Event driven qrexec

[DemiMarie]

Qubes OS version:

R4.0

Affected component(s):

qrexec

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Steps to reproduce the behavior:

Run many qrexec connections in parallel.

Expected behavior:

Qrexec connections can be done without creating new processes.

Actual behavior:

Qrexec connections require creating new processes.

General notes:

There is no way to use qrexec to connect to (say) a Unix domain socket or Windows named pipe. Furthermore, qrexecd forks for each connection.

This causes problems when wanting to use qrexec for proxying, where a large number of connections may be required (such as if someone is running a server).

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Related issues:

[marmarek]

You're right, but I think it isn't the most limiting factor right now. Much bigger bottleneck is qrexec policy and we do plan to improve it (see #3293 (comment)).
On the other hand, adding different mode for qrexec calls not based on separate processes (either on calling or called side) is not something we plan to work on in foreseeable future. But we'd gladly accept (quality) patches for that. That said, changing qubes-qrexec-agent to only fork(), but connect to a socket instead of exec() shouldn't be much work.

[marmarek]

You're right, but I think it isn't the most limiting factor right now. Much bigger bottleneck is qrexec policy and we do plan to improve it (see #3293 (comment)).
On the other hand, adding different mode for qrexec calls not based on separate processes (either on calling or called side) is not something we plan to work on in foreseeable future. But we'd gladly accept (quality) patches for that. That said, changing qubes-qrexec-agent to only fork(), but connect to a socket instead of exec() shouldn't be much work.