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BUG/MAJOR: quic: fix wrong packet building due to already acked frames

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If a packet build was asked to probe the peer with frames which have just
been acked, the frames build run by qc_build_frms() could be cancelled  by
qc_stream_frm_is_acked() whose aim is to check that current frames to
be built have not been already acknowledged. In this case the packet build run
by qc_do_build_pkt() is not interrupted, leading to the build of an empty packet
which should be ack-eliciting.

This is a bug detected by the BUG_ON() statement in qc_do_build_pk():

	    BUG_ON(qel->pktns->tx.pto_probe &&
           !(pkt->flags & QUIC_FL_TX_PACKET_ACK_ELICITING));

Thank you to @Tristan971 for having reported this issue in GH #2709

This is an old bug which must be backported as far as 2.6.
This commit is contained in:
Frederic Lecaille 2024-11-25 11:14:20 +01:00
parent d41273c633
commit 96b2641fc8
1 changed files with 17 additions and 1 deletions
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18
src/quic_tx.c
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@ -2012,7 +2012,23 @@ static int qc_do_build_pkt(unsigned char *pos, const unsigned char *end,
goto comp_pkt_len;
}
if (!ack_frm_len && !qel->pktns->tx.pto_probe)
if (qel->pktns->tx.pto_probe) {
/* If a probing packet was asked and could not be built,
* this is not because there was not enough room, but due to
* its frames which were already acknowledeged.
* See qc_stream_frm_is_acked()) called by qc_build_frms().
* Note that qc_stream_frm_is_acked() logs a trace in this
* case mentionning some frames were already acknowledged.
*
* That said, the consequence must be the same: cancelling
* the packet build as if there was not enough room in the
* TX buffer.
*/
qel->pktns->tx.pto_probe--;
goto no_room;
}
if (!ack_frm_len)
goto no_room;
}
}