Xrdp: Dynamic resolution update (resizing without reconnection)

[metalefty]

The feature "Dynamic resolution update" was introduced in RDP 8.1. It enables to resize screen resolution on-the-fly.

Dynamic resolution update

One of the changes we’ve made as part of RDP 8.1 is the addition of a new message that can be sent from the client to the server to dynamically update the resolution inside the remote session to match what is available on the client without the need to do a complete reconnect of the session. Previously, we only set the remote resolution during the initial connection. With this change, the resolution is set at connect time and can be updated when the client-side resolution changes while the app is in full screen mode, or when the app transitions from windowed mode to full screen. The resolution change is quick enough to be practically the same as a local change.

https://blogs.technet.microsoft.com/enterprisemobility/2013/12/16/resolution-and-scaling-level-updates-in-rdp-8-1/

Let's bring this to xrdp if possible. I'm still looking for MS documents about dynamic resolution update. If anyone know where it is, I'd appriciate leting me know.

[jsorg71]

xrdp Xorg driver and X11rdp are ready to accept resizing. The RandR extension is there and working.

[metalefty]

AFAIK, xrdp resizes session but it is only connect time, right? What I want to implement is different from it. As xorgxrdp and x11rdp are ready to accept resizing, what we need to do is to catch "a new resize message" from the client and tell xorgxrdp/x11rdp to resize.

I'm looking for "a new message" of resizing in MS documents.

[jsorg71]

Yes, I know what you mean. I can't find it in the protocol docs. It's either added to MS-RDPBCGR or it's a new virtual channel.

[metalefty]

Quick lookup for "resolution" in [MS-RDP*], is "DISPLAYCONTROL_MONITOR_LAYOUT_PDU" of [MS-RDPEDISP] related to dynamic resolution update? I haven't read MS-RDPEDISP deeply but just FYI.

Dynamic resolution update is introduced in RDP 8.1. MS-RDPEDISP is added on Aug 8, 2013. Windows 8.1 was released in October 2013. The date of the MS blog article is December 2013. Probably they're relevant.

[speidy]

It's a new virtual channel, but I think it's dynamic channel.
בתאריך יום ה׳, 20 באוק׳ 2016 ב-7:03 מאת metalefty <[email protected]

:

Quick lookup for "resolution" in [MS-RDP*], is
"DISPLAYCONTROL_MONITOR_LAYOUT_PDU" of [MS-RDPEDISP] related to dynamic
resolution update? I haven't read MS-RDPEDISP deeply but just FYI.

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[jsorg71]

Yup, this is it
MS-RDPEDISP

[metalefty]

I noticed RemoteFX session cannot be resized with this virtual channel function. It sounds I can gain little benefit.

1.5 Prerequisites/Preconditions

If the RemoteFX codec ([MS-RDPRFX] sections 2.2.2 and 3.1.8) is being used to encode graphics data from a remote session, then the Remote Desktop Protocol: Display Control Virtual Channel Extension SHOULD NOT be used to request display configuration changes.

https://msdn.microsoft.com/en-us/library/dn364841.aspx

[mrichar1]

Hi - Can I check on the state of this issue? Is it still the case that there isn't a mechanism for resizing without reconnecting in xrdp?

[metalefty]

Still on TODO list but nothing's being done. If you want the feature, react with 👍 icon on the first post. Then I can know how many people want the feature.

[jsorg71]

I implemented MS-RDPEDISP and MSTSC seems to only send client data to the server when in full screen mode. I was expecting non full screen resizing to work but I don't see any data. I wonder how MSTSC to Windows 10 does this.

[metalefty]

Nice, can you share your work?

I've found a document about display update not only in MS-RDPEDISP.
https://msdn.microsoft.com/en-us/library/dd303566.aspx

[jsorg71]

Sure I can share it. I had to move the drdynvc handling to libxrdp from chansrv but we need that anyway for GFX and a bunch of other new work.

[speidy]

I’ve also implemented it as a standalone executable at the past.

It doesn’t work in non full screen scenarios by design it’s wirtten
somewhere at the docs

בתאריך יום ג׳, 17 באפר׳ 2018 ב-4:04 מאת jsorg71 [e-mail]:

I implemented MS-RDPEDISP and MSTSC seems to only send client data to the
server when in full screen mode. I was expecting non full screen resizing
to work but I don't see any data. I wonder how MSTSC to Windows 10 does
this.

