MINOR: mux-quic: support stream opening via MAX_STREAM_DATA

MAX_STREAM_DATA can be used as the first frame of a stream. In this
case, the stream should be opened, if it respects flow-control limit. To
implement this, simply replace plain lookup in stream tree by
qcc_get_qcs() at the start of the parsing function. This automatically
takes care of opening the stream if not already done.

As specified by RFC 9000, if MAX_STREAM_DATA is receive for a
receive-only stream, a STREAM_STATE_ERROR connection error is emitted.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 6cf2504..f03a581 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -762,18 +762,29 @@
 /* Handle a new MAX_STREAM_DATA frame. <max> must contains the maximum data
  * field of the frame and <id> is the identifier of the QUIC stream.
  *
- * Returns 0 on success else non-zero.
+ * Returns 0 on success else non-zero. On error, the received frame should not
+ * be acknowledged.
  */
 int qcc_recv_max_stream_data(struct qcc *qcc, uint64_t id, uint64_t max)
 {
 	struct qcs *qcs;
-	struct eb64_node *node;
 
 	TRACE_ENTER(QMUX_EV_QCC_RECV, qcc->conn);
 
-	node = eb64_lookup(&qcc->streams_by_id, id);
-	if (node) {
-		qcs = eb64_entry(node, struct qcs, by_id);
+	/* RFC 9000 19.10. MAX_STREAM_DATA Frames
+	 *
+	 * Receiving a MAX_STREAM_DATA frame for a locally
+	 * initiated stream that has not yet been created MUST be treated as a
+	 * connection error of type STREAM_STATE_ERROR.  An endpoint that
+	 * receives a MAX_STREAM_DATA frame for a receive-only stream MUST
+	 * terminate the connection with error STREAM_STATE_ERROR.
+	 */
+	if (qcc_get_qcs(qcc, id, 0, 1, &qcs)) {
+		TRACE_LEAVE(QMUX_EV_QCC_RECV, qcc->conn);
+		return 1;
+	}
+
+	if (qcs) {
 		if (max > qcs->tx.msd) {
 			qcs->tx.msd = max;
 			TRACE_DEVEL("increase remote max-stream-data", QMUX_EV_QCC_RECV|QMUX_EV_QCS_RECV, qcc->conn, qcs);
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index ce4a2f9..728aaf5 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -2523,8 +2523,10 @@
 		case QUIC_FT_MAX_STREAM_DATA:
 			if (qc->mux_state == QC_MUX_READY) {
 				struct quic_max_stream_data *data = &frm.max_stream_data;
-				qcc_recv_max_stream_data(qc->qcc, data->id,
-				                         data->max_stream_data);
+				if (qcc_recv_max_stream_data(qc->qcc, data->id,
+				                              data->max_stream_data)) {
+				        goto err;
+				}
 			}
 			break;
 		case QUIC_FT_MAX_STREAMS_BIDI: