CoDel marking statistics for DCTCP mode
This carries over an unresolved issue from MR 122. In Linux CoDel, when CE_threshold is enabled (i.e. for DCTCP), if there is a delay spike, it is possible for a packet to be marked first for exceeding target delay and again for exceeding CE_threshold delay (both counters are incremented). See:
Mohit took the action item to learn from the original authors why it is coded this way.
We will need to resolve whether we also count the same way (that the same packet can cause two marking events to be logged in the same queue disc).