lib: Refactor nested netlink APIs.

Future patches will make use of those changes.

Signed-off-by: Andy Zhou <azhou@ovn.org>
Acked-by: Jarno Rajahalme <jarno@ovn.org>

2 files changed, 18 insertions, 4 deletions

diff --git a/lib/netlink.c b/lib/netlink.c
index ad7d35af4..ae4c72a55 100644
--- a/lib/netlink.c
+++ b/lib/netlink.c
@@ -467,16 +467,29 @@ nl_msg_end_nested(struct ofpbuf *msg, size_t offset)
     attr->nla_len = msg->size - offset;
 }
 
-/* Same as nls_msg_end_nested() when the nested Netlink contains non empty
- * message. Otherwise, drop the nested message header from 'msg'.    */
+/* Cancel a nested Netlink attribute in 'msg'.  'offset' should be the value
+ * returned by nl_msg_start_nested(). */
 void
+nl_msg_cancel_nested(struct ofpbuf *msg, size_t offset)
+{
+    msg->size = offset;
+}
+
+/* Same as nls_msg_end_nested() when the nested Netlink contains non empty
+ * message. Otherwise, drop the nested message header from 'msg'.
+ *
+ * Return true if the nested message has been dropped.  */
+bool
 nl_msg_end_non_empty_nested(struct ofpbuf *msg, size_t offset)
 {
     nl_msg_end_nested(msg, offset);
 
     struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
     if (!nl_attr_get_size(attr)) {
-        msg->size = offset;
+        nl_msg_cancel_nested(msg, offset);
+        return true;
+    } else {
+        return false;
     }
 }
 
diff --git a/lib/netlink.h b/lib/netlink.h
index 7646f91da..bb4dbf661 100644
--- a/lib/netlink.h
+++ b/lib/netlink.h
@@ -79,7 +79,8 @@ void nl_msg_put_string(struct ofpbuf *, uint16_t type, const char *value);
 
 size_t nl_msg_start_nested(struct ofpbuf *, uint16_t type);
 void nl_msg_end_nested(struct ofpbuf *, size_t offset);
-void nl_msg_end_non_empty_nested(struct ofpbuf *, size_t offset);
+void nl_msg_cancel_nested(struct ofpbuf *, size_t offset);
+bool nl_msg_end_non_empty_nested(struct ofpbuf *, size_t offset);
 void nl_msg_put_nested(struct ofpbuf *, uint16_t type,
                        const void *data, size_t size);