1.2.1.1.5.0", "1.3.6.1.2.1.1.6.0"];

session.get (oids, function (error, varbinds) {
    if (error) {
        console.error (error);
    } else {
        for (var i = 0; i < varbinds.length; i++)
            if (snmp.isVarbindError (varbinds[i]))
                console.error (snmp.varbindError (varbinds[i]))
            else
                console.log (varbinds[i].oid + " = " + varbinds[i].value);
    }
    session.close ();
});

session.trap (snmp.TrapType.LinkDown, function (error) {
    if (error)
        console.error (error);
});

Applications

RFC 3413 describes five types of SNMP applications:

  1. Command Generator Applications — which initiate read or write requests
  2. Command Responder Applications — which respond to received read or write requests
  3. Notification Originator Applications — which generate notifications (traps or informs)
  4. Notification Receiver Applications — which receive notifications (traps or informs)
  5. Proxy Forwarder Applications — which forward SNMP messages

This library provides support for all of the above applications, with the documentation for each shown in this table:

Application Common Use Documentation
Command Generator NMS / SNMP tools Using This Module: Command & Notification Generator
Command Responder SNMP agents Using This Module: SNMP Agent
Notification Originator SNMP agents / NMS-to-NMS notifications Using This Module: Command & Notification Generator
Notification Receiver NMS Using This Module: Notification Receiver
Proxy Forwarder SNMP agents Forwarder Module

Features

  • Support for all SNMP versions: SNMPv1, SNMPv2c and SNMPv3
  • SNMPv3 message authentication using MD5 or SHA, and privacy using DES or AES encryption
  • Community-based and user-based authorization
  • SNMP initiator for all relevant protocol operations: Get, GetNext, GetBulk, Set, Trap, Inform
  • Convenience methods for MIB "walking", subtree collection, table and table column collection
  • SNMPv3 context support
  • Notification receiver for traps and informs
  • MIB parsing and MIB module store
  • SNMP agent with MIB management for both scalar and tabular data
  • Agent table index support for non-integer keys, foreign keys, composite keys and table augmentation
  • SNMP proxy forwarder for agent
  • IPv4 and IPv6

Not implemented, but on the roadmap:

Standards Compliance

This module aims to be fully compliant with the following RFCs:

  • 1155 - Structure and Identification of Management Information
  • 1098 - A Simple Network Management Protocol (version 1)
  • 2578 - Structure of Management Information Version 2 (SMIv2)
  • 3413 - Simple Network Management Protocol (SNMP) Applications
  • 3414 - User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)
  • 3416 - Version 2 of the Protocol Operations for the Simple Network Management Protocol (SNMP)
  • 3417 - Transport Mappings for the Simple Network Management Protocol (SNMP)
  • 3826 - The Advanced Encryption Standard (AES) Cipher Algorithm in the SNMP User-based Security Model

Constants

The following sections describe constants exported and used by this module.

snmp.Version1, snmp.Version2c, snmp.Version3

These constants are used to specify which of version supported by this module should be used.

snmp.ErrorStatus

This object contains constants for all valid values the error-status field in response PDUs can hold. If when parsing a PDU the error-index field contains a value not defined in this object the constant snmp.ErrorStatus.GeneralError will be used instead of the value in the error-status field. The following constants are defined in this object:

  • NoError
  • TooBig
  • NoSuchName
  • BadValue
  • ReadOnly
  • GeneralError
  • NoAccess
  • WrongType
  • WrongLength
  • WrongEncoding
  • WrongValue
  • NoCreation
  • InconsistentValue
  • ResourceUnavailable
  • CommitFailed
  • UndoFailed
  • AuthorizationError
  • NotWritable
  • InconsistentName

snmp.ObjectType

This object contains constants used to specify syntax for varbind objects, e.g.:

var varbind = {
    oid: "1.3.6.1.2.1.1.4.0",
    type: snmp.ObjectType.OctetString,
    value: "user.name@domain.name"
};

The following constants are defined in this object:

  • Boolean
  • Integer
  • OctetString
  • Null
  • OID
  • IpAddress
  • Counter
  • Gauge
  • TimeTicks
  • Opaque
  • Integer32
  • Counter32
  • Gauge32
  • Unsigned32
  • Counter64
  • NoSuchObject
  • NoSuchInstance
  • EndOfMibView

snmp.TrapType

This object contains constants used to specify a type of SNMP trap. These constants are passed to the trap() and inform() methods exposed by the Session class. The following constants are defined in this object:

  • ColdStart
  • WarmStart
  • LinkDown
  • LinkUp
  • AuthenticationFailure
  • EgpNeighborLoss
  • EnterpriseSpecific

snmp.PduType

This object contains constants used to identify the SNMP PDU types specified in RFC 3416. The values, along with their numeric codes, are:

  • 160 - GetRequest
  • 161 - GetNextRequest
  • 162 - GetResponse
  • 163 - SetRequest
  • 164 - Trap
  • 165 - GetBulkRequest
  • 166 - InformRequest
  • 167 - TrapV2
  • 168 - Report

snmp.SecurityLevel

This object contains constants to specify the security of an SNMPv3 message as per RFC 3414:

  • noAuthNoPriv - for no message authentication or encryption
  • authNoPriv - for message authentication and no encryption
  • authPriv - for message authentication and encryption

snmp.AuthProtocols

This object contains constants to select a supported digest algorithm for SNMPv3 messages that require authentication:

  • md5 - for MD5 message authentication (HMAC-MD5-96)
  • sha - for SHA message authentication (HMAC-SHA-96)

These are the two hash algorithms specified in RFC 3414. Other digest algorithms are not supported.

snmp.PrivProtocols

This object contains constants to select a supported encryption algorithm for SNMPv3 messages that require privacy:

  • des - for DES encryption (CBC-DES)
  • aes - for AES encryption (CFB-AES-128)

DES is the sole encryption algorithm specified in the original SNMPv3 User-Based Security Model RFC (RFC 3414); AES for SNMPv3 was added later in RFC 3826. Other encryption algorithms are not supported.

OID Strings & Varbinds

Some parts of this module accept simple OID strings, e.g.:

var oid = "1.3.6.1.2.1.1.5.0";

Other parts take an OID string, it's type and value. This is collectively referred to as a varbind, and is specified as an object, e.g.:

var varbind = {
    oid: "1.3.6.1.2.1.1.5.0",
    type: snmp.ObjectType.OctetString,
    value: new Buffer ("host1")
};

The type parameter is one of the constants defined in the snmp.ObjectType object.

The JavaScript true and false keywords are used for the values of varbinds with type Boolean.

All integer based types are specified as expected (this includes Integer, Counter, Gauge, TimeTicks, Integer32, Counter32, Gauge32, and Unsigned32), e.g. -128 or 100.

Since JavaScript does not offer full 64 bit integer support objects with type Counter64 cannot be supported in the same way as other integer types, instead Node.js Buffer objects are used. Users are responsible for producing (i.e. for set() requests) and consuming (i.e. the varbinds passed to callback functions) Buffer objects. That is, this module does not work with 64 bit integers, it simply treats them as opaque Buffer objects.

Dotted decimal strings are used for the values of varbinds with type OID, e.g. 1.3.6.1.2.1.1.5.0.

Dotted quad formatted strings are used for the values of varbinds with type IpAddress, e.g. 192.168.1.1.

Node.js Buffer objects are used for the values of varbinds with type Opaque and OctetString. For varbinds with type OctetString this module will accept JavaScript strings, but will always give back Buffer objects.

The NoSuchObject, NoSuchInstance and EndOfMibView types are used to indicate an error condition. Currently there is no reason for users of this module to to build varbinds using these types.

Callback Functions & Error Handling

Most of the request methods exposed by this module require a mandatory callback function. This function is called once a request has been processed. This could be because an error occurred when processing the request, a trap has been dispatched or a successful response was received.

The first parameter to every callback is an error object. In the case no error occurred this parameter will be "null" indicating no error, e.g.:

function responseCb (error, varbinds) {
    if (error) {
        console.error (error);
    } else {
        // no error, do something with varbinds
    }
}

When defined, the error parameter is always an instance of the Error class, or a sub-class described in one of the sub-sections contained in this section.

The semantics of error handling is slightly different between SNMP version 1 and subsequent versions 2c and 3. In SNMP version 1 if an error occurs when calculating the value for one OID the request as a whole will fail, i.e. no OIDs will have a value.

This failure manifests itself within the error-status and error-index fields of the response. When the error-status field in the response is non-zero, i.e. not snmp.ErrorStatus.NoError the callback will be called with error defined detailing the error.

