Re: (missing) pre-up and pre-down

[Dan Williams <dcbw redhat com>]

On Sat, 2009-08-08 at 01:50 +0100, Graham Lyon wrote:
> 
> 
> 2009/8/7 Dan Williams <dcbw redhat com>
>         On Wed, 2009-08-05 at 11:30 +0100, Marc Herbert wrote:
>         > Dan Williams a écrit :
>         > >
>         > > There are two reasons I've not yet added pre-up and
>         pre-down.  They are:
>         > >
>         > > 2) appropriateness
>         >
>         > Hmmm, the good old "just do not do this" answer... the best
>         answer to
>         > any feature request ever ;-) Especially to people having
>         using this
>         > feature for ages and being suddendly deprived of it.
>         
>         
>         Please note I didn't say *all* uses were inappropriate.  Just
>         that
>         because we've done something the same way forever, doesn't
>         *necessarily*
>         mean that it should always be done that way until the end of
>         time.
>         
>         >
>         > >     b) by the time any pre-down script will run, often the
>         connection
>         > > has already gone away (the AP is out of range, the cable
>         has been
>         > > unplugged already, etc) so any operation a pre-down script
>         does *cannot*
>         > > depend on the interface being up; it must gracefully
>         fail.  Common
>         > > things people wanted to do here were unmount network
>         shares;
>         > > but since the script must always handle unexpected
>         disconnects (which
>         > > not all network file systems do well), you might as well
>         just run this
>         > > from post-down anyway.
>         >
>         > I think "pre-down" cleanup scripts could (should?) simply
>         NOT be run on
>         > unexpected disconnects (as opposed to explicit disconnection
>         > requests). Simply because they are called PRE-down, not
>         AT-down.
>         
>         
>         I did think about this a lot while composing the mail, and
>         couldn't come
>         up with a good reason to not run pre-down scripts on
>         unexpected
>         disconnect.  I don't really care either way.
>  
> Not running them on unexpected disconnects would breed inconsistency
> and would be confusing for tracking issues/users who aren't aware of
> this quirk. Running them on unexpected disconnections would be
> pointless - they are scripts that, by definition, expect the interface
> to be up. There's no winning.
> 
> Perhaps when a connection drops unexpectedly the pre-down scripts
> should be run with an argument of some kind to inform them that the
> interface has already dropped? That way they can clean up the mess
> that's created but avoid any action that requires the interface to
> still be up...

That was my thinking too, and probably the right thing to do.

Dan

> Just two my cents
> 
> -Graham
> 
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