[vlc-devel] [PATCH 1/2] cli: remove TCP mode (--rc-host)

[Alexandre Janniaux]

On Sat, Nov 21, 2020 at 11:43:34AM +0100, Pierre Ynard via vlc-devel wrote:
> > There are several issues with TCP mode:
> > - It can only handle one client at a time, and will ignore any new
> >   connection until the current one properly ends, making it as
> >   unreliable as it comes.
> > - Most commands are not acknowledged.
> > - It has no security whatsoever.
> >
> > There is not much point trying to "fix" those issues, as it would
> > not provide backward compatibility, which was the only reason to keep
> > this.
>
> This is problematic.
>
> The lua CLI handled multiple TCP clients fine. I'd like if you could
> please clarify how most commands are unacknowledged, because I'm seeing
> messages for them; but at least the lua CLI always returned a new "> "
> prompt as acknowledgement. And the lua CLI even had password security
> with the telnet mode.
>
> So you broke this by removing the lua CLI, then you refused fixing
> broken features, and now you're using the fact that they're broken as
> rationale to remove them. This process is problematic.
>
> I'm going to state again what was decided at the last technical meeting
> about this:
>
> > Regressions will be fixed by Rémi (or other) if there are track
> > issues
>
> But you've wontfix'd several of these trac tickets relevant to this
> patchset now, and despite my efforts you have been avoiding frank and
> open discussion about them, too often leaving me to infer some rationale
> from partial or incorrect statements of yours.
>
> So not only this removal runs counter to earlier agreed-on guidelines,
> at least its commit log is wrong and misleading, and this way of going
> about it is backwards: we can decide to remove or alter features, but
> that should be discussed on the features' own merits beforehand, not on
> the basis that this subsystem has started to be dismantled and features
> that worked fine in 3.0 are now thrown in a half-broken limbo state: I
> mean, cli.lua, as well as host.lua, with proper multiple client support
> and even multiple endpoint support, are still in the repository and
> still functional with `-I telnet`, so what are we really doing here?
>
> I disagree with this patchset. TCP mode is a good and practical feature,
> with valid and secure use cases, for example a custom streaming
> application involving controller and streaming components split
> across several application servers on a trusted server LAN. I refute
> all the issues you point out, which wouldn't even be real motivation
> for removal. And I disagree with the direction and process of the
> developments of the CLI, and disagree with this kind of feature removal
> without resolving this first, and disagree with the ordering of the
> dismantling process you're putting forward should we even agree on some
> of its substance.

I agree with Pierre on this.

> > For remote control, the HTTP interface is much better. It is insecure,
> > but at least it handles multiple clients, acknowledges requests and
> > requires a password.
>
> The exact same thing can be said about the lua CLI. In fact the lua
> CLI is even better because contrary to the HTTP interface, it works
> without internet access, doesn't leak or advertise the location of the
> VLC instance interface, and doesn't open cross-site attack vectors.
>
> > For reliability and security, a much better approach is to pass the
> > CLI commands over SSH (or similar) - which is what people actually do.
>
> Do you have data to back up that assertion about what people do? I can
> see how it sounds like a better approach with interactive sessions,
> but for non-interactive application interfacing, an SSH channel as
> dependency sounds very heavy, and slow especially if you don't keep
> it open, also for example can you forward a connection to VLC's Unix
> control socket over an SSH tunnel the way you can with a TCP socket?

I agree, the usage of SSH seems opinionated. Why would an
encrypted VPN setup not being a valid case for instance
here? It's also much more reliable.

My use case is typically with an iPad, so I cannot use
the HTTP interface nor the Lua RC interface as it's using
Lua (this was my point for keeping the C RC interface and
potentially prioritizing it) and cannot install a ssh server
on it, and private networks is typically what I'm using here.

Regards,
--
Alexandre Janniaux
Videolabs