Re: Can't use XDMCP, "winProcEstablishConnection - ProcEstablishConnection failed, bailing" shows in log

[Alexander Pokluda <apokluda at gmail dot com>]

Hi Jon,

I don't have any idea why the XDMCP request packets from XWin would be
dropped by the network either.

What I thought was interesting is that the value of Connection 4 in
the XDMCP REQUEST packet from XWin in the Wireshark trace is
fe80::5efe:a03:149f. I'm still familiarizing myself with IPv6, but the
handy tool at ip-lookup.net shows this for that address:

This IPv6 address contains an IPv4 address:
IPv6 compressed???????? :? FE80::5EFE:A03:149F
IPv6 uncompressed?????? :? FE80:0:0:0:0:5EFE:A03:149F
IPv6 fully uncompressed??? :? FE80:0000:0000:0000:0000:5EFE:0A03:149F

IP v4:
decimal???????????????? :? 10.3.20.159
binary????????????????? :? 00001010000000110001010010011111
octal?????????????????? :? 012.03.024.0237
hexadecimal???????????? :? 0x0A.0x03.0x14.0x9F
long??????????????????? :? 167974047

IP v6 :
6 to 4 address????????? :? 2002:A03:149F:0:0:0:0:0
??????????????????????? :? 2002:A03:149F::
IPv4-mapped address ??? :? 0:0:0:0:0:FFFF:10.3.20.159
??????????????????????? :? ::FFFF:10.3.20.159
??????????????????????? :? ::FFFF:0A03:149F
IPv4-compatibility address :? 0:0:0:0:0:0:10.3.20.159
??????????????????????? :? ::10.3.20.159
??????????????????????? :? ::0A03:149F

It seems there are some interesting things going on here, but, the
modified XWin you link to at the bottom of your email works
perfectly!!

Thanks for all of your help :-)

On Mon, Feb 14, 2011 at 9:46 AM, Jon TURNEY <jon.turney@dronecode.org.uk> wrote:
>
> > On Wed, Feb 9, 2011 at 6:37 PM, Jon TURNEY <jon.turney@dronecode.org.uk> wrote:
> >> I wonder if you could send me privately the Wireshark .pcap files for these
> >> traces, I'd like to examine them further.
>
> On 11/02/2011 18:45, Alexander Pokluda wrote:
> > I've attached a zip archive containing a number of files. The pcap
> > files were created by running Wireshark on both ends while attempting
> > to establish an XDMCP session between the hosts. Here is a description
> > of the files:
>
> Thanks very much for these.
>
> Unfortunately, these seem to show that the XDMCP request packet leaves the
> machine running XWin, but doesn't arrive at the VM.
>
> I've no idea why that might be, but that suggests to me they are being dropped
> in your network, or between the host running the VM and the guest VM?
>
> > After I took the above screenshot, I realized that I had a VirtualBox
> > adapter with IPv6 enabled, so I disabled the VirtualBox adapter and
> > ran the XWin command again, capturing packets on both ends. These
> > files contain the captured packets. One interesting thing to note is
> > that the request packet sent from XWin contains my IPv4 address
> > converted to an IPv6 address even when IPv6 is disabled on my physical
> > adapter.
>
> These look like link-local IPv6 addresses (prefix fe80::) to me, rather than
> IPv6 mapped IPv4 addresses (prefix ::ffff:)?
>
> However, this does look like a bug (or at least the code not doing what it
> says it does): when the -from option is used, the XDMCP request contains the
> specified address *and* any other addresses we have of different address
> families to the specified address (e.g., if we specify an IPv4 address, we get
> only that IPv4 address, but all the IPv6 addresses as well)
>
> I've built a snapshot which contains a change which modifies the behaviour of
> -from so only the specified address is included in the XDMCP request, and
> uploaded it at [1].
>
> With this change, the XDMCP request sent by XWin and XMing should be nearly
> identical. Perhaps you could try that out and see if that makes a difference.
>
> ftp://cygwin.com/pub/cygwinx/XWin.20110214-git-d593beaadac1371e.exe.bz2

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