Module load and unload support

[matt335672]

See neutrinolabs/xrdp#1910

This PR makes the following changes to the pulseaudio modules:-

• The first commit allows the modules to be configured via parameters instead of environment variables. This is to simplify using them on systems using systemd --user
• The first commit makes sure file descriptors are closed before the modules are unloaded. Without this, pulseaudio leaks file descriptors, and chansrv does not re-listen on the audio sockets.
• The third commit adds support for sink rewinds (needed for a buffer underrun), and the pulseaudio set_state_in_io_thread callback, for versions of pulseaudio that support it.

With these changes, the following script can be used to configure pulseaudio in an xrdp session using systemctl --user

#!/bin/sh

if [ -z "$XRDP_SOCKET_PATH" -o \
     -z "$XRDP_PULSE_SINK_SOCKET" -o \
     -z "$XRDP_PULSE_SOURCE_SOCKET" ]; then
    echo "** This does not appear to be an xrdp session" >&1
    false
else
    # Remove legacy environment variable if set
    systemctl --user unset-environment PA_SCRIPT || :

    # Unload modules
    pacmd unload-module module-xrdp-sink >/dev/null 2>&1
    pacmd unload-module module-xrdp-source >/dev/null 2>&1

    # Reload modules
    pacmd load-module module-xrdp-sink \
	xrdp_socket_path=$XRDP_SOCKET_PATH \
	xrdp_pulse_sink_socket=$XRDP_PULSE_SINK_SOCKET && \
    \
    pacmd load-module module-xrdp-source \
	xrdp_socket_path=$XRDP_SOCKET_PATH \
	xrdp_pulse_source_socket=$XRDP_PULSE_SOURCE_SOCKET
fi

exit $?

I've tested the module with these platforms:-

Platform	pulseaudio version	systemd --user ?	Comments
Ubuntu 18.04	11.1	No	Hard to configure as xrdp is old
Ubuntu 20.04	13.99.1	Yes
CentOS 7	10.0	No
CentOS 8	14.0	Yes	Hard to build - wiki page added

Clearly we've got more work to do to support systemd --user properly, but this is a start.

[matt335672]

@jsorg71 - I've just noticed that 6f18573 replaces a lot of the stuff you removed in #38, but it adds in the support for the set_state_in_io_thread callback which seemed to sort things out quite a bit on the platforms above. I'd be grateful if you could take a look at this, as you are doubtless more aware than I am how all this stuff hangs together.

[jsorg71]

@matt335672 that should be ok. I was fixing a latency issue and I remember that the PA guys told me 'don't claim to support rewind if you don't implement it right'
As long as rewind works, it should be ok

[metalefty]

This is a definitely useful improvement! I think the script should be included in the installation. The location may be $PREFIX/libexec/xrdp/pulse/pa-reload or somewhere like there. Then, users can run the script to reload pa modules.

Also, is the service file for user-mode systemd required?

[metalefty]

Ah, I looked at #44.

The location of the reload script should be under libexec dir because it is a supplemental script/command. Actually, we should put startwm.sh/reconnectwm.sh scripts under libexec dir (Fedora does in local patch: https://src.fedoraproject.org/rpms/xrdp/tree/epel8 ). But let's put it aside.

Also, the desktop entry file should be included in installation
$PREFIX/share/xrdp/helpers/pulseaudio-xrdp.desktop or somewhere like there. Then, users can perform

cp /usr/share/xrdp/helpers/pulseaudio-xrdp.desktop /etc/xdg/autostart/

[matt335672]

Thanks for that - it's useful.

I think I need to spit this into a couple of PRs. One will be the code changes, and the other will be the extra files for desktop integration. I'll need to do a bit more testing on various distros to see exactly what is required.

The script above needs some mods to be more generic. One thing I've found is that I should be using pactl to load the modules rather than pacmd, as this will start pulseaudio if it isn't already active. More info on this debian thread post

[metalefty]

Okay, let's make a new release when desktop integration PR is finished (and README update).

[matt335672]

Are you happy for the README to just point to the Wiki? It's going to be easier to add platform instructions there I think, on multiple pages.

[metalefty]

Yes, how to build & install section can be a pointer to Wiki.

[metalefty]

Let's go ahead.

[matt335672]

OK - thanks.

I'm still hoping to hear from @davidcbcs on Gitter about CentOS 8, as I'm worried I might have missed something. I'll give him a couple of days to get back to me.

[davidcbcs]

Matt, Does the wiki still need the additional steps of: ./configure PULSE_DIR=/var/lib/mock/epel-8-x86_64/root/builddir/build/BUILD/pulseaudio-14.0 And sudo make install I can make those changes if you like. Dave From: matt335672 ***@***.***> Sent: Tuesday, November 9, 2021 3:45 AM To: neutrinolabs/pulseaudio-module-xrdp ***@***.***> Cc: David Culbertson ***@***.***>; Mention ***@***.***> Subject: Re: [neutrinolabs/pulseaudio-module-xrdp] Module load and unload support (#59) Merged #59<#59> into devel. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#59 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AOO42ZNAYVXEY2FPIZTGRRTULD3TBANCNFSM5FCSORQA>. Triage notifications on the go with GitHub Mobile for iOS<https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android<https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[matt335672]

Hi @davidcbcs

The wiki should be up to date for CentOS 8:-

https://github.com/neutrinolabs/pulseaudio-module-xrdp/wiki/Build-on-CentOS-8.x

Please tell me if there's anything missing.

[davidcbcs]

One thing is missing. In the Build the xrdp module section, after the make, it needs: sudo make install From: matt335672 ***@***.***> Sent: Tuesday, November 9, 2021 8:07 AM To: neutrinolabs/pulseaudio-module-xrdp ***@***.***> Cc: David Culbertson ***@***.***>; Mention ***@***.***> Subject: Re: [neutrinolabs/pulseaudio-module-xrdp] Module load and unload support (#59) Hi @davidcbcs<https://github.com/davidcbcs> The wiki should be up to date for CentOS 8:- https://github.com/neutrinolabs/pulseaudio-module-xrdp/wiki/Build-on-CentOS-8.x Please tell me if there's anything missing. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#59 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AOO42ZKZMMLI42PWEYRM7ADULE2HRANCNFSM5FCSORQA>. Triage notifications on the go with GitHub Mobile for iOS<https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android<https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[matt335672]

Fair point. Each of the sections is referred to from the main page which has that on. I think I'll need to refer back to the main page from the sections for that.