Re: Changing bonding <-> ifenslave interface [was: Problem with current /proc entries]

Re: Changing bonding <-> ifenslave interface [was: Problem with current /proc entries]

[Shmulik Hen]

On Monday 20 October 2003 06:42 pm, Jay Vosburgh wrote:
>
> >I disagree. I think that the latest version of ifenslave should
> > work with all versions of the bonding module that we can
> > reasonably expect people to use. This means that if ifenslave
> > fails to use the new interface it can try the old one. (This is
> > how I understood Jeff's position).
>
>         When we discussed this previously, my understanding was:
>
>         An ifenslave only had to work forwards, it didn't need to
> go backwards.  So, an ifenslave from 2.4.X would run on that
> version, as well as any future 2.4.Y (where Y > X).  But, the
> reverse isn't true: ifenslave from 2.4.Y need not work on kernel
> 2.4.X (again, Y > X).

Suppose a user updates an application package (in this case iputils). 
It seems unreasonable to require a kernel upgrade to make the updated 
app work.

Likewise, if the user updates the kernel, existing apps should still 
work. The sole exception is when switching major kernel versions (and 
even this should be avoided where possible). This is similar to the 
modutils package that has to be updated to work with 2.6. (and once 
updated it works with 2.4 as well).

This is how we've understood Jeff's approach when the ABI issue was 
first raised:
[From <http://sourceforge.net/mailarchive/message.php?msg_id=4875256>]
    On 12 May 2003, Jeff Garzik wrote:
    > FWIW the main worry is users booting into "new bonding" and "old
    > bonding" kernels, with the same userspace.  (which of course
    > implies an ifenslave userspace upgrade, but that's ok)


Based on the above assumptions, and on the fact that removing 
SIOCDEVPRIVATE support from bonding in 2.6 already breaks 
compatibility with existing ifenslave apps, we thought the sensible 
thing to do would be to drop all support of old interfaces from 
bonding in 2.6 (including the current SIOCBOND* ioctls), and thus 
force users that upgrade to 2.6 to use a new ifenslave (that can be 
found either in the 2.6 kernel tree or at sourceforge). This new 
ifenslave will also support any 2.4 bonding.

After a while, we will probably backport the new interface into the 
2.4 bonding module, so it too will benefit from the its new 
capabilities.

>         Applying this to 2.6, a 2.6 ifenslave shouldn't need to
> control a 2.4 bonding driver, but a 2.4 ifenslave should control a
> 2.6 kernel (for reasonable ranges of 2.4.X, in particular excluding
> SIOCDEVPRIVATE).
>
>         I was thinking that the 2.4 ifenslave should work with 2.4
> or 2.6 (including the new shiny API, to make kernel upgrades less
> hassle), but the 2.6 ifenslave need not work with 2.4, so we could
> hopefully vacuum it clean of the various ABI gook once we have a
> new shiny interface.  The 2.6 ifenslave presumably won't be
> included in a distro until they ship a 2.6 kernel, so that would
> theoretically be sufficient.

The thing to note here is that there is no "2.6 ifenslave" and "2.4 
ifenslave" per se. The ifenslave app lives in several places: the 
kernel source tree, the bonding sourceforge site, the iputils RPM, 
etc. The important thing is that updating this app should not require 
a kernel upgrade.

> >We can probably provide a version of bonding/ifenslave that works
> > with the new interface within two weeks (hopefully less). This
> > is, of course, assuming we reach a consensus on the compatibility
> > issue.
>
>         Would that be dependant upon the cleanup stuff, or not?

Yes, it will. We do all our code developement on top of the cleanup 
stuff.