Requests made with SNMP version 1 can simply assume all OIDs have a value when no error object is passed to the callback, i.e.:

var oids = ["1.3.6.1.2.1.1.5.0", "1.3.6.1.2.1.1.6.0"];

session.get (oids, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        var sysName = varbinds[0].value; // this WILL have a value
    }
});

In SNMP versions 2c and 3, instead of using the error-status and error-index fields of the response to signal an error, the value for the varbind placed in the response for an OID will have an object syntax describing an error. The error-status and error-index fields of the response will indicate the request was successul, i.e. snmp.ErrorStatus.NoError.

This changes the way in which error checking is performed in the callback. When using SNMP version 2c each varbind must be checked to see if its value was computed and returned successfully:

var oids = ["1.3.6.1.2.1.1.5.0", "1.3.6.1.2.1.1.6.0"];

session.get (oids, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        if (varbinds[0].type != snmp.ErrorStatus.NoSuchObject
                && varbinds[0].type != snmp.ErrorStatus.NoSuchInstance
                && varbinds[0].type != snmp.ErrorStatus.EndOfMibView) {
            var sysName = varbinds[0].value;
        } else {
            console.error (snmp.ObjectType[varbinds[0].type] + ": "
                    + varbinds[0].oid);
        }
    }
});

This module exports two functions and promotes a specifc pattern to make error checking a little simpler. Firstly, regardless of version in use varbinds can always be checked. This results in a generic callback that can be used for both versions.

The isVarbindError() function can be used to determine if a varbind has an error condition. This function takes a single varbind parameter and returns true if the varbind has an error condition, otherwise false. The exported varbindError() function can then be used to obtain the error string describing the error, which will include the OID for the varbind:

session.get (oids, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        if (snmp.isVarbindError (varbinds[0])) {
            console.error (snmp.varbindError (varbinds[0]));
        } else {
            var sysName = varbinds[0].value;
        }
    }
});

If the varbindError function is called with a varbind for which isVarbindError would return false, the string NotAnError will be returned appended with the related OID.

The sections following defines the error classes used by this module.

snmp.RequestFailedError

This error indicates a remote host failed to process a request. The exposed message attribute will contain a detailed error message. This error also exposes a status attribute which contains the error-index value from a response. This will be one of the constants defined in the snmp.ErrorStatus object.

snmp.RequestInvalidError

This error indicates a failure to render a request message before it could be sent. The error can also indicate that a parameter provided was invalid. The exposed message attribute will contain a detailed error message.

snmp.RequestTimedOutError

This error states that no response was received for a particular request. The exposed message attribute will contain the value Request timed out.

snmp.ResponseInvalidError

This error indicates a failure to parse a response message. The exposed message attribute will contain a detailed error message.

Using This Module: Command & Notification Generator

This library provides a Session class to provide support for building "Command Generator" and "Notification Originator" SNMP applications.

All SNMP requests are made using an instance of the Session class. This module exports two functions that are used to create instances of the Session class:

  • createSession() - for v1 and v2c sessions
  • createV3Session() - for v3 sessions

snmp.createSession ([target], [community], [options])

The createSession() function instantiates and returns an instance of the Session class for SNMPv1 or SNMPv2c:

// Default options
var options = {
    port: 161,
    retries: 1,
    timeout: 5000,
    backoff: 1.0,
    transport: "udp4",
    trapPort: 162,
    version: snmp.Version1,
    idBitsSize: 32
};

var session = snmp.createSession ("127.0.0.1", "public", options);

The optional target parameter defaults to 127.0.0.1. The optional community parameter defaults to public. The optional options parameter is an object, and can contain the following items:

  • port - UDP port to send requests too, defaults to 161
  • retries - Number of times to re-send a request, defaults to 1
  • sourceAddress - IP address from which SNMP requests should originate, there is no default for this option, the operating system will select an appropriate source address when the SNMP request is sent
  • sourcePort - UDP port from which SNMP requests should originate, defaults to an ephemeral port selected by the operation system
  • timeout - Number of milliseconds to wait for a response before re-trying or failing, defaults to 5000
  • backoff - The factor by which to increase the timeout for every retry, defaults to 1 for no increase
  • transport - Specify the transport to use, can be either udp4 or udp6, defaults to udp4
  • trapPort - UDP port to send traps and informs too, defaults to 162
  • version - Either snmp.Version1 or snmp.Version2c, defaults to snmp.Version1
  • idBitsSize - Either 16 or 32, defaults to 32. Used to reduce the size of the generated id for compatibility with some older devices.

When a session has been finished with it should be closed:

session.close ();

snmp.createV3Session (target, user, [options])

The createV3Session() function instantiates and returns an instance of the same Session class as createSession(), only instead initialized for SNMPv3:

// Default options for v3
var options = {
    port: 161,
    retries: 1,
    timeout: 5000,
    transport: "udp4",
    trapPort: 162,
    version: snmp.Version3,
    idBitsSize: 32,
    context: ""
};

// Example user
var user = {
    name: "blinkybill",
    level: snmp.SecurityLevel.authPriv,
    authProtocol: snmp.AuthProtocols.sha,
    authKey: "madeahash",
    privProtocol: snmp.PrivProtocols.des,
    privKey: "privycouncil"
};

var session = snmp.createV3Session ("127.0.0.1", user, options);

The target and user parameters are mandatory. The optional options parameter has the same meaning as for the createSession() call. The one additional field in the options parameter is the context field, which adds an SNMPv3 context to the session.

The user object must contain a name and level field. The level field can take these values from the snmp.SecurityLevel object:

  • snmp.SecurityLevel.noAuthNoPriv - for no message authentication or encryption
  • snmp.SecurityLevel.authNoPriv - for message authentication and no encryption
  • snmp.SecurityLevel.authPriv - for message authentication and encryption

The meaning of these are as per RFC3414. If the level supplied is authNoPriv or authPriv, then the authProtocol and authKey fields must also be present. The authProtocol field can take values from the snmp.AuthProtocols object:

  • snmp.AuthProtocols.md5 - for MD5 message authentication
  • snmp.AuthProtocols.sha - for SHA message authentication

If the level supplied is authPriv, then the privProtocol and privKey fields must also be present. The privProtocol field can take values from the snmp.PrivProtocols object:

  • snmp.PrivProtocols.des - for DES encryption
  • snmp.PrivProtocols.aes - for AES encryption

Once a v3 session is created, the same set of session methods are available as for v1 and v2c.

session.on ("close", callback)

The close event is emitted by the session when the sessions underlying UDP socket is closed.

No arguments are passed to the callback.

Before this event is emitted all outstanding requests are cancelled, resulting in the failure of each outstanding request. The error passed back through to each request will be an instance of the Error class with the errors message attribute set to Socket forcibly closed.

The following example prints a message to the console when a sessions underlying UDP socket is closed:

session.on ("close", function () {
    console.log ("socket closed");
});

session.on ("error", callback)

The error event is emitted by the session when the sessions underlying UDP socket emits an error.

The following arguments will be passed to the callback function:

  • error - An instance of the Error class, the exposed message attribute will contain a detailed error message.

The following example prints a message to the console when an error occurs with a sessions underlying UDP socket, the session is then closed:

session.on ("error", function (error) {
    console.log (error.toString ());
    session.close ();
});

session.close ()

The close() method closes the sessions underlying UDP socket. This will result in the close event being emitted by the sessions underlying UDP socket which is passed through to the session, resulting in the session also emitting a close event.

The following example closes a sessions underlying UDP socket:

session.close ();

session.get (oids, callback)

The get() method fetches the value for one or more OIDs.

The oids parameter is an array of OID strings. The callback function is called once the request is complete. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred
  • varbinds - Array of varbinds, will not be provided if an error occurred

The varbind in position N in the varbinds array will correspond to the OID in position N in the oids array in the request.

Each varbind must be checked for an error condition using the snmp.isVarbindError() function when using SNMP version 2c.

The following example fetches values for the sysName (1.3.6.1.2.1.1.5.0) and sysLocation (1.3.6.1.2.1.1.6.0) OIDs:

var oids = ["1.3.6.1.2.1.1.5.0", "1.3.6.1.2.1.1.6.0"];

session.get (oids, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        for (var i = 0; i < varbinds.length; i++) {
            // for version 1 we can assume all OIDs were successful
            console.log (varbinds[i].oid + "|" + varbinds[i].value);
        
            // for version 2c we must check each OID for an error condition
            if (snmp.isVarbindError (varbinds[i]))
                console.error (snmp.varbindError (varbinds[i]));
            else
                console.log (varbinds[i].oid + "|" + varbinds[i].value);
        }
    }
});

session.getBulk (oids, [nonRepeaters], [maxRepetitions], callback)

The getBulk() method fetches the value for the OIDs lexicographically following one or more OIDs in the MIB tree.

