[openib-general] [RFC] [PATCH 1/3] RDMA CM: add rdma_get/set_optioncalls to get/set path records

[Caitlin Bestler]

openib-general-bounces at openib.org wrote:
> Quoting r. Sean Hefty <mshefty at ichips.intel.com>:
>>> How about doing copy_from_user in ucma, and implementing
>>> rdma_set_path/rdma_get_path in cma?
>> 
>> I don't think that we want to start adding a new set of APIs for
>> every option that may eventually need to be supported.
> 
> Why not?

At least on the iWARP side you must definitely do not
want to make it easy to add new options casually. That
will lead to users wanting to micro-manage the TCP
stack using existing knobs and dials that were 
designed for host-based TCP stacks. Example: you
do NOT want to allow the user to enable Nagle for
a TCP connection carrying iWARP/MPA.

The only classic L4 layer sockopt that is even
vaguely relevant to an RDMA capable device is
enabling/disabling keepalive.

What about for IB HCAs? Are there a large number
of options that have not yet been exposed but
which are device independent and *might* be
desirable to control? If not, then why introduce
a "catchall" interface as opposed to specific
interfaces that have to justified on a per
method basis?