So the problem arises because the headers we have in userspace might
be older and not match what we have in the kernel. In that case, the
actual value of AF_MAX in the userspace headers might be a valid
protocol family in the new kernel.

That happens relatively often for us because we support different
kernel versions at the same time in a given Ubuntu series.

An alternative is to use the headers we have in the kernel tree, but I
believe that might cause other issues.

On Mon, Sep 16, 2019 at 10:09:13AM -0600, shuah wrote:
> On 9/16/19 9:03 AM, Marcelo Henrique Cerri wrote:
> > Use INT_MAX instead of AF_MAX, since libc might have a smaller value
> > of AF_MAX than the kernel, what causes the test to fail.
> > 
> > Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
> > ---
> >   tools/testing/selftests/net/socket.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/net/socket.c b/tools/testing/selftests/net/socket.c
> > index afca1ead677f..10e75ba90124 100644
> > --- a/tools/testing/selftests/net/socket.c
> > +++ b/tools/testing/selftests/net/socket.c
> > @@ -6,6 +6,7 @@
> >   #include <sys/types.h>
> >   #include <sys/socket.h>
> >   #include <netinet/in.h>
> > +#include <limits.h>
> >   struct socket_testcase {
> >   	int	domain;
> > @@ -24,7 +25,10 @@ struct socket_testcase {
> >   };
> >   static struct socket_testcase tests[] = {
> > -	{ AF_MAX,  0,           0,           -EAFNOSUPPORT,    0 },
> > +	/* libc might have a smaller value of AF_MAX than the kernel
> > +	 * actually supports, so use INT_MAX instead.
> > +	 */
> > +	{ INT_MAX, 0,           0,           -EAFNOSUPPORT,    0  },
> >   	{ AF_INET, SOCK_STREAM, IPPROTO_TCP, 0,                1  },
> >   	{ AF_INET, SOCK_DGRAM,  IPPROTO_TCP, -EPROTONOSUPPORT, 1  },
> >   	{ AF_INET, SOCK_DGRAM,  IPPROTO_UDP, 0,                1  },
> > 
> 
> What failure are you seeing? It sounds arbitrary to use INT_MAX
> instead of AF_MAX. I think it is important to understand the
> failure first.
> 
> Please note that AF_MAX is widely used in the kernel.
> 
> thanks,
> -- Shuah

-- 
Regards,
Marcelo