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.. _code_overview:

Code Overview

This section provides an overview of the Cilium & Hubble source code directory structure. It is useful to get an initial overview on where to find what.

High-level

Top-level directories github.com/cilium/cilium <https://github.com/cilium/cilium>_:

api The Cilium & Hubble API definition.

bpf The eBPF datapath code

bugtool CLI for collecting agent & system information for bug reporting

cilium Cilium CLI client

contrib, tools Additional tooling and resources used for development

daemon The cilium-agent running on each node

examples Various example resources and manifests. Typically require to be modified before usage is possible.

hubble-relay Hubble Relay server

install Helm deployment manifests for all components

pkg Common Go packages shared between all components

operator Operator responsible for centralized tasks which do not require to be performed on each node.

plugins Plugins to integrate with Kubernetes and Docker

test End-to-end integration tests run in the :ref:testsuite-legacy.

Cilium

api/v1/openapi.yaml API specification of the Cilium API. Used for code generation.

api/v1/models/ Go code generated from openapi.yaml representing all API resources

bpf The eBPF datapath code

cilium Cilium CLI client

cilium-health Cilium cluster connectivity CLI client

daemon cilium-agent specific code

plugins/cilium-cni The CNI plugin to integrate with Kubernetes

plugins/cilium-docker The Docker integration plugin

Hubble

The server-side code of Hubble is integrated into the Cilium repository. The Hubble CLI can be found in the separate repository github.com/cilium/hubble <https://github.com/cilium/hubble>. The Hubble UI can be found in the separate repository github.com/cilium/hubble-ui <https://github.com/cilium/hubble-ui>.

api/v1/external, api/v1/flow, api/v1/observer, api/v1/peer, api/v1/relay API specifications of the Hubble APIs.

hubble-relay Hubble Relay agent

pkg/hubble All Hubble specific code

pkg/hubble/container Ring buffer implementation

pkg/hubble/filters Flow filtering capabilities

pkg/hubble/metrics Metrics plugins providing Prometheus based on Hubble's visibility

pkg/hubble/observe Layer running on top of the Cilium datapath monitoring, feeding the metrics and ring buffer.

pkg/hubble/parser Network flow parsers

pkg/hubble/peer Peer service implementation

pkg/hubble/relay Hubble Relay service implementation

pkg/hubble/server The server providing the API for the Hubble client and UI

Important common packages

pkg/allocator Security identity allocation

pkg/bpf Abstraction layer to interact with the eBPF runtime

pkg/client Go client to access Cilium API

pkg/clustermesh Multi-cluster implementation including control plane and global services

pkg/controller Base controller implementation for any background operation that requires retries or interval-based invocation.

pkg/datapath Abstraction layer for datapath interaction

pkg/defaults All default values

pkg/elf ELF abstraction library for the eBPF loader

pkg/endpoint Abstraction of a Cilium endpoint, representing all workloads.

pkg/endpointmanager Manager of all endpoints

pkg/envoy Envoy proxy interactions

pkg/fqdn FQDN proxy and FQDN policy implementation

pkg/health Network connectivity health checking

pkg/hive A dependency injection framework for modular composition of applications

pkg/identity Representation of a security identity for workloads

pkg/ipam IP address management

pkg/ipcache Global cache mapping IPs to endpoints and security identities

pkg/k8s All interactions with Kubernetes

pkg/kvstore Key-value store abstraction layer with backends for etcd

pkg/labels Base metadata type to describe all label/metadata requirements for workload identity specification and policy matching.

pkg/loadbalancer Control plane for load-balancing functionality

pkg/maps eBPF map representations

pkg/metrics Prometheus metrics implementation

pkg/monitor eBPF datapath monitoring abstraction

pkg/node Representation of a network node

pkg/option All available configuration options

pkg/policy Policy enforcement specification & implementation

pkg/proxy Layer 7 proxy abstraction

pkg/trigger Implementation of trigger functionality to implement event-driven functionality