BUG/MINOR: mux-quic: support initial 0 max-stream-data

Support stream opening with an initial max-stream-data of 0.

In normal case, QC_SF_BLK_SFCTL is set when a qcs instance cannot
transfer more data due to flow-control. This flag is set when
transfering data from MUX to quic-conn instance.

However, it's possible to define an initial value of 0 for
max-stream-data. In this case, qcs instance is blocked despite
QC_SF_BLK_SFCTL not set. No STREAM frame is prepared for this stream as
it's not possible to emit any byte, so QC_SF_BLK_SFCTL flag is never
set.

This behavior should cause no harm. However, this can cause a BUG_ON()
crash on qcc_io_send(). Indeed, when sending is retried, it ensures that
only qcs instance waiting for a new qc_stream_buf or with
QC_SF_BLK_SFCTL set is present in the send_list.

To fix this, initialize qcs with 0 value for msd and QC_SF_BLK_SFCTL.
The flag is removed only if transport parameter msd value is non null.

This should be backported up to 2.6.

diff --git a/src/mux_quic.c b/src/mux_quic.c
index 8a765190e5e6515dbfb5bda2aff959e33484dc6f..5be382fab4d0a0383f86bae1349eb8c4ac78a29f 100644 (file)
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -131,6 +131,10 @@ static struct qcs *qcs_new(struct qcc *qcc, uint64_t id, enum qcs_type type)
                qcs->tx.msd = qcc->rfctl.msd_uni_l;
        }
 
+       /* Properly set flow-control blocking if initial MSD is nul. */
+       if (!qcs->tx.msd)
+               qcs->flags |= QC_SF_BLK_SFCTL;
+
        qcs->rx.ncbuf = NCBUF_NULL;
        qcs->rx.app_buf = BUF_NULL;
        qcs->rx.offset = qcs->rx.offset_max = 0;