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[hardening]

@speidy well in fact fullscreen doesn't mean anything at the protocol level. Except if you consider that the DesktopWidth/DesktopHeight match the size of a single monitor means fullscreen...
When I've implemented dynamic resolution in FreeRDP I'm just announcing a monitor that has the size of the window...

[jsorg71]

That is what I was hoping mstsc would do, report a dummy monitor that is the size of the window.

[speidy]

It’s not documented at the protocol docs but in technet blog w.r.t Mstsc.exe

To leverage the dynamic update features for resolution and scaling level, you must start the desktop session with a Display configuration set to Full Screen on the Display tab. Doing so tells Remote Desktop Connection to manage the resolution and scaling level for you and keep it in sync with changes happening locally.

ref: https://blogs.technet.microsoft.com/enterprisemobility/2013/12/16/resolution-and-scaling-level-updates-in-rdp-8-1/

[jsorg71]

@hardening What version of freerdp has your dynamic resolution change?

[hardening]

@jsorg71 current master has it (/dynamic-resolution on the command line)

[jsorg71]

That works as I'd expect. It does look like you are setting the PhysicalWidth and PhysicalHeight wrong. They should not be the same as width and height. They should be in mm. The DPI per monitor is calculated from this. In X11 xandr can supply this.

[rahulm-gdb]

@jsorg71 can u tell me how to configure xrdp to accept display-update on resize method.? on master branch, I'm trying to build xrdp with dynamic-resolution option. But i can't see the option. I've loaded the git repo locally. Installed dependencies. Then did ./bootstrap. followed by ./configure . IN the ./configure -help i can't see any option for dynamic-resolution.

[jsorg71]

I ran into problems. The FreeRDP implementation does not work well with a Windows 10 server because the mmWidth and mmHeight are same as width and height and not mm. The MS client does not do this at all if not in full screen. I think there is a HyperV connection to xrdp that does work but I didn't find out how that works. It looks like the dynamic virtual channel is used to report the new monitor layout to the server but the server(xrdp) needs to send a new 'demand active'. Xrdp has a 'server_reset' function for this but FreeRDP did not like it and I stopped there.

[speidy]

@jsorg71 I think i was stopping at the same point at the past.

I'm not sure if we can send a demand_active again, afaik mstsc will throw an error.
I think mstsc will resize the local screen area after the dynamic channel message accepted by the server and we just need to resize it remotely in xrdp_wm and X11

[jterry75]

The channel in mstscax that Hyper-V uses is done in two ways from a client perspective:

1. When a full screen mode is entered a call to SyncSessionDisplaySettings is made which takes into account the use of all monitors (if enabled).
2. When the client UX resize in windowed mode a call to UpdateSessionDisplaySettings is sent for only the size of the client display area in the DPI of the current display monitor the UX is on.

[speidy]

We should use libxrdp_reset on server to trigger capabilites re-exchange after MS-RDPEDSIP message exchange is done.

[comphilip]

Any further update?

[shanselman]

Say @jsorg71 can you share/upstream your code? It feels like you are very close? I work for Microsoft with @scooley and I know the world would LOVE to see this! Let us know how we can help.

[jsorg71]

Yup, lets push this ahead. I have the needed changes to drdynvc done and tested. After that, this should be much easier. One thing that would be nice is if mstsc supported this feature. I think it does if you connect "full screen" but mstsc could support this in windowed mode too.
Anyway, I'll prepare a PR.

[speidy]

I can help implementing this after ‘drdynvc’ changes will be pushed.

One thing me and Jay talked about was maintaining a user process like
rdpclip.exe in Windows which will take care over session related stuff just
like Xrandr monitor changes etc.
בתאריך יום ד׳, 3 באוק׳ 2018 ב-10:29 מאת jsorg71 [e-mail]:

Yup, lets push this ahead. I have the needed changes to drdynvc done and
tested. After that, this should be much easier. One thing that would be
nice is if mstsc supported this feature. I think it does if you connect
"full screen" but mstsc could support this in windowed mode too.
Anyway, I'll prepare a PR.

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[jsorg71]

I created #1222 to track the DVC progress.

[scooley]

Awesome! I work with @jterry75 - we're excited to pick this up for better Linux VM viewing. Thanks!

[jsorg71]

I created branch
https://github.com/jsorg71/xrdp/commits/dynamic_monitor
for working on this. So far it only the xrdp login screen that resizes.

