Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Abdoulaye Walsimou GAYE]

Hello,
While trying to compile busybox-1.20.2, the following issue raised:

   CC      networking/ifplugd.o
In file included from /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/net/ethernet.h:10:0,
                  from networking/ifplugd.c:41:
/home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/netinet/if_ether.h:75:8: error: redefinition of 'struct ethhdr'
/home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/linux/if_ether.h:127:8: note: originally defined here

Note that uClibc strategy here is to include linux/if_ether.h

Thanks,
AWG

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Rich Felker]

On Tue, Oct 09, 2012 at 12:45:17AM +0200, Abdoulaye Walsimou GAYE wrote:
> Hello,
> While trying to compile busybox-1.20.2, the following issue raised:
> 
>   CC      networking/ifplugd.o
> In file included from /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/net/ethernet.h:10:0,
>                  from networking/ifplugd.c:41:
> /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/netinet/if_ether.h:75:8: error: redefinition of 'struct ethhdr'
> /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/linux/if_ether.h:127:8: note: originally defined here
> 
> Note that uClibc strategy here is to include linux/if_ether.h

It's a bug to be including linux/if_ether.h, and there's no way to
work around this without depending on kernel headers, which musl will
not do for two reasons:

1. We can't control conformance issues and/or breakage if they expose
crap into the namespace that they shouldn't be exposing, and this
tends to vary by version.

2. It makes it so you can't build or use musl without kernel headers.

It should be a one-line patch to fix ifplugd.

Rich

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Isaac Dunham]

On Mon, 8 Oct 2012 19:33:07 -0400
Rich Felker <dalias@aerifal.cx> wrote:

> On Tue, Oct 09, 2012 at 12:45:17AM +0200, Abdoulaye Walsimou GAYE wrote:
> > Hello,
> > While trying to compile busybox-1.20.2, the following issue raised:
> > 
> >   CC      networking/ifplugd.o
> > In file included from /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/net/ethernet.h:10:0,
> >                  from networking/ifplugd.c:41:
> > /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/netinet/if_ether.h:75:8: error: redefinition of 'struct ethhdr'
> > /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/linux/if_ether.h:127:8: note: originally defined here
> > 
> > Note that uClibc strategy here is to include linux/if_ether.h
> 
> It's a bug to be including linux/if_ether.h, and there's no way to
> work around this without depending on kernel headers, which musl will

Patch that does work around it:

-#ifndef _NETINET_IF_ETHER_H
+/* Check for <linux/if_ether.h> - _LINUX_IF_ETHER_H will also work */
+#if !defined(_NETINET_IF_ETHER_H) || !defined(ETH_ALEN)
#define _NETINET_IF_ETHER_H
+#define _LINUX_IF_ETHER_H /* linux/if_ether.h defines the same stuff */

#include <stdint.h>
#include <sys/types.h>


Not really clean, but all that an application can rely on getting from either header can be found in the other:
on my install, the content of linux/if_ether.h is exactly the same except it uses kernel types.

-- 
Isaac Dunham <idunham@lavabit.com>

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Rich Felker]

On Tue, Oct 09, 2012 at 04:13:43PM -0700, Isaac Dunham wrote:
> > It's a bug to be including linux/if_ether.h, and there's no way to
> > work around this without depending on kernel headers, which musl will
> 
> Patch that does work around it:
> 
> -#ifndef _NETINET_IF_ETHER_H
> +/* Check for <linux/if_ether.h> - _LINUX_IF_ETHER_H will also work */
> +#if !defined(_NETINET_IF_ETHER_H) || !defined(ETH_ALEN)
> #define _NETINET_IF_ETHER_H
> +#define _LINUX_IF_ETHER_H /* linux/if_ether.h defines the same stuff */

That is a clever workaround, but the way it's written it breaks
include-guard heuristics. Instead, it should be..

#ifndef _NETINET_IF_ETHER_H
#define _NETINET_IF_ETHER_H

#ifndef ETH_ALEN
...
#endif

#endif

But does it work the other way around, i.e. if <netinet/if_ether.h> is
included first?

