func()

in plugins/inputs/snmp/snmp.go [562:672]
90 lines of code
23 McCabe index (conditional complexity)

func (s *Snmp) getConnection(agent string) (snmpConnection, error) {
	if s.connectionCache == nil {
		s.connectionCache = map[string]snmpConnection{}
	}
	if gs, ok := s.connectionCache[agent]; ok {
		return gs, nil
	}

	gs := gosnmpWrapper{&gosnmp.GoSNMP{}}

	host, portStr, err := net.SplitHostPort(agent)
	if err != nil {
		if err, ok := err.(*net.AddrError); !ok || err.Err != "missing port in address" {
			return nil, Errorf(err, "parsing host")
		}
		host = agent
		portStr = "161"
	}
	gs.Target = host

	port, err := strconv.ParseUint(portStr, 10, 16)
	if err != nil {
		return nil, Errorf(err, "parsing port")
	}
	gs.Port = uint16(port)

	gs.Timeout = s.Timeout.Duration

	gs.Retries = s.Retries

	switch s.Version {
	case 3:
		gs.Version = gosnmp.Version3
	case 2, 0:
		gs.Version = gosnmp.Version2c
	case 1:
		gs.Version = gosnmp.Version1
	default:
		return nil, fmt.Errorf("invalid version")
	}

	if s.Version < 3 {
		if s.Community == "" {
			gs.Community = "public"
		} else {
			gs.Community = s.Community
		}
	}

	gs.MaxRepetitions = s.MaxRepetitions

	if s.Version == 3 {
		gs.ContextName = s.ContextName

		sp := &gosnmp.UsmSecurityParameters{}
		gs.SecurityParameters = sp
		gs.SecurityModel = gosnmp.UserSecurityModel

		switch strings.ToLower(s.SecLevel) {
		case "noauthnopriv", "":
			gs.MsgFlags = gosnmp.NoAuthNoPriv
		case "authnopriv":
			gs.MsgFlags = gosnmp.AuthNoPriv
		case "authpriv":
			gs.MsgFlags = gosnmp.AuthPriv
		default:
			return nil, fmt.Errorf("invalid secLevel")
		}

		sp.UserName = s.SecName

		switch strings.ToLower(s.AuthProtocol) {
		case "md5":
			sp.AuthenticationProtocol = gosnmp.MD5
		case "sha":
			sp.AuthenticationProtocol = gosnmp.SHA
		case "":
			sp.AuthenticationProtocol = gosnmp.NoAuth
		default:
			return nil, fmt.Errorf("invalid authProtocol")
		}

		sp.AuthenticationPassphrase = s.AuthPassword

		switch strings.ToLower(s.PrivProtocol) {
		case "des":
			sp.PrivacyProtocol = gosnmp.DES
		case "aes":
			sp.PrivacyProtocol = gosnmp.AES
		case "":
			sp.PrivacyProtocol = gosnmp.NoPriv
		default:
			return nil, fmt.Errorf("invalid privProtocol")
		}

		sp.PrivacyPassphrase = s.PrivPassword

		sp.AuthoritativeEngineID = s.EngineID

		sp.AuthoritativeEngineBoots = s.EngineBoots

		sp.AuthoritativeEngineTime = s.EngineTime
	}

	if err := gs.Connect(); err != nil {
		return nil, Errorf(err, "setting up connection")
	}

	s.connectionCache[agent] = gs
	return gs, nil
}