Re: If your networking is failing after updating to the latest git version of QEMU...

[Jakob Bohm]

On 2022-09-29 08:34, Thomas Huth wrote:
> On 29/09/2022 04.32, Jason Wang wrote:
> > On Thu, Sep 29, 2022 at 1:06 AM Philippe Mathieu-Daudé 
> > <f4bug@amsat.org> wrote:
> > > On 28/9/22 10:27, Thomas Huth wrote:
> > > > ... it might have happened due to the removal of the "slirp" submodule
> > > > from the git repository. For example if you see an error message 
> > > > like this:
> > > >
> > > >    Parameter 'type' expects a netdev backend type
> > > >
> > > > this likely means that the "user" mode backend type is not 
> > > > available in
> > > > your binary anymore. To fix it, simply install "libslirp-devel" (or
> > > > libslirp-dev or however it is called) from your OS distribution and
> > > > recompile.
> > >
> > > Thanks for the hint Thomas. I'm afraid many developers will miss your
> > > email.
> > >
> > > Jason, Marc-André, could we improve the buildsys check or display
> > > a more helpful information from the code instead?
> >
> > It looks to me we need to improve the build.
>
> I'm not sure there is anything to improve in the build system - 
> configure/meson.build are just doing what they should: Pick the 
> default value for "slirp" if the user did not explicitly specify 
> "--enable-slirp".
>
> But the error message is not very helpful. It should rather say 
> something like (partly suggested by Daniel in IRC yesterday already):
>
>  Type 'user' is not a supported netdev backend by this QEMU build. 
> Please check the spelling or whether it has been enabled at 
> compilation time.
>
> ... or something like this.
>
> Someone interested to write a patch?
Maybe a more actionable error message such as:

Type 'user' is not a supported netdev backend by this QEMU build
because the libslirp development files were not found during build
of QEMU.

The condition for this error message should be that both the
user backend is not compiled AND the build system did not detect
libslirp.

Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
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