netobserv

Network Observability secondary interface support

By: Mohamed S. Mahmoud

Network observability for secondary interfaces with Multus and SR-IOV plugins in Kubernetes can be a complex task, but it’s crucial for monitoring and troubleshooting network issues in a Kubernetes cluster.

Overview of how you can achieve network observability for secondary interface

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Multus CNI Plugin: Multus is a CNI (Container Network Interface) plugin for Kubernetes that allows you to attach multiple network interfaces to pods. In Openshift Multus is used to attach SR-IOV vfs to your pods. For reference and more details about Multus CNI please refer to Multus OCP documentation
SR-IOV Plugin: SR-IOV (Single Root I/O Virtualization) is a technology that enables the partitioning of a single PCIe network adapter into multiple virtual functions (VFs). Pods can then use these VFs as secondary network interfaces, achieving higher network performance and isolation. For reference and more details about SR-IOV pls refer to SR-IOV OCP documentation

Network observability eBPF agent enhancements to support the secondary interface

To ensure network observability for secondary interfaces in this setup, and make the eBPF agent network namespace aware, eBPF agents need to implement the following steps:

Using fsNotify Package: Utilize the fsNotify package to be notified when new network namespaces are created. This allows the eBPF agent to keep track of network namespace creation events.
Using netlink Package: Employ the netlink package to register when the network interfaces are created or deleted within each network namespace. This will enable the eBPF agent to monitor the interface changes on a per-namespace basis.
Attach/Detach eBPF TC Hooks: Add support to the eBPF agent to attach and detach eBPF Traffic Control (TC) hook for network interfaces in non-default network namespaces. This step is crucial for monitoring and controlling network traffic within these network namespaces.

Configuring SR-IOV objects

Install the SR-IOV operator in the environment.
Identify the SR-IOV capable device on the node.
Label the node which has SR-IOV interface with the label feature.node.kubernetes.io/network-sriov.capable=true
Create the SriovNetworkNodePolicy object

apiVersion: sriovnetwork.openshift.io/v1
kind: SriovNetworkNodePolicy
metadata:
  name: mypolicy
  namespace: openshift-sriov-network-operator
spec:
  resourceName: netdeviceresource
  nodeSelector:
    feature.node.kubernetes.io/network-sriov.capable: "true"
  priority: 99
  numVfs: 50
  nicSelector:
    pfNames: ["ens7f0np0#25-49"]
  deviceType: netdevice

Create the SriovNetwork object. This will create net-attach-def in the openshift-sriov-network-operator namespace.

apiVersion: sriovnetwork.openshift.io/v1
kind: SriovNetwork
metadata:
  name: sriov-test
  namespace: openshift-sriov-network-operator
spec:
  resourceName: netdeviceresource
  networkNamespace: test
  ipam: '{ "type": "static", "addresses": [{"address": "192.168.122.71/24"}]}'

Create a test pod using the SRIOVNetwork object created above and denoted by annotation, k8s.v1.cni.cncf.io/networks: "sriov-test"

apiVersion: v1
kind: Pod
metadata:
  name: httpd-2
  namespace: openshift-sriov-network-operator
  labels:
    app: sriov
  annotations:
    k8s.v1.cni.cncf.io/networks: "sriov-test"
spec:
  containers:
  - name: httpd
    command: ["sleep", "30d"]
    image: registry.redhat.io/rhel8/support-tools
    ports:
    - containerPort: 8080
    securityContext:
      allowPrivilegeEscalation: false
      seccompProfile:
        type: RuntimeDefault
      capabilities:
        drop:
        - ALL

Configuring the network observability operator to work with SR-IOV

Deploy the network observability operator.
Create the FollowCollector object with privileged set to true.

apiVersion: flows.netobserv.io/v1beta1
kind: FlowCollector
metadata:
  name: cluster
spec:
  agent:
    type: EBPF
    ebpf:
      privileged: true

Network observability operator will deploy it’s components (eBPF agent, flowlogs pipeline and console plugin), the eBPF agent will start discovering all the interfaces and attach the eBPF hooks, flows start being collected

Sample Network observability raw flow output by filtering on Pod VF interface `net1`

By opening the console plugin and looking in the Traffic Flows table and filter by Network interface name == net1 like the following for TCP flow packets as an example