dnsdist: function to clear/remove EDNS Options

[pieterlexis-tomtom]

• Program: dnsdist
• Issue type: Feature request

Short description

dnsdist already supports adding and modifying EDNS options in queries (e.g. DNSQuestion:setEDNSOption). There is no way, however, to remove an option from the EDNS Options. It would be great to have one.

Usecase

There might be options one does not wish to pass to a backend as it might not be properly supported, or one does not want the backend to receive these options for any other reason.

Description

Having a function e.g. like DNSQuestion:clearEDNSOptions([TABLE]) that removes the options specified in TABLE. if TABLE is non-existent, wipe all options.

e.g.

function removeAllOptions(dq)
  dq:clearEDNSOptions()
  return DNSAction.None, ""
end

function removeCookieOption(dq)
  dq:clearEDNSOptions({EDNSOptionCode.COOKIE})
  return DNSAction.None, ""
end

-- dumb matching rules
addAction(HTTPPathRule('/foo'), LuaAction(removeCookieOption))
addAction(OpcodeRule(DNSOpcode.NOTIFY), LuaAction(removeAllOptions))

Another option would be to have a ClearEDNSOptionsAction([TABLE]), but I think this functionality is sufficiently advanced to hide behind a Lua(Response)Action.