Development Setup


You need to have the following tools available in order to effectively contribute to Cilium:

Dependency Version / Commit ID Download Command
git latest N/A (OS-specific)
clang >= 10.0 (latest recommended) N/A (OS-specific)
llvm >= 10.0 (latest recommended) N/A (OS-specific)
libelf-devel latest N/A (OS-specific)
go 1.15.15 N/A (OS-specific)
ginkgo >= 1.4.0 go get -u
gomega >= 1.2.0 go get -u
golangci-lint >= v1.27
Docker OS-Dependent N/A (OS-specific)
Docker-Compose OS-Dependent N/A (OS-specific)
python3-pip latest N/A (OS-specific)

For Unit Testing, you will need to run docker without privileges. You can usually achieve this by adding your current user to the docker group.

Finally, in order to run Cilium locally on VMs, you need:

Dependency Version / Commit ID Download Command
Vagrant >= 2.0 Vagrant Install Instructions
VirtualBox (if not using libvirt) >= 5.2 N/A (OS-specific)

You should start with the Getting Started Guides, which walks you through the set-up, such as installing Vagrant, getting the Cilium sources, and going through some Cilium basics.

Vagrant Setup

While the Getting Started Guides uses a Vagrantfile tuned for the basic walk through, the setup for the Vagrantfile in the root of the Cilium tree depends on a number of environment variables and network setup that are managed via contrib/vagrant/

Using the provided Vagrantfile

To bring up a Vagrant VM with Cilium plus dependencies installed, run:

$ contrib/vagrant/ [vm_name]

This will create and run a vagrant VM based on the base box cilium/ubuntu. The vm_name argument is optional and allows you to add new nodes to an existing cluster. For example, to add a net-next VM to a one-node cluster:

$ NWORKERS=1 NETNEXT=1 ./contrib/vagrant/ k8s2+

The box is currently available for the following providers:

  • virtualbox


The following environment variables can be set to customize the VMs brought up by vagrant:

  • NWORKERS=n: Number of child nodes you want to start with the master, default 0.
  • RELOAD=1: Issue a vagrant reload instead of vagrant up, useful to resume halted VMs.
  • NO_PROVISION=1: Avoid provisioning Cilium inside the VM. Supports quick restart without recompiling all of Cilium.
  • K8S=1: Build & install kubernetes on the nodes. k8s1 is the master node, which contains both master components: etcd, kube-controller-manager, kube-scheduler, kube-apiserver, and node components: kubelet, kube-proxy, kubectl and Cilium. When used in combination with NWORKERS=1 a second node is created, where k8s2 will be a kubernetes node, which contains: kubelet, kube-proxy, kubectl and cilium.
  • NETNEXT=1: Run with net-next kernel.
  • IPV4=1: Run Cilium with IPv4 enabled.
  • RUNTIME=x: Sets up the container runtime to be used inside a kubernetes cluster. Valid options are: docker, containerd and crio. If not set, it defaults to docker.
  • VAGRANT_DEFAULT_PROVIDER={virtualbox \| libvirt \| ...}
  • VM_SET_PROXY= Sets up VM’s https_proxy.
  • INSTALL=1: Restarts the installation of Cilium, Kubernetes, etc. Only useful when the installation was interrupted.
  • MAKECLEAN=1: Execute make clean before building cilium in the VM.
  • NO_BUILD=1: Does not run the “build” provision step in the VM. Assumes the developer had previously executed make build before provisioning the VM.
  • SHARE_PARENT: Share the parent of your Cilium directory instead. This requires your Cilium directory to be named cilium, but will also make all other files and folders in the parent directory available for the VM. This is useful to share all the cilium repos to the VM, for example.
  • USER_MOUNTS: Additional mounts for the VM in a comma-separated list of mount specifications. Each mount specification can be simply a directory name relative to the home directory, or include a ‘=’ character separating the destination mount point from the host directory. For example:
    • USER_MOUNTS=foo
      • Mounts host directory ~/foo as /home/vagrant/foo
    • USER_MOUNTS=foo,/tmp/bar=/tmp/bar
      • Mounts host directory ~/foo as /home/vagrant/foo in the VM, and host directory /tmp/bar as /tmp/bar in the VM.
  • VM_MEMORY: Memory in megabytes to configure for the VMs (default 4096).
  • VM_CPUS: Number of CPUs to configure for the VMs (default 2).

