According to RFC1982: "Addition of a value outside the range
[0 .. (2^(SERIAL_BITS - 1) - 1)] is undefined.". Mds uses 16
bits for mds flow control, thus the maximum allowed range of
window size is 2^15 - 1 = 32767.
The 'mdstest 27 8' has randomly hit this limitation with the
counter errors that is detected in mds as belog logging:
FCTRL: [me] <-- [node:1001001, ref:2784751213],
RcvChkAck[fseq:31067, chunk:3], sndwnd[acked:31064,
send:63850, nacked:1901634], queue[size:32785],
Error[msg disordered]
The fseq should always be less then sndwnd_.send_, hence mds
should check the sender being capable of sending more message
only if D = sndwnd_.send_ - sndwnd_.acked_ < 2^15 - 1 = 32767
If a burst of message is sent, D could be > 32767, mds in this
case should notify the sender try to send again later; which
however could leads to a backward compatibility. For now mds
weaken the windown size verification, only logs a warning and
let the transmission continue.
---
src/mds/mds_tipc_fctrl_portid.cc | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/src/mds/mds_tipc_fctrl_portid.cc b/src/mds/mds_tipc_fctrl_portid.cc
index a9fa7d3..6eae7d4 100644
--- a/src/mds/mds_tipc_fctrl_portid.cc
+++ b/src/mds/mds_tipc_fctrl_portid.cc
@@ -378,7 +378,28 @@ void TipcPortId::ReceiveChunkAck(uint16_t fseq, uint16_t
chksize) {
txprob_cnt_, (uint8_t)state_);
}
// update sender sequence window
- if (sndwnd_.acked_ < Seq16(fseq) && Seq16(fseq) < sndwnd_.send_) {
+ if (sndwnd_.acked_ < Seq16(fseq)) {
+ // The fseq_ should always be less then sndwnd_.send_, hence
+ // mds should check the sender being capable of sending more
+ // message only if D = sndwnd_.send_ - sndwnd_.acked_ < 2^15 - 1 = 32767
+ // If a burst of message is sent, D could be > 32767
+ // mds in this case should notify the sender try to send again
+ // later; which however could leads to a backward compatibility
+ // For now mds logs a warning and let the transmission continue
+ // (mds could be changed to return try again if it is not a backward
+ // compatibility problem to a specific client.
+ if (Seq16(fseq) >= sndwnd_.send_) {
+ m_MDS_LOG_ERR("FCTRL: [me] <-- [node:%x, ref:%u], "
+ "RcvChkAck[fseq:%u, chunk:%u], "
+ "sndwnd[acked:%u, send:%u, nacked:%" PRIu64 "], "
+ "queue[size:%" PRIu64 "], "
+ "Warning[ack sequence out of window]",
+ id_.node, id_.ref,
+ fseq, chksize,
+ sndwnd_.acked_.v(), sndwnd_.send_.v(), sndwnd_.nacked_space_,
+ sndqueue_.Size());
+ }
+
m_MDS_LOG_DBG("FCTRL: [me] <-- [node:%x, ref:%u], "
"RcvChkAck[fseq:%u, chunk:%u], "
"sndwnd[acked:%u, send:%u, nacked:%" PRIu64 "], "
--
2.7.4
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