[Openib-windows] IPOIB virtualization What was already done, what still has to be done to finish the job.

[Hal Rosenstock]

Hi Tzachi,

On Fri, 2006-04-21 at 09:23, Tzachi Dar wrote:
> Hi Fab,
>  
> The following mail summarizes the place the work that I did on
> IPOIB virtualization, that is running IPOIB on Microsoft virtual
> server R2.
>  
> Please note that the current status is that ping works in all
> directions, still there is a lot of work needed in order to bring it
> to product quality. The biggest issue that still has to be done is
> allow for packets that are bigger than 1500 bytes, and smaller than
> 2048 to pass to the guest OS. Currently, I have implemented a hack
> that tells windows that we only support MTU of 1500 bytes (like
> Ethernet). My change assumes that all machines are windows machines,
> and all have my changes, but this is not always true. One example that
> breaks this assumption is Linux.

Is this issue with Windows or Linux in terms of this interoperation ?
Can you elaborate on this ?

>  It seems that a better solution to this problem is either talk to MS
> and see if they have a solution to this problem or accept bigger
> packets and break them by demand.
>  
> Due to the time that is needed to complete the work (see also problems
> bellow) we have decided not to support virtualization for this
> release. 
>  
> Attached to this mail is the latest version that I created. It should
> fit less or more to the version of IPOIB.
>  
> The changes that I have made are in the following areas. I'll describe
> shortly what the problem was, what I did and what still has to be
> done. Some of the problems described are not really related to
> virtualization.
>  
> 1) checking where to pass the packets. I have implemented the code
> that sniffs arps and creates a table of IP, Mac. Packets are later
> changed based on that table. Code is almost complete, however there is
> a need to take the correct lock when writing the table (shouldn't be
> that complicated).
>  
> 2) DHCP support. A few general comments: 1) The current code
> introduced changes to DHCP packets both in the receiver side as well
> as in the sender side. This works well if we write the software in
> both sides. Assuming that the other side is Linux, this is not true.
> I'm not sure that there is a spec that solves these problems.

Please elaborate on this.

-- Hal

>  2) If we get a message that we can not format but looks as DHCP
> packet, we silently drop it. I believe that we should allow it to
> pass. Maybe someone else will find what to do with it. Another issue
> that is somewhat problematic is keeping the old addresses that was
> once assigned to us. Currently, we use GID+QP as our unique
> identifier, however the QP changes, and therefore the IP's also.
> As for virtualization: I was using GUID+QP+base Mac as unique
> identifier, and changed the receiver size to almost not do anything,
> and things seems to work.
>  
> 3) support for packets that are bigger that 1500, but smaller than
> 2048, see description above.
>  
> 4) Multicast requests of guest OS: In the current implementation NDIS
> notifies the driver to what multicast groups to join. We register to
> them, and we are also notified when the host leaves the group. When a
> guest OS asks to be registered to a multicast group, there is no NDIS
> query that tells us what has happened, and it seems that the only way
> around that is by sniffing IGMP packets. I have implemented the code
> that sniffs the packets and registers to such a group, but not the
> code that will remove us from the multicast group. Much more than
> that, windows allows us to register to a certain group and accept
> packets only from some hosts, while another virtual machine (or even
> another application on the same machine?) might ask to be registered
> to another machines (or even deny them). If we want to follow the
> spec, exactly, there is a lot of work that has to be done.
>  
> Thanks
> Tzachi
> 
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