[openib-general] RDMA connection and address translation API

[Christoph Hellwig]

On Thu, Aug 25, 2005 at 01:18:06PM -0400, Talpey, Thomas wrote:
> At 12:56 PM 8/25/2005, Caitlin Bestler wrote:
> >Generic code MUST support both IPv4 and IPv6 addresses.
> >I've even seen code that actually does this.
> 
> Let me jump ahead to the root question. How will the NFS layer know
> what address to resolve?
> 
> On IB mounts, it will need to resolve a hostname or numeric string to
> a GID, in order to provide the address to connect. On TCP/UDP, or
> iWARP mounts, it must resolve to IP address. The mount command
> has little or no context to perform these lookups, since it does not
> know what interface will be used to form the connection.
> 
> In exports, the server must inspect the source network of each
> incoming request, in order to match against /etc/exports. If there
> are wildcards in the file, a GID-specific algorithm must be applied.
> Historically, /etc/exports contains hostnames and IPv4 netmasks/
> addresses.
> 
> In either case, I think it is a red herring to assume that the GID
> is actually an IPv6 address. They are not assigned by the sysadmin,
> they are not subnetted, and they are quite foreign to many users.
> IPv6 support for Linux NFS isn't even submitted yet, btw.
> 
> With an IP address service, we don't have to change a line of 
> NFS code.

I think this shows that using IP addresses in any service over
infiniband that isn't actually IP networking is extremly stupid.
Just stop living in the illusion that it makes sense and use IB-specific
addressing, namely IB and stop all this layering violations into IP,
which is much higher up the stack.