a self-awareness "interface" for NFT pod

[jayunit100]

The NFT tables pod is susceptible to naughty bhaviour when iptables is installed.

To remediate this, and also, to create a precendent for other service proxy backends, lets:

• add a "SystsemCheck()" or similar implementatino in the NFT backend
• Have it verify that all iptables rules (i.e. see the ones in hack/kind recipe: Coredns cant resolve 10.96.0.1 #12) are empty
• if iptables rules non-empty print continous warnings that are extremely idiot-proof , i.e.
  warning: ip routing may not work properly due to mutliple kernel firewalls !

This will make it really easy for folks struggling w/ the incompatibilities (iptables, legacy iptables, and nft, and so on) to know why loadbalancing rules written by NFT arent getting honored.

[jayunit100]

/assign @hanlins

[jayunit100]

@mcluseau let us know if any details we need to update here

[hanlins]

Had some discussion with @mcluseau, later we might introduce subcommand to-best-fit which selects the best sink backend based on the system check results. Will add some functionality here to check whether the nft requirement is met. In the nft sink, will invoke this backend but won't error out if the system is not compatible. We will leave this flexibility of using nft backend to the users, only leave some logs the potential compatibility issues.

[jayunit100]

make sure those logs are really explicit and repeated periodically :)

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@k8s-triage-robot: Closing this issue.

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues and PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
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/close

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