I'd still rather just press upstream to fix this stupid bug if we can.
This is the kind of thing that only affects a small number of broken
applications, and as such, I really question whether it merits ugly
workarounds.


Rich

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Isaac Dunham]

On Tue, 9 Oct 2012 19:15:53 -0400
Rich Felker <dalias@aerifal.cx> wrote:

> On Tue, Oct 09, 2012 at 04:13:43PM -0700, Isaac Dunham wrote:
> > > It's a bug to be including linux/if_ether.h, and there's no way to
> > > work around this without depending on kernel headers, which musl will
> > 
> > Patch that does work around it:
> > 
> > -#ifndef _NETINET_IF_ETHER_H
> > +/* Check for <linux/if_ether.h> - _LINUX_IF_ETHER_H will also work */
> > +#if !defined(_NETINET_IF_ETHER_H) || !defined(ETH_ALEN)
> > #define _NETINET_IF_ETHER_H
> > +#define _LINUX_IF_ETHER_H /* linux/if_ether.h defines the same stuff */
> 
> That is a clever workaround, but the way it's written it breaks
> include-guard heuristics. Instead, it should be..
> 
> #ifndef _NETINET_IF_ETHER_H
> #define _NETINET_IF_ETHER_H
> 
> #ifndef ETH_ALEN
> ...
> #endif
> 
> #endif
> 
> But does it work the other way around, i.e. if <netinet/if_ether.h> is
> included first?
That's what the second change is for:
> > +#define _LINUX_IF_ETHER_H /* linux/if_ether.h defines the same stuff */

> I'd still rather just press upstream to fix this stupid bug if we can.
> This is the kind of thing that only affects a small number of broken
> applications, and as such, I really question whether it merits ugly
> workarounds.

Agreed. I mainly mentioned that because I take "*can't* do <xyz> without <abc>" as a challenge.

-- 
Isaac Dunham <idunham@lavabit.com>

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Abdoulaye Walsimou GAYE]

On 10/09/2012 01:33 AM, Rich Felker wrote:
> On Tue, Oct 09, 2012 at 12:45:17AM +0200, Abdoulaye Walsimou GAYE wrote:
>> Hello,
>> While trying to compile busybox-1.20.2, the following issue raised:
>>
>>    CC      networking/ifplugd.o
>> In file included from /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/net/ethernet.h:10:0,
>>                   from networking/ifplugd.c:41:
>> /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/netinet/if_ether.h:75:8: error: redefinition of 'struct ethhdr'
>> /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/linux/if_ether.h:127:8: note: originally defined here
>>
>> Note that uClibc strategy here is to include linux/if_ether.h
> It's a bug to be including linux/if_ether.h, and there's no way to
> work around this without depending on kernel headers, which musl will
> not do for two reasons:
>
> 1. We can't control conformance issues and/or breakage if they expose
> crap into the namespace that they shouldn't be exposing, and this
> tends to vary by version.
>
> 2. It makes it so you can't build or use musl without kernel headers.
>
> It should be a one-line patch to fix ifplugd.
>
> Rich


Hi Rich,

I understand your point to not pollute the namespace, but there is others files
under linux/ doing #include <linux/if_ether.h>.

linux/ethtool.h:17:#include <linux/if_ether.h>
linux/if_tun.h:20:#include <linux/if_ether.h>
linux/if_bonding.h:48:#include <linux/if_ether.h>
linux/virtio_net.h:31:#include <linux/if_ether.h>
linux/netfilter_bridge.h:8:#include <linux/if_ether.h>
linux/bpqether.h:9:#include <linux/if_ether.h>
linux/netdevice.h:29:#include <linux/if_ether.h>
linux/if_fddi.h:12: *        if_fddi.h is based on previous if_ether.h and if_tr.h work by
linux/if_arcnet.h:20:#include <linux/if_ether.h>
linux/atmlec.h:13:#include <linux/if_ether.h>
linux/if_pppox.h:24:#include <linux/if_ether.h>
linux/if_ether.h:8: * Version:    @(#)if_ether.h    1.0.1a 02/08/94
linux/netfilter_bridge/ebtables.h:17:#include <linux/if_ether.h>


Does it means all these files should not be used in userspace application beside netinet/if_ether.h?
Or does it means that these files should not be exported to userspace headers or should include
<netinet/if_ether.h> instead?
If yes, then It's a bug and should be reported to upstream kernel network maintainers.

