sqlippool, allocate_find and duplicate address if NAS packets are received in the reverse order

[Matteo Sgalaberni]

Hi, I found on this patch a huge change on the sqlippool: 

https://github.com/FreeRADIUS/freeradius-server/commit/38e475f424d4abb1b3ec52c533a21fd413495d99 

I see that it's well documented on wiki. I have a doubt about the "allocate_existing". 

I'm using the oldest query "allocate_find" that do in the same query "allocate_existing+allocate_find" and works well. I can probably understand why the developer who wrote this patch divided this, so it's simpler to disable the sticky ip. 

I'm running in a problem with "sticky ip" (old query allocate_existing): 
allocate_find = " \ SELECT framedipaddress \ FROM ${ ippool_table } \ WHERE pool_name = '%{control:${pool_name}}' \ AND ( \ expiry_time < 'now' :: timestamp ( 0 ) \ OR ( nasipaddress = '%{NAS-IP-Address}' AND pool_key = '${pool_key}' ) \ ) \ ORDER BY \ ( username <> '%{SQL-User-Name}' ), \ ( callingstationid <> '%{Calling-Station-Id}' ), \ expiry_time \ LIMIT 1 \ FOR UPDATE " Sometimes, in rare case when the customer have a very quick disconnection/reconnection happen that the NAS send the Access-Request before the stop Accounting-Request. So in that case happen: 

1) Access_Request -> allocate_find (find the same ip to the same user) + allocate_update (assign same ip, renew lease) 
2) Accounting-Request Stop -> allocate_free (clear ip) 

Now, the IP is assigned, but on sqlippool is marked as free...and sometime in the future another user will obtain the same IP and I have a duplicate assignment. 

Is this behaviour normal and "known"? I can't find this "warn" on wiki/documentation. 

If this is normal and known I think that I need to kill the "stitky ip" capability to solve the issue in these way: 
Way A)  remove " nasipaddress = '%{NAS-IP-Address}' AND pool_key = '${pool_key}'" and ORDER BY \ (username <> '%{SQL-User-Name}') from allocate_find 
or 
Way B) using the new queries.conf of the last branch  and commenting the "allocate_existing" 

The IP in that case is not assigned again to the same user and I'm sure that the NAS packets order are not creating issues. 

Thanks 
Matteo