Architecture

This section explains key components, data structures and relationships between them.

Key components

Provider

Abstraction of cloud provider, responsible for detecting network type and creating Network.

Network

Cloud-specific container network. A Network should configure all resources that the diagnosis progress needs, including Plugin, Diagnostor, InfraShim, etc.

Diagnostor

Implementation of the diagnosis algorithm. It generates the initial links and nodes on source NetNode by executing Send action, and continuously generates new links and nodes by executing Receive action on later added NetNode, until the entire graph has been constructed.

Plugin

Network plugin(flannel, calico, etc.). It creates the actual NetNode from the network config and return NetNodeAction.

NetNodeManager

Create and cache NetNodeAction. It collects Kubernetes pod/node netstack info from CollectorManager, and create NetNodeAction from Plugin.

CollectorManager

Manage collect tasks, which collect netstack info of Kubernetes pod/nodes.

IPCache

Cache major Kubernetes objects used by diagnosis, to prevent redundant access to the API Server.

NetNodeAction

An interface represents the network action of a NetNode. It should be implemented by any NetNode type.

InfraShim

Assertions of infra resources. Should be implemented by cloud providers.

service.Processor

The component stands for a service processor (like kube-proxy). It gets the backends of a service, and check its configuration in from netstack info.

(Package)assertions

Assertion utilities for diagnosis. Including NetstackAssertion and KubernetesAssertion.

(Package)netstack

Components and utilities of the Linux netstack. Including Router, Netfilter, IPTables, etc.

Key structures

Context

type Context struct {
    Ctx *sync.Map
}

Context is used to store runtime configurations. It is responsible for binding flags for modules and providing interfaces for registration.

Endpoint

type Endpoint struct {
   IP   string
   Type EndpointType
   Port uint16
}

Endpoint for the network layer, including IP, Port and Type.

Packet

type Packet struct {
    Src      net.IP
    Sport    uint16
    Dst      net.IP
    Dport    uint16
    Protocol Protocol
    Encap    *Packet
    Mark     uint32
}

A data packet.

• Encap: If the packet is an encapsuled packet (such as an IPIP packet), the real packet is in this field.

• Mark: Used in router and iptables simulation.

NetNode

type NetNode struct {
   Type       NetNodeType
   ID         string
   Actions    map[*Link]*Action
   Suspicions []Suspicion
   initiative *Action
}

Node in the network graph. It can be Pod or Node in Kubernetes, or can also be a network resources on the cloud. NetNode implements NetNodeAction for handle network traffic, and Assertion for storing assertions.

Transmission

type Transmission struct {
   NextHop Hop
   Link    *Link
}

A transmit operation created by Send() or Receive() action of a NetNode. It contains NextHop pointing to the next NetNode, and Link to describe the transmission info.

Hop

type Hop struct {
   Type NetNodeType
   ID   string
}

Information for a hop, used to find a NetNode.

Link

type Link struct {
   Type                 LinkType
   Source               NetNodeAction
   Destination          NetNodeAction
   Packet               *Packet
   SourceAttribute      LinkAttribute
   DestinationAttribute LinkAttribute

   Level int // for print
}

type LinkAttribute interface {
   GetAttrs() map[string]string
}

The link between two nodes.

• Type: Contains external, vpc, veth, ipvlan, local, and more.

• SourceAttribute&DestinationAttribute: The key-value attributes of this link on source and destination nodes.

k8s.Pod

type PodMeta struct {
    Namespace   string
    PodName     string
    NodeName    string
    HostNetwork bool
}

type Pod struct {
    model.NetNode
    netstack.NetNS
    PodMeta
}

Information for a Pod of Kubernetes. Includes Pod's metadata and netstack info.

k8s.NodeInfo

type NodeInfo struct {
    netstack.NetNS
    SubNetNSInfo []netstack.NetNSInfo
    NodeMeta
}

type NodeNetworkStackDump struct {
    Pods  []PodNetInfo         `json:"pods"`
    Netns []netstack.NetNSInfo `json:"netns"`
}

type NodeMeta struct {
    NodeName string
}

Information for a Node of Kubernetes. Includes Node's metadata and netstack info of node and pods on it.

Suspicion

type Suspicion struct {
   Level   SuspicionLevel
   Message string
}

The problem occurred on a NetNode.

• Level: Severity of the problem. Contains Info, Warning, Critical and Fatal.

• Message: Problem description.