[Engine-devel] Import/snapshots duplicate MAC support

[Mike Kolesnik]

Hi, 

The current situation dictates that if the configuration value AllowDuplicateMacAddresses 
is set to false (this is the default setting), then we block import or switching snapshots where 
a MAC address in one or more of the snapshot/ovf's virtual NICs is already used. 

Given that we don't currently give the admin any option to select otherwise, I'm not sure 
that's a very robust behaviour.. 
First of all the MAC address should be unique per network and not in the whole system (like 
it is currently). 
Furthermore, as long as in the same network there are no two virtual NIC s running with the 
same address, it is not such a bad situation. 

Therefore, I would like to propose a couple of solutions (from backend perspective): 
1. Keep blocking. 
2. Keep blocking but fix the mac pools to be per network basis. 
3. Don't block, and allow duplicate MACs in these scenarios, but block on activating a NIC 
with duplicate MAC address. Warn the user that the NIC is with duplicate MAC, and 
perhaps even unplug or unwire it so that it would be obvious that it's using someone else's 
MAC. 
4. Don't block, and give the problematic NIC a new MAC from the pool. 

Solution 1 is obviously not the greatest (hence this email). 
In my opinion, 4 is sort of a cat in a bag, since I'm not sure changing the HWADDR for the 
guest OS is really a good idea. 
Solution 2 would be nice going forward, but it just reduces the chances of an admin to come 
across this situation and doesn't solve it entirely. 
Hence, I would favour solution 3 which seems to solve the problem and allow the admin to 
choose what to do. 

Please voice your opinion, or propose an alternate solution. 


Regards, 
Mike 

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