The oids parameter is an array of OID strings. The optional nonRepeaters parameter specifies the number of OIDs in the oids parameter for which only 1 varbind should be returned, and defaults to 0. For each remaining OID in the oids parameter the optional maxRepetitions parameter specifies how many OIDs lexicographically following an OID for which varbinds should be fetched, and defaults to 20.

The callback function is called once the request is complete. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred
  • varbinds - Array of varbinds, will not be provided if an error occurred

The varbind in position N in the varbinds array will correspond to the OID in position N in the oids array in the request.

For for the first nonRepeaters items in varbinds each item will be a single varbind. For all remaining items in varbinds each item will be an array of varbinds - this makes it easy to tie response varbinds with requested OIDs since response varbinds are grouped and placed in the same position in varbinds.

Each varbind must be checked for an error condition using the snmp.isVarbindError() function when using SNMP version 2c.

The following example fetches values for the OIDs following the sysContact (1.3.6.1.2.1.1.4.0) and sysName (1.3.6.1.2.1.1.5.0) OIDs, and up to the first 20 OIDs in the ifDescr (1.3.6.1.2.1.2.2.1.2) and ifType (1.3.6.1.2.1.2.2.1.3) columns from the ifTable (1.3.6.1.2.1.2.2) table:

var oids = [
    "1.3.6.1.2.1.1.4.0",
    "1.3.6.1.2.1.1.5.0",
    "1.3.6.1.2.1.2.2.1.2",
    "1.3.6.1.2.1.2.2.1.3"
];

var nonRepeaters = 2;

session.getNext (oids, nonRepeaters, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        // step through the non-repeaters which are single varbinds
        for (var i = 0; i < nonRepeaters; i++) {
            if (i >= varbinds.length)
                break;

            if (snmp.isVarbindError (varbinds[i]))
                console.error (snmp.varbindError (varbinds[i]));
            else
                console.log (varbinds[i].oid + "|" + varbinds[i].value);
        }

        // then step through the repeaters which are varbind arrays
        for (var i = nonRepeaters; i < varbinds.length; i++) {
            for (var j = 0; j < varbinds[i].length; j++) {
                if (snmp.isVarbindError (varbinds[i][j]))
                    console.error (snmp.varbindError (varbinds[i][j]));
                else
                    console.log (varbinds[i][j].oid + "|"
                    		+ varbinds[i][j].value);
            }
    }
});

session.getNext (oids, callback)

The getNext() method fetches the value for the OIDs lexicographically following one or more OIDs in the MIB tree.

The oids parameter is an array of OID strings. The callback function is called once the request is complete. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred
  • varbinds - Array of varbinds, will not be provided if an error occurred

The varbind in position N in the varbinds array will correspond to the OID in position N in the oids array in the request.

Each varbind must be checked for an error condition using the snmp.isVarbindError() function when using SNMP version 2c.

The following example fetches values for the next OIDs following the sysObjectID (1.3.6.1.2.1.1.1.0) and sysName (1.3.6.1.2.1.1.4.0) OIDs:

var oids = [
    "1.3.6.1.2.1.1.1.0",
    "1.3.6.1.2.1.1.4.0"
];

session.getNext (oids, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        for (var i = 0; i < varbinds.length; i++) {
            // for version 1 we can assume all OIDs were successful
            console.log (varbinds[i].oid + "|" + varbinds[i].value);
        
            // for version 2c we must check each OID for an error condition
            if (snmp.isVarbindError (varbinds[i]))
                console.error (snmp.varbindError (varbinds[i]));
            else
                console.log (varbinds[i].oid + "|" + varbinds[i].value);
        }
    }
});

session.inform (typeOrOid, [varbinds], [options], callback)

The inform() method sends a SNMP inform.

The typeOrOid parameter can be one of two types; one of the constants defined in the snmp.TrapType object (excluding the snmp.TrapType.EnterpriseSpecific constant), or an OID string.

The first varbind to be placed in the request message will be for the sysUptime.0 OID (1.3.6.1.6.3.1.1.4.1.0). The value for this varbind will be the value returned by the process.uptime () function multiplied by 100 (this can be overridden by providing upTime in the optional options parameter, as documented below).

This will be followed by a second varbind for the snmpTrapOID.0 OID (1.3.6.1.6.3.1.1.4.1.0). The value for this will depend on the typeOrOid parameter. If a constant is specified the trap OID for the constant will be used as supplied for the varbinds value, otherwise the OID string specified will be used as is for the value of the varbind.

The optional varbinds parameter is an array of varbinds to include in the inform request, and defaults to the empty array [].

The optional options parameter is an object, and can contain the following items:

  • upTime - Value of the sysUptime.0 OID (1.3.6.1.6.3.1.1.4.1.0) in the inform, defaults to the value returned by the process.uptime () function multiplied by 100

The callback function is called once a response to the inform request has been received, or an error occurred. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred
  • varbinds - Array of varbinds, will not be provided if an error occurred

The varbind in position N in the varbinds array will correspond to the varbind in position N in the varbinds array in the request. The remote host should echo back varbinds and their values as specified in the request, and the varbinds array will contain each varbind as sent back by the remote host.

Normally there is no reason to use the contents of the varbinds parameter since the varbinds are as they were sent in the request.

The following example sends a generic cold-start inform to a remote host, it does not include any varbinds:

session.inform (snmp.TrapType.ColdStart, function (error) {
    if (error)
        console.error (error);
});

The following example sends an enterprise specific inform to a remote host, and includes two enterprise specific varbinds:

var informOid = "1.3.6.1.4.1.2000.1";

var varbinds = [
    {
        oid: "1.3.6.1.4.1.2000.2",
        type: snmp.ObjectType.OctetString,
        value: "Periodic hardware self-check"
    },
    {
        oid: "1.3.6.1.4.1.2000.3",
        type: snmp.ObjectType.OctetString,
        value: "hardware-ok"
    }
];

// Override sysUpTime, specfiying it as 10 seconds...
var options = {upTime: 1000};
session.inform (informOid, varbinds, options, function (error) {
    if (error)
        console.error (error);
});

session.set (varbinds, callback)

The set() method sets the value of one or more OIDs.

The varbinds parameter is an array of varbind objects. The callback function is called once the request is complete. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred
  • varbinds - Array of varbinds, will not be provided if an error occurred

The varbind in position N in the varbinds array will correspond to the varbind in position N in the varbinds array in the request. The remote host should echo back varbinds and their values as specified in the request unless an error occurred. The varbinds array will contain each varbind as sent back by the remote host.

Each varbind must be checked for an error condition using the snmp.isVarbindError() function when using SNMP version 2c.

The following example sets the value of the sysName (1.3.6.1.2.1.1.4.0) and sysLocation (1.3.6.1.2.1.1.6.0) OIDs:

var varbinds = [
    {
        oid: "1.3.6.1.2.1.1.5.0",
        type: snmp.ObjectType.OctetString,
        value: "host1"
    }, {
        oid: "1.3.6.1.2.1.1.6.0",
        type: snmp.ObjectType.OctetString,
        value: "somewhere"
    }
];

session.set (varbinds, function (error, varbinds) {
    if (error) {
        console.error (error.toString ());
    } else {
        for (var i = 0; i < varbinds.length; i++) {
            // for version 1 we can assume all OIDs were successful
            console.log (varbinds[i].oid + "|" + varbinds[i].value);
        
            // for version 2c we must check each OID for an error condition
            if (snmp.isVarbindError (varbinds[i]))
                console.error (snmp.varbindError (varbinds[i]));
            else
                console.log (varbinds[i].oid + "|" + varbinds[i].value);
        }
    }
});

session.subtree (oid, [maxRepetitions], feedCallback, doneCallback)

The subtree() method fetches the value for all OIDs lexicographically following a specified OID in the MIB tree which have the specified OID as their base. For example, the OIDs sysName (1.3.6.1.2.1.1.5.0) and sysLocation (1.3.6.1.2.1.1.6.0) both have the same base system (1.3.6.1.2.1.1) OID.

For SNMP version 1 repeated get() calls are made until the one of the returned OIDs does not use the specified OID as its base. For SNMP version 2c repeated getBulk() calls are made until the one of the returned OIDs does no used the specified OID as its base.

