gosnmp
GoSNMP is an SNMP client library fully written in Go. It provides Get, GetNext, GetBulk, Walk, BulkWalk, Set and Traps. It supports IPv4 and IPv6, using SNMPv1, SNMPv2c or SNMPv3. Builds are tested against linux/amd64 and linux/386.
About
gosnmp was started by Andreas Louca, then completely rewritten by Sonia Hamilton (2012-2020), and now ownership has been transferred to the community at gosnmp/gosnmp.
For support and help, join us in the #snmp channel of Gophers Slack.
Overview
GoSNMP has the following SNMP functions:
- Get (single or multiple OIDs)
- GetNext
- GetBulk (SNMPv2c and SNMPv3 only)
- Walk - retrieves a subtree of values using GETNEXT.
- BulkWalk - retrieves a subtree of values using GETBULK (SNMPv2c and SNMPv3 only).
- Set - supports Integers and OctetStrings.
- SendTrap - send SNMP TRAPs.
- Listen - act as an NMS for receiving TRAPs.
GoSNMP has the following helper functions:
- ToBigInt - treat returned values as
*big.Int - Partition - facilitates dividing up large slices of OIDs
gosnmp/gosnmp has completely diverged from alouca/gosnmp, your code will require modification in these (and other) locations:
- the Get function has a different method signature
- the NewGoSNMP function has been removed, use Connect instead (see Usage below).
Connectuses theGoSNMPstruct;gosnmp.Defaultis provided for you to build on. - GoSNMP no longer relies on alouca/gologger - you can use your logger if it conforms to the
gosnmp.Loggerinterface; otherwise debugging will be discarded (/dev/null).
type Logger interface {
Print(v ...interface{})
Printf(format string, v ...interface{})
}
Installation
go get github.com/gosnmp/gosnmp
Documentation
https://pkg.go.dev/github.com/gosnmp/gosnmp
Usage
Here is examples/example/main.go, demonstrating how to use GoSNMP:
// Default is a pointer to a GoSNMP struct that contains sensible defaults
// eg port 161, community public, etc
g.Default.Target = "192.168.1.10"
err := g.Default.Connect()
if err != nil {
log.Fatalf("Connect() err: %v", err)
}
defer g.Default.Conn.Close()
oids := []string{"1.3.6.1.2.1.1.4.0", "1.3.6.1.2.1.1.7.0"}
result, err2 := g.Default.Get(oids) // Get() accepts up to g.MAX_OIDS
if err2 != nil {
log.Fatalf("Get() err: %v", err2)
}
for i, variable := range result.Variables {
fmt.Printf("%d: oid: %s ", i, variable.Name)
// the Value of each variable returned by Get() implements
// interface{}. You could do a type switch...
switch variable.Type {
case g.OctetString:
bytes := variable.Value.([]byte)
fmt.Printf("string: %s\n", string(bytes))
default:
// ... or often you're just interested in numeric values.
// ToBigInt() will return the Value as a BigInt, for plugging
// into your calculations.
fmt.Printf("number: %d\n", g.ToBigInt(variable.Value))
}
}
Running this example gives the following output (from my printer):
% go run example.go
0: oid: 1.3.6.1.2.1.1.4.0 string: Administrator
1: oid: 1.3.6.1.2.1.1.7.0 number: 104
examples/example2.gois similar toexample.go, however it uses a custom&GoSNMPrather thang.Defaultexamples/walkexample.godemonstrates usingBulkWalkexamples/example3.godemonstratesSNMPv3examples/trapserver.godemonstrates writing an SNMP v2c trap server
MIB Parser
I don't have any plans to write a mib parser. Others have suggested https://github.com/sleepinggenius2/gosmi
Contributions
Contributions are welcome, especially ones that have packet captures (see below).
If you've never contributed to a Go project before, here is an example workflow.
