amazon-vpc-cni-k8s
Networking plugin for pod networking in Kubernetes using Elastic Network Interfaces on AWS.
Setup
Download the latest version of the yaml and apply it the cluster.
kubectl apply -f aws-k8s-cni.yaml
Launch kubelet with network plugins set to cni (--network-plugin=cni), the cni directories configured (--cni-config-dir
and --cni-bin-dir) and node ip set to the primary IPv4 address of the primary ENI for the instance
(--node-ip=$(curl http://169.254.169.254/latest/meta-data/local-ipv4)).
It is also recommended to set --max-pods equal to (the number of ENIs for the instance type ×
(the number of IPs per ENI - 1)) + 2; for details, see vpc_ip_resource_limit.go. Setting --max-pods will prevent
scheduling that exceeds the IP address resources available to the kubelet.
The default manifest expects --cni-conf-dir=/etc/cni/net.d and --cni-bin-dir=/opt/cni/bin.
L-IPAM requires following IAM policy:
{
"Effect": "Allow",
"Action": [
"ec2:AssignPrivateIpAddresses",
"ec2:AttachNetworkInterface",
"ec2:CreateNetworkInterface",
"ec2:DeleteNetworkInterface",
"ec2:DescribeInstances",
"ec2:DescribeInstanceTypes",
"ec2:DescribeTags",
"ec2:DescribeNetworkInterfaces",
"ec2:DetachNetworkInterface",
"ec2:ModifyNetworkInterfaceAttribute",
"ec2:UnassignPrivateIpAddresses"
],
"Resource": "*"
},
{
"Effect": "Allow",
"Action": [
"ec2:CreateTags"
],
"Resource": ["arn:aws:ec2:*:*:network-interface/*"]
}
Alternatively there is also a Helm chart: eks/aws-vpc-cni
Building
makedefaults tomake build-linuxthat builds the Linux binaries.unit-test,format,lintandvetprovide ways to run the respective tests/tools and should be run before submitting a PR.make dockerwill create a docker container using the docker-build with the finished binaries, with a tag ofamazon/amazon-k8s-cni:latestmake docker-builduses a docker container (golang:1.13) to build the binaries.make docker-unit-testsuses a docker container (golang:1.13) to run all unit tests.
Components
There are 2 components:
- CNI Plugin, which will wire up host's and pod's network stack when called.
L-IPAMD, which is a long running node-Local IP Address Management (IPAM) daemon, is responsible for:- maintaining a warm-pool of available IP addresses, and
- assigning an IP address to a Pod.
The details can be found in Proposal: CNI plugin for Kubernetes networking over AWS VPC.
Troubleshooting Guide provides tips on how to debug and troubleshoot CNI.
ENI Allocation
When a worker node first joins the cluster, there is only 1 ENI along with all of its addresses in the ENI. Without any
configuration, ipamD always try to keep one extra ENI.
When number of pods running on the node exceeds the number of addresses on a single ENI, the CNI backend start allocating
a new ENI and start using following allocation scheme:
For example, a m4.4xlarge node can have up to 8 ENIs, and each ENI can have up to 30 IP addresses.
(https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html).
- If the number of current running Pods is between 0 to 29, ipamD will allocate one more eni. And Warm-Pool size is 2 eni * (30 -1) = 58
- If the number of current running Pods is between 30 and 58, ipamD will allocate 2 more eni. And Warm-Pool size is 3 eni * (30 -1) = 87
CNI Configuration Variables
The Amazon VPC CNI plugin for Kubernetes supports a number of configuration options, which are set through environment variables.
The following environment variables are available, and all of them are optional.
AWS_VPC_CNI_NODE_PORT_SUPPORT
Type: Boolean
Default: true
Specifies whether NodePort services are enabled on a worker node's primary network interface. This requires additional
iptables rules and that the kernel's reverse path filter on the primary interface is set to loose.
AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG
Type: Boolean
Default: false
Specifies that your pods may use subnets and security groups that are independent of your worker node's VPC configuration.
By default, pods share the same subnet and security groups as the worker node's primary interface. Setting this variable
to true causes ipamD to use the security groups and VPC subnet in a worker node's ENIConfig for elastic network interface
allocation. You must create an ENIConfig custom resource for each subnet that your pods will reside in, and then annotate or
label each worker node to use a specific ENIConfig (multiple worker nodes can be annotated or labelled with the same ENIConfig).
Worker nodes can only be annotated with a single ENIConfig at a time, and the subnet in the ENIConfig must belong to the
same Availability Zone that the worker node resides in.
For more information, see CNI Custom Networking
in the Amazon EKS User Guide.
ENI_CONFIG_ANNOTATION_DEF
Type: String
Default: k8s.amazonaws.com/eniConfig
Specifies node annotation key name. This should be used when AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG=true. Annotation value
will be used to set ENIConfig name. Note that annotations take precedence over labels.