[metalefty]

Works well!

[jsorg71]

Works well with freerdp with /dynamic-resolution and works with mstsc when you go full screen after resizing desktop. I have not got the hyper-v session working yet.

[jterry75]

@cwilhit - Did you give this a shot with Hyper-V yet?

[cwilhit]

@jterry75 tested with Hyper-V but was not able to get past the xrdp login.

I did try connecting via mstsc and saw that I could resize the xrdp login window.

[jsorg71]

To complete this, we have to serialize some things. I think this is how this needs to work.

1 - client sends dynamic resize message over the virtual channel.
2 - xrdp starts the demand active / confirm active process. This involves capabilities re negotiation. At this point, xrdp and client are resized.
3 - xrdp starts the reset / resize of the backend (Xorg )
4 - full screen invalidate.

[BiatuAutMiahn]

Any updates on this feature?

[mikov]

Does anyone know if resizing via "xrandr" executed in the VM should work with xrdp on Hyper-V ?
For some reason when I invoke xrandr, nothing happens. In the output of xrandr I see that the size of the screen does get changed, but the resolution of the "rdp0" output remains unchanged.

[Nexarian]

Jay told me that one of the reasons he'd stopped working on it was that MSTSC, the official Microsoft Windows client, didn't seem to support it.

However, the Mac RDP client does support it, and knowing that, he told me he could be unblocked on it.

So stay tuned, this feature has not been forgotten!

[nahun]

I believe mRemoteNG also supports it.

[Ebrithil95]

Any update on this?

[krisss85]

would be nice to have it merged, we have to apply this patch to our custom build

[bolkedebruin]

@jsorg71 @metalefty FYI: the official MS Remote Desktop client app for Mac now supports resizing

[terrencewei]

Any update on this? I want to move my ubuntu18.04 from vmware to hyper-v, but the dynamic resolution things blocked me, using linux-vm-tools only gives me a fixed resolution

[BiatuAutMiahn]

Any update on this? I want to move my ubuntu18.04 from vmware to hyper-v, but the dynamic resolution things blocked me, using linux-vm-tools only gives me a fixed resolution

I ended up using tigervnc with noVNC over secured websockets.

Edit:
The issue has been resolved

[artis3n]

@BiatuAutMiahn
How do you get dynamic resolution with TigerVNC? I am using it over SSH local port forward and do not see dynamic resolution resizing capability.

[BiatuAutMiahn]

I simply run tigervncserver.

with noVNC theres an option called Scaling Mode which I set to Remote Resizing

[akallabeth]

Any updates on this? Getting some bug reports regarding this for freerdp and can not do much on my side :/

[Nexarian]

So as I'd like to start traction on this, I'm trying to figure out how to make this code change myself.

I've studied the code a little bit, and concluded that "xrdp_bitmap" is really code for the login screen, or really, it can be any bitmap but defaults to blue, and the network communication is set up and working, but we've yet to connect it to the xorgxrdp driver.

What I don't understand is how xrdp and xorgxrdp communicate. In order to build xorgxrdp you need a header file from xrdp, which I'm guessing is where some callbacks are set up, but I'm having trouble finding it.

My thought is to try to send the "randr" signal through that communication mechanism at the same place where the xrdp_bitmap_resize call is being made in the dynamic_monitor branch, and then see what happens.

@jsorg71 am I on the right track here? I'm happy to do the implementation if you give me some further pointers.

[Nexarian]

Ah ha! Found it: https://github.com/neutrinolabs/xorgxrdp/blob/devel/module/rdpClientCon.c

Saw the reference that it communicated with the client through a unix socket.

Now to figure out how to send the signal when this happens.

[Nexarian]

This looks like the right signal to process it: https://github.com/neutrinolabs/xorgxrdp/blob/devel/module/rdpClientCon.c#L682

[Nexarian]

This looks like the place where the message is sent FROM xrdp: https://github.com/neutrinolabs/xrdp/blob/devel/xup/xup.c#L272

Looks like it may require a bit of refactoring to get this wired up.

[jsorg71]

@Nexarian yes, I think you are right about the message. There is also the monitor list message. I think either can resize the backend.
I think it's still the best plan to get the login screen resizing without logging in. After that works, then start working on resizing a logged in session. My thinking is that when it's just the login screen, you can minimize the moving parts.

[Nexarian]

I thought the login screen already worked? (At least, that's my interpretation of the comments from a few years ago).

