abh1sar opened a new pull request, #9240:
URL: https://github.com/apache/cloudstack/pull/9240

   ### Description
   
   Fixes https://github.com/apache/cloudstack/issues/7907
   
   This PR fixes the issue where two VMs can be assigned the same IP if they 
are created at the same time.
   `NetworkOrchestrator.allocateNic()` calls `guru.alocate()` which returns a 
free IP address.
   `NetworkOrchestrator.allocateNic()` then calls `_nicDao.persists()`
   
   But `guru.allocate()` can return same IPs to two VMs if the first VM hasn't 
persisted the nic to the DB yet.
   Doing the whole thing in a transaction might be costly.
   
   So the fix is to check if the IP returned by guru.allocate is already 
assigned just before persisting the NicVO in a transaction.
   Check will be done only for cases where Ipv4 allocation might race. 
   
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   ### Types of changes
   
   - [ ] Breaking change (fix or feature that would cause existing 
functionality to change)
   - [ ] New feature (non-breaking change which adds functionality)
   - [x] Bug fix (non-breaking change which fixes an issue)
   - [ ] Enhancement (improves an existing feature and functionality)
   - [ ] Cleanup (Code refactoring and cleanup, that may add test cases)
   - [ ] build/CI
   
   ### Feature/Enhancement Scale or Bug Severity
   
   #### Feature/Enhancement Scale
   
   - [ ] Major
   - [ ] Minor
   
   #### Bug Severity
   
   - [ ] BLOCKER
   - [ ] Critical
   - [ ] Major
   - [x] Minor
   - [ ] Trivial
   
   
   ### Screenshots (if appropriate):
   
   
   ### How Has This Been Tested?
   Wasn't possible to reproduce the actual race, but I tested by manually 
setting values with debugger and verifying that the code does what it is 
supposed to.
   
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   #### How did you try to break this feature and the system with this change?
   
   <!-- see how your change affects other areas of the code, etc. -->
   
   
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