ENI_CONFIG_LABEL_DEF
Type: String
Default: k8s.amazonaws.com/eniConfig
Specifies node label key name. This should be used when AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG=true. Label value will be used
to set ENIConfig name. Note that annotations will take precedence over labels. To use labels ensure annotation with key
k8s.amazonaws.com/eniConfig or defined key (in ENI_CONFIG_ANNOTATION_DEF) is not set on the node.
To select an ENIConfig based upon availability zone set this to failure-domain.beta.kubernetes.io/zone and create an
ENIConfig custom resource for each availability zone (e.g. us-east-1a).
AWS_VPC_ENI_MTU (Since v1.6.0)
Type: Integer
Default: 9001
Used to configure the MTU size for attached ENIs. The valid range is from 576 to 9001.
AWS_VPC_K8S_CNI_EXTERNALSNAT
Type: Boolean
Default: false
Specifies whether an external NAT gateway should be used to provide SNAT of secondary ENI IP addresses. If set to true, the
SNAT iptables rule and off-VPC IP rule are not applied, and these rules are removed if they have already been applied.
Disable SNAT if you need to allow inbound communication to your pods from external VPNs, direct connections, and external VPCs,
and your pods do not need to access the Internet directly via an Internet Gateway. However, your nodes must be running in a
private subnet and connected to the internet through an AWS NAT Gateway or another external NAT device.
AWS_VPC_K8S_CNI_RANDOMIZESNAT
Type: String
Default: hashrandom
Valid Values: hashrandom, prng, none
Specifies weather the SNAT iptables rule should randomize the outgoing ports for connections. This should be used when
AWS_VPC_K8S_CNI_EXTERNALSNAT=false. When enabled (hashrandom) the --random flag will be added to the SNAT iptables
rule. To use pseudo random number generation rather than hash based (i.e. --random-fully) use prng for the environment
variable. For old versions of iptables that do not support --random-fully this option will fall back to --random.
Disable (none) this functionality if you rely on sequential port allocation for outgoing connections.
Note: Any options other than none will cause outbound connections to be assigned a source port that's not necessarily part of the ephemeral port range set at the OS level (/proc/sys/net/ipv4/ip_local_port_range). This is relevant for any customers that might have NACLs restricting traffic based on the port range found in ip_local_port_range
AWS_VPC_K8S_CNI_EXCLUDE_SNAT_CIDRS (Since v1.6.0)
Type: String
Default: empty
Specify a comma separated list of IPv4 CIDRs to exclude from SNAT. For every item in the list an iptables rule and off-VPC
IP rule will be applied. If an item is not a valid ipv4 range it will be skipped. This should be used when AWS_VPC_K8S_CNI_EXTERNALSNAT=false.
WARM_ENI_TARGET
Type: Integer
Default: 1
Specifies the number of free elastic network interfaces (and all of their available IP addresses) that the ipamD daemon should
attempt to keep available for pod assignment on the node. By default, ipamD attempts to keep 1 elastic network interface and all
of its IP addresses available for pod assignment. The number of IP addresses per network interface varies by instance type. For more
information, see IP Addresses Per Network Interface Per Instance Type
in the Amazon EC2 User Guide for Linux Instances.
For example, an m4.4xlarge launches with 1 network interface and 30 IP addresses. If 5 pods are placed on the node and 5 free IP
addresses are removed from the IP address warm pool, then ipamD attempts to allocate more interfaces until WARM_ENI_TARGET free
interfaces are available on the node.
If WARM_IP_TARGET is set, then this environment variable is ignored and the WARM_IP_TARGET behavior is used instead.
WARM_IP_TARGET
Type: Integer
Default: None
Specifies the number of free IP addresses that the ipamD daemon should attempt to keep available for pod assignment on the node.
For example, if WARM_IP_TARGET is set to 5, then ipamD attempts to keep 5 free IP addresses available at all times. If the
elastic network interfaces on the node are unable to provide these free addresses, ipamD attempts to allocate more interfaces
until WARM_IP_TARGET free IP addresses are available.
NOTE! Avoid this setting for large clusters, or if the cluster has high pod churn. Setting it will cause additional calls to the
EC2 API and that might cause throttling of the requests. It is strongly suggested to set MINIMUM_IP_TARGET when using WARM_IP_TARGET.
If both WARM_IP_TARGET and MINIMUM_IP_TARGET are set, ipamD will attempt to meet both constraints.
This environment variable overrides WARM_ENI_TARGET behavior.
MINIMUM_IP_TARGET (Since v1.6.0)
Type: Integer
Default: None
Specifies the number of total IP addresses that the ipamD daemon should attempt to allocate for pod assignment on the node.
MINIMUM_IP_TARGET behaves identically to WARM_IP_TARGET except that instead of setting a target number of free IP
addresses to keep available at all times, it sets a target number for a floor on how many total IP addresses are allocated.