If not, I'll try to get that to work. I should also probably get my own personal fork of XRDP and merge dynamic_monitor with the current master branch. One step at a time...

[Nexarian]

Performed this merge to my own fork: https://github.com/Nexarian/xrdp/commit/7f3d33df09340b42e42af436790acc25be1afc08

Any ideas as to what these errors are?

[20210131-02:03:26] [ERROR] error unknown xrdp_sec_process_mcs_data tag 0xc006 size 8
[20210131-02:03:26] [ERROR] error unknown xrdp_sec_process_mcs_data tag 0xc00a size 8

From looking them up it looks like they are these:

https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/f50e791c-de03-4b25-b17e-e914c9020bc3

and

https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/3801236b-b5ba-4b6e-bf0d-afbde1fe391c

Uncertain if they're related or not.

[Nexarian]

@jsorg71 You may be interested to know that there is now a "version" of MSTSC that supports dynamic resizing!

The old-skool actual MSTSC does not support it, but if you go to the Windows 10 app store and search for "Microsoft Remote Desktop" you'll find the UI is similar to that of the Mac OS client, and it DOES support dynamic resizing. This should make testing much, much easier!

[Nexarian]

[Nexarian]

I was able to get the branch of mine merged with devel linked above working with this new Microsoft Remote Desktop client on the login screen. Now I'm working on figuring out how logging works and turning it on. I've verified that even after I log into the main session, the dynamic monitor channel is still active and the data is being logged.

Still working on the plumbing to the xorg part. It seems like xrdp_mm.c is where most of this happens, and I'm working on figuring out how the "mod_init" struct is used. I was up late spelunking through the code.

Will continue to try to update regularly on my adventures

[Nexarian]

Next update is more about tactical development. I have Ubuntu 20.04.2 that I'm running inside VirtualBox, and while running GNOME the UI and Visual Studio Code would become unresponsive. I had to reboot it so frequently that I got fed up and switched to MATE. XRDP often works better with MATE anyway, though I am able to get it working with GNOME most of the time.

[Nexarian]

Further documentation of my investigation.

Here is where Jay added the original ability to resize the session on connect: https://github.com/neutrinolabs/xrdp/commit/4c603d985535b44d1a6806fe32e39326fd09d906#diff-c3c65bb5a14ac4b7f1173e29399efa3c9be1daf1df0b9f84ae4c18d9cc930502

And here is where a new function was added to xup.c, which provides a template for how to do this:
https://github.com/neutrinolabs/xrdp/commit/1dd191ab1bfadb108dae3440d5c15f278830220d

However, what is still unclear is in the massive switch statement, of which my function will be 62, where that value is used to call the function in the order list. Continuing to look.

[Nexarian]

I suspect the answer to how to wire up a new xup.c function to xrdp_mm.c is here, the very next commit in the history: https://github.com/neutrinolabs/xrdp/commit/1dd191ab1bfadb108dae3440d5c15f278830220d

[Nexarian]

Ugh I'm still having trouble figuring out how to connect xrdp_mm.c to xup.c. I've moved what appears to be the resize monitor function into its own function: https://github.com/Nexarian/xrdp/commit/d06b37f635af4df7cf8d042b7f16ef4881f2ad55

Do I invoke it from here (https://github.com/Nexarian/xrdp/commit/d06b37f635af4df7cf8d042b7f16ef4881f2ad55#diff-e60b8fc679e75b5fda6f69663b8379a1bdf2f74c47cdb2db31a0c8fa7b2dce3bR1142) or somewhere else? And how do I make that connection in the code. From what I can tell, passing a network message directly to xorgxrdp, as we wish to do in this case, is a rare event. Most of the code seems to deal with xrdp <-> client communication, and messages TO xorgxrdp are few? But where are they?

[Nexarian]

I tried to simply add int send_server_monitor_resize(struct mod *mod, struct stream *s); to xup.h and then including that in xrdp_mm.c but the mod structures are different and don't inherit from each other, so I have to do the real work of figuring out the proper signaling mechanism... This could take a bit.

Next lead, looks like this change may contain the type of interaction I need, maybe: https://github.com/neutrinolabs/xrdp/commit/21f90e3ca288bacb6d6c69bf9d3b0f0d1aca977e#diff-dd6dc787788bd1b54555c7f4daec8a3ca70cd02f072124436a4619e0561a239c