snmp
-- import "github.com/PromonLogicalis/snmp"
Package snmp implements low-level support for SNMP with focus in SNMP agents.
At the encoding level it uses the PromonLogicalis/asn1 to parse and serialize SNMP messages providing Go types for that.
The package also provides transport-independent support for creating custom SNMP agents with small footprint.
A example of a simple SNMP UDP agent:
package main
import (
"log"
"net"
"time"
"github.com/PromonLogicalis/asn1"
"github.com/PromonLogicalis/snmp"
)
func main() {
agent := snmp.NewAgent()
// Set the read-only and read-write communities
agent.SetCommunities("publ", "priv")
// Register a read-only OID.
since := time.Now()
agent.AddRoManagedObject(
// sysUpTime
asn1.Oid{1, 3, 6, 1, 2, 1, 1, 3, 0},
func(oid asn1.Oid) (interface{}, error) {
seconds := int(time.Now().Sub(since) / time.Second)
return seconds, nil
})
// Register a read-write OID.
name := "example"
agent.AddRwManagedObject(
// sysName
asn1.Oid{1, 3, 6, 1, 2, 1, 1, 5, 0},
func(oid asn1.Oid) (interface{}, error) {
return name, nil
},
func(oid asn1.Oid, value interface{}) error {
strValue, ok := value.(string)
if !ok {
return snmp.VarErrorf(snmp.BadValue, "invalid type")
}
name = strValue
return nil
})
// Bind to an UDP port
addr, err := net.ResolveUDPAddr("udp", ":161")
if err != nil {
log.Fatal(err)
}
conn, err := net.ListenUDP("udp", addr)
if err != nil {
log.Fatal(err)
}
// Serve requests
for {
buffer := make([]byte, 1024)
n, source, err := conn.ReadFrom(buffer)
if err != nil {
log.Fatal(err)
}
buffer, err = agent.ProcessDatagram(buffer[:n])
if err != nil {
log.Println(err)
continue
}
_, err = conn.WriteTo(buffer, source)
if err != nil {
log.Fatal(err)
}
}
}
Usage
const (
NoError = 0
TooBig = 1
NoSuchName = 2
BadValue = 3
ReadOnly = 4
GenErr = 5
NoAccess = 6
WrongType = 7
WrongLength = 8
WrongEncoding = 9
WrongValue = 10
NoCreation = 11
InconsistentValue = 12
ResourceUnavailable = 13
CommitFailed = 14
UndoFailed = 15
AuthorizationError = 16
NotWritable = 17
InconsistentName = 18
)
SNMP error codes.
func Asn1Context
func Asn1Context() *asn1.Context
Asn1Context returns a new allocated asn1.Context and registers all the choice types necessary for SNMPv1 and SNMPv2.
type Agent
type Agent struct {
}
Agent is a transport independent engine to process SNMP requests.
func NewAgent
func NewAgent() *Agent
NewAgent create and initialize an agent.
func (*Agent) AddRoManagedObject
func (a *Agent) AddRoManagedObject(oid asn1.Oid, getter Getter) error
AddRoManagedObject registers a read-only managed object.
func (*Agent) AddRwManagedObject
func (a *Agent) AddRwManagedObject(oid asn1.Oid, getter Getter,
setter Setter) error
AddRwManagedObject registers a read-write managed object.
The inteface{} values returned by a Getter or received by a Setter must be of one of the following types:
int
string
asn1.Null
asn1.Oid
snmp.Counter32
snmp.Counter64
snmp.IpAddress
snmp.Opaque
snmp.TimeTicks
snmp.Unsigned32
func (*Agent) ProcessDatagram
func (a *Agent) ProcessDatagram(requestBytes []byte) (responseBytes []byte, err error)
ProcessDatagram handles a binany SNMP message.
func (*Agent) ProcessMessage
func (a *Agent) ProcessMessage(request *Message) (response *Message, err error)
ProcessMessage handles a SNMP Message.
func (*Agent) SetCommunities
func (a *Agent) SetCommunities(public, private string)
SetCommunities defines the public and private communities.
func (*Agent) SetLogger
func (a *Agent) SetLogger(logger *log.Logger)
SetLogger defines the logger used for internal messages.
type BulkPdu
type BulkPdu struct {
Identifier int
NonRepeaters int
MaxRepetitions int
Variables []Variable
}
BulkPdu is a generic type for other Protocol Data Units.
type Counter32
type Counter32 uint32
Counter32 is a counter type.
type Counter64
type Counter64 uint64
Counter64 is a counter type.
type EndOfMibView
type EndOfMibView asn1.Null
EndOfMibView exception.
func (EndOfMibView) String
func (e EndOfMibView) String() string
type GetBulkRequestPdu
type GetBulkRequestPdu BulkPdu
GetBulkRequestPdu is used for bulk requests.
type GetNextRequestPdu
type GetNextRequestPdu Pdu
GetNextRequestPdu works similarly to GetRequestPdu, but it's returned the value for the next valid Oid.
type GetRequestPdu
type GetRequestPdu Pdu
GetRequestPdu is used to request data.
type GetResponsePdu
type GetResponsePdu Pdu
GetResponsePdu is used in responses to SNMP requests.
type Getter
type Getter func(oid asn1.Oid) (interface{}, error)
Getter is a function called to return a managed object value.
type IPAddress
type IPAddress [4]byte
IPAddress is a IPv4 address.
func (IPAddress) String
func (ip IPAddress) String() string
String returns a representation of IPAddress in dot notation.
type InformRequestPdu
type InformRequestPdu Pdu
InformRequestPdu is used for inform requests.
type Message
type Message struct {
Version int
Community string
Pdu interface{} `asn1:"choice:pdu"`
}
Message is the top level element of the SNMP protocol.
type NoSuchInstance
type NoSuchInstance asn1.Null
NoSuchInstance exception.
func (NoSuchInstance) String
func (e NoSuchInstance) String() string
type NoSuchObject
type NoSuchObject asn1.Null
NoSuchObject exception.
func (NoSuchObject) String
func (e NoSuchObject) String() string
type Opaque
type Opaque []byte
Opaque is a type for blobs.
type Pdu
type Pdu struct {
Identifier int
ErrorStatus int
ErrorIndex int
Variables []Variable
}
Pdu is a generic type for other Protocol Data Units.
type SetRequestPdu
type SetRequestPdu Pdu
SetRequestPdu is used to request data to be updated.
type Setter
type Setter func(oid asn1.Oid, value interface{}) error
Setter is a function called to set a managed object value.
type TimeTicks
type TimeTicks uint32
TimeTicks is a type for time.
type Unsigned32
type Unsigned32 uint32
Unsigned32 is an integer type.
type V1TrapPdu
type V1TrapPdu struct {
Enterprise asn1.Oid
AgentAddr IPAddress
GenericTrap int
SpecificTrap int
Timestamp TimeTicks
Variables []Variable
}
V1TrapPdu is used when sending a trap in SNMPv1.
type V2TrapPdu
type V2TrapPdu Pdu
V2TrapPdu is used when sending a trap in SNMPv2.
type VarError
type VarError struct {
Status int
Message string
}
VarError is an error type that can be returned by a Getter or a Setter. When VarError is returned, it Status is used in the SNMP response.
func VarErrorf
func VarErrorf(status int, format string, values ...interface{}) VarError
VarErrorf creates a new Error with a formatted message.
func (VarError) Error
func (e VarError) Error() string
type Variable
type Variable struct {
Name asn1.Oid
Value interface{} `asn1:"choice:val"`
}
Variable represents an entry of the variable bindings