lib: Add nl_msg_end_non_empty_nested()

Later patch will make use of nl_msg_end_non_empty_nested()

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

2 files changed, 14 insertions, 0 deletions

diff --git a/lib/netlink.c b/lib/netlink.c
index 4715d68d8..ad7d35af4 100644
--- a/lib/netlink.c
+++ b/lib/netlink.c
@@ -467,6 +467,19 @@ 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'.    */
+void
+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;
+    }
+}
+
 /* Appends a nested Netlink attribute of the given 'type', with the 'size'
  * bytes of content starting at 'data', to 'msg'. */
 void
diff --git a/lib/netlink.h b/lib/netlink.h
index b931a412f..7646f91da 100644
--- a/lib/netlink.h
+++ b/lib/netlink.h
@@ -79,6 +79,7 @@ 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_put_nested(struct ofpbuf *, uint16_t type,
                        const void *data, size_t size);