Flag draft: loopback on the reverse path

[talmi]

In IETF 106 it was suggested to avoid pushing data fields on the reverse path of a looped back packet.
However, the current flag draft specifies that a transit nodes that sends back a looped back packet clears the loopback flag prior to transmission, which means that transit nodes do not have a way of knowing this is a looped back message.

Possible solutions:
(1) Push data on the reverse path - as currently defined in the draft,
or
(2) Define a new flag "Loopback reply", that indicates that data should not be pushed.