On Wed, Aug 19, 2026 at 4:30 PM Alexandra Rukomoinikova via dev <
[email protected]> wrote:
> Older kernels don't support NDA_NH_ID and NHA_FDB, so
> their headers lack these definitions, breaking the build.
> Add configure checks and fall back to their known constant
> values when unsupported.
>
> Fixes: 0f8551611cfe ("controller: Support FDB entries with nexthop ID
> defined.")
> Fixes: c9af703c618a ("controller: Add support for syncing the nexthop
> table.")
> Signed-off-by: Alexandra Rukomoinikova <[email protected]>
> ---
> configure.ac | 2 ++
> controller/neighbor-exchange-netlink.c | 6 ++++++
> controller/nexthop-exchange.c | 6 ++++++
> m4/ovn.m4 | 24 ++++++++++++++++++++++++
> 4 files changed, 38 insertions(+)
>
> diff --git a/configure.ac b/configure.ac
> index cfa4cc386..f0628d687 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -171,6 +171,8 @@ OVS_CHECK_PRAGMA_MESSAGE
> OVN_CHECK_VERSION_SUFFIX
> OVN_CHECK_OVS
> OVN_CHECK_VIF_PLUG_PROVIDER
> +OVN_CHECK_LINUX_NDA_NH_ID
> +OVN_CHECK_LINUX_NHA_FDB
> OVN_CHECK_LINUX_NEXTHOP_WEIGHT
> OVN_ENABLE_VIF_PLUG
> OVS_CTAGS_IDENTIFIERS
> diff --git a/controller/neighbor-exchange-netlink.c
> b/controller/neighbor-exchange-netlink.c
> index f01bfda5b..c6b21e7a2 100644
> --- a/controller/neighbor-exchange-netlink.c
> +++ b/controller/neighbor-exchange-netlink.c
> @@ -27,6 +27,12 @@
> #include "neighbor-exchange-netlink.h"
> #include "neighbor.h"
>
> +/* NDA_NH_ID was added in Linux 5.8 and might be missing in older kernel
> + * headers. */
> +#ifndef HAVE_NDA_NH_ID
> +#define NDA_NH_ID 13
> +#endif
> +
> VLOG_DEFINE_THIS_MODULE(neighbor_exchange_netlink);
>
> #define NETNL_REQ_BUFFER_SIZE 128
> diff --git a/controller/nexthop-exchange.c b/controller/nexthop-exchange.c
> index 8718b893f..37e80f161 100644
> --- a/controller/nexthop-exchange.c
> +++ b/controller/nexthop-exchange.c
> @@ -39,6 +39,12 @@ static int nh_table_parse__(struct ofpbuf *, size_t ofs,
> static void nh_populate_grp_pointers(struct nexthop_entry *, struct hmap
> *);
> static uint32_t nexthop_entry_hash(uint32_t id);
>
> +/* NHA_FDB was added in Linux 5.8 and might be missing in older kernel
> + * headers. */
> +#ifndef HAVE_NHA_FDB
> +#define NHA_FDB 11
> +#endif
> +
> /* The following definition should be available in Linux 6.12 and might be
> * missing if we have older headers. */
> #ifndef HAVE_NH_GRP_WEIGHT
> diff --git a/m4/ovn.m4 b/m4/ovn.m4
> index 22ad1a27f..6be2bba09 100644
> --- a/m4/ovn.m4
> +++ b/m4/ovn.m4
> @@ -453,6 +453,30 @@ AC_DEFUN([OVS_CHECK_LINUX_NETLINK], [
> [Define to 1 if struct nla_bitfield32 is available.])])
> ])
>
> +dnl OVN_CHECK_LINUX_NDA_NH_ID
> +dnl
> +dnl Configure Linux netlink neighbour NDA_NH_ID compat.
> +AC_DEFUN([OVN_CHECK_LINUX_NDA_NH_ID], [
> + AC_COMPILE_IFELSE([
> + AC_LANG_PROGRAM([#include <linux/neighbour.h>], [
> + int x = NDA_NH_ID;
> + ])],
> + [AC_DEFINE([HAVE_NDA_NH_ID], [1],
> + [Define to 1 if NDA_NH_ID is available.])])
> +])
> +
> +dnl OVN_CHECK_LINUX_NHA_FDB
> +dnl
> +dnl Configure Linux netlink nexthop NHA_FDB compat.
> +AC_DEFUN([OVN_CHECK_LINUX_NHA_FDB], [
> + AC_COMPILE_IFELSE([
> + AC_LANG_PROGRAM([#include <linux/nexthop.h>], [
> + int x = NHA_FDB;
> + ])],
> + [AC_DEFINE([HAVE_NHA_FDB], [1],
> + [Define to 1 if NHA_FDB is available.])])
> +])
> +
> dnl OVN_CHECK_LINUX_NEXTHOP_WEIGHT
> dnl
> dnl Configure Linux netlink nexthop compat.
> --
> 2.48.1
>
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> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>
>
Thank you Alexandra,
applied to main.
Regards,
Ales
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