nixpkgs/nixos/modules/services/cluster/kubernetes/flannel.nix

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{ config, lib, pkgs, ... }:
with lib;
let
top = config.services.kubernetes;
cfg = top.flannel;
# we want flannel to use kubernetes itself as configuration backend, not direct etcd
storageBackend = "kubernetes";
# needed for flannel to pass options to docker
mkDockerOpts = pkgs.runCommand "mk-docker-opts" {
buildInputs = [ pkgs.makeWrapper ];
} ''
mkdir -p $out
# bashInteractive needed for `compgen`
makeWrapper ${pkgs.bashInteractive}/bin/bash $out/mk-docker-opts --add-flags "${pkgs.kubernetes}/bin/mk-docker-opts.sh"
'';
in
{
###### interface
options.services.kubernetes.flannel = {
enable = mkEnableOption "enable flannel networking";
};
###### implementation
config = mkIf cfg.enable {
services.flannel = {
enable = mkDefault true;
network = mkDefault top.clusterCidr;
inherit storageBackend;
nodeName = config.services.kubernetes.kubelet.hostname;
};
services.kubernetes.kubelet = {
networkPlugin = mkDefault "cni";
cni.config = mkDefault [{
name = "mynet";
type = "flannel";
delegate = {
isDefaultGateway = true;
bridge = "docker0";
};
}];
};
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systemd.services.mk-docker-opts = {
description = "Pre-Docker Actions";
path = with pkgs; [ gawk gnugrep ];
script = ''
${mkDockerOpts}/mk-docker-opts -d /run/flannel/docker
systemctl restart docker
'';
serviceConfig.Type = "oneshot";
};
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systemd.paths.flannel-subnet-env = {
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wantedBy = [ "flannel.service" ];
pathConfig = {
PathModified = "/run/flannel/subnet.env";
Unit = "mk-docker-opts.service";
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};
};
systemd.services.docker = {
environment.DOCKER_OPTS = "-b none";
serviceConfig.EnvironmentFile = "-/run/flannel/docker";
};
# read environment variables generated by mk-docker-opts
virtualisation.docker.extraOptions = "$DOCKER_OPTS";
networking = {
firewall.allowedUDPPorts = [
8285 # flannel udp
8472 # flannel vxlan
];
dhcpcd.denyInterfaces = [ "docker*" "flannel*" ];
};
services.kubernetes.pki.certs = {
flannelClient = top.lib.mkCert {
name = "flannel-client";
CN = "flannel-client";
action = "systemctl restart flannel.service";
};
};
# give flannel som kubernetes rbac permissions if applicable
services.kubernetes.addonManager.bootstrapAddons = mkIf ((storageBackend == "kubernetes") && (elem "RBAC" top.apiserver.authorizationMode)) {
flannel-cr = {
apiVersion = "rbac.authorization.k8s.io/v1beta1";
kind = "ClusterRole";
metadata = { name = "flannel"; };
rules = [{
apiGroups = [ "" ];
resources = [ "pods" ];
verbs = [ "get" ];
}
{
apiGroups = [ "" ];
resources = [ "nodes" ];
verbs = [ "list" "watch" ];
}
{
apiGroups = [ "" ];
resources = [ "nodes/status" ];
verbs = [ "patch" ];
}];
};
flannel-crb = {
apiVersion = "rbac.authorization.k8s.io/v1beta1";
kind = "ClusterRoleBinding";
metadata = { name = "flannel"; };
roleRef = {
apiGroup = "rbac.authorization.k8s.io";
kind = "ClusterRole";
name = "flannel";
};
subjects = [{
kind = "User";
name = "flannel-client";
}];
nixos/kubernetes: Stabilize services startup across machines by adding targets and curl wait loops to services to ensure services are not started before their depended services are reachable. Extra targets cfssl-online.target and kube-apiserver-online.target syncronize starts across machines and node-online.target ensures docker is restarted and ready to deploy containers on after flannel has discussed the network cidr with apiserver. Since flannel needs to be started before addon-manager to configure the docker interface, it has to have its own rbac bootstrap service. The curl wait loops within the other services exists to ensure that when starting the service it is able to do its work immediately without clobbering the log about failing conditions. By ensuring kubernetes.target is only reached after starting the cluster it can be used in the tests as a wait condition. In kube-certmgr-bootstrap mkdir is needed for it to not fail to start. The following is the relevant part of systemctl list-dependencies default.target ● ├─certmgr.service ● ├─cfssl.service ● ├─docker.service ● ├─etcd.service ● ├─flannel.service ● ├─kubernetes.target ● │ ├─kube-addon-manager.service ● │ ├─kube-proxy.service ● │ ├─kube-apiserver-online.target ● │ │ ├─flannel-rbac-bootstrap.service ● │ │ ├─kube-apiserver-online.service ● │ │ ├─kube-apiserver.service ● │ │ ├─kube-controller-manager.service ● │ │ └─kube-scheduler.service ● │ └─node-online.target ● │ ├─node-online.service ● │ ├─flannel.target ● │ │ ├─flannel.service ● │ │ └─mk-docker-opts.service ● │ └─kubelet.target ● │ └─kubelet.service ● ├─network-online.target ● │ └─cfssl-online.target ● │ ├─certmgr.service ● │ ├─cfssl-online.service ● │ └─kube-certmgr-bootstrap.service
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};
};
};
}