Red Hat Bugzilla – Bug 214479
kdm no answer to xdmcp forward_query
Last modified: 2012-01-17 13:11:45 EST
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Description of problem:
querying from xtermianl "A" the chooser "B" with "Xnest :1 -indirect B" gives me a list of hosts including "C". connecting "C" fails.
this is reproduceable with Xnest, X or Xming.exe from differnt (including windows) hosts "A".
this also reproduceabel withh different hosts "B" or "C".
the connection works fine when i replace kdm with gdm.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. try to query a kdm host from a chooser
kdm greeter dialog
on host "C" kdm -debug 0x85 delivers something like:
Nov 7 20:08:20 kdm debug: select returns 1
Nov 7 20:08:20 kdm debug: ProcessRequestSocket
Nov 7 20:08:20 kdm debug: header: 1 4 11
Nov 7 20:08:20 kdm debug: <forward> respond 11
Nov 7 20:08:20 kdm debug: <forward> client address (port 32981) 192 168 54 107
Nov 7 20:08:22 kdm debug: select returns 1
Nov 7 20:08:22 kdm debug: ProcessRequestSocket
Nov 7 20:08:22 kdm debug: header: 1 4 11
Nov 7 20:08:22 kdm debug: <forward> respond 11
Nov 7 20:08:22 kdm debug: <forward> client address (port 32981) 192 168 54 107
after viewing the sources i found that a line with somethning like
"debug: all_query_respond:" should be the next line but is missing.
the forward_query package from "B" to "C" with the correct address of "A" is delivered to "C", but "C" gives no answer at all.
It seems the option "KDM should listen to XDMCP requests" is disable!
Could you please change the line "Enable=false" to "Enable=true" from the
section [Xdmcp] in /etc/X11/xdm/kdmrc and try again? Thanks
please make sure that you have to restart kdm after changing the kdmrc!
works fine. but this is NOT the bug reported about "indirect" requests and no
answers to the "forward_query".
Xnest :1 -query "C"
everything works fine, but
Xnest :1 -indirect "B"
"C" is listed but the connection fails as discribed.
Fedora apologizes that these issues have not been resolved yet. We're
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For what it's worth, I can report exactly the same trouble symptom
that Mr. Dorfmeister describes, except that I am running Fedora *8*
Specifically: Fedora 8, kernel-22.214.171.124-64.fc8 with gdm-2.20.3-1.fc8.
In my case the forward queries do not even go to the correct host, e.g.,
with my internal net being 192.168.200.0/24 and the selected host
being 192.168.200.4, wireshark shows the forward queries being sent
to addresses like 126.96.36.199, 188.8.131.52, 184.108.40.206, etc. Something
in the chooser or some underlying library is generating garbage
As Mr. Dorfmeister describes, the chooser was working with gdm
in Fedora 6. Now it's broken in Fedora 8. I use gnome and haven't
tested with kde/kdm.
thanks for your update. changing version to '8'
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I tried cloning this bug to make a new posting out of it, but
nothing happened, so let me try just add a comment.
This bug occurs identically as described above in Fedora 10
*and* Fedora 11.
Since gdm no long supports xdmcp, I am now using kdm like the
1) kdm correctly configured on machine A and machine B
2) At the graphical login screen of either, select menu->remote login,
and see A and B in the chooser list
3) Select the other machine
4) Successful connection occurs, and login to the remote machine is possible
So far, so good. Now the failure scenario:
2) Login to either machine, from e.g., a gnome-terminal, run
Xephyr -indirect localhost :1
(or substitute the local machine's name for localhost)
and see A and B in the chooser list
3) Select the other machine
4) Xephyr screen goes grey with an X cursor and stays that way
until the connection attempt times out, then the chooser reappears.
During the timeout period, wireshark shows FORWARD_QUERY packets going
to the remote machine, and wireshark running on the remote machine shows
the arrival of the FORWARD_QUERYs. The remote machine generates no response.
When the remote connection is attempted from the login screen menu as in
1-4) earlier, the local machine is not sending FORWARD_QUERYs, it is sending
a direct query to the remote.
This bug has now been demonstrated using kdm and, previously, gdm, spanning
multiple versions of Fedora over a three year period.
The three conspicuous features of this bug are:
* recipients of xdmcp FORWARD_QUERYs don't seem to know what to do with them
* a connection attempt via kdm from the login screen results in a direct
query while an attempt via kdm from a nested server such as Xnest or
Xephyr results in a forward query. Whey the different behavior?
* Xnest or Xephyr both work when a direct query is forced on the
command line, e.g.,
Xephyr -query other_machine :1
Please keep this bug alive. Broken xdmcp/chooser in a nested server is
a real sore spot.
Bug persists as of january 2012, with EL6 (Scientific Linux 6.1)
It manifests as Dennis has wrote in previous comment.
Maybe this should be fixed after 6 years? ...