Network Flow Visibility in Antrea

Table of Contents

• Overview
• Flow Exporter
  • Configuration
  • IPFIX Information Elements (IEs) in a Flow Record
    • IEs from IANA-assigned IE registry
    • IEs from Reverse IANA-assigned IE Registry
    • IEs from Antrea IE Registry
  • Supported capabilities
    • Types of Flows and Associated Information
    • Connection Metrics
• Flow Aggregator
  • Deployment
  • Configuration
  • IPFIX Information Elements (IEs) in an Aggregated Flow Record
    • IEs from IANA-assigned IE registry
    • IEs from Antrea IE Registry
  • Supported capabilities
    • Storage of Flow Records
    • Correlation of Flow Records
    • Aggregation of Flow Records
• Quick deployment
• ELK Flow Collector
  • Purpose
  • About Elastic Stack
  • Deployment Steps
  • Pre-built Dashboards
    • Overview
    • Pod-to-Pod Flows
    • Pod-to-Service Flows
    • Flow Records
    • Node Throughput
    • Network Policy

Overview

Antrea is a Kubernetes network plugin that provides network connectivity and security features for Pod workloads. Considering the scale and dynamism of Kubernetes workloads in a cluster, Network Flow Visibility helps in the management and configuration of Kubernetes resources such as Network Policy, Services, Pods etc., and thereby provides opportunities to enhance the performance and security aspects of Pod workloads.

For visualizing the network flows, Antrea monitors the flows in Linux conntrack module. These flows are converted to flow records, and then flow records are post-processed before they are sent to the configured external flow collector. High-level design is given below:

Flow Exporter

In Antrea, the basic building block for the Network Flow Visibility is the Flow Exporter. Flow Exporter operates within Antrea Agent; it builds and maintains a connection store by polling and dumping flows from conntrack module periodically. Connections from the connection store are exported to the Flow Aggregator Service using the IPFIX protocol, and for this purpose we use the IPFIX exporter process from the go-ipfix library.

Configuration

To enable the Flow Exporter feature at the Antrea Agent, the following config parameters have to be set in the Antrea Agent ConfigMap:

  antrea-agent.conf: |
    # FeatureGates is a map of feature names to bools that enable or disable experimental features.
    featureGates:
    # Enable flowexporter which exports polled conntrack connections as IPFIX flow records from each agent to a configured collector.
      FlowExporter: true
    # Provide the IPFIX collector address as a string with format <HOST>:[<PORT>][:<PROTO>].
    # HOST can either be the DNS name or the IP of the Flow Collector. For example,
    # "flow-aggregator.flow-aggregator.svc" can be provided as a DNS name to connect
    # to the Antrea Flow Aggregator Service. If IP, it can be either IPv4 or IPv6.
    # However, IPv6 address should be wrapped with [].
    # If PORT is empty, we default to 4739, the standard IPFIX port.
    # If no PROTO is given, we consider "tcp" as default. We support "tcp" and "udp"
    # L4 transport protocols.
    #flowCollectorAddr: "flow-aggregator.flow-aggregator.svc:4739:tcp"
    # Provide flow poll interval as a duration string. This determines how often the
    # flow exporter dumps connections from the conntrack module. Flow poll interval
    # should be greater than or equal to 1s (one second).
    # Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
    #flowPollInterval: "5s"
    # Provide the active flow export timeout, which is the timeout after which a flow
    # record is sent to the collector for active flows. Thus, for flows with a continuous
    # stream of packets, a flow record will be exported to the collector once the elapsed
    # time since the last export event is equal to the value of this timeout.
    # Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
    #activeFlowExportTimeout: "60s"
    # Provide the idle flow export timeout, which is the timeout after which a flow
    # record is sent to the collector for idle flows. A flow is considered idle if no
    # packet matching this flow has been observed since the last export event.
    # Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
    #idleFlowExportTimeout: "15s"
    # Enable TLS communication from flow exporter to flow aggregator.
    #enableTLSToFlowAggregator: true

Please note that the default value for flowCollectorAddr is "flow-aggregator.flow-aggregator.svc:4739:tcp", which uses the DNS name of the Flow Aggregator Service, if the Service is deployed with the Name and Namespace set to flow-aggregator. If you deploy the Flow Aggregator Service with a different Name and Namespace, then either use the appropriate DNS name or the Cluster IP of the Service. Please note that the default values for flowPollInterval, activeFlowExportTimeout, and idleFlowExportTimeout parameters are set to 5s, 60s, and 15s, respectively. TLS communication between the Flow Exporter and the Flow Aggregator is enabled by default. Please modify them as per your requirements.

