[openib-general] Microsoft virtual machine and Infiniband

[Tzachi Dar]

Hi Fab,
 
When trying to run windows 2003 server on a Microsoft virtual machine we
have found out that there is one problem that prevents IPOIB from
running.
 
The problem as you can guess is related to the way MAC addresses are
being handled. On such a machine, a fake Mac addresses is being created
and it is later used for communication (one MAC per guest OS). However
although this packets return to the correct computer, IPOIB doesn't
restore their correct dest MAC and therefore pinging to a remote host is
impossible.
 
In order to solve this problem there is a need to create a mechanism
that will allow the IPOIB driver to correct the MAC addresses of packets
based on their IP addresses.
 
It seems that the best way to do this is to have a "static" table of
IP's and MAC addresses and to check every IP packet as well as every ARP
reply. We have done such an experiment and it did seems to work.
 
We are still looking for a way to configure the table of guest OS and
their IPs and MACs. One way to achieve this is simply having a static
table that will be entered through some file. Although this is the
simplest way, it has an obvious disadvantage (the need to manually
configure the machine). A different way is to find some configuration
API's that the remote machine has, while the last possibility is trying
to find the information by sniffing for packets (the way that an
Ethernet switch does things).
 
One bug that I have already found is that if a broadcast packet is sent
for example an ARP request, we send the packet as a multicast, and we
also receive the packet ourselves, and later we send this packet to
NDIS. This is not the correct behavior (assuming we are emulating
Ethernet behavior) and we should remove this packets.
 
In the next week I'll try to create a patch that will allow the virtual
machine to work, I just wanted to know what your opinion about this
issue.
 
Thanks
Tzachi
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