[swg] RE: [openib-general] RE: [dat-discussions] socketbased connectionmodel for IB proposal - round 3

[Fab Tillier]

> From: Caitlin Bestler [mailto:caitlinb at broadcom.com]
> 
> Fab Tillier wrote:
> >> From: Caitlin Bestler [mailto:caitlinb at broadcom.com]
> >> Sent: Friday, November 11, 2005 1:12 PM
> >>
> >> How does this prevent a non-privileged client running on a remote
> >> host with current CM software from generating a connection request
> >> to the targeted Service ID with the entire private data coming from
> >> the non-privileged consumer.
> >
> > There is no need to prevent a non-privileged client from
> > generating connection requests.  Where does this requirement
> > come from?  Who cares where the private data comes from as
> > long as the recipient, whether privileged or not, has a way
> > of validating that it matches the path record information?
> >
> > Specifically, adding the logic in the low level IB CM to
> > validate the private data will tie the IB CM to address
> > translation for IPoIB, which I think is better done at a
> > higher level (like the CMA).
> >
> > If a higher level entity is going to be responsible for
> > validating the private data, the low level IB CM doesn't do
> > squat with the reserved bit.  The low level CM API must now
> > expose the bit to allow clients to specify it so that REQs
> > can be routed to them, so that two requests with the same SID
> > can be distinguished form one another by this reserved bit.
> > Thus if the bit has to be exposed through the low-level IB CM
> > it is no more than a 65th bit for a service ID.
> >
> By the time the connection request is passed to the application
> the remote IP address needs to be validated.

I agree - by the time the upper-most, IP addressing aware application gets it,
whoever is sending the connection request up must have done the validation.

> I don't care whether the remote CM validated it (and is known
> to be privileged software) or if the local CM validates it
> with a reverse lookup.

A reverse lookup isn't needed - a forward lookup is.  The whole point of passing
the IP addresses in the private data was to solve the ambiguity of reverse
lookups.

> What I do not want is to kick this problem up to the application.
> If it is kicked up to the application it is no longer TCP-compatible
> connection setup, because that responsibility does not exist over TCP.

I agree.  I'm just pointing out that the validation of the private data does not
have to be done by a privileged entity, so trying to put a bunch of bits in the
protocol to require enforcement by privileged code is unnecessary.  That means
that the CMA functionality could (not should) be implemented in user-mode.

- Fab