K8s >= 1.21, hostNetwork: true needs to be set for tcp-services and udp-services to work.

[martyav]

Creating an issue based on an internal request.

The documentation outlines that hostNetwork: true is no longer the default for k8s 1.21 and up. However, this will cause problems if you have tcp-services and/or udp-services configured. The documentation should note that hostNetwork: true needs to be set for tcp-services and udp-services to work.

Business impact:

After upgrading to k8s 1.21.x, tcp-services and udp-services stop working.

[martyav]

The original ask points to a docs page in rancher.com/docs/rke

Although we have similar language in https://ranchermanager.docs.rancher.com/how-to-guides/new-user-guides/kubernetes-resources-setup/load-balancer-and-ingress-controller/ingress-configuration#docusaurus_skipToContent_fallback and the corresponding page for 2.6, it's not exactly the same. In any case, none of these pages have a warning about TCP- or UDP-services not being able to run unless hostNetwork is set to true.

Related: I'm not sure if the issue is general or confined to RKE. The problem was validated, on RKE:

• tcp-services-configmap and udp-services-configmap are not applied upon upgrade to k8s version using nginx-0.49.3-rancher1 rancher#35943 (comment)
• tcp-services-configmap and udp-services-configmap are not applied upon upgrade to k8s version using nginx-0.49.3-rancher1 rancher#35943 (comment)

Note: this comment notes that if NetworkMode is set to hostNetwork, the hostNetwork is still set to true: rancher/rancher#35943 (comment)

[martyav]

Related to https://github.com/rancher/docs/issues/3420

As noted in that thread, this affects Rancher 2.6 and above.

[btat]

The source code for rancher.com/docs/rke is currently still in the rancher/docs repo, but as we're about to launch the Docusaurus site for RKE updates for the RKE portion should be made to https://github.com/rancher/rke1-docs instead.