[openib-general] mapping between IP address and device name

[James Lentini]

On Thu, 23 Jun 2005, Roland Dreier wrote:

>    James> Perhaps a bit of motivation of how the GID->IP service can
>    James> be used is in order.
>
>    James> kDAPL uses this feature to provide the passive side of a
>    James> connection with the IP address of the remote peer. kDAPL
>    James> consumers can use this information as a weak authentication
>    James> mechanism.
>
> This seems so weak as to be not useful,

My understanding is that a full featured NFS implementation needs this 
capability.

My original email didn't state the requirement very well. We don't 
necessarily need to map the GID to an IP address (although that might 
be the best thing to do).  What we really want is:

  Given an InfiniBand connection request, the ability to determine
  an IP address of the source node in an interoperable way.

> and rather expensive to boot.

Let's defer discussing how to implement it until we agree that it is 
required.

> To implement this, a system receiving a connection request would have
> to perform an SA query to map the remote LID back to a GuidInfo
> record, and then for each GID attached to the remote LID, somehow
> retrieve the set of IP addresses configured for that GID (assuming
> that is somehow even possible).
>
>    James> Could SDP make use of this service to validate a connection
>    James> request's source IP address?
>
> No, SDP passes the remote peer's IP address directly as part of its
> connection establishment.  In fact, the SDP annex in the IBA spec
> contains this rather enlightening passage:
>
>    IP over InfiniBand does not define a mechanism to perform an
>    inverse lookup (from an InfiniBand address to an IP address). It
>    is also possible for a single InfiniBand address to have many IP
>    addresses, providing a one-to-many mapping when attempting to
>    perform an inverse lookup. To resolve these issues, the complete
>    source and destination IP address is provided during connection
>    setup to enable mapping the destination and source LID/GID to an
>    IP address at the accepting peer of the connection.
>
> - R.
>