route-exchange-netlink: Use existing RTPROT_OVN.

The RTPROT_OVN value has been merged to the net-next tree [1].
Until it is available on all systems ovs forward declares this value.

This allows us to drop the definition of the value from OVN.

[1]: https://web.git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=6002850fdfe0b4343136670a9895b6ba4ee3285b

Signed-off-by: Felix Huettner <felix.huettner@stackit.cloud>

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "ovs"]
 	path = ovs
-	url = https://github.com/openvswitch/ovs.git
+	url = https://github.com/felixhuettner/ovs.git

controller/route-exchange-netlink.h

@@ -22,12 +22,12 @@
 #include "openvswitch/list.h"
 #include <netinet/in.h>
 #include <net/if.h>
+#include <linux/rtnetlink.h>
 
-/* This value is arbitrary but currently unused.
- * See the kernel rtnetlink UAPI at
- * https://github.com/torvalds/linux/blob/master/include/uapi/linux/rtnetlink.h
- * */
-#define RTPROT_OVN 84
+/* RTPROT_OVN is defined in the kernel rtnetlink.h and forward declared in the
+ * OVS submodule. While the value should always be 84 we validate this here as
+ * tests will fail if that value ever changes. */
+BUILD_ASSERT_DECL(RTPROT_OVN == 84);
 
 struct in6_addr;
 struct hmap;

m4/ovn.m4

@@ -584,4 +584,10 @@ AC_DEFUN([OVS_CHECK_LINUX_NETLINK], [
     ])],
     [AC_DEFINE([HAVE_NLA_BITFIELD32], [1],
     [Define to 1 if struct nla_bitfield32 is available.])])
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([#include <linux/rtnetlink.h>], [
+        int x = RTPROT_OVN;
+    ])],
+    [AC_DEFINE([HAVE_RTPROT_OVN], [1],
+               [Define to 1 if RTPROT_OVN is available.])])
 ])