IPFIX Information Elements (IEs) in a Flow Record

There are 34 IPFIX IEs in each exported flow record, which are defined in the IANA-assigned IE registry, the Reverse IANA-assigned IE registry and the Antrea IE registry. The reverse IEs are used to provide bi-directional information about the flow. All the IEs used by the Antrea Flow Exporter are listed below:

IEs from IANA-assigned IE registry

IEs from Reverse IANA-assigned IE Registry

IEs from Antrea IE Registry

Supported capabilities

Types of Flows and Associated Information

Currently, the Flow Exporter feature provides visibility for Pod-to-Pod, Pod-to-Service and Pod-to-External network flows along with the associated statistics such as data throughput (bits per second), packet throughput (packets per second), cumulative byte count and cumulative packet count. Pod-To-Service flow visibility is supported only when Antrea Proxy enabled, which is the case by default starting with Antrea v0.11. In the future, we will enable the support for External-To-Service flows.

Kubernetes information such as Node name, Pod name, Pod Namespace, Service name, NetworkPolicy name and NetworkPolicy Namespace, is added to the flow records. For flow records that are exported from any given Antrea Agent, the Flow Exporter only provides the information of Kubernetes entities that are local to the Antrea Agent. In other words, flow records are only complete for intra-Node flows, but incomplete for inter-Node flows. It is the responsibility of the Flow Aggregator to correlate flows from the source and destination Nodes and produce complete flow records.

Both Flow Exporter and Flow Aggregator are supported in IPv4 clusters, IPv6 clusters and dual-stack clusters.

Connection Metrics

We support following connection metrics as Prometheus metrics that are exposed through Antrea Agent apiserver endpoint: antrea_agent_conntrack_total_connection_count, antrea_agent_conntrack_antrea_connection_count and antrea_agent_conntrack_max_connection_count

Flow Aggregator

Flow Aggregator is deployed as a Kubernetes Service. The main functionality of Flow Aggregator is to store, correlate and aggregate the flow records received from the Flow Exporter of Antrea Agents. More details on the functionality are provided in the Supported Capabilities section.

Flow Aggregator is implemented as IPFIX mediator, which consists of IPFIX Collector Process, IPFIX Intermediate Process and IPFIX Exporter Process. We use the go-ipfix library to implement the Flow Aggregator.

Deployment

To deploy a released version of Flow Aggregator Service, pick a deployment manifest from the list of releases. For any given release <TAG> (e.g. v0.12.0), you can deploy Flow Aggregator as follows:

kubectl apply -f https://github.com/vmware-tanzu/antrea/releases/download/<TAG>/flow-aggregator.yml

To deploy the latest version of Flow Aggregator Service (built from the main branch), use the checked-in deployment yaml:

kubectl apply -f https://raw.githubusercontent.com/vmware-tanzu/antrea/main/build/yamls/flow-aggregator.yml

Configuration

The following configuration parameters have to be provided through the Flow Aggregator ConfigMap. externalFlowCollectorAddr is a mandatory parameter. We provide an example value for this parameter in the following snippet.

flow-aggregator.conf: |
  # Provide the flow collector address as a string with format <IP>:<port>[:<proto>], where proto is tcp or udp.
  # If no L4 transport proto is given, we consider tcp as default.
  externalFlowCollectorAddr: "192.168.86.86:4739:tcp"
  # Provide flow export interval as a duration string. This determines how often the flow aggregator exports flow
  # records to the flow collector.
  # Flow export interval should be greater than or equal to 1s (one second).
  # Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
  #flowExportInterval: 60s
  # Provide the transport protocol for the flow aggregator collecting process, which is tls, tcp or udp.
  #aggregatorTransportProtocol: "tls"
  # Provide DNS name or IP address of flow aggregator for generating TLS certificate. It must match
  # the flowCollectorAddr parameter in the antrea-agent config.    
  #flowAggregatorAddress: "flow-aggregator.flow-aggregator.svc"

Please note that the default values for flowExportInterval, aggregatorTransportProtocol, and flowAggregatorAddress parameters are set to 60s, tls and flow-aggregator.flow-aggregator.svc, respectively. Please make sure that aggregatorTransportProtocol is set to tls and enableTLSToFlowAggregator in agent-agent.conf is set to true to guarantee secure communication works properly. enableTLSToFlowAggregator and aggregatorTransportProtocol must always match, so TLS must either be enabled for both sides or disabled for both sides. Please modify the parameters as per your requirements.

IPFIX Information Elements (IEs) in an Aggregated Flow Record

In addition to IPFIX information elements provided in the above section, the Flow Aggregator adds the following fields to the flow records.

IEs from IANA-assigned IE registry

IEs from Antrea IE Registry

Supported capabilities

Storage of Flow Records

Flow Aggregator stores the received flow records from Antrea Agents in a hash map, where the flow key is 5-tuple of a network connection. 5-tuple consists of Source IP, Destination IP, Source Port, Destination Port and Transport protocol. Therefore, Flow Aggregator maintains one flow record for any given connection, and this flow record gets updated till the connection in the Kubernetes cluster becomes invalid.