If you want to start the VM with cilium enabled with containerd, with kubernetes installed and plus a worker, run:

$ RUNTIME=containerd K8S=1 NWORKERS=1 contrib/vagrant/

If you want to get VM status, run:

$ RUNTIME=containerd K8S=1 NWORKERS=1 vagrant status

If you want to connect to the Kubernetes cluster running inside the developer VM via kubectl from your host machine, set KUBECONFIG environment variable to include new kubeconfig file:


and add k8s1 to your hosts file.

If you have any issue with the provided vagrant box cilium/ubuntu or need a different box format, you may build the box yourself using the packer scripts

Launch CI VMs

The test directory also contains a Vagrantfile that can be used to bring up the CI VM images that will cache a Vagrant box locally (in test/.vagrant/ that prepulls all the docker images needed for the CI tests. Unfortunately some of the options are different from the main Vagrantfile, for example:

  • K8S_NODES determines the total number of k8s nodes, including the master. - NWORKERS is not supported.
  • USER_MOUNTS is not available.

To start a local k8s 1.18 cluster with one CI VM locally, run:

$ cd test
$ K8S_VERSION=1.18 K8S_NODES=1 ./

This will first destroy any CI VMs you may have running on the current K8S_VERSION, and then create a local Vagrant box if not already created. This can take some time.

VM preloading can be turned off by exporting VM_PRELOAD=false. You can run make clean in tests to delete the cached vagrant box.

To start the CI runtime VM locally, run:

$ cd test
$ ./

The runtime VM is connected to the same private VirtualBox network as the local CI k8s nodes.

The runtime VM uses the same cached box as the k8s nodes, but does not start K8s, but runs Cilium as a systemd service.

Manual Installation

Alternatively you can import the vagrant box cilium/ubuntu directly and manually install Cilium:

$ vagrant init cilium/ubuntu
$ vagrant up
$ vagrant ssh [...]
$ go get
$ cd go/src/
$ make
$ sudo make install
$ sudo mkdir -p /etc/sysconfig/
$ sudo cp contrib/systemd/cilium.service /etc/systemd/system/
$ sudo cp contrib/systemd/cilium-docker.service /etc/systemd/system/
$ sudo cp contrib/systemd/cilium-consul.service /etc/systemd/system/
$ sudo cp contrib/systemd/cilium  /etc/sysconfig/cilium
$ sudo usermod -a -G cilium vagrant
$ sudo systemctl enable cilium-docker
$ sudo systemctl restart cilium-docker
$ sudo systemctl enable cilium-consul
$ sudo systemctl restart cilium-consul
$ sudo systemctl enable cilium
$ sudo systemctl restart cilium


Your Cilium tree is mapped to the VM so that you do not need to keep manually copying files between your host and the VM. Folders are by default synced automatically using VirtualBox Shared Folders with NFS. Note that your host firewall must have a variety of ports open. The Vagrantfile will inform you of the configuration of these addresses and ports to enable NFS.


OSX file system is by default case insensitive, which can confuse git. At the writing of this Cilium repo has no file names that would be considered referring to the same file on a case insensitive file system. Regardless, it may be useful to create a disk image with a case sensitive file system for holding your git repos.


VirtualBox for OSX currently (version 5.1.22) always reports host-only networks’ prefix length as 64. Cilium needs this prefix to be 16, and the startup script will check for this. This check always fails when using VirtualBox on OSX, but it is safe to let the startup script to reset the prefix length to 16.


Make sure your host NFS configuration is setup to use tcp:

# cat /etc/nfs.conf
# grace-time=90
# vers2=n
# vers3=y

If for some reason, running of the provisioning script fails, you should bring the VM down before trying again:

$ vagrant halt

Local Development in Vagrant Box

See Development Setup for information on how to setup the development environment.

When the development VM is provisioned, it builds and installs Cilium. After the initial build and install you can do further building and testing incrementally inside the VM. vagrant ssh takes you to the Cilium source tree directory (/home/vagrant/go/src/ by default, and the following commands assume that you are working within that directory.

Build Cilium

When you make changes, the tree is automatically kept in sync via NFS. You can issue a build as follows:

$ make

Install to dev environment

After a successful build and test you can re-install Cilium by:

$ sudo -E make install

Restart Cilium service

To run the newly installed version of Cilium, restart the service:

$ sudo systemctl restart cilium

You can verify the service and cilium-agent status by the following commands, respectively:

$ sudo systemctl status cilium
$ cilium status

Making Changes

  1. Create a topic branch: git checkout -b myBranch master
  2. Make the changes you want
  3. Separate the changes into logical commits.
    1. Describe the changes in the commit messages. Focus on answering the question why the change is required and document anything that might be unexpected.
    2. If any description is required to understand your code changes, then those instructions should be code comments instead of statements in the commit description.
  4. Make sure your changes meet the following criteria:
    1. New code is covered by Unit Testing.
    2. End to end integration / runtime tests have been extended or added. If not required, mention in the commit message what existing test covers the new code.
    3. Follow-up commits are squashed together nicely. Commits should separate logical chunks of code and not represent a chronological list of changes.
  5. Run git diff --check to catch obvious white space violations
  6. Run make to build your changes. This will also run make lint and error out on any golang linting errors. The rules are configured in .golangci.yaml
  7. See Unit Testing on how to run unit tests.
  8. See End-To-End Testing Framework for information how to run the end to end integration tests
  9. If you are making documentation changes, you can generate documentation files and serve them locally on http://localhost:9081 by running make render-docs. This make target works both inside and outside the Vagrant VM, assuming that docker is running in the environment.

Add/update a golang dependency

Let’s assume we want to add version v0.5.2:

$ go get
$ go mod tidy
$ go mod vendor
$ git add go.mod go.sum vendor/

For a first run, it can take a while as it will download all dependencies to your local cache but the remaining runs will be faster.

Updating k8s is a special case which requires updating the client-go library first and then the remaining dependencies:

  1. Clone
  2. Add the new remote fork: git remote add origin-cilium
  3. Fetch all branches from the remote fork git fetch origin-cilium
  4. Checkout to the release that we are updating git fetch origin --tags && git checkout kubernetes-1.19.0
  5. Create a new branch git checkout -b kubernetes-1.19.0-with-hot-fix
  6. Cherry pick the patches that are not merged upstream from the older branches, there are currently 2 patches not merged upstream: git cherry-pick kubernetes-1.18.5-with-hot-fix^ kubernetes-1.18.5-with-hot-fix
  7. Push the new branch to the remote fork git push origin-cilium kubernetes-1.19.0-with-hot-fix
  8. Save the commit SHA of the kubernetes-1.19.0-with-hot-fix branch to use it in the next step.

After updating the client-go fork, update the commit SHA in the replace directive of the go.mod file for the client-go library in the Cilium repository.

At the same time, update the tags of the Kubernetes libraries:

$ # get the tag we are updating (for example ``v0.17.3`` corresponds to k8s ``v1.17.3``)
$ # open go.mod and search and replace all ``v0.17.3`` with the version
$ # that we are trying to upgrade with, for example: ``v0.17.4``.
$ # Close the file and run:
$ go mod tidy
$ go mod vendor
$ make generate-k8s-api
$ git add go.mod go.sum vendor/

Add/update a new Kubernetes version

Let’s assume we want to add a new Kubernetes version v1.19.0:

  1. Follow the above instructions to update the Kubernetes libraries.
  2. Follow the next instructions depending on if it is a minor update or a patch update.

Minor version

  1. Check if it is possible to remove the last supported Kubernetes version from Kubernetes Compatibility, Requirements, Testing matrix, Running Kubernetes Tests, and add the new Kubernetes version to that list.
  2. If the minimal supported version changed, leave a note in the upgrade guide stating the minimal supported Kubernetes version.
  3. If the minimal supported version changed, search over the code, more likely under pkg/k8s, if there is code that can be removed which specifically exists for the compatibility of the previous Kubernetes minimal version supported.
  4. If the minimal supported version changed, update the field MinimalVersionConstraint in pkg/k8s/version/version.go
  5. Sync all “slim” types by following the instructions in pkg/k8s/slim/
  6. If necessary, update the coredns files from contrib/vagrant/deployments with newer versions.
  7. Open all files in the jenkinsfiles/ directory, and bump all versions being tested. More important is to make sure the pipeline used on all PRs is running with the new Kubernetes version by default. Make sure the files contributing/testing/{ci,e2e.rst} are up to date with these changes.
  8. Update the Kubernetes version with the newer version in test/Vagrantfile, test/test_suite_test.go and test/
  9. Update the constraint in the function getK8sSupportedConstraints, that exists in the test/helpers/utils.go, with the new Kubernetes version that Cilium supports.
  10. Add the new version in test/provision/, if it is an RC install it using binaries.
  11. Add the new coredns files specific for the Kubernetes version, for 1.19 is test/provision/manifest/1.19.
  12. Bump the Kubernetes version in contrib/vagrant/scripts/helpers.bash
  13. Submit all your changes into a new PR.

