refresh: reset TCP connection when fallback from IXFR to AXFR

src/knot/events/handlers/refresh.c

@@ -835,6 +835,7 @@ static int transfer_consume(knot_layer_t *layer, knot_pkt_t *pkt)
 		REFRESH_LOG(LOG_WARNING, data->zone->name, data->remote,
 		            "fallback to AXFR");
 		ixfr_cleanup(data);
+		layer->flags |= KNOT_RQ_LAYER_CLOSE;
 		data->xfr_type = XFR_TYPE_AXFR;
 		return KNOT_STATE_RESET;
 	}

src/knot/query/layer.h

@@ -48,6 +48,7 @@ struct knot_layer {
 	void *data;                   //!< Module specific.
 	const struct knot_layer_api *api;
 	tsig_ctx_t *tsig;             //!< TODO: remove
+	unsigned flags;               //!< Custom flags.
 };
 
 /*! \brief Packet processing module API. */

src/knot/query/requestor.c

@@ -197,6 +197,14 @@ static int request_reset(struct knot_requestor *req,
 	knot_layer_reset(&req->layer);
 	tsig_reset(&last->tsig);
 
+	if (req->layer.flags & KNOT_RQ_LAYER_CLOSE) {
+		req->layer.flags &= ~KNOT_RQ_LAYER_CLOSE;
+		if (last->fd >= 0) {
+			close(last->fd);
+			last->fd = -1;
+		}
+	}
+
 	if (req->layer.state == KNOT_STATE_RESET) {
 		return KNOT_LAYER_ERROR;
 	}

src/knot/query/requestor.h

@@ -31,6 +31,10 @@ enum {
 	KNOT_RQ_UDP = 1 << 0  /* Use UDP for requests. */
 };
 
+enum {
+	KNOT_RQ_LAYER_CLOSE = 1 << 0
+};
+
 /*! \brief Requestor structure.
  *
  *  Requestor holds a FIFO of pending queries.
@@ -48,7 +52,6 @@ struct knot_request {
 	knot_pkt_t *query;
 	knot_pkt_t *resp;
 	tsig_ctx_t tsig;
-	knot_layer_t layer;
 
 	knot_sign_context_t sign; /* TODO: Remove. Used in updates only, should
 	                             be part of the zone update context. */