For application pods in the Istio service mesh, all traffic to/from the pods needs to go through the sidecar proxies (istio-proxy containers). This istio-cni CNI plugin PoC will set up the pods' networking to fullfill this requirement in place of the current Istio injected pod initContainers istio-init approach.

This is currently accomplished (for IPv4) via configuring the iptables rules in the netns for the pods.

The CNI handling the netns setup replaces the current Istio approach using a NET_ADMIN privileged initContainers container, istio-init, injected in the pods along with istio-proxy sidecars. This removes the need for a privileged, NET_ADMIN container in the Istio users' application pods.

The proposed Istio pod network controller has the problem of synchronizing the netns setup with the rest of the pod init. This approach requires implementing custom synchronization between the controller and pod initialization.

Kubernetes has already solved this problem by not starting any containers in new pods until the full CNI plugin chain has completed successfully. Also, architecturally, the CNI plugins are the components responsible for network setup for container runtimes.

The following are the steps to install and use the CNI plugin.

1. clone this repo

2. Install Istio control-plane

3. Modify istio-cni.yaml

   1. set CNI_CONF_NAME to the filename for your k8s cluster's CNI config file in /etc/cni/net.d
   2. set exclude_namespaces to include the namespace the Istio control-plane is installed in
   3. set cni_bin_dir to your kubernetes install's CNI bin location (the value of kubelet's --cni-bin-dir)
      1. default is /opt/cni/bin

4. Install istio-cni: kubectl apply -f deployments/kubernetes/install/manifests/istio-cni.yaml

5. remove the initContainers section from the result of helm template's rendering of istio/templates/sidecar-injector-configmap.yaml and apply it to replace the istio-sidecar-injector configmap. --e.g. pull the istio-sidecar-injector configmap from istio.yaml and remove the initContainers section and kubectl apply -f <configmap.yaml>

   1. restart the istio-sidecar-injector pod via kubectl delete pod ...

6. With auto-sidecar injection, the init containers will no longer be added to the pods and the CNI will be the component setting the iptables up for the pods.

Not all hosted Kubernetes clusters are created with the kubelet configured to use the CNI plugin so compatibility with this istio-cni solution is not ubiquitous. The istio-cni plugin is expected to work with any hosted kubernetes leveraging CNI plugins. The below table indicates the known CNI status of hosted Kubernetes environments and whether istio-cni has been trialed in the cluster type.

1. Enable network-policy in your cluster. NOTE: for existing clusters this redeploys the nodes.

2. Make sure your kubectl user (service-account) has a ClusterRoleBinding to the cluster-admin role. This is also a typical pre-requisite for installing Istio on GKE.

   1. kubectl create clusterrolebinding cni-cluster-admin-binding --clusterrole=cluster-admin [email protected]
      1. User [email protected] is an admin user associated with the gcloud GKE cluster

3. Install istio-cni: kubectl apply -f deployments/kubernetes/install/manifests/istio-cni_gke.yaml

4. Install Istio

5. remove the initContainers section from the result of helm template's rendering of istio/templates/sidecar-injector-configmap.yaml and apply it to replace the istio-sidecar-injector configmap. --e.g. pull the istio-sidecar-injector configmap from istio.yaml and remove the initContainers section and kubectl apply -f <configmap.yaml>

   1. restart the istio-sidecar-injector pod via kubectl delete pod ...

6. With auto-sidecar injection, the init containers will no longer be added to the pods and the CNI will be the component setting the iptables up for the pods.

For linux targets:

$ GOOS=linux make build
$ export HUB=docker.io/tiswanso
$ export TAG=dev
$ GOOS=linux make docker.push

NOTE: Set HUB and TAG per your docker registry.

TODOs

• Figure out any CNI version specific semantics.
• Add plugin parameters for included/exclude IP CIDRs
• Add plugin parameters for proxy params, ie. listen port, UID, etc.
• Make istio-cni.yaml into a helm chart

• istio-cni.yaml

  • manifest for deploying install-cni container as daemonset
  • istio-cni-config configmap with CNI plugin config to add to CNI plugin chained config
  • creates service-account istio-cni with ClusterRoleBinding to allow gets on pods' info

• install-cni container

  • copies istio-cni binary and istio-iptables.sh to /opt/cni/bin
  • creates kubeconfig for the service account the pod is run under
  • injects the CNI plugin config to the config file pointed to by CNI_CONF_NAME env var
    • example: CNI_CONF_NAME: 10-calico.conflist
    • jq is used to insert CNI_NETWORK_CONFIG into the plugins list in /etc/cni/net.d/${CNI_CONF_NAME}

• istio-cni

  • CNI plugin executable copied to /opt/cni/bin
  • currently implemented for k8s only
  • on pod add, determines whether pod should have netns setup to redirect to Istio proxy
    • if so, calls istio-iptables.sh with params to setup pod netns

• istio-iptables.sh

  • direct copy of Istio's [istio-iptables.sh0(https://github.com/istio/istio/blob/master/tools/deb/istio-iptables.sh)
  • sets up iptables to redirect a list of ports to the port envoy will listen

The framework for this implementation of the CNI plugin is based on the containernetworking sample plugin.

The Istio makefiles and container build logic was leveraged heavily/lifted for this repo.

Specifically:

• golang build logic
• multi-arch target logic
• k8s lib versions (Gopkg.toml)
• docker container build logic
  • setup staging dir for docker build
  • grab built executables from target dir and cp to staging dir for docker build
  • tagging and push logic

The details for the deployment & installation of this plugin were pretty much lifted directly from the Calico CNI plugin.

Specifically:

• CNI installation script
  • This does the following
    • sets up CNI conf in /host/etc/cni/net.d/*
    • copies calico CNI binaries to /host/opt/cni/bin
    • builds kubeconfig for CNI plugin from service-account info mounted in the pod: https://github.com/projectcalico/cni-plugin/blob/master/k8s-install/scripts/install-cni.sh#L142
    • reference: https://kubernetes.io/docs/reference/access-authn-authz/service-accounts-admin/
• The CNI installation script is containerized and deployed as a daemonset in k8s. The relevant calico k8s manifests were used as the model for the istio-cni plugin's manifest:
  • daemonset and configmap
    • search for the calico-node Daemonset and its install-cni container deployment
  • RBAC
    • this creates the service account the CNI plugin is configured to use to access the kube-api-server

The installation script install-cni.sh injects the istio-cni plugin config at the end of the CNI plugin chain config. It creates or modifies the file from the configmap created by the Kubernetes manifest.

Workflow:

1. Check k8s pod namespace against exclusion list (plugin config)
   1. Config must exclude namespace that Istio control-plane is installed in
   2. if excluded, ignore the pod and return prevResult
2. Get k8s pod info
   1. determine containerPort list
3. Determine if the pod needs to be setup for Istio sidecar proxy
   1. if pod has a container named istio-proxy AND pod has more than 1 container
      1. Final Logic TBD -- e.g. pod labels? namespace checks?
4. Setup iptables with the required port list
   1. nsenter --net=<k8s pod netns> /opt/cni/bin/istio-iptables.sh ...
5. Return prevResult

TBD istioctl / auto-sidecar-inject logic for handling things like specific include/exclude IPs and any other features.

• Watch configmaps or CRDs and update the istio-cni plugin's config with these options.

Anything needed? The netns is destroyed by kubelet so ideally this is a NOOP.

The plugin leverages logrus & directly utilizes some Calico logging lib util functions.