Patch version

  1. Bump the Kubernetes version in contrib/vagrant/scripts/helpers.bash
  2. Submit all your changes into a new PR.

Optional: Docker and IPv6

Note that these instructions are useful to you if you care about having IPv6 addresses for your Docker containers.

If you’d like IPv6 addresses, you will need to follow these steps:

  1. Edit /etc/docker/daemon.json and set the ipv6 key to true.
  "ipv6": true

If that doesn’t work alone, try assigning a fixed range. Many people have reported trouble with IPv6 and Docker. Source here.

  "ipv6": true,
  "fixed-cidr-v6": "2001:db8:1::/64"

And then:

ip -6 route add 2001:db8:1::/64 dev docker0
sysctl net.ipv6.conf.default.forwarding=1
sysctl net.ipv6.conf.all.forwarding=1
  1. Restart the docker daemon to pick up the new configuration.
  2. The new command for creating a network managed by Cilium:
$ docker network create --ipv6 --driver cilium --ipam-driver cilium cilium-net

Now new containers will have an IPv6 address assigned to them.


Datapath code

The tool cilium monitor can also be used to retrieve debugging information from the eBPF based datapath. Debugging messages are sent if either the cilium-agent itself or the respective endpoint is in debug mode. The debug mode of the agent can be enabled by starting cilium-agent with the option --debug enabled or by running cilium config debug=true for an already running agent. Debugging of an individual endpoint can be enabled by running cilium endpoint config ID debug=true. Running cilium monitor -v will print the normal form of monitor output along with debug messages:

$ cilium endpoint config 731 debug=true
Endpoint 731 configuration updated successfully
$ cilium monitor -v
Press Ctrl-C to quit
level=info msg="Initializing dissection cache..." subsys=monitor
<- endpoint 745 flow 0x6851276 identity 4->0 state new ifindex 0 orig-ip 8e:3c:a3:67:cc:1e -> 16:f9:cd:dc:87:e5 ARP
-> lxc_health: 16:f9:cd:dc:87:e5 -> 8e:3c:a3:67:cc:1e ARP
CPU 00: MARK 0xbbe3d555 FROM 0 DEBUG: Inheriting identity=1 from stack
<- host flow 0xbbe3d555 identity 1->0 state new ifindex 0 orig-ip -> tcp ACK
CPU 00: MARK 0xbbe3d555 FROM 0 DEBUG: Successfully mapped addr= to identity=1
CPU 00: MARK 0xbbe3d555 FROM 0 DEBUG: Attempting local delivery for container id 745 from seclabel 1
CPU 00: MARK 0xbbe3d555 FROM 745 DEBUG: Conntrack lookup 1/2: src= dst=
CPU 00: MARK 0xbbe3d555 FROM 745 DEBUG: Conntrack lookup 2/2: nexthdr=6 flags=0
CPU 00: MARK 0xbbe3d555 FROM 745 DEBUG: CT entry found lifetime=21925, revnat=0
CPU 00: MARK 0xbbe3d555 FROM 745 DEBUG: CT verdict: Established, revnat=0
-> endpoint 745 flow 0xbbe3d555 identity 1->4 state established ifindex lxc_health orig-ip -> tcp ACK

Passing -v -v supports deeper detail, for example:

