I dont know if this means anything, but Im not using DHCP, Im using PPPoE. I didnt know FR could even be a dhcp server. Im just throwing out ideas, but is there a way to not thread the sqlippool module ? Let one request at a time for an IP, sure it would be slower, but for my use would be fine. Ben Wiechman wrote:
Can’t you do the select and update as part of one transaction?
For example with MySQL:
START TRANSACTION;
SELECT @A:=SUM(salary) FROM table1 WHERE type=1;
UPDATE table2 SET summary=@A WHERE type=1;
COMMIT;
The transaction may need to be changed to serializable as well. I don’t know how the DHCP RFC handles preallocations.
You could probably use Repeatable Read level if it is acceptable to mark an address as taken when a DHCPOFFER is sent while waiting for a DHCPREQUEST from the client, so long as the address if confirmed to be free before the DHCPACK is sent, or a DHCPNAK in the case that the address was offered to multiple clients.
Ben Wiechman
*From:* freeradius-users-bounces+ben=wisper-wireless.com@lists.freeradius.org [mailto:freeradius-users-bounces+ben=wisper-wireless.com@lists.freeradius.org] *On Behalf Of *Padam J Singh *Sent:* Thursday, January 15, 2009 9:39 AM *To:* FreeRadius users mailing list *Subject:* Re: Handing out duplicate IP addresses
Hello Ivan,
Would adding a mutex around the select-update code in the sqlippool module solve this issue?
Padam
tnt@kalik.net <mailto:tnt@kalik.net> wrote:
The requests all came in at the same time, to the second (among others),
its like FR took 3 requests and looked at the database at the exact same
time, saw it was an available IP and all those 3 requests assigned it.
That can't be avoided. SELECT (allocate-find) will always work much faster than UPDATE (allocate-update).
My NAS rejects two of the 3 because the IP is assigned,
I think that you make a good point here. If the allocate-update query was made to fail in the case that the IP address was already issued to another thread between allocate-find and allocate-update (by expanding it with AND expiry_time IS NULL in WHERE), point of failure will be in sqlippool module and not on the NAS. Logic can then perhaps try to issue a new IP address (best just once more in order not to create a loop). That way issuing same IP address to multiple threads can be handled by the sqlippool module.
Ivan Kalik Kalik Informatika ISP
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