Re: XT_ALIGN changed to use ALIGN breaks iproute2

[Ben Hutchings <bhutchings@solarflare.com>]

On Tue, 2010-03-30 at 16:15 +0300, Alexey Dobriyan wrote:
> On Tue, Mar 30, 2010 at 12:28 PM, Andreas Henriksson <andreas@fatal.se> wrote:
> > You updated the kernel header include/linux/netfilter/x_tables.h
> > in torvalds/linux-2.6.git commit 42107f5009da223daa800d6da6904d77297ae829
> > with the comment "Use ALIGN() macro while I'm at it for same types.".
> >
> > When this header was synced into iproute2 the build broke because the
> > ALIGN macro apparently only is defined in kernel headers.
> >
> > (For iproute2 the problem was introduced in
> > 8ecdcce08319d0e39b0d32c1d17db3f69d85a35c and found by Stephen
> > and worked around in 609ceb807deba8e23 and edaaa11e5a3cf2c9c1a39)
> >
> > I'm guessing the problem in the iproute2 header sync is just a heads
> > up for what's going to happen when distributions updates their
> > system headers to match linux 2.6.33.
> >
> >
> > Could someone who knows how the userspace version of the kernel
> > headers are generated please find a suitable solution?
> 
> We can export ALIGN to userspace, but the name is so generic,
> so it's not clear what breakage more risky.

Right.

> XT_ALIGN is a macro so breakage will appear only when it's used,
> not when header is included directly or indirectly.
> 
> We have tc, iptables, both carry their own copy of headers, what else?
> 
> Right now, I'd say, do nothing, and iptables will carry fixlet as in tc,
> eventually.

Why should every user-space consumer have to fix this up?  We've been
through this with ethtool.h in the past (wrong type names); please don't
repeat that mistake.

Note that <linux/kernel.h> is exported and could be changed to define a
macro named e.g. __KERNEL_ALIGN() for user-space.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.