[Info-vax] [7.3 VAX] XDM configuration

[chris]

On 11/18/22 08:11, JKB wrote:
> Le 17-11-2022, chris <chris-nospam at tridac.net> a écrit :
>>
>> I would use wireshark or tcpdump to monitor the src and dest hosts, so
>> you can analyse the traffic. Used recently here to debug a vnc
>> connection, both network and local loopback, which xdmcp makes use of...
> 
> 	Xephyr runs fine. I can access to legendre.systella.fr with:
> 	Xephyr :1 -listen tcp -query legendre
> 
> 	If I tri to access to fermat (this VAX), I only obtain a black
> 	screen. But it seems to answer to request:
> 
> Root hilbert:[~] > tcpdump -p -i eth0 -vvv host fermat
> tcpdump: listening on eth0, link-type EN10MB (Ethernet), snapshot length 262144 bytes
> 09:06:58.114604 IP (tos 0x0, ttl 64, id 39927, offset 0, flags [DF], proto UDP (17), length 35)
>      hilbert.systella.fr.39124 > fermat.systella.fr.xdmcp: [udp sum ok] UDP, length 7
> 09:06:58.246108 IP (tos 0x0, ttl 30, id 37659, offset 0, flags [DF], proto UDP (17), length 75)
>      fermat.systella.fr.xdmcp > hilbert.systella.fr.39124: [udp sum ok] UDP, length 47
> 09:06:58.246283 IP (tos 0x0, ttl 64, id 39952, offset 0, flags [DF], proto UDP (17), length 134)
>      hilbert.systella.fr.39124 > fermat.systella.fr.xdmcp: [bad udp cksum 0x96a6 -> 0x899a!] UDP, length 106
> 09:06:59.483783 IP (tos 0x0, ttl 30, id 37660, offset 0, flags [DF], proto UDP (17), length 80)
>      fermat.systella.fr.xdmcp > hilbert.systella.fr.39124: [udp sum ok] UDP, length 52
> 09:06:59.483837 IP (tos 0x0, ttl 64, id 40214, offset 0, flags [DF], proto UDP (17), length 57)
>      hilbert.systella.fr.39124 > fermat.systella.fr.xdmcp: [bad udp cksum 0x9659 -> 0xb434!] UDP, length 29
> 09:07:01.485945 IP (tos 0x0, ttl 64, id 40658, offset 0, flags [DF], proto UDP (17), length 57)
>      hilbert.systella.fr.39124 > fermat.systella.fr.xdmcp: [bad udp cksum 0x9659 -> 0xb434!] UDP, length 29
> 09:07:05.488721 IP (tos 0x0, ttl 64, id 41488, offset 0, flags [DF], proto UDP (17), length 57)
>      hilbert.systella.fr.39124 > fermat.systella.fr.xdmcp: [bad udp cksum 0x9659 -> 0xb434!] UDP, length 29
> 09:07:06.672721 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has fermat.systella.fr tell hilbert.systella.fr, length 28
> 09:07:06.702501 ARP, Ethernet (len 6), IPv4 (len 4), Reply fermat.systella.fr is-at 08:00:2b:7a:39:2e (oui Unknown), length 46
> ^C
> 9 packets captured
> 633 packets received by filter
> 0 packets dropped by kernel
> 
> 	Of course, xdm is running :
> 
> $ pipe show sys | search SYS$INPUT XDM
> 00000113 TCPIP$XDM_1     LEF     10      532   0 00:00:10.72      2123   2109  N
> 
> 	I suppose my xdm configuration is faulty somewhere.
> 
> 	Best regards,
> 
> 	JKB
> 


Looks like you are getting a reply from the third enquiry, then the last
three enquiries are being ignored by the xdmcp host. First thing I would
do is to temporarily disable all X security, as that may be enabled by
default. Other than that, no idea, other a config issue. Also, wireshark
to look at packet contents in depth...

Chris