The oid parameter is an OID string. The optional maxRepetitions parameter is passed to getBulk() requests when SNMP version 2c is being used.

This method will not call a single callback once all OID values are fetched. Instead the feedCallback function will be called each time a response is received from the remote host. The following arguments will be passed to the feedCallback function:

  • varbinds - Array of varbinds, and will contain at least one varbind

Each varbind must be checked for an error condition using the snmp.isVarbindError() function when using SNMP version 2c.

Once at least one of the returned OIDs does not use the specified OID as its base, or an error has occurred, the doneCallback function will be called. The following arguments will be passed to the doneCallback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred

Once the doneCallback function has been called the request is complete and the feedCallback function will no longer be called.

If the feedCallback function returns a true value when called no more get() or getBulk() method calls will be made and the doneCallback will be called.

The following example fetches all OIDS under the system (1.3.6.1.2.1.1) OID:

var oid = "1.3.6.1.2.1.1";

function doneCb (error) {
    if (error)
        console.error (error.toString ());
}

function feedCb (varbinds) {
    for (var i = 0; i < varbinds.length; i++) {
        if (snmp.isVarbindError (varbinds[i]))
            console.error (snmp.varbindError (varbinds[i]));
        else
            console.log (varbinds[i].oid + "|" + varbinds[i].value);
    }
}

var maxRepetitions = 20;

// The maxRepetitions argument is optional, and will be ignored unless using
// SNMP verison 2c
session.subtree (oid, maxRepetitions, feedCb, doneCb);

session.table (oid, [maxRepetitions], callback)

The table() method fetches the value for all OIDs lexicographically following a specified OID in the MIB tree which have the specified OID as their base, much like the subtree() method.

This method is designed to fetch conceptial tables, for example the ifTable (1.3.6.1.2.1.2.2) table. The values for returned varbinds will be structured into objects to represent conceptual rows. Each row is then placed into an object with the rows index being the key, e.g.:

var table = {
    // Rows keyed by ifIndex (1 and 2 are shown)
    1: {
        // ifDescr (column 2) and ifType (columnd 3) are shown
        2: "interface-1",
        3: 6,
        ...
    },
    2: {
        2: "interface-2",
        3: 6,
        ...
    },
    ...
}

Internally this method calls the subtree() method to obtain the subtree of the specified table.

The oid parameter is an OID string. If an OID string is passed which does not represent a table the resulting object produced to hold table data will be empty, i.e. it will contain no indexes and rows. The optional maxRepetitions parameter is passed to the subtree() request.

The callback function will be called once the entire table has been fetched. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred
  • table - Object containing object references representing conceptual rows keyed by index (e.g. for the ifTable table rows are keyed by ifIndex), each row object will contain values keyed by column number, will not be provided if an error occurred

If an error occurs with any varbind returned by subtree() no table will be passed to the callback function. The reason for failure, and the related OID string (as returned from a call to the snmp.varbindError() function), will be passed to the callback function in the error argument as an instance of the RequestFailedError class.

The following example fetches the ifTable (1.3.6.1.2.1.2.2) table:

var oid = "1.3.6.1.2.1.2.2";

function sortInt (a, b) {
    if (a > b)
        return 1;
    else if (b > a)
        return -1;
    else
        return 0;
}

function responseCb (error, table) {
    if (error) {
        console.error (error.toString ());
    } else {
        // This code is purely used to print rows out in index order,
        // ifIndex's are integers so we'll sort them numerically using
        // the sortInt() function above
        var indexes = [];
        for (index in table)
            indexes.push (parseInt (index));
        indexes.sort (sortInt);
        
        // Use the sorted indexes we've calculated to walk through each
        // row in order
        for (var i = 0; i < indexes.length; i++) {
            // Like indexes we sort by column, so use the same trick here,
            // some rows may not have the same columns as other rows, so
            // we calculate this per row
            var columns = [];
            for (column in table[indexes[i]])
                columns.push (parseInt (column));
            columns.sort (sortInt);
            
            // Print index, then each column indented under the index
            console.log ("row for index = " + indexes[i]);
            for (var j = 0; j < columns.length; j++) {
                console.log ("   column " + columns[j] + " = "
                        + table[indexes[i]][columns[j]]);
            }
        }
    }
}

var maxRepetitions = 20;

// The maxRepetitions argument is optional, and will be ignored unless using
// SNMP verison 2c
session.table (oid, maxRepetitions, responseCb);

session.tableColumns (oid, columns, [maxRepetitions], callback)

The tableColumns() method implements the same interface as the table() method. However, only the columns specified in the columns parameter will be in the resulting table.

This method should be used when only selected columns are required, and will be many times faster than the table() method since a much smaller amount of data will be fected.

The following example fetches the ifTable (1.3.6.1.2.1.2.2) table, and specifies that only the ifDescr (1.3.6.1.2.1.2.2.1.2) and ifPhysAddress (1.3.6.1.2.1.2.2.1.6) columns should actually be fetched:

var oid = "1.3.6.1.2.1.2.2";
var columns = [2, 6];

function sortInt (a, b) {
    if (a > b)
        return 1;
    else if (b > a)
        return -1;
    else
        return 0;
}

function responseCb (error, table) {
    if (error) {
        console.error (error.toString ());
    } else {
        // This code is purely used to print rows out in index order,
        // ifIndex's are integers so we'll sort them numerically using
        // the sortInt() function above
        var indexes = [];
        for (index in table)
            indexes.push (parseInt (index));
        indexes.sort (sortInt);
        
        // Use the sorted indexes we've calculated to walk through each
        // row in order
        for (var i = 0; i < indexes.length; i++) {
            // Like indexes we sort by column, so use the same trick here,
            // some rows may not have the same columns as other rows, so
            // we calculate this per row
            var columns = [];
            for (column in table[indexes[i]])
                columns.push (parseInt (column));
            columns.sort (sortInt);
            
            // Print index, then each column indented under the index
            console.log ("row for index = " + indexes[i]);
            for (var j = 0; j < columns.length; j++) {
                console.log ("   column " + columns[j] + " = "
                        + table[indexes[i]][columns[j]]);
            }
        }
    }
}

var maxRepetitions = 20;

// The maxRepetitions argument is optional, and will be ignored unless using
// SNMP verison 2c
session.tableColumns (oid, columns, maxRepetitions, responseCb);

session.trap (typeOrOid, [varbinds], [agentAddrOrOptions], callback)

The trap() method sends a SNMP trap.

The typeOrOid parameter can be one of two types; one of the constants defined in the snmp.TrapType object (excluding the snmp.TrapType.EnterpriseSpecific constant), or an OID string.

For SNMP version 1 when a constant is specified the following fields are set in the trap:

  • The enterprise field is set to the OID 1.3.6.1.4.1
  • The generic-trap field is set to the constant specified
  • The specific-trap field is set to 0

When an OID string is specified the following fields are set in the trap:

  • The final decimal is stripped from the OID string and set in the specific-trap field
  • The remaining OID string is set in the enterprise field
  • The generic-trap field is set to the constant snmp.TrapType.EnterpriseSpecific

In both cases the time-stamp field in the trap PDU is set to the value returned by the process.uptime () function multiplied by 100.

SNMP version 2c messages are quite different in comparison with version 1. The version 2c trap has a much simpler format, simply a sequence of varbinds. The first varbind to be placed in the trap message will be for the sysUptime.0 OID (1.3.6.1.6.3.1.1.4.1.0). The value for this varbind will be the value returned by the process.uptime () function multiplied by 100 (this can be overridden by providing upTime in the optional options parameter, as documented below).

This will be followed by a second varbind for the snmpTrapOID.0 OID (1.3.6.1.6.3.1.1.4.1.0). The value for this will depend on the typeOrOid parameter. If a constant is specified the trap OID for the constant will be used as supplied for the varbinds value, otherwise the OID string specified will be used as is for the value of the varbind.

The optional varbinds parameter is an array of varbinds to include in the trap, and defaults to the empty array [].

The optional agentAddrOrOptions parameter can be one of two types; one is the IP address used to populate the agent-addr field for SNMP version 1 type traps, and defaults to 127.0.0.1, or an object, and can contain the following items:

  • agentAddr - IP address used to populate the agent-addr field for SNMP version 1 type traps, and defaults to 127.0.0.1
  • upTime - Value of the sysUptime.0 OID (1.3.6.1.6.3.1.1.4.1.0) in the trap, defaults to the value returned by the process.uptime () function multiplied by 100

NOTE When using SNMP version 2c the agentAddr parameter is ignored if specified since version 2c trap messages do not have an agent-addr field.

