feat(NLB): Introduce Service annotation to allow ICMP for Path MTU Discovery

[chriswachira]

Issue

#3897

Description

It might be necessary for some environments to allow Path MTU discovery for negotiation of MTU between two hosts. If a receiving host has a smaller MTU than the sending host, the receiving host sends an ICMP message to instruct the sending host to split the payload into multiple smaller packets and retransmit them:

• Destination Unreachable: Fragmentation Needed and Don't Fragment was Set (Type 3, Code 4) for IPv4 networks.
• ICMPv6 Packet Too Big (PTB) (Type 2) for IPv6 networks.

This work introduces a Service annotation (below) that when configured, will automatically add a security group rule to the managed security group, depending on the IP address type.

service.beta.kubernetes.io/aws-load-balancer-enable-icmp-for-path-mtu-discovery: "on"

 

For IPv4 VPCs, an explicit rule is added to the managed security group to allow ICMPv4 Type 3 Code 4.

 

For dual stack VPCs, an explicit rule is added to the managed security group to allow both ICMPv4 Type 3 Code 4 and ICMPv6 Type 2 Code 0.

 

If the service.beta.kubernetes.io/load-balancer-source-ranges annotation is also present, it will also create an explicit rule for each source range.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

Hi @chriswachira. Thanks for your PR.

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[zac-nixon]

the sample is incorrect, we need to surround the boolean value with quotes:

        service.beta.kubernetes.io/aws-load-balancer-enable-icmp-for-path-mtu-discovery: "on"

otherwise we get this error:

error: unable to decode "/Users/nixozach/echoserver/svc.yaml": json: cannot unmarshal bool into Go struct field ObjectMeta.metadata.annotations of type string

[chriswachira]

I've made this fix, kindly test.

[zac-nixon]

Seems that once the rules are added, they can't be removed using:

service.beta.kubernetes.io/aws-load-balancer-enable-icmp-for-path-mtu-discovery: "off"

[chriswachira]

I've added a check to make sure it only adds the security group rules if the annotation value is "on", kindly test.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: chriswachira, zac-nixon
Once this PR has been reviewed and has the lgtm label, please assign oliviassss for approval. For more information see the Kubernetes Code Review Process.

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[shraddhabang]

/ok-to-test

[chriswachira]

/retest