Correlation of Flow Records

In the case of inter-Node flows, there are two flow records, one from the source Node, where the flow originates from, and another one from the destination Node, where the destination Pod resides. Both the flow records contain incomplete information as mentioned here. Flow Aggregator provides support for the correlation of the flow records from the source Node and the destination Node, and it exports a single flow record with complete information for both inter-Node and intra-Node flows.

Aggregation of Flow Records

Flow Aggregator aggregates the flow records that belong to a single connection. As part of aggregation, fields such as flow timestamps, flow statistics etc. are updated. For the purpose of updating flow statistics fields, Flow Aggregator introduces the new fields in Antrea Enterprise IPFIX registry corresponding to the Source Node and Destination Node, so that flow statistics from different Nodes can be preserved.

Quick deployment

If you would like to quickly try Network Flow Visibility feature, you can deploy Antrea and the Flow Aggregator Service with the required configuration on a vagrant setup. You can use the following command:

./infra/vagrant/push_antrea.sh -fc <externalFlowCollectorAddr>

For example, the address of ELK Flow Collector can be provided as externalFlowCollectorAddr after successfully following the steps given in here.

ELK Flow Collector

Purpose

Antrea supports sending IPFIX flow records through the Flow Exporter feature described above. The Elastic Stack (ELK Stack) works as the data collector, data storage and visualization tool for flow records and flow-related information. This document provides the guidelines for deploying Elastic Stack with support for Antrea-specific IPFIX fields in a Kubernetes cluster.

About Elastic Stack

Elastic Stack is a group of open source products to help collect, store, search, analyze and visualize data in real time. We will use Logstash, Elasticsearch and Kibana in Antrea flow visualization. Logstash works as data collector to centralize flow records. Logstash Netflow codec plugin supports Netflow v5/v9/v10(IPFIX) protocols for flow data collection. The flow exporter feature in Antrea Agent uses the IPFIX (Netflow v10) protocol to export flow records.

Elasticsearch, as a RESTful search engine, supports storing, searching and indexing records received. Kibana is mainly for data visualization and exploration.

Deployment Steps

First step is to fetch the necessary resources from the Antrea repository. You can either clone the entire repo or download the particular folder using the subversion (svn) utility. If the deployed version of Antrea has a release <TAG> (e.g. v0.10.0), then you can use the following command:

git clone --depth 1 --branch <TAG> https://github.com/vmware-tanzu/antrea.git && cd antrea/build/yamls/
or
svn export https://github.com/vmware-tanzu/antrea/tags/<TAG>/build/yamls/elk-flow-collector/

If the deployed version of Antrea is the latest version, i.e., built from the main branch, then you can use the following command:

git clone --depth 1 --branch main https://github.com/vmware-tanzu/antrea.git && cd antrea/build/yamls/
or
svn export https://github.com/vmware-tanzu/antrea/trunk/build/yamls/elk-flow-collector/

To configure the export interval as flowExportInterval in Configuration, modify the interval value (in seconds) in elk-flow-collector/logstash/logstash.conf

script_params => { "interval" => 60 }

To create the required K8s resources in the elk-flow-collector folder and get everything up-and-running, run following commands:

kubectl create namespace elk-flow-collector
kubectl create configmap logstash-configmap -n elk-flow-collector --from-file=./elk-flow-collector/logstash/
kubectl apply -f ./elk-flow-collector/elk-flow-collector.yml -n elk-flow-collector

Kibana dashboard is exposed as a Nodeport Service, which can be accessed via http://[NodeIP]: 30007

elk-flow-collector/kibana.ndjson is an auto-generated reusable file containing pre-built objects for visualizing Pod-to-Pod, Pod-to-Service and Node-to-Node flow records. To import the dashboards into Kibana, go to Management -> Saved Objects and import elk-flow-collector/kibana.ndjson.

Pre-built Dashboards

The following dashboards are pre-built and are recommended for Antrea flow visualization.

Overview

An overview of Pod-based flow records information is provided.

Pod-to-Pod Flows

Pod-to-Pod Tx and Rx traffic is shown in sankey diagrams. Corresponding source or destination Pod throughput is visualized using line graph.

Pod-to-Service Flows

Pod-to-Service traffic is presented similar to Pod-to-Pod traffic. Corresponding source or destination IP addresses is shown in tooltips.

Aggregated Tx and Rx traffic based on destination Service is shown in line graph.

Flow Records

Flow Records dashboard shows the raw flow records over time with support for filters.

Node Throughput

Node Throughput dashboard shows the visualization of inter-Node and intra-Node traffic by aggregating all the Pod traffic per Node.

We also present aggregated Tx and Rx Mbps by Node in heatmap to give a better overview of Node bandwidth consumption.

Network Policy

Network Policy dashboard provides filters over ingress network policy name and namespace, egress network policy name and namespace to view corresponding flow throughput under network policy. Flows are grouped by egress network policies (source) and ingress network policies (destination) in the sankey diagram. When hovering over the flow, it will show corresponding Pod-to-Pod traffic details and network policies.

With filters applied: