Question

I have a public server(configured with indy 10) . some unknown clients are sending thousands of no content messages that it change the server’s cpu usage to 50% . i have no firewall on my server , so i tried to block the unknown clients with this codes :

This is a function that works with a Timer :

var
  i, j: integer;
begin
  IX2 := IX2 + 1;
  SetLength(ClientIPs, IX2);
  ClientIPs[IX2 - 1] := StrIP;
  j := 0;
  for i := low(ClientIPs) to high(ClientIPs) do
  begin
    Application.ProcessMessages;
    if ClientIPs[i] = StrIP then
      j := j + 1;
  end;
  if j > 10 then
  begin
    Result := false;
    exit;
  end;
  Result := true;

And it’s my Timer code :

  //Reset filtering measures
  IX2 := 0;
  SetLength(ClientIPs, 0);

So i use it in OnExecute event :

  LogIP := AContext.Connection.Socket.Binding.PeerIP;

  if IPFilter(LogIP) <> true then
  begin
    AContext.Connection.disconnect;
    exit;
  end;

  //Get Data *********
  Data := AContext.Connection.IOHandler.ReadLn();

finally , if a client sends many message in a short time , it will be disconnect . but there is a problem . in fact , after client disconnection , the Onexecute event is still working and i can not stop the operation Fully .anyway i need to block some IPs completely .

Thank you

Answer 1

Followup to my earlier comment:

function TForm1.IPFilter(const StrIP: string): Boolean;
var 
  i, j: integer; 
  list: TList;
begin 
  j := 0; 
  list := IdTCPServer1.Contexts.LockList;
  try
    for i := 0 to list.Count-1 do 
    begin 
      if TIdContext(list[i]).Binding.PeerIP = StrIP then
        Inc(j); 
    end; 
    Result := j <= 10; 
  finally
    IdTCPServer1.Contexts.UnlockList;
  end;
end;

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
begin
  // the simpliest way to force a disconnect and stop
  // the calling thread is to raise an exception...
  if not IPFilter(AContext.Binding.PeerIP) then
    Abort();

  // alternatively, if you call Disconnect(), make sure
  // the IOHandler's InputBuffer is empty, or else
  // AContext.Connection.Connected() will continue
  // returning True!...
  {if not IPFilter(AContext.Binding.PeerIP) then
  begin
    AContext.Connection.Disconnect;
    AContext.Connection.IOHandler.InputBuffer.Clear;
    Exit;
  end;}

  //Get Data ********* 
  Data := AContext.Connection.IOHandler.ReadLn(); 
end;