# Re: SANE protocol error ?

From: Henning Meier-Geinitz (henning@meier-geinitz.de)
Date: Sat May 19 2001 - 09:40:11 PDT

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  Hi,

  On Mon, Apr 30, 2001 at 12:07:41AM +0200, Petter Reinholdtsen wrote:
  > If I understand correctly, the function sanei_w_control_option_req()
  > will try to send the value of the option even if the action is
  > SANE_ACTION_GET_VALUE, and thus mostly send uninitialized values to
  > the SANE server. I haven't examined this part, but I suspect the
  > server ignore the value, and send a reply with the value of the
  > option.

  Not exactly. It just send the data to sane_control_option, where it's
  overwritten if action is SANE_ACTION_GET_VALUE.

  > Why isn't the test == SANE_ACTION_GET_VALUE?

  I don't know. Probably this was forgotten when the bug concerning
  SET_AUTO was found.

  > What would be the effect of changing this test to only send the value
  > if it contains anything interesting?

  I think there wouldn't be a problem. But the net protocl version
  number must be increased and yet another test for this version number
  has to be inserted so the new version remains compatible to old saned/net.
  I'm not sure if it's worth it.

  > The problem is triggered by
  > calls like:
  >
  > SANE_Int num_dev_options;
  > status = sane_control_option (device, 0, SANE_ACTION_GET_VALUE,
  > &num_dev_options, 0);
  >
  > In this case, the 'value' of num_dev_options is pushed on the wire.

  Yes, but isn't the only problem with this that some garbage is
  transported through the wire?

  Bye,
  Henning

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