long seqno = PipelineAck.UNKOWN_SEQNO;
long ackRecvNanoTime = 0;
try {
if (type != PacketResponderType.LAST_IN_PIPELINE && !mirrorError) {
// read an ack from downstream datanode
ack.readFields(downstreamIn);
ackRecvNanoTime = System.nanoTime();
if (LOG.isDebugEnabled()) {
LOG.debug(myString + " got " + ack);
}
// Process an OOB ACK.