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BUG/MAJOR: quic: do not loop on emission on closing/draining state

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To emit CONNECTION_CLOSE frame, a special buffer is allocated via
qc_txb_store(). This is due to QUIC_FL_CONN_IMMEDIATE_CLOSE flag.
However this flag is reset after qc_send_ppkts() invocation to prevent
reemission of CONNECTION_CLOSE frame.

qc_send() can invoke multiple times a series of qc_prep_pkts() +
qc_send_ppkts() to emit several datagrams. However, this may cause a
crash if on first loop a CONNECTION_CLOSE is emitted. On the next loop
iteration, QUIC_FL_CONN_IMMEDIATE_CLOSE is resetted, thus qc_prep_pkts()
will use the wrong buffer size as end delimiter. In some cases, this may
cause a BUG_ON() crash due to b_add() outside of buffer.

This bug can be reproduced by using a while loop of ngtcp2-client and
interrupting them randomly via Ctrl+C.

Here is the patch which introduce this regression :
  cdfceb10ae136b02e51f9bb346321cf0045d58e0
  MINOR: quic: refactor qc_prep_pkts() loop
This commit is contained in:
Amaury Denoyelle 2024-06-17 15:39:24 +02:00
parent c714b6bb55
commit 937324d493
1 changed files with 13 additions and 2 deletions
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15
src/quic_tx.c
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@ -708,8 +708,13 @@ int qc_send(struct quic_conn *qc, int old_data, struct list *send_list)
qc->flags |= QUIC_FL_CONN_RETRANS_OLD_DATA;
}
/* Prepare and send packets until we could not further prepare packets. */
while (!LIST_ISEMPTY(send_list)) {
/* Prepare and send packets until we could not further prepare packets.
* Sending must be interrupted if a CONNECTION_CLOSE was already sent
* previously and is currently not needed.
*/
while (!LIST_ISEMPTY(send_list) &&
(!(qc->flags & (QUIC_FL_CONN_CLOSING|QUIC_FL_CONN_DRAINING)) ||
(qc->flags & QUIC_FL_CONN_IMMEDIATE_CLOSE))) {
/* Buffer must always be empty before qc_prep_pkts() usage.
* qc_send_ppkts() ensures it is cleared on success.
*/
@ -728,6 +733,12 @@ int qc_send(struct quic_conn *qc, int old_data, struct list *send_list)
TRACE_DEVEL("stopping on qc_prep_pkts() return", QUIC_EV_CONN_TXPKT, qc);
break;
}
if ((qc->flags & QUIC_FL_CONN_DRAINING) &&
!(qc->flags & QUIC_FL_CONN_IMMEDIATE_CLOSE)) {
TRACE_DEVEL("draining connection", QUIC_EV_CONN_TXPKT, qc);
break;
}
}
qc_txb_release(qc);