stream module programming problem...
How does a stream module know a reply message is destined
to him? For example, there is a stream constructed as following:
[stream head]--[module A]--[module B]--[driver]
If both module A and module B send a DL_INFO_REQ
message to driver and that driver replys two
DL_INFO_ACK,then when module B find this upstream
message, how can he know is it a reply to him
or to module A? If he thinks this reply message
is destined to him, he shall free this message,
else he shall passthru it. So, how to tell?