link: Fix rtnl_link_af_data_compare return value

This patch fixes a bug where because of the af_ops check
being first in the function, we were returning ~0 if af_ops
was null even if both objects really did not have af_data
and we should be returning 0.

Its better to have the af_data present check before anything else.

So, Rearranged some of the code in rtnl_link_af_data_compare.
Changes include:
	- Do the attribute present check before anything else
	- If ao_compare op not present, return ~0

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Reviewed-by: Nolan Leake <nolan@cumulusnetworks.com>
Reviewed-by: Shrijeet Mukherjee <shm@cumulusnetworks.com>
Reviewed-by: Wilson Kok <wkok@cumulusnetworks.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>

1 files changed, 11 insertions, 7 deletions

diff --git a/lib/route/link/api.c b/lib/route/link/api.c
index 63ff99c..352bb83 100644
--- a/lib/route/link/api.c
+++ b/lib/route/link/api.c
@@ -365,22 +365,26 @@ errout:
 int rtnl_link_af_data_compare(struct rtnl_link *a, struct rtnl_link *b,
 			      int family)
 {
-	struct rtnl_link_af_ops *af_ops = rtnl_link_af_ops_lookup(family);
+	struct rtnl_link_af_ops *af_ops;
 	int ret = 0;
 
-	if (!af_ops)
+	if (!a->l_af_data[family] && !b->l_af_data[family])
+		return 0;
+
+	if (!a->l_af_data[family] || !b->l_af_data[family])
 		return ~0;
 
-	if (!a->l_af_data[family] && !b->l_af_data[family])
-		goto out;
+	af_ops = rtnl_link_af_ops_lookup(family);
+	if (!af_ops)
+		return ~0;
 
-	if (!a->l_af_data[family] || !b->l_af_data[family]) {
+	if (af_ops->ao_compare == NULL) {
 		ret = ~0;
 		goto out;
 	}
 
-	if (af_ops->ao_compare)
-		ret = af_ops->ao_compare(a, b, family, ~0, 0);
+	ret = af_ops->ao_compare(a, b, family, ~0, 0);
+
 out:
 	rtnl_link_af_ops_put(af_ops);