Kube-proxy doesn't remove stale CNI-HOSTPORT-DNAT rule after Kubernetes upgrade to 1.26

[raelix]

RKE version:

v1.4.6

Docker version: (docker version,docker info preferred)
20.10.24

Operating system and kernel: (cat /etc/os-release, uname -r preferred)
NAME="Red Hat Enterprise Linux"
VERSION="8.6 (Ootpa)"

Type/provider of hosts: (VirtualBox/Bare-metal/AWS/GCE/DO)
Openstack

cluster.yml file:

nodes:
    - address: 10.94.1.8
      internal_address: 172.16.10.53
      ssh_key_path: /home/user/.ssh/id_rsa
      user: user
      role:
        - controlplane
        - etcd
        - worker
ignore_docker_version: true
enable_cri_dockerd: true
cluster_name: mycluster
kubernetes_version: v1.26.4-rancher2-1
network:
  plugin: flannel
ingress:
  provider: nginx

Steps to Reproduce:
Source versions -> rke: v1.4.3 - kubernetes_version: v1.23.10-rancher1-1
Dest versions -> rke: v.1.4.6 - kubernetes_version: v1.26.4-rancher2-1

Trying to upgrade Kubernetes with RKE from v1.23.10 to v1.26.4 I was not able anymore to reach my ingresses through the nginx-ingress-controller which listens on hostPort 80 and 443.

I investigated further and I found that the CNI-HOSTPORT-DNAT Chain had still the old entry.

Before the upgrade:

[root@rancher user]# iptables -t nat -L CNI-HOSTPORT-DNAT  --line-numbers 
Chain CNI-HOSTPORT-DNAT (2 references)
num  target     prot opt source               destination         
1    CNI-DN-ff3905f57536228de6b29  tcp  --  anywhere             anywhere             /* dnat name: "cbr0" id: "e96c642e169acf789be84e8fbcd0e5c3da1a53c8e8a459227c06bdf423deb482" */ multiport dports http,https

[root@rancher user]# iptables -t nat -L CNI-DN-ff3905f57536228de6b29  --line-numbers 
Chain CNI-DN-ff3905f57536228de6b29 (1 references)
num  target     prot opt source               destination         
1    CNI-HOSTPORT-SETMARK  tcp  --  rancher.internal.com/24  anywhere             tcp dpt:http
2    CNI-HOSTPORT-SETMARK  tcp  --  localhost            anywhere             tcp dpt:http
3    DNAT       tcp  --  anywhere             anywhere             tcp dpt:http to:10.42.0.7:80
4    CNI-HOSTPORT-SETMARK  tcp  --  rancher.internal.com/24  anywhere             tcp dpt:https
5    CNI-HOSTPORT-SETMARK  tcp  --  localhost            anywhere             tcp dpt:https
6    DNAT       tcp  --  anywhere             anywhere             tcp dpt:https to:10.42.0.7:443

This looks good.

After the upgrade:

[root@rancher user]# iptables -t nat -L CNI-HOSTPORT-DNAT  --line-numbers 
Chain CNI-HOSTPORT-DNAT (2 references)
num  target     prot opt source               destination         
1    CNI-DN-ff3905f57536228de6b29  tcp  --  anywhere             anywhere             /* dnat name: "cbr0" id: "e96c642e169acf789be84e8fbcd0e5c3da1a53c8e8a459227c06bdf423deb482" */ multiport dports http,https
2    CNI-DN-4c3eba344b3e2fffe3698  tcp  --  anywhere             anywhere             /* dnat name: "cbr0" id: "aa3202e02a9fefbc97400df0685d864bc3894a580d4b2069542621371e1cfde8" */ multiport dports http,https

The second entry is the right one which points to the new pod IP but the first one should not be there.
Looks like kube-proxy doesn't delete the old entry making it impossible to access the ingresses.

As workaround I had to reboot the server or delete manually the entry:
iptables -t nat -D CNI-HOSTPORT-DNAT 1

Results:
After the upgrade can't talk to the ingress controller listening on hostPort.

[manuelbuil]

Thanks for reporting this issue. I'll try to reproduce this. Note that:

• kube-proxy has nothing to do with CNI-HOSTPORT-DNAT chain. That chain is part of the cni plugin: Port-mapping plugin, which gets chained after the default CNI plugin (in your case flannel). You can check this in /etc/cni/net.d/
• What should actually happen is that when the old nginx pod is removed, kubelet must call the CNI plugin with that information: "please remove the networking stuff belonging to this pod". Apart from flannel, port-mapping plugin should get also called and hence remove the rule under CNI-HOSTPORT-DNAT from the old pod.

Can you confirm that after doing the upgrade the old nginx pod is removed?

[raelix]

thanks @manuelbuil , yes it is, the old pod is removed and a new one is started but the entry of the old one is still there.
By deleting again the pod or by removing manually the rule fixes the issue which is a bit weird.

[manuelbuil]

I am not able to reproduce the issue. Could it be that you did a rke remove at some point? I noticed that rke remove does not remove the chains of CNI-HOSTPORT-DNAT

[raelix]

@manuelbuil did you use RHEL 8? I was not able to reproduce on Oracle 9 nor on Ubuntu.
I didn't run rke remove, just rke up

[manuelbuil]

Let me try again with something that might the reason why.

BTW, the upgrade you are trying is not really supported because you are jumping several RKE versions and several minors: https://www.suse.com/support/kb/doc/?id=000020061. We must update the docs to avoid these big jumps

[raelix]

@manuelbuil, good point I also tried one by one but it happened as well (src version 1.23).
What are you going to try? I can also try that if you want.

