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

[Daniel P. Berrange]

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

Daniel
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