AWG,

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[Rich Felker]

On Wed, Oct 10, 2012 at 10:06:35PM +0200, Abdoulaye Walsimou GAYE wrote:
> On 10/09/2012 01:33 AM, Rich Felker wrote:
> >On Tue, Oct 09, 2012 at 12:45:17AM +0200, Abdoulaye Walsimou GAYE wrote:
> >>Hello,
> >>While trying to compile busybox-1.20.2, the following issue raised:
> >>
> >>   CC      networking/ifplugd.o
> >>In file included from /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/net/ethernet.h:10:0,
> >>                  from networking/ifplugd.c:41:
> >>/home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/netinet/if_ether.h:75:8: error: redefinition of 'struct ethhdr'
> >>/home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/linux/if_ether.h:127:8: note: originally defined here
> >>
> >>Note that uClibc strategy here is to include linux/if_ether.h
> >It's a bug to be including linux/if_ether.h, and there's no way to
> >work around this without depending on kernel headers, which musl will
> >not do for two reasons:
> >
> >1. We can't control conformance issues and/or breakage if they expose
> >crap into the namespace that they shouldn't be exposing, and this
> >tends to vary by version.
> >
> >2. It makes it so you can't build or use musl without kernel headers.
> >
> >It should be a one-line patch to fix ifplugd.
> >
> >Rich
> 
> 
> Hi Rich,
> 
> I understand your point to not pollute the namespace, but there is others files
> under linux/ doing #include <linux/if_ether.h>.
> 
> linux/ethtool.h:17:#include <linux/if_ether.h>
> linux/if_tun.h:20:#include <linux/if_ether.h>
> linux/if_bonding.h:48:#include <linux/if_ether.h>
> linux/virtio_net.h:31:#include <linux/if_ether.h>
> linux/netfilter_bridge.h:8:#include <linux/if_ether.h>
> linux/bpqether.h:9:#include <linux/if_ether.h>
> linux/netdevice.h:29:#include <linux/if_ether.h>
> linux/if_fddi.h:12: *        if_fddi.h is based on previous if_ether.h and if_tr.h work by
> linux/if_arcnet.h:20:#include <linux/if_ether.h>
> linux/atmlec.h:13:#include <linux/if_ether.h>
> linux/if_pppox.h:24:#include <linux/if_ether.h>
> linux/if_ether.h:8: * Version:    @(#)if_ether.h    1.0.1a 02/08/94
> linux/netfilter_bridge/ebtables.h:17:#include <linux/if_ether.h>
> 
> 
> Does it means all these files should not be used in userspace
> application beside netinet/if_ether.h?
> Or does it means that these files should not be exported to
> userspace headers or should include
> <netinet/if_ether.h> instead?
> If yes, then It's a bug and should be reported to upstream kernel
> network maintainers.

I think it's a bug that should be reported to the upstream kernel
network maintainers. But I'm not sure what the right fix is. In
general, kernel headers should never define anything that clashes with
userspace headers. However, netinet/if_ether.h is not a "standard"
header by any standard I know of; it seems to have been invented by
glibc (correct me if I'm mistaken). In this case, if I'm right, it may
actually be glibc that trampled namespace belonging to the kernel.

With that said, as the headers currently stand, I think the code bug
is the act of including both netinet/if_ether.h and linux/if_ether.h
(or any other linux/ header that includes linux/if_ether.h). An
application should use _either_ the userspace _or_ the kernel headers
for this extended functionality, not both.

