Re: [RFC PATCH 2/2] rtnl: Check if RTA_EXPIRES enum value is available

Hi,

> Work around the missing RTA_EXPIRES settings of really really old
> kernels and disable setting that attribute if the enum value is not
> present.
> ---
> acinclude.m4 | 15 +++++++++++++++
> configure.ac |  2 ++
> ell/rtnl.c   |  4 ++++
> 3 files changed, 21 insertions(+)
> 
> diff --git a/acinclude.m4 b/acinclude.m4
> index 6fb1de565a1d..3bb7b51d9ee6 100644
> --- a/acinclude.m4
> +++ b/acinclude.m4
> @@ -75,3 +75,18 @@ AC_DEFUN([COMPILER_FLAGS], [
> CFLAGS+=" -Wno-unknown-pragmas"
> fi
> ])
> +
> +AC_DEFUN([TEST_RTNL], [
> + AC_MSG_CHECKING([for RTA_EXPIRES])
> + AC_LANG_PUSH([C])
> + ac_rtnl_save_CFLAGS="$CFLAGS"
> + CFLAGS=""
> + AC_COMPILE_IFELSE([
> + AC_LANG_PROGRAM([#include <linux/rtnetlink.h>],
> + [enum rtattr_type_t t = RTA_EXPIRES;])],
> + AC_DEFINE(HAVE_RTA_EXPIRES, 1,
> + [Define to 1 if you have the RTA_EXPIRES enum value.])
> + AC_MSG_RESULT([yes]), AC_MSG_RESULT([no]))
> + CFLAGS=$ac_rtnl_save_CFLAGS
> + AC_LANG_POP([C])
> +])
> diff --git a/configure.ac b/configure.ac
> index cf3b53cfb574..44084bc4384b 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -111,6 +111,8 @@ AC_CHECK_FUNC(epoll_create, dummy=yes,
> 
> AC_CHECK_HEADERS(linux/types.h linux/if_alg.h)
> 
> +TEST_RTNL
> +
> AC_ARG_ENABLE(glib, AS_HELP_STRING([--enable-glib],
> [enable ell/glib main loop example]),
> [enable_glib=${enableval}])
> diff --git a/ell/rtnl.c b/ell/rtnl.c
> index ad2dca2f9e3c..5b392eae3fb3 100644
> --- a/ell/rtnl.c
> +++ b/ell/rtnl.c
> @@ -1348,7 +1348,9 @@ static uint32_t _rtnl_route_change(struct l_netlink *rtnl,
> size_t bufsize;
> void *rta_buf;
> uint16_t flags;
> +#ifdef HAVE_RTA_EXPIRES
> uint64_t now = l_time_now();
> +#endif
> 
> bufsize = NLMSG_ALIGN(sizeof(struct rtmsg)) +
> RTA_SPACE(sizeof(uint32_t)) +        /* RTA_OIF */
> @@ -1404,9 +1406,11 @@ static uint32_t _rtnl_route_change(struct l_netlink *rtnl,
> if (rt->preference)
> rta_buf += rta_add_u8(rta_buf, RTA_PREF, rt->preference);
> 
> +#ifdef HAVE_RTA_EXPIRES
> if (rt->expiry_time > now)
> rta_buf += rta_add_u32(rta_buf, RTA_EXPIRES,
> l_time_to_secs(rt->expiry_time - now));
> +#endif

while I think this is simple enough, it might make sense to actually add RTA_EXPIRES even if older kernels don’t support it.

What other obstacles do we have to get ELL compiled and working on older kernels?

Regards

Marcel