[raelix]

Here it is the pod removal and re-creation:

kuberuntime_container.go:709] "Killing container with a grace period" pod="ingress-nginx/nginx-ingress-controller-rgm7x" podUID=6b31ab54-f37e-47cb-8b68-fdabef7ac43c containerName="controller" containerID="docker://df269fffce7b55884298f37253df61942a167bbca0686f53186f93283f7ec810" gracePeriod=3000

kubelet.go:2215] "SyncLoop DELETE" source="api" pods="[ingress-nginx/nginx-ingress-controller-rgm7x]"
kubelet.go:2209] "SyncLoop REMOVE" source="api" pods="[ingress-nginx/nginx-ingress-controller-rgm7x]"
kubelet.go:2199] "SyncLoop ADD" source="api" pods="[ingress-nginx/nginx-ingress-controller-rghd5]"
kubelet.go:2303] "SyncLoop (probe)" probe="readiness" status="ready" pod="ingress-nginx/nginx-ingress-controller-rghd5"

[manuelbuil]

Unfortunately, I don't have access right now to a RHEL8 machine but I can't reproduce it on RHEL9. I tried changing a couple of things but I still see the pod being removed correctly. Could you try with a newer RKE version and see if you still get the error?

[raelix]

Thanks @manuelbuil. On RHEL 9 I was not able to reproduce it as well.

I just tested rke 1.4.11 and it doesn't work, I tested then with Calico and the issue is not present I suspect that it could be related to flannel.
Do you have any suggestion in the meantime that I can try? Thanks in advance!

[manuelbuil]

I have just tried on RHEL8 and still can't reproduce it. I think it must be something in your env. Could you check if the old IP is still in /var/lib/cni/networks/cbr0? If that is the case, could check the content of the file with that IP? Perhaps something weird happened and flannel was unable to really remove it. In that case, it is even possible that the network namespace is still there

[manuelbuil]

Are you able to reproduce it constantly or it just happened once?

[manuelbuil]

I kind of remember an issue with very old flannel versions in which sometimes there was a race condition which made flannel "forget" about removing the pods correctly. So the IPs stayed in that directory and the node was exhausting all IPs and was unable to create new pods. Maybe you are hitting that since 1.23 must be using an ancient flannel version

[raelix]

Thanks @manuelbuil , I just checked but the file is not there. This is the result:

After fresh install

[root@redhat-8 cloud-user]# cat /var/lib/cni/networks/cbr0/10.42.0.7 
5da22186031931381f9961358dedf1ad905aab6bfcde3b4c2cf21890f556c2f7

And just one entry in the chain:

iptables -t nat -L CNI-HOSTPORT-DNAT
Chain CNI-HOSTPORT-DNAT (2 references)
target     prot opt source               destination         
CNI-DN-1dfb697df81c370bbec19  tcp  --  anywhere             anywhere             /* dnat name: "cbr0" id: "5da22186031931381f9961358dedf1ad905aab6bfcde3b4c2cf21890f556c2f7" */ multiport dports http,https

After the upgrade

The IP is not anymore there:

[root@redhat-8 cloud-user]# ls -ltria /var/lib/cni/networks/cbr0/*
193123737 -rwxr-x---. 1 root root  0 28 nov 10.09 /var/lib/cni/networks/cbr0/lock
193123763 -rw-r--r--. 1 root root 70 28 nov 10.12 /var/lib/cni/networks/cbr0/10.42.0.8
193123764 -rw-r--r--. 1 root root 70 28 nov 10.12 /var/lib/cni/networks/cbr0/10.42.0.9
193123741 -rw-r--r--. 1 root root 70 28 nov 10.13 /var/lib/cni/networks/cbr0/10.42.0.10
193123739 -rw-r--r--. 1 root root 10 28 nov 10.13 /var/lib/cni/networks/cbr0/last_reserved_ip.0
193123727 -rw-r--r--. 1 root root 70 28 nov 10.13 /var/lib/cni/networks/cbr0/10.42.0.13

The new one is:

[root@redhat-8 cloud-user]# cat /var/lib/cni/networks/cbr0/10.42.0.13
88c0dbed427446618212eefc226917f672178717f1d7b8fa4b290e882d41746e

But now there are two entries in iptables which is causing the issue:

[cloud-user@redhat-8 ~]$ sudo iptables -t nat -L CNI-HOSTPORT-DNAT
Chain CNI-HOSTPORT-DNAT (2 references)
target     prot opt source               destination         
CNI-DN-1dfb697df81c370bbec19  tcp  --  anywhere             anywhere             /* dnat name: "cbr0" id: "5da22186031931381f9961358dedf1ad905aab6bfcde3b4c2cf21890f556c2f7" */ multiport dports http,https
CNI-DN-7a4104b730b66c4894a01  tcp  --  anywhere             anywhere             /* dnat name: "cbr0" id: "88c0dbed427446618212eefc226917f672178717f1d7b8fa4b290e882d41746e" */ multiport dports http,https

Thanks for your help! It's anything else do you suggest me to check? I also tried to change the flannel version from the very beginning by using:

system_images:
  flannel: rancher/mirrored-flannel-flannel:v0.23.0

But didn't help

[raelix]

Are you able to reproduce it constantly or it just happened once?

I'm able to reproduce it constantly unfortunately. Consider that I spawn a VM every time so the machine is brand new. Moreover even if I delete the pod only the last entry is updated, the first one remain there unless I reboot or I remove it manually.