MINIMUM_IP_TARGET is for pre-scaling, WARM_IP_TARGET is for dynamic scaling. For example, suppose a cluster has an
expected pod density of approximately 30 pods per node. If WARM_IP_TARGET is set to 30 to ensure there are enough IPs
allocated up front by the CNI, then 30 pods are deployed to the node, the CNI will allocate an additional 30 IPs, for
a total of 60, accelerating IP exhaustion in the relevant subnets. If instead MINIMUM_IP_TARGET is set to 30 and
WARM_IP_TARGET to 2, after the 30 pods are deployed the CNI would allocate an additional 2 IPs. This still provides
elasticity, but uses roughly half as many IPs as using WARM_IP_TARGET alone (32 IPs vs 60 IPs).
This also improves reliability of the EKS cluster by reducing the number of calls necessary to allocate or deallocate
private IPs, which may be throttled, especially at scaling-related times.
MAX_ENI
Type: Integer
Default: None
Specifies the maximum number of ENIs that will be attached to the node. When MAX_ENI is unset or 0 (or lower), the setting
is not used, and the maximum number of ENIs is always equal to the maximum number for the instance type in question. Even when
MAX_ENI is a positive number, it is limited by the maximum number for the instance type.
AWS_VPC_K8S_CNI_LOGLEVEL
Type: String
Default: DEBUG
Valid Values: trace, debug, info, warn, error, critical or off. (Not case sensitive)
Specifies the loglevel for ipamd.
AWS_VPC_K8S_CNI_LOG_FILE
Type: String
Default: Unset
Valid Values: stdout or a file path
Specifies where to write the logging output. Either to stdout or to override the default file.
INTROSPECTION_BIND_ADDRESS
Type: String
Default: 127.0.0.1:61679
Specifies the bind address for the introspection endpoint.
A Unix Domain Socket can be specified with the unix: prefix before the socket path.
DISABLE_INTROSPECTION
Type: Boolean
Default: false
Specifies whether introspection endpoints are disabled on a worker node. Setting this to true will reduce the debugging
information we can get from the node when running the aws-cni-support.sh script.
DISABLE_METRICS
Type: Boolean
Default: false
Specifies whether the prometheus metrics endpoint is disabled or not for ipamd. By default metrics are published
on :61678/metrics.
AWS_VPC_K8S_CNI_VETHPREFIX
Type: String
Default: eni
Specifies the veth prefix used to generate the host-side veth device name for the CNI. The prefix can be at most 4 characters long.
ADDITIONAL_ENI_TAGS
Type: String
Default: {}
Example values: {"tag_key": "tag_val"}
Metadata applied to ENI help you categorize and organize your resources for billing or other purposes. Each tag consists of a custom-defined key and an optional value. Tag keys can have a maximum character length of 128 characters. Tag values can have a maximum length of 256 characters. These tags will be added to all ENIs on the host.
Important: Custom tags should not contain k8s.amazonaws.com prefix as it is reserved. If the tag has k8s.amazonaws.com string, tag addition will ignored.
CLUSTER_NAME
Type: String
Default: ""
Specifies the cluster name to tag allocated ENIs with. See the "Cluster Name tag" section below.
ENI tags related to Allocation
This plugin interacts with the following tags on ENIs:
cluster.k8s.amazonaws.com/namenode.k8s.amazonaws.com/instance_idnode.k8s.amazonaws.com/no_manage
Cluster Name tag
The tag cluster.k8s.amazonaws.com/name will be set to the cluster name of the
aws-node daemonset which created the ENI.
Instance ID tag
The tag node.k8s.amazonaws.com/instance_id will be set to the instance ID of
the aws-node instance that allocated this ENI.
No Manage tag
The tag node.k8s.amazonaws.com/no_manage is read by the aws-node daemonset to
determine whether an ENI attached to the machine should not be configured or
used for private IPs.
This tag is not set by the cni plugin itself, but rather may be set by a user
to indicate that an ENI is intended for host networking pods, or for some other
process unrelated to Kubernetes.
Note: Attaching an ENI with the no_manage tag will result in an incorrect
value for the Kubelet's --max-pods configuration option. Consider also
updating the MAX_ENI and --max-pods configuration options on this plugin
and the kubelet respectively if you are making use of this tag.
Notes
L-IPAMD(aws-node daemonSet) running on every worker node requires access to kubernetes API server. If it can not reach
kubernetes API server, ipamD will exit and CNI will not be able to get any IP address for Pods. Here is a way to confirm if
L-IPAMD has access to the kubernetes API server.
# find out kubernetes service IP, e.g. 10.0.0.1
kubectl get svc kubernetes
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.0.0.1 <none> 443/TCP 29d
# ssh into worker node, check if worker node can reach API server
telnet 10.0.0.1 443
Trying 10.0.0.1...
Connected to 10.0.0.1.
Escape character is '^]'. <-------- kubernetes API server is reachable
Security disclosures
If you think you’ve found a potential security issue, please do not post it in the Issues. Instead, please follow the
instructions here or email AWS security directly.
