SRIOV CNI Plugin

The Single Root I/O Virtualization (SR-IOV) specification is a standard for a type of PCI device assignment that can share a single device with multiple pods. 

SR-IOV enables you to segment a compliant network device, recognized on the host node as a physical function (PF), into multiple virtual functions (VFs), and make them available for direct IO to the POD.

This plugin enables the configuration and usage of SR-IOV VF networks in containers and orchestrators like Kubernetes. 

Network Interface Cards (NICs) with SR-IOV capabilities are managed through physical functions (PFs) and virtual functions (VFs). A PF is used by the host and usually represents a single NIC port. VF configurations are applied through the PF. With SR-IOV CNI each VF can be treated as a separate network interface, assigned to a container, and configured with it's own MAC, VLAN, IP and more.

SR-IOV CNI plugin works with SR-IOV device plugin for VF allocation in Kubernetes. A metaplugin such as Multus gets the allocated VF's deviceID(PCI address) and is responsible for invoking the SR-IOV CNI plugin with that deviceID.

The end result will be similar to the in the picture except for the SRIOV-CNI and the DPDK userspace.

Reference:

https://github.com/ramanujadasu/sriov-cni

https://dramasamy.medium.com/high-performance-containerized-applications-in-kubernetes-f494cef3f8e8

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Understanding the Kubernetes Node

Kubernetes is an open-source orchestration engine for automating deployments, scaling, managing, and providing the infrastructure to host containerized applications. At the infrastructure level, a Kubernetes cluster is comprised of a set of physical or virtual machines, each acting in a specific role.

Master components are responsible for managing the Kubernetes cluster. They manage the life cycle of pods, the base unit of a deployment within a Kubernetes cluster. Master servers run the following components:

kube-apiserver – the main component, exposing APIs for the other master components.

etcd – distributed key/value store which Kubernetes uses for persistent storage of all cluster information.

kube-scheduler – uses information in the pod spec to decide on which node to run a pod.

kube-controller-manager – responsible for node management (detecting if a node fails), pod replication, and endpoint creation.

cloud-controller-manager – daemon acting like an abstraction layer between the APIs and the different cloud providers’ tools (storage volumes, load balancers etc.)

Node components are worker machines in Kubernetes and are managed by the Master. A node may be a virtual machine (VM) or physical machine, and Kubernetes runs equally well on both types of systems. Each node contains the necessary components to run pods:

kubelet – watches the API server for pods on that node and makes sure they are running

cAdvisor – collects metrics about pods running on that particular node

kube-proxy – watches the API server for pods/services changes in order to maintain the network up to date

container runtime – responsible for managing container images and running containers on that node

Reference:

https://www.suse.com/c/rancher_blog/understanding-the-kubernetes-node/#:~:text=kubelet%20%E2%80%93%20watches%20the%20API%20server,the%20network%20up%20to%20date

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TCPDUMP useful commands for debugging

How to Install tcpdump in Linux:

$ sudo apt-get install tcpdump  [On Debian, Ubuntu and Mint]

$ sudo yum install tcpdump           [On RHEL/CentOS/Fedora and Rocky Linux/AlmaLinux]

$ sudo emerge -a sys-apps/tcpdump    [On Gentoo Linux]

$ sudo pacman -S tcpdump             [On Arch Linux]

$ sudo zypper install tcpdump        [On OpenSUSE]    

Useful scenarios: 

Capture Packets from Specific Interface: tcpdump -i eth0

Capture Only N Number of Packets: tcpdump -c 5 -i eth0

Print Captured Packets in ASCII: tcpdump -A -i eth0

Display Available Interfaces: tcpdump -D

Display Captured Packets in HEX and ASCII: tcpdump -XX -i eth0

Capture and Save Packets in a File: tcpdump -w 0001.pcap -i eth0

Read Captured Packets File: tcpdump -r 0001.pcap

Capture IP Address Packets: tcpdump -n -i eth0

Capture only TCP Packets: tcpdump -i eth0 tcp

Capture Packet from Specific Port: tcpdump -i eth0 port 22

Capture Packets from source IP: tcpdump -i eth0 src 192.168.0.2

Capture Packets from destination IP: tcpdump -i eth0 dst 50.116.66.139

Reference: 

https://www.tecmint.com/12-tcpdump-commands-a-network-sniffer-tool/,

https://www.brianstorti.com/tcp-flow-control/,

https://www.researchgate.net/figure/TCPDump-Overview-shows-the-TCP-IP-Characteristics-flow-7_fig1_326419957

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