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:

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 End-To-End Testing Framework.

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. The Hubble UI can be found in the separate repository 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/default

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/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/kafka

Kafka protocol proxy and policy implementation

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/service

Representation of a load-balancing service

pkg/trigger

Implementation of trigger functionality to implement event-driven functionality