nf_conntrack_max too small in EKS AMI

[Raoni Timo de Castro Cambiaghi]

The default net.netfilter.nf_conntrack_max value is not sufficient for cloud servers, EKS nodes specifically. Large deployments will see the error message "nf_conntrack: table full, dropping packet".

My suggestion is to set it to a larger default value (bottlerocket uses 1048576 - 1M) and add 'nf_conntrack' to /etc/modules.

See following references:
https://bugs.launchpad.net/cloud-images/+bug/2060001
https://www.dzombak.com/blog/2024/03/Setting-net-netfilter-nf-conntrack-max-on-Ubuntu-22-04.html
https://tuyencbq.wordpress.com/2018/05/19/persisting-nf_conntrack_max-across-reboots/
https://bugs.launchpad.net/charm-nova-compute/+bug/1922778 with the fix: https://review.opendev.org/c/openstack/charm-nova-compute/+/915910.

[Jess Jang (jessica-youjeong)]

EKS images with serial 20240506 or newer have default nf_conntrack_max value as 1048576.