Work around libnl address caching bug

rtnl_addr requires that all addresses have the "peer" attribute set in
order to be compared for equality, but this attribute is not normally
set. As a result, most addresses will not compare as equal even to
themselves, busting caching. We fix this for now by poking into the
guts of libnl if it is broken...

1 files changed, 65 insertions, 0 deletions

diff --git a/m4/libnl-check.m4 b/m4/libnl-check.m4
new file mode 100644
index 0000000000..f7d6d70715
--- /dev/null
+++ b/m4/libnl-check.m4
@@ -0,0 +1,65 @@
+AC_DEFUN([NM_LIBNL_CHECK], [
+    AC_MSG_CHECKING([for libnl address caching bug])
+    save_CFLAGS="$CFLAGS"
+    save_LDFLAGS="$LDFLAGS"
+    CFLAGS="$CFLAGS $LIBNL_CFLAGS"
+    LDFLAGS="$LDFLAGS $LIBNL_LIBS"
+    AC_RUN_IFELSE([
+#include <stdio.h>
+#include <netlink/route/addr.h>
+#include <netlink/object-api.h>
+
+int
+main (int argc, char **argv)
+{
+	struct nl_handle *nlh;
+	struct nl_cache *cache;
+	struct nl_object *obj;
+
+	nlh = nl_handle_alloc ();
+	if (nl_connect (nlh, NETLINK_ROUTE) < 0) {
+		fprintf (stderr, "couldn't connect to netlink: %s", nl_geterror ());
+		return 3;
+	}
+
+	cache = rtnl_addr_alloc_cache (nlh);
+	if (!cache || nl_cache_nitems (cache) == 0) {
+		fprintf (stderr, "couldn't fill address cache: %s", nl_geterror ());
+		return 3;
+	}
+
+	obj = nl_cache_get_first (cache);
+	if (nl_object_identical (obj, obj))
+		return 0;
+
+	nl_cache_get_ops (cache)->co_obj_ops->oo_id_attrs &= ~0x80;
+	if (nl_object_identical (obj, obj))
+		return 1;
+	else
+		return 2;
+}
+], libnl_bug=$?, libnl_bug=$?, libnl_bug=cross)
+
+    CFLAGS="$save_CFLAGS"
+    LDFLAGS="$save_LDFLAGS"
+
+    case $libnl_bug in
+    0) AC_MSG_RESULT([no])
+       ;;
+
+    1) AC_MSG_RESULT([yes, using workaround])
+       AC_DEFINE(LIBNL_NEEDS_ADDR_CACHING_WORKAROUND, 1, [Define this to hack around buggy libnl rtnl_addr caching])
+       ;;
+
+    2) AC_MSG_RESULT([yes, and workaround doesn't work])
+       AC_MSG_ERROR([Installed libnl has broken address caching; please patch or upgrade])
+       ;;
+
+    cross) AC_MSG_RESULT([cross-compiling... assuming it works!])
+           ;;
+
+    *) AC_MSG_RESULT([?])
+       AC_MSG_ERROR([libnl test program failed])
+       ;;
+esac
+])