Re: [Qemu-devel] [PATCH] syscall.c: Fix build with older linux-headers

[Peter Maydell]

On 16 August 2016 at 17:41, Laurent Vivier <address@hidden> wrote:
> Le 16/08/2016 à 11:47, Michal Privoznik a écrit :
>> In c5dff280 we tried to make us understand netlink messages more.
>> So we've added a code that does some translation. However, the
>> code assumed linux-headers to be at least version 4.4 of it
>> because most of the symbols there (if not all of them) were added
>> in just that release. This, however, breaks build on systems with
>> older versions of the package.
>>
>> Signed-off-by: Michal Privoznik <address@hidden>
>
> Are you sure this "#ifdef" are correct while all these symbols are enums
> not #define?
>
> Or do I miss something?

I think you're right (some of the IFLA constants have #defines in
the headers I have but not the IFLA_BR_ or IFLA_BRPORT_ ones).
Unfortunately I've just committed this patch and tagged rc3, so we'll
have to fix this up for rc4 :-(

The best approach I can think of is to add something at the
top of syscall.c that does:
#if IFLA_BR_MAX < 9
#define IFLA_BR_GROUP_FWD_MASK 9
#endif
#if IFLA_BR_MAX < 10
#define IFLA_BR_ROOT_ID 10
#endif
etc etc

and then we can unconditionally use the symbols in the switches.

Anybody got a better idea?

Michal, can you produce a patch?

thanks
-- PMM