Can I determine a rule based upon another state ?

  • Hi,

    I want to setup some rules such that, for example, traffic can only pass through to a local port if the remote host already has a connection to another local port:

    Remote tries to connect to port 1234 - only allowed if they already have a valid connection to port 3456


    Remote tries to connect to port 1234 - only allowed already a local connection out to remote on port 5678

    I have a feeling this isn't possible, but I thought I'd check. If not, does anyone have suggestions what I can use to achieve this ?


  • Not possible.

    Why would you want that?
    For "security"?

    Set up a VPN if you need secure access.

  • Thanks for the clarification.

    I'd want it for port-knocking, or for allowing servers which I connect to (and therefore approve) connect back for additional services whilst I'm connected to them.

    It's not a scenario that's used too often, but it's nice to be able to handle it.

  • Search the forum about port-knocking.
    There have been discussions about that, and why it's not such a good idea.

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