[Filebeat] udp input metrics - indicate when system_packet_drops is unavailable

[andrewkroh]

Describe the enhancement:

For the UDP input metrics, make it clear when the data is invalid. The availability of these two metrics depends on the host:

• system_packet_drops
• receive_queue_length

My suggestion is to report the values as -1 at initialization or after any error.

Describe a specific use case for the enhancement or feature:

A system_packet_drops value of 0 is a indicator of health, but if zero is being reported because of a collection failure (or because we are on Windows), then we have a false sense of the current state. When troubleshooting I need to know if the metric is valid.

References

• https://github.com/elastic/beats/blob/c70d2d8ce0c990de16528fcfae812a44a23ba435/filebeat/input/netmetrics/udp.go#L69C1-L70C67

[elasticmachine]

Pinging @elastic/sec-deployment-and-devices (Team:Security-Deployment and Devices)