[libvirt] [PATCH] lxc: Fix return value handlings of vethInterfaceUpOrDown and moveInterfaceToNetNs

[Ryota Ozaki]

On Mon, Jul 26, 2010 at 6:51 PM, Daniel P. Berrange <berrange at redhat.com> wrote:
> On Sun, Jul 25, 2010 at 02:25:05AM +0900, Ryota Ozaki wrote:
>> On Sat, Jul 24, 2010 at 11:44 PM, Ryota Ozaki <ozaki.ryota at gmail.com> wrote:
>> > Hi Laine,
>> >
>> > On Sat, Jul 24, 2010 at 2:58 AM, Laine Stump <laine at laine.org> wrote:
>> >>  On 07/23/2010 01:25 PM, Ryota Ozaki wrote:
>> >>>
>> >>> Both may return a positive value when they fail. We should check
>> >>> if the value is not zero instead of checking if it's negative.
>> >>
>> >> I notice that  lxcSetupInterfaces has a comment saying that it returns -1 on
>> >> failure, but it actually just passes on what is returned by
>> >> vethInterfaceUpOrDown.
>> >
>> > Oh, I didn't know that.
>> >
>> > Additionally, I found that other functions, e.g., setMacAddr, are also handled
>> > with the wrong way. And also handling return values with virReportSystemError
>> > is also wrong because it expects an errno, not an exit code. We have to fix
>> > all of them ;-<
>> >
>> >>
>> >> Would you be willing to consider instead just changing vethInterfaceUpOrDown
>> >> and moveInterfaceToNetNs to return -1 in all error cases (and checking the
>> >> return for < 0), rather than grabbing the exit code of the exec'ed command?
>> >> None of the callers do anything with that extra information anyway, and it
>> >> would help to make the return values more consistent (which makes it easier
>> >> to catch bugs like this, or eliminates them altogether ;-)
>> >
>> > Yeah, I'm also a bit annoying with the return values. Hmm, but we now show error
>> > messages with the return values outside the functions. Without that, we have to
>> > show the error message in the functions or some other place, otherwise we lose
>> > useful information of errors. It seems not good idea.
>> >
>> > One option is to let virRun show an error message by passing NULL to the second
>> > argument (status) of it, like brSetEnableSTP in util/bridge.c, and
>> > always return -1
>> > on a failure. It'd satisfy what you suggest.
>> >
>> > Honestly said, I cannot decide. Anyone has any suggestions on that?
>
> You could just change
>
>   return cmdResult
>
> to
>
>   return -cmdResult;
>
> That would still let you give the error code, while also keeping the value
> < 0

It looks better than mine ;-) I'll rewrite my patch in such a way.

Laine, is it ok for you too?

Thanks,
  ozaki-r

>
> Daniel
> --
> |: Red Hat, Engineering, London    -o-   http://people.redhat.com/berrange/ :|
> |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :|
> |: http://autobuild.org        -o-         http://search.cpan.org/~danberr/ :|
> |: GnuPG: 7D3B9505  -o-   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|
>