Add an option to limit the rate of logged messages

[LionelCons]

The default logging of incoming packets comes from:

    'INPUT-log_discarded':
      order   => '97',
      content => "log prefix \"${sprintf($_log_prefix_discard, { 'chain' => 'INPUT' })}\" flags all counter";

This contains no rate limiting so this opens the door to DoS attacks.

All the rules that log something should use rate limiting, at least via an option.

[keachi]

That's a good point. Rate limit the logging via an option would be my preferred way. The default could then be enabled, but it should be possible to disable it.

[nbarrientos]

Yeah, it makes sense. What about this as default?

limit rate 3/minute burst 5 

of a parameter in nftables, say nftables::log_rate?

Happy to provide a patch once the pending merge requests have been cleared out.

[LionelCons]

LGTM