The callback function is called once the trap has been sent, or an error occurred. The following arguments will be passed to the callback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred

The following example sends an enterprise specific trap to a remote host using a SNMP version 1 trap, and includes the sysName (1.3.6.1.2.1.1.5.0) varbind in the trap. Before the trap is sent the agentAddr field is calculated using DNS to resolve the hostname of the local host:

var enterpriseOid = "1.3.6.1.4.1.2000.1"; // made up, but it may be valid

var varbinds = [
    {
        oid: "1.3.6.1.2.1.1.5.0",
        type: snmp.ObjectType.OctetString,
        value: "host1"
    }
];

dns.lookup (os.hostname (), function (error, agentAddress) {
    if (error) {
        console.error (error);
    } else {
        // Override sysUpTime, specfiying it as 10 seconds...
        var options = {agentAddr: agentAddress, upTime: 1000};
        session.trap (enterpriseOid, varbinds, agentAddress,
                function (error) {
            if (error)
                console.error (error);
        });
    }
});

The following example sends a generic link-down trap to a remote host using a SNMP version 1 trap, it does not include any varbinds or specify the agentAddr parameter:

session.trap (snmp.TrapType.LinkDown, function (error) {
    if (error)
        console.error (error);
});

The following example sends an enterprise specific trap to a remote host using a SNMP version 2c trap, and includes two enterprise specific varbinds:

var trapOid = "1.3.6.1.4.1.2000.1";

var varbinds = [
    {
        oid: "1.3.6.1.4.1.2000.2",
        type: snmp.ObjectType.OctetString,
        value: "Hardware health status changed"
    },
    {
        oid: "1.3.6.1.4.1.2000.3",
        type: snmp.ObjectType.OctetString,
        value: "status-error"
    }
];

// version 2c should have been specified when creating the session
session.trap (trapOid, varbinds, function (error) {
    if (error)
        console.error (error);
});

session.walk (oid, [maxRepetitions], feedCallback, doneCallback)

The walk() method fetches the value for all OIDs lexicographically following a specified OID in the MIB tree.

For SNMP version 1 repeated get() calls are made until the end of the MIB tree is reached. For SNMP version 2c repeated getBulk() calls are made until the end of the MIB tree is reached.

The oid parameter is an OID string. The optional maxRepetitions parameter is passed to getBulk() requests when SNMP version 2c is being used.

This method will not call a single callback once all OID values are fetched. Instead the feedCallback function will be called each time a response is received from the remote host. The following arguments will be passed to the feedCallback function:

  • varbinds - Array of varbinds, and will contain at least one varbind

Each varbind must be checked for an error condition using the snmp.isVarbindError() function when using SNMP version 2c.

Once the end of the MIB tree has been reached, or an error has occurred, the doneCallback function will be called. The following arguments will be passed to the doneCallback function:

  • error - Instance of the Error class or a sub-class, or null if no error occurred

Once the doneCallback function has been called the request is complete and the feedCallback function will no longer be called.

If the feedCallback function returns a true value when called no more get() or getBulk() method calls will be made and the doneCallback will be called.

The following example walks to the end of the MIB tree starting from the ifTable (1.3.6.1.2.1.2.2) OID:

var oid = "1.3.6.1.2.1.2.2";

function doneCb (error) {
    if (error)
        console.error (error.toString ());
}

function feedCb (varbinds) {
    for (var i = 0; i < varbinds.length; i++) {
        if (snmp.isVarbindError (varbinds[i]))
            console.error (snmp.varbindError (varbinds[i]));
        else
            console.log (varbinds[i].oid + "|" + varbinds[i].value);
    }
}

var maxRepetitions = 20;

// The maxRepetitions argument is optional, and will be ignored unless using
// SNMP verison 2c
session.walk (oid, maxRepetitions, feedCb, doneCb);

Using This Module: Notification Receiver

RFC 3413 classifies a "Notification Receiver" SNMP application that receives "Notification-Class" PDUs. Notifications include both SNMP traps and informs. This library is able to receive all types of notification PDU:

  • Trap-PDU (original v1 trap PDUs, which are now considered obselete)
  • Trapv2-PDU (unacknowledged notifications)
  • InformRequest-PDU (same format as Trapv2-PDU but with message acknowledgement)

The library provides a Receiver class for receiving SNMP notifications. This module exports the createReceiver() function, which creates a new Receiver instance.

The receiver creates an Authorizer instance to control incoming access. More detail on this is found below in the Authorizer Module section below.

snmp.createReceiver (options, callback)

The createReceiver() function instantiates and returns an instance of the Receiver class:

// Default options
var options = {
    port: 162,
    disableAuthorization: false,
    engineID: "8000B98380XXXXXXXXXXXX", // where the X's are random hex digits
    transport: "udp4"
};

var callback = function (error, notification) {
    if ( error ) {
        console.error (error);
    } else {
        console.log (JSON.stringify(notification, null, 2));
    }
};

receiver = snmp.createReceiver (options, callback);

Note that binding to the default port (162) on some systems requires the receiver process to be run with administrative privilege. If this is not possible

The options and callback parameters are mandatory. The options parameter is an object, possibly empty, and can contain the following fields:

  • port - the port to listen for notifications on - defaults to 162. Note that binding to port 162 on some systems requires the receiver process to be run with administrative privilege. If this is not possible then choose a port greater than 1024.
  • disableAuthorization - disables local authorization for all community-based notifications received and for those user-based notifications received with no message authentication or privacy (noAuthNoPriv) - defaults to false
  • engineID - the engineID used for SNMPv3 communications, given as a hex string - defaults to a system-generated engineID containing elements of random
  • transport - the transport family to use - defaults to udp4

The callback parameter is a callback function of the form function (error, notification). On an error condition, the notification parameter is set to null. On successful reception of a notification, the error parameter is set to null, and the notification parameter is set as an object with the notification PDU details in the pdu field and the sender socket details in the rinfo field. For example:

{
    "pdu": {
        "type": 166,
        "id": 45385686,
        "varbinds": [
            {
                "oid": "1.3.6.1.2.1.1.3.0",
                "type": 67,
                "value": 5
            },
            {
                "oid": "1.3.6.1.6.3.1.1.4.1.0",
                "type": 6,
                "value": "1.3.6.1.6.3.1.1.5.2"
            }
        ],
        "scoped": false
    },
    "rinfo": {
        "address": "127.0.0.1",
        "family": "IPv4",
        "port": 43162,
        "size": 72
    }
}

receiver.getAuthorizer ()

Returns the receiver's Authorizer instance, used to control access to the receiver. See the Authorizer section for further details.

receiver.close ()

Closes the receiver's listening socket, ending the operation of the receiver.

Using This Module: SNMP Agent

The SNMP agent responds to all four "request class" PDUs relevant to a Command Responder application:

  • GetRequest - request exactly matched OID instances
  • GetNextRequest - request lexicographically "next" OID instances in the MIB tree
  • GetBulkRequest - request a series of "next" OID instances in the MIB tree
  • SetRequest - set values for specified OIDs

The agent sends a GetResponse PDU to all four request PDU types, in conformance to RFC 3416.

The agent - like the notification receiver - maintains an Authorizer instance to control access to the agent, details of which are in the Authorizer Module section below.

The central data structure that the agent maintains is a Mib instance, the API of which is detailed in the Mib Module section below. The agent allows the MIB to be queried and manipulated through the API, as well as queried and manipulated through the SNMP interface with the above four request-class PDUs.

The agent also supports SNMP proxy forwarder applications with its singleton Forwarder instance, which is documented in the Forwarder Module section below.

snmp.createAgent (options, callback)

The createAgent() function instantiates and returns an instance of the Agent class:

// Default options
var options = {
    port: 161,
    disableAuthorization: false,
    engineID: "8000B98380XXXXXXXXXXXX", // where the X's are random hex digits
    transport: "udp4"
};

var callback = function (error, data) {
    if ( error ) {
        console.error (error);
    } else {
        console.log (JSON.stringify(data, null, 2));
    }
};

agent = snmp.createAgent (options, callback);

The options and callback parameters are mandatory. The options parameter is an object, possibly empty, and can contain the following fields:

  • port - the port for the agent to listen on - defaults to 161. Note that binding to port 161 on some systems requires the receiver processto be run with administrative privilege. If this is not possible, then choose a port greater than 1024.
  • disableAuthorization - disables local authorization for all community-based notifications received and for those user-based notifications received with no message authentication or privacy (noAuthNoPriv) - defaults to false
  • engineID - the engineID used for SNMPv3 communications, given as a hex string - defaults to a system-generated engineID containing elements of random
  • transport - the transport family to use - defaults to udp4

agent.getAuthorizer ()

Returns the agent's singleton Authorizer instance, used to control access to the agent. See the Authorizer section for further details.

agent.getMib ()

Returns the agent's singleton Mib instance, which holds all of the management data for the agent.

agent.getForwarder ()

Returns the agent's singleton Forwarder instance, which holds a list of registered proxies that specify context-based forwarding to remote hosts.

agent.close ()

Closes the receiver's listening socket, ending the operation of the receiver.

