gosnmp

README

gosnmp

GoSNMP is a simple SNMP client library, written fully in Go. Currently it supports only GetRequest (with the rest GetNextRequest, SetRequest in the pipe line). Support for traps is also in the plans.

Install

The easiest way to install is via go get:

go get github.com/alouca/gosnmp

License

Some parts of the code are borrowed by the Golang project (specifically some functions for unmarshaling BER responses), which are under the same terms and conditions as the Go language, which are marked appropriately in the source code. The rest of the code is under the BSD license.

See the LICENSE file for more details.

Usage

The library usage is pretty simple:

// Connect to 192.168.0.1 with timeout of 5 seconds

import (
"github.com/alouca/gosnmp"
"log"
)

s, err := gosnmp.NewGoSNMP("61.147.69.87", "public", gosnmp.Version2c, 5)
if err != nil {
	log.Fatal(err)
}
resp, err := s.Get(".1.3.6.1.2.1.1.1.0")
if err == nil {
	for _, v := range resp.Variables {
		switch v.Type {
		case gosnmp.OctetString:
			log.Printf("Response: %s : %s : %s \n", v.Name, v.Value.(string), v.Type.String())
		}
	}
}

The response value is always given as an interface{} depending on the PDU response from the SNMP server. For an example checkout examples/example.go.

Responses are a struct of the following format:

type Variable struct {
  Name  asn1.ObjectIdentifier
  Type  Asn1BER
  Value interface{}
}

Where Name is the OID encoded as an object identifier, Type is the encoding type of the response and Value is an interface{} type, with the response appropriately decoded.

SNMP BER Types can be one of the following:

type Asn1BER byte

const (
  Integer          Asn1BER = 0x02
	BitString                = 0x03
	OctetString              = 0x04
	Null                     = 0x05
	ObjectIdentifier         = 0x06
	Counter32                = 0x41
	Gauge32                  = 0x42
	TimeTicks                = 0x43
	Opaque                   = 0x44
	NsapAddress              = 0x45
	Counter64                = 0x46
	Uinteger32               = 0x47
)

GoSNMP supports most of the above values, subsequent releases will support all of them.

Documentation

Index

• Constants
• Variables
• func ParseUint16(content []byte) int
• func Uvarint(buf []byte) (x uint64)
• type Asn1BER
  • func (dataType Asn1BER) String() string
• type BitStringValue
  • func (b BitStringValue) At(i int) int
  • func (b BitStringValue) RightAlign() []byte
• type GoSNMP
  • func NewGoSNMP(target, community string, version SnmpVersion, timeout int64) (*GoSNMP, error)
  • func (x *GoSNMP) BulkWalk(max_repetitions uint8, oid string) (results []SnmpPDU, err error)
  • func (x *GoSNMP) Debug(data []byte) (*SnmpPacket, error)
  • func (x *GoSNMP) Get(oid string) (ret *SnmpPacket, err error)
  • func (x *GoSNMP) GetBulk(non_repeaters, max_repetitions uint8, oids ...string) (ret *SnmpPacket, err error)
  • func (x *GoSNMP) GetMulti(oids []string) (ret *SnmpPacket, err error)
  • func (x *GoSNMP) GetNext(oid string) (ret *SnmpPacket, err error)
  • func (x *GoSNMP) SetDebug(d bool)
  • func (x *GoSNMP) SetTimeout(seconds int64)
  • func (x *GoSNMP) SetVerbose(v bool)
  • func (x *GoSNMP) StreamWalk(oid string, c chan *Variable) error
  • func (x *GoSNMP) Walk(oid string) (results []SnmpPDU, err error)
• type RawBER
• type SnmpPDU
• type SnmpPacket
  • func Unmarshal(packet []byte) (*SnmpPacket, error)
• type SnmpVersion
  • func (s SnmpVersion) String() string
• type Variable

Constants

const (
	Integer          Asn1BER = 0x02
	BitString                = 0x03
	OctetString              = 0x04
	Null                     = 0x05
	ObjectIdentifier         = 0x06
	Sequence                 = 0x30
	IpAddress                = 0x40
	Counter32                = 0x41
	Gauge32                  = 0x42
	TimeTicks                = 0x43
	Opaque                   = 0x44
	NsapAddress              = 0x45
	Counter64                = 0x46
	Uinteger32               = 0x47
	NoSuchObject             = 0x80
	NoSuchInstance           = 0x81
	GetRequest               = 0xa0
	GetNextRequest           = 0xa1
	GetResponse              = 0xa2
	SetRequest               = 0xa3
	Trap                     = 0xa4
	GetBulkRequest           = 0xa5
	EndOfMibView             = 0x82
)

