[openib-general] Re: [PATCH] CMA: allow/require bind beforeconnect

[Sean Hefty]

Roland Dreier wrote:
> OK, fair enough.  I was really replying to the first sentence of:
> 
>      Caitlin> From the perspective of any given host, IP addresses are
>      Caitlin> unique across all interface devices. A given connection
>      Caitlin> can therefore be identified by just the 4-tuple, with no
>      Caitlin> need to explicitly state "via this device".
> 
> IP addresses are not unique.  However, I do agree that a 4-tuple
> uniquely identifies a TCP connection.

I agree with this as well.  But the CMA, when running over IB, does not 
establish TCP connections.  It's simply mapping addresses.  RDMA connections 
will end up being identified by QPs.

If a user tries to establish a connection, the CMA will determine which device 
that connection will go out on.  If it's an IB device, there's no need for a 
local port number.  If it's an iWarp device, then the iWarp CM will need to 
allocate a usable port number.

What I'm still trying to understand is why the CMA should allocate a port number 
for active connections.  The port space over IB is separate, and the port number 
is not needed for connecting or routing data.  Are there specific applications 
that will run over RDMA that will have a problem with this?

- Sean