Authorizer Module

Both the receiver and agent maintain an singleton Authorizer instance, which is responsible for maintaining an authorization list of SNMP communities (for v1 and v2c notifications) and also an authorization list of SNMP users (for v3 notifications). These lists are used to authorize notification access to the receiver, and to store security protocol and key settings. RFC 3414 terms the user list as the the "usmUserTable" stored in the receiver's "Local Configuration Database".

If a v1 or v2c notification is received with a community that is not in the receiver's community authorization list, the receiver will not accept the notification, instead returning a error of class RequestFailedError to the supplied callback function. Similarly, if a v3 notification is received with a user whose name is not in the receiver's user authorization list, the receiver will return a RequestFailedError. If the disableAuthorization option is supplied for the receiver on start-up, then these local authorization list checks are disabled for community notifications and noAuthNoPriv user notifications. Note that even with this setting, the user list is still checked for authNoPriv and authPriv notifications, as the library still requires access to the correct keys for the message authentication and encryption operations, and these keys are stored against a user in the user authorization list.

The API allows the receiver's community authorization and user authorization lists to be managed with adds, queries and deletes.

The authorizer instance can be obtained by using the getAuthorizer() call, for both the receiver and the agent. For example:

receiver.getAuthorizer() .getCommunities();

authorizer.addCommunity (community)

Adds a community string to the receiver's community authorization list. Does nothing if the community is already in the list, ensuring there is only one occurence of any given community string in the list.

authorizer.getCommunity (community)

Returns a community string if it is stored in the receiver's community authorization list, otherwise returns null.

authorizer.getCommunities ()

Returns the receiver's community authorization list.

authorizer.deleteCommunity (community)

Deletes a community string from the receiver's community authorization list. Does nothing if the community is not in the list.

authorizer.addUser (user)

Adds a user to the receiver's user authorization list. If a user of the same name is in the list, this call deletes the existing user, and replaces it with the supplied user, ensuring that only one user with a given name will exist in the list. The user object is in the same format as that used for the session.createV3Session() call.

var user = {
    name: "elsa"
    level: snmp.SecurityLevel.authPriv,
    authProtocol: snmp.AuthProtocols.sha,
    authKey: "imlettingitgo",
    privProtocol: snmp.PrivProtocols.des,
    privKey: "intotheunknown"
};

receiver.getAuthorizer ().addUser (elsa);

authorizer.getUser (userName)

Returns a user object if a user with the supplied name is stored in the receiver's user authorization list, otherwise returns null.

authorizer.getUsers ()

Returns the receiver's user authorization list.

authorizer.deleteUser (userName)

Deletes a user from the receiver's user authorization list. Does nothing if the user with the supplied name is not in the list.

Mib Module

An Agent instance, when created, in turn creates an instance of the Mib class. There is no direct API call to create a Mib instance; this creation is the responsibility of the agent. An agent always has one and only one Mib instance. The agent's Mib instance is accessed through the agent.getMib () call.

The MIB is a tree structure that holds management information. Information is "addressed" in the tree by a series of integers, which form an Object ID (OID) from the root of the tree down.

There are only two kinds of data structures that hold data in a MIB:

  • scalar data - the scalar variable is stored at a node in the MIB tree, and the value of the variable is a single child node of the scalar variable node, always with address "0". For example, the sysDescr scalar variable is located at "1.3.6.1.2.1.1.1". The value of the sysDescr variable is stored at "1.3.6.1.2.1.1.1.0"

    1.3.6.1.2.1.1.1   <= sysDescr (scalar variable)
    1.3.6.1.2.1.1.1.0 = OctetString: MyAwesomeHost  <= sysDescr.0 (scalar variable value)
    
  • table data - the SNMP table stores data in columns and rows. Typically, if a table is stored at a node in the MIB, it has an "entry" object addressed as "1" directly below the table OID. Directly below the "entry" is a list of columns, which are typically numbered from "1" upwards. Directly below each column are a series of rows. In the simplest case a row is "indexed" by a single column in the table, but a row index can be a series of columns, or columns that give multiple integers (e.g. an IPv4 address has four integers to its index), or both. Here is an example of the hierarchy of an SNMP table for part of the ifTable:

    1.3.6.1.2.1.2.2   <= ifTable (table)
    1.3.6.1.2.1.2.2.1   <= ifEntry (table entry)
    1.3.6.1.2.1.2.2.1.1   <= ifIndex (column 1)
    1.3.6.1.2.1.2.2.1.1.1 = Integer: 1   <= ifIndex row 1 value = 1
    1.3.6.1.2.1.2.2.1.1.2 = Integer: 2   <= ifIndex row 2 value = 2
    

On creation, an Agent instance creates a singleton instance of the Mib module. You can then register a "provider" to the agent's Mib instance that gives an interface to either a scalar data instance, or a table.

var myScalarProvider = {
    name: "sysDescr",
    type: snmp.MibProviderType.Scalar,
    oid: "1.3.6.1.2.1.1.1",
    scalarType: snmp.ObjectType.OctetString,
    handler: function (mibRequest) {
       // e.g. can update the MIB data before responding to the request here
       mibRequest.done ();
    }
};
var mib = agent.getMib ();
mib.registerProvider (myScalarProvider);
mib.setScalarValue ("sysDescr", "MyAwesomeHost");

This code first gives the definition of a scalar "provider". A further explanation of these fields is given in the mib.registerProvider() section. Importantly, the name field is the unique identifier of the provider, and is used to select the specific provider in subsequent API calls.

The registerProvider() call adds the provider to the list of providers that the MIB holds. Note that this call does not add the "oid" node to the MIB tree. The first call of setScalarValue() will add the instance OID "1.3.6.1.2.1.1.1.0" to the MIB tree, along with its value.

At this point, the agent will serve up the value of this MIB node when the instance OID "1.3.6.1.2.1.1.1.0" is queried via SNMP.

A table provider has a similar definition:

var myTableProvider = {
    name: "smallIfTable",
    type: snmp.MibProviderType.Table,
    oid: "1.3.6.1.2.1.2.2.1",
    tableColumns: [
        {
            number: 1,
            name: "ifIndex",
            type: snmp.ObjectType.Integer
        },
        {
            number: 2,
            name: "ifDescr",
            type: snmp.ObjectType.OctetString
        },
        {
            number: 3,
            name: "ifType",
            type: snmp.ObjectType.Integer
        }
    ],
    tableIndex: [
        {
            columnName: "ifIndex"
        }
    ]
};
var mib = agent.getMib ();
mib.registerProvider (myTableProvider);
mib.addTableRow ("smallIfTable", [1, "eth0", 6]);

Here, the provider definition takes two additions fields: tableColumns for the column defintions, and tableIndex for the columns used for row indexes. In the example the tableIndex is the ifIndex column. The mib.registerProvider() section has further details on the fields that make up the provider definition.

The oid must be that of the "table entry" node, not its parent "table" node e.g. for ifTable, the oid in the provider is "1.3.6.1.2.1.2.2.1" (the OID for ifEntry).

Note that there is no handler callback function in this particular example, so any interaction is directly between SNMP requests and MIB values with no other intervention.

mib.registerProvider (definition)

Registers a provider definition with the MIB. Doesn't add anything to the MIB tree.