SNMP Data Types

Variables

var DEFAULT_PORT = 161

Functions

func ParseUint16

func ParseUint16(content []byte) int

Parses UINT16

func Uvarint

func Uvarint(buf []byte) (x uint64)

Types

type Asn1BER

type Asn1BER byte

func (Asn1BER) String

func (dataType Asn1BER) String() string

type BitStringValue

type BitStringValue struct {
	Bytes     []byte // bits packed into bytes.
	BitLength int    // length in bits.
}

BitStringValue is the structure to use when you want an ASN.1 BIT STRING type. A bit string is padded up to the nearest byte in memory and the number of valid bits is recorded. Padding bits will be zero.

func (BitStringValue) At

func (b BitStringValue) At(i int) int

At returns the bit at the given index. If the index is out of range it returns false.

func (BitStringValue) RightAlign

func (b BitStringValue) RightAlign() []byte

RightAlign returns a slice where the padding bits are at the beginning. The slice may share memory with the BitString.

type GoSNMP

type GoSNMP struct {
	Target    string
	Community string
	Version   SnmpVersion
	Timeout   time.Duration

	Log *l.Logger
	// contains filtered or unexported fields
}

func NewGoSNMP

func NewGoSNMP(target, community string, version SnmpVersion, timeout int64) (*GoSNMP, error)

Creates a new SNMP Client. Target is the IP address, Community the SNMP Community String and Version the SNMP version. Currently only v2c is supported. Timeout parameter is measured in seconds.

func (*GoSNMP) BulkWalk

func (x *GoSNMP) BulkWalk(max_repetitions uint8, oid string) (results []SnmpPDU, err error)

func (*GoSNMP) Debug

func (x *GoSNMP) Debug(data []byte) (*SnmpPacket, error)

Debug function. Unmarshals raw bytes and returns the result without the network part

func (*GoSNMP) Get

func (x *GoSNMP) Get(oid string) (ret *SnmpPacket, err error)

Sends an SNMP GET request to the target. Returns a Variable with the response or an error

func (*GoSNMP) GetBulk

func (x *GoSNMP) GetBulk(non_repeaters, max_repetitions uint8, oids ...string) (ret *SnmpPacket, err error)

Sends an SNMP BULK-GET request to the target. Returns a Variable with the response or an error

func (*GoSNMP) GetMulti

func (x *GoSNMP) GetMulti(oids []string) (ret *SnmpPacket, err error)

Sends an SNMP GET request to the target. Returns a Variable with the response or an error

func (*GoSNMP) GetNext

func (x *GoSNMP) GetNext(oid string) (ret *SnmpPacket, err error)

Sends an SNMP Get Next Request to the target. Returns the next variable response from the OID given or an error

func (*GoSNMP) SetDebug

func (x *GoSNMP) SetDebug(d bool)

Enables debugging

func (*GoSNMP) SetTimeout

func (x *GoSNMP) SetTimeout(seconds int64)

Sets the timeout for network read/write functions. Defaults to 5 seconds.

func (*GoSNMP) SetVerbose

func (x *GoSNMP) SetVerbose(v bool)

Enables verbose logging

func (*GoSNMP) StreamWalk

func (x *GoSNMP) StreamWalk(oid string, c chan *Variable) error

StreamWalk will start walking a specified OID, and push through a channel the results as it receives them, without waiting for the whole process to finish to return the results

func (*GoSNMP) Walk

func (x *GoSNMP) Walk(oid string) (results []SnmpPDU, err error)

Walk will SNMP walk the target, blocking until the process is complete

type RawBER

type RawBER struct {
	Type         Asn1BER
	HeaderLength uint64
	DataLength   uint64
	Data         []byte
	BERVariable  *Variable
}

type SnmpPDU

type SnmpPDU struct {
	Name  string
	Type  Asn1BER
	Value interface{}
}

type SnmpPacket

type SnmpPacket struct {
	Version        SnmpVersion
	Community      string
	RequestType    Asn1BER
	RequestID      uint8
	Error          uint8
	ErrorIndex     uint8
	NonRepeaters   uint8
	MaxRepetitions uint8
	Variables      []SnmpPDU
}

func Unmarshal

func Unmarshal(packet []byte) (*SnmpPacket, error)

type SnmpVersion

type SnmpVersion uint8

const (
	Version1  SnmpVersion = 0x0
	Version2c SnmpVersion = 0x1
)

func (SnmpVersion) String

func (s SnmpVersion) String() string

type Variable

type Variable struct {
	Name  []int
	Type  Asn1BER
	Size  uint64
	Value interface{}
}