- fork this repo on the GitHub webpage
go get github.com/gosnmp/gosnmpcd $GOPATH/src/github.com/gosnmp/gosnmpgit remote rename origin upstreamgit remote add origin [email protected]:<your-github-username>/gosnmp.gitgit checkout -b developmentgit push -u origin development(setup where you push to, check it works)
Packet Captures
Create your packet captures in the following way:
Expected output, obtained via an snmp command. For example:
% snmpget -On -v2c -c public 203.50.251.17 1.3.6.1.2.1.1.7.0 \
1.3.6.1.2.1.2.2.1.2.6 1.3.6.1.2.1.2.2.1.5.3
.1.3.6.1.2.1.1.7.0 = INTEGER: 78
.1.3.6.1.2.1.2.2.1.2.6 = STRING: GigabitEthernet0
.1.3.6.1.2.1.2.2.1.5.3 = Gauge32: 4294967295
A packet capture, obtained while running the snmpget. For example:
sudo tcpdump -s 0 -i eth0 -w foo.pcap host 203.50.251.17 and port 161
Bugs
Rane's document SNMP: Simple? Network Management Protocol was useful when learning the SNMP protocol.
Please create an issue on Github with packet captures (upload capture to Google Drive, Dropbox, or similar) containing samples of missing BER types, or of any other bugs you find. If possible, please include 2 or 3 examples of the missing/faulty BER type.
The following BER types have been implemented:
- 0x00 UnknownType
- 0x01 Boolean
- 0x02 Integer
- 0x03 BitString
- 0x04 OctetString
- 0x05 Null
- 0x06 ObjectIdentifier
- 0x07 ObjectDescription
- 0x40 IPAddress (IPv4 & IPv6)
- 0x41 Counter32
- 0x42 Gauge32
- 0x43 TimeTicks
- 0x44 Opaque (Float & Double)
- 0x45 NsapAddress
- 0x46 Counter64
- 0x47 Uinteger32
- 0x78 OpaqueFloat
- 0x79 OpaqueDouble
- 0x80 NoSuchObject
- 0x81 NoSuchInstance
- 0x82 EndOfMibView
Running the Tests
Local testing in Docker
docker build -t gosnmp/gosnmp:latest .
docker run -it gosnmp/gosnmp:latest
or
export GOSNMP_TARGET=1.2.3.4
export GOSNMP_PORT=161
export GOSNMP_TARGET_IPV4=1.2.3.4
export GOSNMP_PORT_IPV4=161
export GOSNMP_TARGET_IPV6='0:0:0:0:0:ffff:102:304'
export GOSNMP_PORT_IPV6=161
go test -v -tags all # for example
go test -v -tags helper # for example
Tests are grouped as follows:
- Unit tests (validating data packing and marshalling):
marshal_test.gomisc_test.go
- Public API consistency tests:
gosnmp_api_test.go
- End-to-end integration tests:
generic_e2e_test.go
The generic end-to-end integration test generic_e2e_test.go should work against any SNMP MIB-2 compliant host (e.g. a router, NAS box, printer).
Mocks were generated using:
mockgen -source=interface.go -destination=mocks/gosnmp_mock.go -package=mocks
However they're currently removed, as they were breaking linting.
To profile cpu usage:
go test -cpuprofile cpu.out
go test -c
go tool pprof gosnmp.test cpu.out
To profile memory usage:
go test -memprofile mem.out
go test -c
go tool pprof gosnmp.test mem.out
To check test coverage:
go get github.com/axw/gocov/gocov
go get github.com/matm/gocov-html
gocov test github.com/gosnmp/gosnmp | gocov-html > gosnmp.html && firefox gosnmp.html &
License
Parts of the code are taken from the Golang project (specifically some functions for unmarshaling BER responses), which are under the same terms and conditions as the Go language. The rest of the code is under a BSD license.
See the LICENSE file for more details.
The remaining code is Copyright 2012 the GoSNMP Authors - see AUTHORS.md for a list of authors.
