Re: [PATCH v3 1/3] docs: add a document describing the 'channels' mechanism

[Ian Campbell <Ian.Campbell@citrix.com>]

On Tue, 2014-06-24 at 12:15 +0100, Dave Scott wrote:
> On 24 Jun 2014, at 11:43, Ian Jackson <Ian.Jackson@eu.citrix.com> wrote:
> 
> > Dave Scott writes ("Re: [PATCH v3 1/3] docs: add a document describing the 'channels' mechanism"):
> >> On 23 Jun 2014, at 15:53, Ian Jackson <Ian.Jackson@eu.citrix.com> wrote:
> >>> I forgot to ask: what will a guest do that doesn't understand these
> >>> special-purpose "console"s ?
> >> 
> >> In a Linux VM they’ll just appear as /dev/hvcX devices. I assume something similar in a *BSD.
> > 
> > ... and then what would happen with them ?  Nothing ?  If so, fine.
> > 
> > I'm just worried that something might automatically mess with them.
> > E.g. I have found a horrid thing called "modem-manager" on some
> > desktop Linuces which opens (all?) serial devices and tries blathering
> > AT commands at them…
> 
> The uses for these channels all involve talking to some specific
> software inside the guest, for example an “early configuration”
> service or a guest agent. It only makes sense to connect a channel to
> a guest if your guest has been configured to expect it. You would
> install your VM as normal, install your special software, shutdown,
> add the channels, possibly clone/publish your guest as a template and
> then restart.
> 
> You’re right that an unconfigured or misconfigured guest could do
> anything in theory. Your AT command scenario sounds quite realistic
> and would make a good example in the docs of why in-guest
> configuration is necessary.
> 
> I think I should elaborate more on the use-cases in the docs to make all this clearer.

it also implies that the backend should be tolerant of frontends talking
nonsense at them, but of course that's also true for security reasons...

Ian.


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