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Inside Hubble: From eBPF Events to Cluster-Wide Network Flows

Hubble lets us see every connection in a Kubernetes cluster by pod name, service, and policy verdict — without a sidecar in any pod. This article dissects the mechanism: Cilium's eBPF datapath (the 74 sched_cls programs from Article 12) calls bpf_perf_event_output to push events into a perf ring buffer named cilium_events; cilium-agent reads them out with numeric identities; then Hubble enriches them — turning identity 18203 into kube-system/coredns — via the identity-to-label store.