Re: include/linux/netlink.h: problem when included by an application

Ben Hutchings
2011-08-07T01:15:11Z

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On Fri, 2011-08-05 at 17:45 -0400, Michel Machado wrote:
> Hi there,
>
> When an application includes header <linux/netlink.h> obtained with
> 'make headers_install' or from /usr/include/, it produces the following
> error:
>
> /usr/include/linux/netlink.h:31:2: error: expected
> specifier-qualifier-list before ‘sa_family_t’

Yeah, I know.

> The error doesn't come up in the kernel because
> include/linux/netlink.h has the following line:
>
> #include <linux/socket.h> /* for sa_family_t */
>
> However, <linux/socket.h> from /usr/include/ doesn't have sa_family_t
> because it's protected by an $ifdef __KERNEL__ in
> include/linux/socket.h.

Which is correct, as it would otherwise conflict with <sys/socket.h>.

Previous history:
http://thread.gmane.org/gmane.linux.debian.devel.bugs.general/622621
http://thread.gmane.org/gmane.linux.network/143380

> A workaround for an application is to include <sys/socket.h> before
> <linux/netlink.h>. However, shouldn't include/linux/netlink.h be fixed?
>
> The simplest solution that I came up was replacing sa_family_t in
> include/linux/netlink.h to 'unsigned short' as header
> include/linux/socket.h does for struct __kernel_sockaddr_storage
> available to applications.

Maybe we should do something like this in <linux/socket.h>:

typedef unsigned short __kernel_sa_family_t;
#ifdef __KERNEL__
typedef __kernel_sa_family_t sa_family_t;
#endif

and then use __kernel_sa_family_t in <linux/netlink.h>.

Ben.

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