-- 
| Shmulik Hen   Advanced Network Services  |
| Israel Design Center, Jerusalem          |
| LAN Access Division, Platform Networking |
| Intel Communications Group, Intel corp.  |

Re: Changing bonding <-> ifenslave interface [was: Problem with current /proc entries]

[Jay Vosburgh]

[...]
>Based on the above assumptions, and on the fact that removing 
>SIOCDEVPRIVATE support from bonding in 2.6 already breaks 
>compatibility with existing ifenslave apps, we thought the sensible 
>thing to do would be to drop all support of old interfaces from 
>bonding in 2.6 (including the current SIOCBOND* ioctls), and thus 
>force users that upgrade to 2.6 to use a new ifenslave (that can be 
>found either in the 2.6 kernel tree or at sourceforge). This new 
>ifenslave will also support any 2.4 bonding.
>
>After a while, we will probably backport the new interface into the 
>2.4 bonding module, so it too will benefit from the its new 
>capabilities.

	I was leaning towards supporting existing 2.4 ifenslaves (not
the ancient ones using SIOCDEVPRIVATE, but more recent versions) so
that end users could hypothetically dabble with the 2.6 bonding
without messing with their 2.4 user space.  In that way, the 2.6 (or
"new ifenslave," if you prefer) ifenslave wouldn't have all of the old
2.4-style bonding API stuff in it.

	Anyway, I can live with the above; it does require an
ifenslave upgrade to dabble with 2.6, but as long as the 2.4
reliability isn't affected, I don't see a problem with it.

[...]
>The thing to note here is that there is no "2.6 ifenslave" and "2.4 
>ifenslave" per se. The ifenslave app lives in several places: the 
>kernel source tree, the bonding sourceforge site, the iputils RPM, 
>etc. The important thing is that updating this app should not require 
>a kernel upgrade.

	I'm having a thought here... Would it be both feasible and
reasonable to pull ifenslave.c out of the kernel source, and maintain
a separate bonding-utils package, wherein the shiny new API has some
knowledge of ifenslave versions?  In this way, the bonding kernel
driver could enforce version requirements for ifenslave, possibly at a
per-feature granularity (e.g., "need ifenslave version X for
frog-blending mode").  In this way, we'd have just one ifenslave
development line (not two), and somewhat better upgrade prospects over
time.

	In the past, I'd thought this (a bonding-utils package for
ifenslave) wasn't an especially good idea, because I didn't really see
much advantage for us in doing it.  Now, it looks like it is to our
advantage to have just one ifenslave development line, distinct from
the kernel development line (if the single ifenslave will be going
both ways there's no reason to keep two separate copies in the 2.4 and
2.6 kernel trees).

	I really do like having ifenslave right there in the kernel
source, it's very handy, but it may be better overall to pull it out
and distribute it separately.

	Comments?  Chad, you out there?  I know you really like having
ifenslave in the kernel source; what do you think about this?

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com

Re: [Bonding-devel] Re: Changing bonding <-> ifenslave interface [was: Problem with current /proc entries]

[Chad N. Tindel]

> 	In the past, I'd thought this (a bonding-utils package for
> ifenslave) wasn't an especially good idea, because I didn't really see
> much advantage for us in doing it.  Now, it looks like it is to our
> advantage to have just one ifenslave development line, distinct from
> the kernel development line (if the single ifenslave will be going
> both ways there's no reason to keep two separate copies in the 2.4 and
> 2.6 kernel trees).
> 
> 	I really do like having ifenslave right there in the kernel
> source, it's very handy, but it may be better overall to pull it out
> and distribute it separately.
> 
> 	Comments?  Chad, you out there?  I know you really like having
> ifenslave in the kernel source; what do you think about this?

I have had many numerous users email me specifically to say that they like
to have the ifenslave.c in the kernel.  They know that no matter what, when
they upgrade their kernel, they can simply compile the ifenslave that is there
and it will work.  They don't want to have to go hunt around on some website
to try to find a working ifenslave. 

In contrast, I have seen nothing but pain when trying to separate userspace
from kernel space.  Trying to get the right iputils package to match up
with the kernel you are using is a pain; and it makes the iputils stuff
just that much harder to maintain, for the same reasons we're discussing.

I have never heard of anyone complaining that ifenslave.c is packaged
with the kernel source.  

Chad