STREAMS: problem of listen connect.ind in module

[Hwa Jin Bae]

Yarran A Lu's question was:
"......
After step 3, if there is another (N-1)connect.indication PDU arrives at  
module Y, there will be no upstream queue in listening state to take the
(N-1)connect.indication primitive.  One may suggest that the new stream
created after step 6 may be used to replace the old stream. But there is
no guaranty that after the (N-1)layer connection is established, when the (N)
layer connect.indication will come (sometime a connection is always 
maintained alive and can be reused again by the upper layer).  The ideal
solution, I think, is that the module should have the same ability, like
the user process has, to create a new queue when it accepts the lower layer
connect.indication.  However, there is no STREAMS functions provided by
AT&T to manipulate the queues.
....."

This is a good point.  However, you don't need a STREAMS function to solve
this problem.  What's needed is some extra data structure and code within
module X to take care of the multiple connections.  Usually when
implementing TCP, a pool of TCB's and sockets are allocated in the beginning.
The number of connections that a socket is willing to accept is recorded
in socket data structure when the user makes a 'listen()' call.  Then
module X is sent a T_BIND_REQ message with CONIND_number field equal to
that number.  With an extra function (call it "listen_one_at_a_time()")
that will go through TCB's and make up a new TCB (which has a pointer
to the socket queue; we are talking about a socket as implemented as
a STREAM head here) and change the state of this TCB to T_WCON_IND.
That is, instead of one-to-one correspondence between socket and TCB,
you can utilize the same queue (allocated to a socket) for multiple
TCB's which may be in various states.

/hjb


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