On Sat, Mar 28, 2020 at 1:11 AM vwguac <[email protected]> wrote: > Tested with Docker and > Guacamole 1.0.0, 1.1.0, 1.2.0 > > It is probably a problem with the windows printer driver. > Unfortunately I haven't found the problem in Windows yet. > There are installations where it works. > > guacd[839]: ERROR: Unknown printer I/O request function: 0x3/0x0 > > I think this is a read request fom the Windows printer driver, to which the > guacd does not respond. >
That 0x3 is indeed a read request (IRP_MJ_READ). My understanding of RDPDR is that such a request makes no sense for printer devices, though. It may be that we should be explicitly returning an error over the channel, rather than ignoring the I/O request, but I'm not sure (1) why you would be seeing this at all and (2) why it should result in overall print failure. It's worth just trying whether something as simple as reporting that the I/O request is unsupported would solve what you're seeing, but I'd also like to understand under what circumstances Windows will try to issue a read request to a printer. - Mike
