PXE boot - WARNING(tftpd): Error packet received!

[robertpenz]

I've just tried to boot a PC (in this case a virtual one with Intel UNDI, PXE-2.1) from the tftpserver.py and got following output on the server:

WARNING(tftpd): Error packet received!

The client just hang. You can download the Wireshark trace from:

http://robert.penz.name/files/pxeboot_error_packet_received.pcapng

Transferring the packet fails after 12 blocks ... using a tftp Linux client does not give that error

[robertpenz]

Just redid it with Debugging enabled:

INFO(tftpd): Serving TFTP requests on eth0:69 in /home/robert/tmp/tftp/tftpboot
INFO(tftpd): Serving file pxeboot.0 to host 10.12.138.11...
WARNING(tftpd): Error packet received!
INFO(tftpd): Serving file pxeboot.0 to host 10.12.138.11...
DEBUG(tftpd):   >  DATA: 12 data packet(s) sent.
DEBUG(tftpd):   <   ACK: Transfer complete, 16756 byte(s).
INFO(tftpd): Transfer of file pxeboot.0 completed.

If I start the server with "-r" I also get the error, but 33 packets are delivered, client still hangs.

INFO(tftpd): Serving file pxeboot.0 to host 10.12.138.11...
WARNING(tftpd): Error packet received!
INFO(tftpd): Serving file pxeboot.0 to host 10.12.138.11...
DEBUG(tftpd):   >  DATA: 33 data packet(s) sent.
DEBUG(tftpd):   <   ACK: Transfer complete, 16756 byte(s).
INFO(tftpd): Transfer of file pxeboot.0 completed.

[robertpenz]

Following URL shows a working PXE boot from the same client with an other TFTP Server (which is not in Python, which is what I need ;-) )

http://robert.penz.name/files/pxeboot_working.pcapng

The problem does not seem to be the "Error packet received!" but that the tftpd sends an malformed packet at the end - at least if Wireshark is correct. not sure why that packet is sent at all, as the working tftpd server does not send it.

[robertpenz]

I found the bug which leads to the empty packet. That's a bug in the DatagramRequestHandler. Here is the Workaround:

class TFTPServerHandler(SocketServer.DatagramRequestHandler):
...
    def finish(self):
        """ Workaround for following bug: http://bugs.python.org/issue1767511 """
        wdata = self.wfile.getvalue()
        if wdata:
            self.socket.sendto(wdata, self.client_address)

but the client still hangs and I don't know ... here is the new trace:

http://robert.penz.name/files/pxeboot_stillnotworking.pcapng

[robertpenz]

Ok this last error was on my side ... damaged the file while testing. now it worked for the first file of the boot process and its looking for the next.

[mpetazzoni]

Could you send a pull request for the fix to the finish() method if it's required? Thanks!

[robertpenz]

I've created the pull request. It also contains some improvements to the serveRRQ handler