Bug#432763: gdm: XDMCP chooser don't forward the client IP address to the server

[Vincent Rivière]

Package: gdm
Version: 2.18.2-1
Severity: important

In the current version of Debian Testing, the gdm chooser is unusable. After
selecting a server in the list, the connection times out, and the list is
displayed again.

I enabled the debug traces on the chooser machine and I found some
interesting things :

Jul 11 21:12:14 quartz gdm[4198]: gdm_xdmcp_decode: Received opcode
INDIRECT_QUERY from client ::ffff:192.168.0.155
Jul 11 21:12:14 quartz gdm[4198]: gdm_xdmcp_handle_query: Opcode 3 from
::ffff:192.168.0.155
Jul 11 21:12:14 quartz gdm[4198]: gdm_xdmcp_host_allow: client->hostname is
192.168.0.155
Jul 11 21:12:14 quartz gdm[4198]: gdm_xdmcp_send_forward_query: Sending
forward query to 10.2.0.9
Jul 11 21:12:14 quartz gdm[4198]: gdm_xdmcp_send_forward_query: Query
contains 0.0.0.0:3030

We can see that gdm_xdmcp_send_forward_query() sends 0.0.0.0 as the address
of the client (X server).

I replaced /usr/sbin/gdm and /usr/lib/gdm/gdmchooser with the versions found
on stable, and it works again.

Now, the good traces are :

Jul 11 21:42:15 quartz gdm[4421]: gdm_xdmcp_decode: Received opcode
INDIRECT_QUERY from client 192.168.0.155
Jul 11 21:42:15 quartz gdm[4421]: gdm_xdmcp_handle_query: Opcode 3 from
192.168.0.155
Jul 11 21:42:15 quartz gdm[4421]: gdm_xdmcp_host_allow: client->hostname is
pcriviere.iut-rodez.fr
Jul 11 21:42:15 quartz gdm[4421]: gdm_xdmcp_send_forward_query: Sending
forward query to 10.2.0.9
Jul 11 21:42:15 quartz gdm[4421]: gdm_xdmcp_send_forward_query: Query
contains 192.168.0.155:3201

We can see 2 things :
- The correct address of the client is now forwarded to the server
- The IP addresses are displayed in IPV4 form, instead of IPV6 in the bad
traces.

So maybe this problem is related to some IPV6 compilation settings ?

-- System Information:
Debian Release: lenny/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)

Kernel: Linux 2.6.21-2-686 (SMP w/8 CPU cores)
Locale: LANG=fr_FR at euro, LC_CTYPE=fr_FR at euro (charmap=ISO-8859-15)
Shell: /bin/sh linked to /bin/bash

Vincent Rivière
riviere at iut-rodez.fr