Cilium is a Kubernetes-native networking, observability, and security solution built on eBPF. It provides CNI plugin functionality with overlay/native routing modes, distributed load balancing (replacing kube-proxy), cluster mesh for multi-cluster connectivity, identity-based network policies (L3-L7), service mesh with mutual authentication, and observability via Hubble (flow metrics, DNS insights). The architecture features a modular design using the Hive dependency injection framework, with components including the cilium-agent daemon, operator for CRD management, CLI tools for management/debugging, and API servers for inter-component communication. The data plane leverages eBPF/XDP for high-performance packet processing, while the control plane integrates deeply with Kubernetes through client-go, controller-runtime, and custom resource definitions.
Yggdrasil is an Envoy control plane that watches Kubernetes ingress resources across multiple clusters and generates dynamic configuration for Envoy proxies. It implements a modular architecture with separate packages for Kubernetes integration (pkg/k8s) and Envoy configuration generation (pkg/envoy). The system uses Kubernetes informers to watch resources, aggregates events from multiple clusters, translates ingress objects into Envoy listeners and clusters, and serves the configuration via xDS gRPC protocol. It also provides metrics and health endpoints for monitoring. The code demonstrates good separation of concerns, proper use of Kubernetes client-go patterns, and clean abstraction for handling multiple Kubernetes API versions.