Rich

Re: Clash between 'netinet/if_ether.h' and 'linux/if_ether.h'

[idunham]

> On Wed, Oct 10, 2012 at 10:06:35PM +0200, Abdoulaye Walsimou GAYE wrote:
>> On 10/09/2012 01:33 AM, Rich Felker wrote:
>> >On Tue, Oct 09, 2012 at 12:45:17AM +0200, Abdoulaye Walsimou GAYE
>> wrote:
>> >>Hello,
>> >>While trying to compile busybox-1.20.2, the following issue raised:
>> >>
>> >>   CC      networking/ifplugd.o
>> >>In file included from
>> /home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/net/ethernet.h:10:0,
>> >>                  from networking/ifplugd.c:41:
>> >>/home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/netinet/if_ether.h:75:8:
>> error: redefinition of 'struct ethhdr'
>> >>/home/walsimou/embtoolkit.git/sysroot-armel-linux-arm920t/usr/include/linux/if_ether.h:127:8:
>> note: originally defined here
>> >>
>> >>Note that uClibc strategy here is to include linux/if_ether.h
>> >It's a bug to be including linux/if_ether.h, and there's no way to
>> >work around this without depending on kernel headers, which musl will
>> >not do for two reasons:
>> >
>> >1. We can't control conformance issues and/or breakage if they expose
>> >crap into the namespace that they shouldn't be exposing, and this
>> >tends to vary by version.
>> >
>> >2. It makes it so you can't build or use musl without kernel headers.
>> >
>> >It should be a one-line patch to fix ifplugd.
>> >
>> >Rich
>>
>>
>> Hi Rich,
>>
>> I understand your point to not pollute the namespace, but there is
>> others files
>> under linux/ doing #include <linux/if_ether.h>.
>>
>> linux/ethtool.h:17:#include <linux/if_ether.h>
>> linux/if_tun.h:20:#include <linux/if_ether.h>
>> linux/if_bonding.h:48:#include <linux/if_ether.h>
>> linux/virtio_net.h:31:#include <linux/if_ether.h>
>> linux/netfilter_bridge.h:8:#include <linux/if_ether.h>
>> linux/bpqether.h:9:#include <linux/if_ether.h>
>> linux/netdevice.h:29:#include <linux/if_ether.h>
>> linux/if_fddi.h:12: *        if_fddi.h is based on previous if_ether.h
>> and if_tr.h work by
>> linux/if_arcnet.h:20:#include <linux/if_ether.h>
>> linux/atmlec.h:13:#include <linux/if_ether.h>
>> linux/if_pppox.h:24:#include <linux/if_ether.h>
>> linux/if_ether.h:8: * Version:    @(#)if_ether.h    1.0.1a 02/08/94
>> linux/netfilter_bridge/ebtables.h:17:#include <linux/if_ether.h>
>>
>>
>> Does it means all these files should not be used in userspace
>> application beside netinet/if_ether.h?
>> Or does it means that these files should not be exported to
>> userspace headers or should include
>> <netinet/if_ether.h> instead?
>> If yes, then It's a bug and should be reported to upstream kernel
>> network maintainers.
>
> I think it's a bug that should be reported to the upstream kernel
> network maintainers. But I'm not sure what the right fix is. In
> general, kernel headers should never define anything that clashes with
> userspace headers. However, netinet/if_ether.h is not a "standard"
> header by any standard I know of; it seems to have been invented by
> glibc (correct me if I'm mistaken). In this case, if I'm right, it may

It's in *BSD with a "(c) 1982,... Regents of the University of California"
notice. So it was part of the original BSD networking stack.
glibc has a strange mix of #include <linux/...> & copy-paste from the BSD
headers.

In summary, while it isn't standardized AFAICT, it's part of just about
every *nix version in recent history (AIX, OS X, Solaris, Unixware, SCO
OpenServer, OSF/1, Linux + *libc, Mach, Hurd, and probably a few more). My
best guess is that the kernel developers needed it for the kernel network
stack (hence <linux/if_ether.h>), and the libc developers included that
copy to avoid exactly this issue.

> actually be glibc that trampled namespace belonging to the kernel.
>
> With that said, as the headers currently stand, I think the code bug
> is the act of including both netinet/if_ether.h and linux/if_ether.h
> (or any other linux/ header that includes linux/if_ether.h). An
> application should use _either_ the userspace _or_ the kernel headers
> for this extended functionality, not both.