Re: [PATCH iproute2] ip: Fix compilation break on old systems

[Leon Romanovsky <leon@kernel.org>]

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On Mon, Nov 13, 2017 at 07:33:37AM -0800, Stephen Hemminger wrote:
> On Mon, 13 Nov 2017 12:21:19 +0200
> Leon Romanovsky <leon@kernel.org> wrote:
>
> > From: Leon Romanovsky <leonro@mellanox.com>
> >
> > As was reported [1], the iproute2 fails to compile on old systems,
> > in Cong's case, it was Fedora 19, in our case it was RedHat 7.2, which
> > failed with the following errors during compilation:
> >
> > ipxfrm.c: In function ‘xfrm_selector_print’:
> > ipxfrm.c:479:7: error: ‘IPPROTO_MH’ undeclared (first use in this
> > function)
> >   case IPPROTO_MH:
> >        ^
> > ipxfrm.c:479:7: note: each undeclared identifier is reported only once
> > for each function it appears in
> > ipxfrm.c: In function ‘xfrm_selector_upspec_parse’:
> > ipxfrm.c:1345:8: error: ‘IPPROTO_MH’ undeclared (first use in this
> > function)
> >    case IPPROTO_MH:
> >         ^                                                                                                                                                            make[1]: *** [ipxfrm.o] Error 1
> >
> > The reason to it is the order of headers files. The IPPROTO_MH field is
> > set in kernel's UAPI header file (in6.h), but only in case
> > __UAPI_DEF_IPPROTO_V6 is set before. That define comes from other kernel's
> > header file (libc-compat.h) and is set in case there are no previous
> > libc relevant declarations.
> >
> > In ip code, the include of <netdb.h> causes to indirect inclusion of
> > <netinet/in.h> and it sets __UAPI_DEF_IPPROTO_V6 to be zero and prevents from
> > IPPROTO_MH declaration.
> >
> > This patch takes the simplest possible approach to fix the compilation
> > error by checking if IPPROTO_MH was defined before and in case it
> > wasn't, it defines it to be the same as in the kernel.
> >
> > [1] https://www.spinics.net/lists/netdev/msg463980.html
> >
> > Cc: Cong Wang <xiyou.wangcong@gmail.com>
> > Cc: Riad Abo Raed <riada@mellanox.com>
> > Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
> > ---
> >  ip/xfrm.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/ip/xfrm.h b/ip/xfrm.h
> > index 8566d639..71be574d 100644
> > --- a/ip/xfrm.h
> > +++ b/ip/xfrm.h
> > @@ -30,6 +30,10 @@
> >  #include <linux/xfrm.h>
> >  #include <linux/ipsec.h>
> >
> > +#ifndef IPPROTO_MH
> > +#define IPPROTO_MH              135
> > +#endif
> > +
>
> Is there some way to add an additional header to the file instead?
> Doing local definitions seems like it might cause a future issue.

I tried various combinations of includes and didn't find working solution.

In this specific case, the value of IPPROTO_MH is defined in kernel UAPI and it
will be with us forever.

Thanks

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