A provider definition has these fields:

  • name (mandatory) - the name of the provider, which serves as a unique key to reference the provider for getting and setting values
  • type (mandatory) - must be either snmp.MibProviderType.Scalar or snmp.MibProviderType.Table (mandatory)
  • oid (mandatory) - the OID where the provider is registered in the MIB tree. Note that this is not the "instance node" (the ".0" node), but the one above it. In this case, the provider registers at "1.3.6.1.2.1.1.1", to provide the value at "1.3.6.1.2.1.1.1.0".
  • scalarType (mandatory for scalar types) - only relevant to scalar provider type, this give the type of the variable, selected from snmp.ObjectType
  • tableColumns (mandatory for table types) - gives any array of column definition objects for the table. Each column object must have a unique number, a name and a type from snmp.ObjectType.
  • tableIndex (optional for table types) - gives an array of index entry objects used for row indexes. Use a single-element array for a single-column index, and multiple values for a composite index. An index entry object has a columnName field, and if the entry is in another provider's table, then include a foreign field with the name of the foreign table's provider. If the tableAugments field is absent, tableIndex is mandatory.
  • tableAugments (optional for table types) - gives the name of another registered provider that this table "augments". This means that the index information is taken from the given provider's table, and doesn't exist in the local table's column definitions. If the tableIndex field is absent, tableAugments is mandatory i.e. one of tableIndex and tableAugments needs to be present to define the table index.
  • handler (optional) - an optional callback function, which is called before the request to the MIB is made. This could update the MIB value(s) handled by this provider. If not given, the values are simply returned from (or set in) the MIB without any other processing. The callback function takes a MibRequest instance, which has a done() function. This must be called when finished processing the request. The MibRequest also has an oid field with the instance OID being operated on, and an operation field with the request type from snmp.PduType.

After registering the provider with the MIB, the provider is referenced by its name in other API calls.

While this call registers the provider to the MIB, it does not alter the MIB tree.

mib.registerProviders ( [definitions] )

Convenience method to register an array of providers in one call. Simply calls registerProvider() for each provider definition in the array.

mib.unregisterProvider (name)

Unregisters a provider from the MIB. This also deletes all MIB nodes from the provider's oid down the tree. It will also do upstream MIB tree pruning of any interior MIB nodes that only existed for the MIB tree to reach the provider oid node.

mib.getProviders ()

Returns an object of provider definitions registered with the MIB, indexed by provider name.

mib.getProvider (name)

Returns a single registered provider object for the given name.

mib.getScalarValue (scalarProviderName)

Retrieves the value from a scalar provider.

mib.setScalarValue (scalarProviderName, value)

Sets the value for a scalar provider. If this is the first time the scalar is set since the provider has registered with the MIB, it will also add the instance (".0") node and all requires ancestors to the MIB tree.

mib.addTableRow (tableProviderName, row)

Adds a table row - in the form of an array of values - to a table provider. If the table is empty, this instantiates the provider's oid node and ancestors, its columns, before adding the row of values. Note that the row is an array of elements in the order of the table columns. If the table has any foreign index columns (i.e. those not belonging to this table), then values for these must be included the at the start of the row array, in the order they appear in the MIB INDEX clause.

mib.getTableColumnDefinitions (tableProviderName)

Returns a list of column definition objects for the provider.

mib.getTableCells (tableProviderName, byRow, includeInstances)

Returns a two-dimensional array of the table data. If byRow is false (the default), then the table data is given in a list of column arrays i.e. by column. If byRow is true, then the data is instead a list of row arrays. If includeInstances is true, then, for the column view there will be an extra first column with instance index information. If includeInstances is true for the row view, then there is an addition element at the start of each row with index information.

mib.getTableColumnCells (tableProviderName, columnNumber, includeInstances)

Returns a single column of table data for the given column number. If includeInstances is true, then two arrays are returned: the first with instance index information, and the second with the column data.

mib.getTableRowCells (tableProviderName, rowIndex)

Returns a single row of table data for the given row index. The row index is an array of integers built from the node immediately under the column down to the node at the end of the row instance, which will be a leaf node in the MIB tree.

mib.getTableSingleCell (tableProviderName, columnIndex, rowIndex)

Returns a single cell value from the column and row specified. The row index array is specified in the same way as for the getTableRowCells() call.

mib.setTableSingleCell (tableProviderName, columnIndex, rowIndex, value)

Sets a single cell value at the column and row specified. The row index array is specified in the same way as for the getTableRowCells() call.

mib.deleteTableRow (tableProviderName, rowIndex)

Deletes a table row at the row index specified. The row index array is specified in the same way as for the getTableRowCells() call. If this was the last row in the table, the table is pruned from the MIB, although the provider still remains registered with the MIB. Meaning that on the addition of another row, the table will be instantiated again.

mib.dump (options)

Dumps the MIB in text format. The options object controls the display of the dump with these options fields (all are booleans that default to true):

  • leavesOnly - don't show interior nodes separately - only as prefix parts of leaf nodes (instance nodes)
  • showProviders - show nodes where providers are attached to the MIB
  • showTypes - show instance value types
  • showValues - show instance values

For example:

mib.dump ();

produces this sort of output:

1.3.6.1.2.1.1.1 [Scalar: sysDescr]
1.3.6.1.2.1.1.1.0 = OctetString: Rage inside the machine!
1.3.6.1.2.1.2.2.1 [Table: ifTable]
1.3.6.1.2.1.2.2.1.1.1 = Integer: 1
1.3.6.1.2.1.2.2.1.1.2 = Integer: 2
1.3.6.1.2.1.2.2.1.2.1 = OctetString: lo
1.3.6.1.2.1.2.2.1.2.2 = OctetString: eth0
1.3.6.1.2.1.2.2.1.3.1 = Integer: 24
1.3.6.1.2.1.2.2.1.3.2 = Integer: 6

Using This Module: Module Store

The library supports MIB parsing by providing an interface to a ModuleStore instance into which you can load MIB modules from files, and fetch the resulting JSON MIB module representations.

Additionally, once a MIB is loaded into the module store, you can produce a list of MIB "provider" definitions that an Agent can register (see the Agent documentation for more details), so that you can start manipulating all the values defined in your MIB file right away.

// Create a module store, load a MIB module, and fetch its JSON representation
var store = snmp.createModuleStore ();
store.loadFromFile ("/path/to/your/mibs/SNMPv2-MIB.mib");
var jsonModule = store.getModule ("SNMPv2-MIB");

// Fetch MIB providers, create an agent, and register the providers with your agent
var providers = store.getProvidersForModule ("SNMPv2-MIB");
// Not recommended - but authorization and callback turned of for example brevity
var agent = snmp.createAgent ({disableAuthorization: true}, function (error, data) {});
var mib = agent.getMib ();
mib.registerProviders (providers);

// Start manipulating the MIB through the registered providers using the `Mib` API calls
mib.setScalarValue ("sysDescr", "The most powerful system you can think of");
mib.setScalarValue ("sysName", "multiplied-by-six");
mib.addTableRow ("sysOREntry", [1, "1.3.6.1.4.1.47491.42.43.44.45", "I've dreamed up this MIB", 20]);

// Then hit those bad boys with your favourite SNMP tools (or library ;-), e.g.
snmpwalk -v 2c -c public localhost 1.3.6.1

Meaning you can get right to the implementation of your MIB functionality with a minimum of boilerplate code.

snmp.createModuleStore ()

Creates a new ModuleStore instance, which comes pre-loaded with some "base" MIB modules that that provide MIB definitions that other MIB modules commonly refer to ("import"). The list of pre-loaded "base" modules is:

  • RFC1155-SMI
  • RFC1158-MIB
  • RFC-1212
  • RFC1213-MIB
  • SNMPv2-SMI
  • SNMPv2-CONF
  • SNMPv2-TC
  • SNMPv2-MIB

store.loadFromFile (fileName)

Loads all MIB modules in the given file into the module store. By convention, there is typically only a single MIB module per file, but there can be multiple module definitions stored in a single file. Loaded MIB modules are then referred to by this API by their MIB module name, not the source file name. The MIB module name is the name preceding the DEFINITIONS ::= BEGIN in the MIB file, and is often the very first thing present in a MIB file.

Note that if your MIB dependends on ("imports") definitions from other MIB files, these must be loaded first e.g. the popular IF-MIB uses definitions from the IANAifType-MIB, which therefore must be loaded first. These dependencies are listed in the IMPORTS section of a MIB module, usually near the top of a MIB file. The pre-loaded "base" MIB modules contain many of the commonly used imports.

store.getModule (moduleName)

Retrieves the named MIB module from the store as a JSON object.

store.getModules (includeBase)

Retrieves all MIB modules from the store. If the includeBase boolean is set to true, then the base MIB modules are included in the list. The modules are returned as a single JSON "object of objects", keyed on the module name, with the values being entire JSON module represenations.

store.getModuleNames (includeBase)

Retrieves a list of the names of all MIB modules loaded in the store. If the includeBase boolean is set to true, then the base MIB modules names are included in the list.

store.getProvidersForModule (moduleName)

Returns an array of Mib "provider" definitions corresponding to all scalar and table instance objects contained in the named MIB module. The list of provider definitions are then ready to be registered to an agent's MIB by using the agent.getMib().registerProviders() call.

