Added a more explanatory comment.

diff --git a/lib/layer/iterate.c b/lib/layer/iterate.c
index f668638a4fc968c77ee0bf17635f14a288ff439d..fe5f3e070ea014923507b346e99c5e5120d42c94 100644 (file)
--- a/lib/layer/iterate.c
+++ b/lib/layer/iterate.c
@@ -512,8 +512,11 @@ static int begin(knot_layer_t *ctx, void *module_param)
                return ctx->state;
        }
        /*
-        * Fail if no query section. DNS cookies must be handled before
-        * this layer.
+        * RFC7873 5.4 extends the QUERY operation code behaviour in order to
+        * be able to generate requests for server cookies. Such requests have
+        * QDCOUNT equal to zero and must contain a cookie option.
+        * Server cookie queries must be handled by the cookie module/layer
+        * before this layer.
         */
        const struct kr_request *req = ctx->data;
        const struct kr_query *qry = req->current_query;