$ cilium endpoint config 3978 debug=true
Endpoint 3978 configuration updated successfully
$ cilium monitor -v -v --hex
Listening for events on 2 CPUs with 64x4096 of shared memory
Press Ctrl-C to quit
CPU 00: MARK 0x1c56d86c FROM 3978 DEBUG: 70 bytes Incoming packet from container ifindex 85
00000000  33 33 00 00 00 02 ae 45  75 73 11 04 86 dd 60 00  |33.....Eus....`.|
00000010  00 00 00 10 3a ff fe 80  00 00 00 00 00 00 ac 45  |....:..........E|
00000020  75 ff fe 73 11 04 ff 02  00 00 00 00 00 00 00 00  |u..s............|
00000030  00 00 00 00 00 02 85 00  15 b4 00 00 00 00 01 01  |................|
00000040  ae 45 75 73 11 04 00 00  00 00 00 00              |.Eus........|
CPU 00: MARK 0x1c56d86c FROM 3978 DEBUG: Handling ICMPv6 type=133
CPU 00: MARK 0x1c56d86c FROM 3978 Packet dropped 131 (Invalid destination mac) 70 bytes ifindex=0 284->0
00000000  33 33 00 00 00 02 ae 45  75 73 11 04 86 dd 60 00  |33.....Eus....`.|
00000010  00 00 00 10 3a ff fe 80  00 00 00 00 00 00 ac 45  |....:..........E|
00000020  75 ff fe 73 11 04 ff 02  00 00 00 00 00 00 00 00  |u..s............|
00000030  00 00 00 00 00 02 85 00  15 b4 00 00 00 00 01 01  |................|
00000040  00 00 00 00                                       |....|
CPU 00: MARK 0x7dc2b704 FROM 3978 DEBUG: 86 bytes Incoming packet from container ifindex 85
00000000  33 33 ff 00 8a d6 ae 45  75 73 11 04 86 dd 60 00  |33.....Eus....`.|
00000010  00 00 00 20 3a ff fe 80  00 00 00 00 00 00 ac 45  |... :..........E|
00000020  75 ff fe 73 11 04 ff 02  00 00 00 00 00 00 00 00  |u..s............|
00000030  00 01 ff 00 8a d6 87 00  20 40 00 00 00 00 fd 02  |........ @......|
00000040  00 00 00 00 00 00 c0 a8  21 0b 00 00 8a d6 01 01  |........!.......|
00000050  ae 45 75 73 11 04 00 00  00 00 00 00              |.Eus........|
CPU 00: MARK 0x7dc2b704 FROM 3978 DEBUG: Handling ICMPv6 type=135
CPU 00: MARK 0x7dc2b704 FROM 3978 DEBUG: ICMPv6 neighbour soliciation for address b21a8c0:d68a0000

One of the most common issues when developing datapath code is that the eBPF code cannot be loaded into the kernel. This frequently manifests as the endpoints appearing in the “not-ready” state and never switching out of it:

$ cilium endpoint list
ENDPOINT   POLICY        IDENTITY   LABELS (source:key[=value])   IPv6                     IPv4            STATUS
48896      Disabled      266        container:id.server           fd02::c0a8:210b:0:bf00     not-ready
60670      Disabled      267        container:id.client           fd02::c0a8:210b:0:ecfe   not-ready

Running cilium endpoint get for one of the endpoints will provide a description of known state about it, which includes eBPF verification logs.

The files under /var/run/cilium/state provide context about how the eBPF datapath is managed and set up. The .h files describe specific configurations used for eBPF program compilation. The numbered directories describe endpoint-specific state, including header configuration files and eBPF binaries.

Current eBPF map state for particular programs is held under /sys/fs/bpf/, and the bpf-map utility can be useful for debugging what is going on inside them, for example:

# ls /sys/fs/bpf/tc/globals/
cilium_calls_15124  cilium_calls_48896        cilium_ct4_global       cilium_lb4_rr_seq       cilium_lb6_services  cilium_policy_25729  cilium_policy_60670       cilium_proxy6
cilium_calls_25729  cilium_calls_60670        cilium_ct6_global       cilium_lb4_services     cilium_lxc           cilium_policy_3978   cilium_policy_reserved_1  cilium_reserved_policy
cilium_calls_3978   cilium_calls_netdev_ns_1  cilium_events           cilium_lb6_reverse_nat  cilium_policy        cilium_policy_4314   cilium_policy_reserved_2  cilium_tunnel_map
cilium_calls_4314   cilium_calls_overlay_2    cilium_lb4_reverse_nat  cilium_lb6_rr_seq       cilium_policy_15124  cilium_policy_48896  cilium_proxy4
# bpf-map info /sys/fs/bpf/tc/globals/cilium_policy_15124
Type:           Hash
Key size:       8
Value size:     24
Max entries:    1024
Flags:          0x0
# bpf-map dump /sys/fs/bpf/tc/globals/cilium_policy_15124
00000000  6a 01 00 00 82 23 06 00                           |j....#..|
00000000  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000010  00 00 00 00 00 00 00 00                           |........|