Change:
buf.WriteByte('n') } <del> func openLocalPort(lp *utilproxy.LocalPort) (utilproxy.Closeable, error) { </del> <ins> func openLocalPort(lp *utilproxy.LocalPort, isIPv6 bool) (utilproxy.Closeable, error) { </ins> // For ports on node IPs, open the actual port and hold it, even though we // use iptables to redirect traffic. // This ensures a) that it's safe to use that port and b) that (a) stays

Discussion:
/kind bug What happened: When creating a node port application (in this case the example guestbook) on a host server that is dual stacked and has AAAA and A DNS entries, the node port on the v6 address is open to kube-proxy and hangs. What you expected to happen: The v6 address would refuse the connection and the client would fall back onto the v4 address which would connect correctly. How to reproduce it (as minimally and precisely as possible): kubeadm init with the above, and join in some workers. Then install the guestbook application Obtain the node port with and telnet to one of the servers on that port from a dual stacked client. The client will connect and refuse to respond to 'GET /' telnet directly to the IPv4 address of the server on the port and all works as expected. Anything else we need to know?: kube-proxy is noted as listening on the port. Environment: Kubernetes version (use ): ubuntu kubectl version Client Version: version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.1", GitCommit:"", GitTreeState:"clean", BuildDate:"2018-07-17T18:53:20Z", GoVersion:"go1.10.3", Compiler:"gc", Platform:"linux/amd64"} Server Version: version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.1", GitCommit:"", GitTreeState:"clean", BuildDate:"2018-07-17T18:43:26Z", GoVersion:"go1.10.3", Compiler:"gc", Platform:"linux/amd64"} Cloud provider or hardware configuration: Brightbox OS (e.g. from /etc/os-release): Ubuntu 18.04.1 LTS Kernel (e.g. ): Linux srv-jidtj 4.15.0-29-generic -Ubuntu SMP Tue Jul 17 15:39:52 UTC 2018 x8664 x8664 x86_64 GNU/Linux Install tools: kubeadm 1.11 Others:
/sig network
Looks like kube-proxy in ipvs mode listens on the nodeport ports to ensure they're not in use by something else. It just binds and listens, it doesn't serve requests.

It binds on both ipv4 and ipv6 but never expects to receive connections because the iptables/ipvs rules intercept them, but on ipv4 clusters there is nothing stopping ipv6 connections coming in. The comment there does admit that only a bind is necessary to do this, but doing a full listen just made e2e tests easier. /cc
Issues go stale after 90d of inactivity. Mark the issue as fresh with . Stale issues rot after an additional 30d of inactivity and eventually close. If this issue is safe to close now please do so with . Send feedback to sig-testing, kubernetes/test-infra and/or . /lifecycle stale
Stale issues rot after 30d of inactivity. Mark the issue as fresh with . Rotten issues close after an additional 30d of inactivity. If this issue is safe to close now please do so with . Send feedback to sig-testing, kubernetes/test-infra and/or . /lifecycle rotten
Rotten issues close after 30d of inactivity. Reopen the issue with . Mark the issue as fresh with . Send feedback to sig-testing, kubernetes/test-infra and/or . /close
Closing this issue. <detailsIn response to : Rotten issues close after 30d of inactivity. Reopen the issue with . Mark the issue as fresh with . /close Instructions for interacting with me using PR comments are available . If you have questions or suggestions related to my behavior, please file an issue against the repository. </details
/reopen This now causes conformance failure on e2e tests due to the promotion of the Nodeport test in
Reopened this issue. <detailsIn response to : /reopen Instructions for interacting with me using PR comments are available . If you have questions or suggestions related to my behavior, please file an issue against the repository. </details
Still an issue on 1.16 when running in standard IPv4 mode
As I understand this thread, I have the same problem. I thought that it is a node configuration or some kubernetes flag that I didn't set but it seems it ain't.

I ask already on SO: Environment Kubernetes version (use kubectl version): Client Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.0", GitCommit:"", GitTreeState:"clean", BuildDate:"2019-09-18T14:36:53Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"} Server Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.1", GitCommit:"", GitTreeState:"clean", BuildDate:"2019-10-02T16:51:36Z", GoVersion:"go1.12.10", Compiler:"gc", Platform:"linux/amd64"} Cloud provider or hardware configuration: On premise, on virtual machines using hyper-v OS (e.g. from /etc/os-release): NAME="Ubuntu" VERSION="18.04.3 LTS (Bionic Beaver)" Kernel (e.g. uname -a): Linux kubernetes 5.0.0-29-generic # 31~18.04.1-Ubuntu SMP Thu Sep 12 18:29:21 UTC 2019 x8664 x8664 x86_64 GNU/Linux Install tools: kubeadm version: &version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.0", GitCommit:"", GitTreeState:"clean", BuildDate:"2019-09-18T14:34:01Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"linux/amd64"}
/lifecycle frozen
/assign bowei
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Looking through the comments, this looks like a bug that could have a targeted fix. /remove-triage unresolved /good-first-issue /help-wanted
This request has been marked as suitable for new contributors. Please ensure the request meets the requirements listed . If this request no longer meets these requirements, the label can be removed by commenting with the command. <detailsIn response to : Looking through the comments, this looks like a bug that could have a targeted fix.

/good-first-issue /help-wanted </details
I will attempt to solve this issue.
any success or progress? If you left this issue I would like to give it a go as a first time contributor. Thanks, Yuval
I'm still working on this as my first issue, and planning to produce a solution by 20th.
I wasn't able to tackle the issue and will not continue trying, feel free to take it.
/assign yuvalsteuer
Still, open -- anyone actively working on this? I would like to attempt if not. :) /assign rkc007
OK, again still open, doesn't look like anyone is working on this. I'd like to try it. The fix that occurs to me is simply to only listen to IPv6 addresses if the cluster is IPv6. If the e2e tests fail in this case (from looking at I don't think they will) then maybe they need to be updated. Does that make sense? What I'm not sure about is if we should do nothing with IPv6 ports or bind (to claim the port) but not listen.
/assign michaelbeaumont