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snmp.go
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snmp.go
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package snmp
import (
"context"
"fmt"
"math"
"math/big"
"strings"
"time"
"github.com/csmith/goplum"
"github.com/gosnmp/gosnmp"
)
type Plugin struct{}
func (p Plugin) Alert(kind string) goplum.Alert {
return nil
}
func (p Plugin) Check(kind string) goplum.Check {
switch kind {
case "string":
return StringCheck{
BaseCheck: BaseCheck{
Community: "public",
Port: 161,
},
ContentExpected: true,
}
case "int":
return IntCheck{
BaseCheck: BaseCheck{
Community: "public",
Port: 161,
},
AtLeast: math.MinInt64,
AtMost: math.MaxInt64,
}
default:
return nil
}
}
type BaseCheck struct {
Agent string
Port int
Community string
Oid []string
client *gosnmp.GoSNMP
}
func (b BaseCheck) Validate() error {
if len(b.Agent) == 0 {
return fmt.Errorf("missing required argument: agent")
}
if b.Port <= 0 || b.Port > 65535 {
return fmt.Errorf("invalid argument: port")
}
if len(b.Community) == 0 {
return fmt.Errorf("missing required argument: community")
}
if len(b.Oid) == 0 {
return fmt.Errorf("missing required argument: oid")
}
return nil
}
func (b BaseCheck) retrieve() (*gosnmp.SnmpPacket, error) {
if b.client == nil {
b.client = &gosnmp.GoSNMP{
Target: b.Agent,
Port: uint16(b.Port),
Transport: "udp",
Community: b.Community,
Version: gosnmp.Version2c,
Timeout: time.Duration(5) * time.Second,
Retries: 3,
ExponentialTimeout: true,
MaxOids: gosnmp.MaxOids,
}
if err := b.client.Connect(); err != nil {
b.client = nil
return nil, err
}
}
return b.client.Get(b.Oid)
}
type StringCheck struct {
BaseCheck `config:",squash"`
Content string
ContentExpected bool `config:"content_expected"`
}
func (s StringCheck) Execute(ctx context.Context) goplum.Result {
packet, err := s.BaseCheck.retrieve()
if err != nil {
return goplum.FailingResult("SNMP failed: %v", err)
}
for i := range packet.Variables {
variable := packet.Variables[i]
if variable.Type == gosnmp.OctetString {
c := variable.Value.(string)
found := strings.Contains(c, s.Content)
if found && !s.ContentExpected {
return goplum.FailingResult("OID %s contained content %s", variable.Name, s.Content)
} else if !found && s.ContentExpected {
return goplum.FailingResult("OID %s did not contain content %s", variable.Name, s.Content)
}
} else {
return goplum.FailingResult("OID did not return a string: %s", variable.Name)
}
}
return goplum.GoodResult()
}
func (s StringCheck) Validate() error {
return s.BaseCheck.Validate()
}
type IntCheck struct {
BaseCheck `config:",squash"`
AtLeast int64 `config:"at_least"`
AtMost int64 `config:"at_most"`
}
func (c IntCheck) Execute(ctx context.Context) goplum.Result {
packet, err := c.BaseCheck.retrieve()
if err != nil {
return goplum.FailingResult("SNMP failed: %v", err)
}
for i := range packet.Variables {
variable := packet.Variables[i]
val := gosnmp.ToBigInt(variable.Value)
if val.Cmp(big.NewInt(c.AtLeast)) == -1 {
return goplum.FailingResult("OID %s returned %d, must be at least %d", variable.Name, val, c.AtLeast)
} else if val.Cmp(big.NewInt(c.AtMost)) == 1 {
return goplum.FailingResult("OID %s returned %d, must be at most %d", variable.Name, val, c.AtMost)
}
}
return goplum.GoodResult()
}
func (c IntCheck) Validate() error {
return c.BaseCheck.Validate()
}