Forwarder Module

An Agent instance, when created, in turn creates an instance of the Forwarder class. There is no direct API call to create a Forwarder instance; this creation is the responsibility of the agent. An agent always has one and only one Forwarder instance. The agent's Forwarder instance is accessed through the agent.getForwarder () call.

A Forwader is what RFC 3413 terms a "Proxy Forwarder Application". It maintains a list of "proxy" entries, each of which configures a named SNMPv3 context name to enable access to a given target host with the given user credentials. The Forwarder supports proxying of SNMPv3 sessions only.

var forwarder = agent.getForwarder ();
forwarder.addProxy({
    context: "slatescontext",
    host: "bedrock",
    user: {
        name: "slate",
        level: snmp.SecurityLevel.authNoPriv,
        authProtocol: snmp.AuthProtocols.sha,
        authKey: "quarryandgravel"
    },
});

Now requests to the agent with the context "slatescontext" supplied will be forwarded to host "bedrock", with the supplied credentials for user "slate".

You can query the proxy with a local agent user (added with the agent's Authorizer instance). Assuming your proxy runs on localhost, port 161, you could add local user "fred", and access the proxy with the new "fred" user.

var authorizer = agent.getAuthorizer();
authorizer.addUser ({
    name: "fred",
    level: snmp.SecurityLevel.noAuthNoPriv
});

// Test access using Net-SNMP tools (-n is the context option):

snmpget -v 3 -u fred -l noAuthNoPriv -n slatescontext localhost 1.3.6.1.2.1.1.1.0

This proxies requests through to "bedrock" as per the proxy definition.

forwarder.addProxy (proxy)

Adds a new proxy to the forwarder. The proxy is an object with these fields.

  • context (mandatory) - the name of the SNMPv3 context for this proxy entry. This is the unique key for proxy entries i.e. there cannot be two proxies with the same context name.
  • transport (optional) - specifies the transport to use to reach the remote target. Can be either udp4 or udp6, defaults to udp4.
  • target (mandatory) - the remote host that will receive proxied requests.
  • port (optional) - the port of the SNMP agent on the remote host. Defaults to 161.
  • user (mandatory) - the SNMPv3 user. The format for the user is described in the createV3Session() call documentation.

forwarder.deleteProxy (context)

Delete the proxy for the given context from the forwarder.

forwarder.getProxy (context)

Returns the forwarder's proxy for the given context.

forwarder.getProxies ()

Returns an object containing a list of all registered proxies, keyed by context name.

forwarder.dumpProxies ()

Prints a dump of all proxy definitions to the console.

Example Programs

Example programs are included under the module's example directory.

Changes

Version 1.0.0 - 14/01/2013

  • Initial release including only SNMP version 1 support

Version 1.1.0 - 20/01/2013

  • Implement SNMP version 2c support

Version 1.1.1 - 21/01/2013

  • Correct name used in example require() call to include this module

Version 1.1.2 - 22/01/2013

  • Implement subtree(), table() and walk() methods
  • Support IPv6 (added transport option to the createSession() function)
  • Re-order some methods in README.md

Version 1.1.3 - 27/01/2013

  • Fix some typos and grammar errors in README.md
  • Example snmp-table program had snmp-subtree in its usage message
  • Implement example snmp-tail program to constantly poll for an OIDs value
  • Add note to README.md about the ability to stop the walk() and subtree() methods by returning true

Version 1.1.4 - 29/01/2013

  • Fix incorrect usage of the term "NPM" in README.md, should be "npm"

Version 1.1.5 - 05/02/2013

  • The transport option to createSession() was not used

Version 1.1.6 - 12/04/2013

  • Implement tableColumns() method
  • Added example program snmp-table-columns.js
  • Correct name of the table parameter to the table() callback
  • Slight OID comparison performance enhancement

Version 1.1.7 - 11/05/2013

  • Use MIT license instead of GPL

Version 1.1.8 - 22/06/2013

  • Added the example program cisco-device-inventory.js
  • Receive Trap failed: TypeError: value is out of bounds when sending traps using SNMP version 2c

Version 1.1.9 - 03/11/2013

  • Corrected a few instances of the parameter named requestCallback to some methods in the README.md file which should have been feedCallback
  • Null type is used for varbinds with a 0 value
  • Correct instances of snmp.Type to snmp.ObjectType in the README.md file

Version 1.1.10 - 01/12/2013

  • Error handler in the dgram.send() callback in the send() method was creating a new instance of the Error class from the error parameter, but it was already an instance of the Error class (thanks Ray Solomon)
  • Add stack traces to Error classes exported by this module (thanks Ray Solomon)
  • Allow users to specify 0 retries when creating a session (thanks Ray Solomon)
  • Update the list of SNMP version 1 related RFCs we adhere to in the Standards Compliance section of the README.md file

Version 1.1.11 - 27/12/2013

  • Add sourceAddress and sourcePort optional options to the Session classes createSession() method, which can be used to control from which IP address and port messages should be sent
  • Allow users to specify sysUpTime for SNMP traps and informs

Version 1.1.12 - 02/04/2014

  • The agentAddr attribute is not used when passed in the options object to the trap() method

Version 1.1.13 - 12/08/2014

  • Not catching error events for the UDP socket returned from the dgram.createSocket() function
  • Some request methods do not copy arguments which results in sometimes unexpected behaviour
  • Use a single UDP socket for all requests in a single SNMP session
  • Use a try/catch block in the timer callback in the Session.send() method
  • The Session can now emit an error event to catch errors in a sessions underlying UDP socket
  • The Session can now emit a close event to catch close events from a sessions underlying UDP socket, which results in the cancellation of all outstanding requests
  • Added a close() method to Session to close a sessions underlying UDP socket, which results a close event
  • Signed integers are treated as unsigned integers when parsing response messages

Version 1.1.14 - 22/09/2015

  • Host repository on GitHub

Version 1.1.15 - 08/02/2016

  • When parsing an invalid response an exception in message parsing does not interupt response processing
  • Incorrectly passing req object in call to req.responseCb when handling errors during response processing

Version 1.1.16 - 29/02/2016

  • Address a number of issues detected with the Mocha test suite by a user

Version 1.1.17 - 21/03/2016

  • Correct reference to non-existant req variable in the Session objects constructor (should be this)

Version 1.1.18 - 15/05/2015

  • Correct argument number and names to the snmp.createSession() function
  • Add missing braces to an example in the README.md file

Version 1.1.19 - 26/08/2016

  • Remove 64bit integer check to ensure a maximum of 8 bytes are given in send and received messages

Version 1.2.0 - 22/07/2017

  • Replace asn1 dependancy with asn1-ber

Version 1.2.1 - 11/02/2018

  • Add support of 16bit ids to help interoperate with older devices (added the idBitsSize option to the createSession() function
  • Add note to README.md that sessions should be closed when done with

Version 1.2.3 - 06/06/2018

  • Set NoSpaceships Ltd to be the owner and maintainer

Version 1.2.4 - 07/06/2018

  • Remove redundant sections from README.md

Version 2.0.0 - 16/01/2020

  • Add SNMPv3 support

Version 2.1.0 - 16/01/2020

  • Add trap and inform receiver

Version 2.1.1 - 17/01/2020

  • Add CONTRIBUTING.md guidelines

Version 2.1.2 - 17/01/2020

  • Add SNMPv3 context to Session class

Version 2.1.3 - 18/01/2020

  • Add IPv6 option for tests

Version 2.2.0 - 21/01/2020

  • Add SNMP agent

Version 2.3.0 - 22/01/2020

  • Add MIB parser and module store

Version 2.4.0 - 24/01/2020

  • Add proxy forwarder to agent

Version 2.5.0 - 25/01/2020

  • Add AES-128 encryption

Version 2.5.1 - 27/01/2020

  • Add non-integer, composite key, foreign key and augmented table index handling

Version 2.5.2 - 29/01/2020

  • Update CONTRIBUTING.md and parser example

Version 2.5.3 - 22/02/2020

  • Add backoff option

Version 2.5.4 - 22/03/2020

  • Fix agent crash with unexpected GetNext start OID

Version 2.5.5 - 31/03/2020

  • Fix double report PDU time synchronisation handling

License

Copyright (c) 2020 Mark Abrahams mark@abrahams.co.nz

Copyright (c) 2018 NoSpaceships Ltd hello@nospaceships.com

Copyright (c) 2013 Stephen Vickers stephen.vickers.sv@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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