Is there anything missing when forwarding my X11 connections?

[Christophe Lohr]

Le 10/02/2025 à 11:19, Carsten Haitzler a écrit :
>> If I guess correctly what's happening with my test: X clients never get
>> this error, and so they wait. Is that it?
> they should...
>
> strace would be the next port of call - but i shall assume they are sitting in
> select/epoll waiting on something.
>
> find the simplest app you can that doesn't work and i guess it's time to dig.
>
> in fact trying your socat thing here.. a lot of things work. libreoffice works.
> gedit works. my stuff (that does ximage fallback) works. anything qt does
> not... in fact... i think i spotted the problem. simplest thing that doesn't
> work:
>
> glxgears
>
> i have not dug much, but it seems qt is trying to use gl ... and thus anything
> using qt is not working. gl is hanging.
>
> so there's your core problem... without digging more i can't be sure but
> getting gl to work remotely these days is not a great idea :)
>
> nothing to do with shm. it's opengl. :)

I wonder if there aren't two (similar but distinct) problems, one with 
GLX (or DRI?), the other with MIT-SHM

-  glxinfo  (rather minimalist), seems to wait for some reply :

$ DISPLAY=localhost:1 xtrace -n glxinfo
../..
000:<:0009: 12: GLX-Request(152,19): glXQueryServerString 
context_tag=0x00000000 name=unknown:0x000020f6
000:>:0009:40: Reply to glXQueryServerString: string='mesa'
000:<:000a: 12: Request(98): QueryExtension name='GLX'
000:>:000a:32: Reply to QueryExtension: present=true(0x01) 
major-opcode=152 first-event=95 first-error=158
000:<:000b: 12: Request(98): QueryExtension name='GLX'
000:>:000b:32: Reply to QueryExtension: present=true(0x01) 
major-opcode=152 first-event=95 first-error=158
000:<:000c: 12: GLX-Request(152,7): glXQueryVersion 
client_major_version=1 client_minor_version=4
000:>:000c:32: Reply to glXQueryVersion: server_major_version=1 
server_minor_version=4
000:<:000d: 12: Request(98): QueryExtension name='DRI3'
000:<:000e: 16: Request(98): QueryExtension name='Present'
000:>:000d:32: Reply to QueryExtension: present=true(0x01) 
major-opcode=149 first-event=0 first-error=0
000:>:000e:32: Reply to QueryExtension: present=true(0x01) 
major-opcode=148 first-event=0 first-error=0
000:<:000f: 12: DRI3-Request(149,0): QueryVersion major_version=1 
minor_version=2
000:<:0010: 12: Present-Request(148,0): QueryVersion majorVersion=1 
minorVersion=2
000:>:000f:32: Reply to QueryVersion: major-version=1 minor-version=2
000:>:0010:32: Reply to QueryVersion: majorVersion=1 minorVersion=2
000:<:0011: 12: DRI3-Request(149,1): Open drawable=0x000003e2 provider=0
000:>:0011:32: Reply to Open: nfd=1
^C
$


- Xephyr (not so minimalist but well known) :

$ DISPLAY=localhost:1  xtrace -n Xephyr :20
../..
000:<:0010: 16: Request(98): QueryExtension name='MIT-SHM'
000:>:0010:32: Reply to QueryExtension: present=true(0x01) 
major-opcode=130 first-event=65 first-error=128
000:<:0011:  4: MIT-SHM-Request(130,0): QueryVersion
000:>:0011:32: Reply to QueryVersion: major-version=1 minor-version=2 
uid=0 gid=0 pixmap-format=ZPixmap(0x02)
000:<:0012: 16: MIT-SHM-Request(130,7): UNKNOWN opcode=0x82 opcode2=0x07 
unparsed-data=0x05,0x00,0x40,0x04,0x01,0x00,0x00,0x00,0x01,0x00,0x00,0x00;
000:>:0012:32: unexpected Reply: data1=0x01 data2=0x01 
unparsed-data=0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00;
^C
$

But disabling SHM makes it working (slow, but works):
$ DISPLAY=localhost:1 XEPHYR_NO_SHM=true xtrace -n Xephyr :20


- My very first need is for using wireshark (definitively not 
minimalist, and with Qt)
It opens a window, but draws nothing.
... very mysterious to me...


Unless there's some other underlying reason?
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