Topic: Duplicate session with same acctstarttime

I have a working hotspot setup using chillispot(dd-wrt) and Freeradius with MySQL.

Everything is working great except for some minor issues. The issue I am facing is with duplicate session/entries in the radacct table.

My chillispot router is running on an ADSL connection (dynamic IP) which tends to renew the connection every 2-3 days, and gets a new WAN IP assigned from the ISP. When that happens, if there are any hotspot users logged in, a new entry in the radacct is created for that user. The old entry has the acctstoptime set to NULL and does not timeout at all. I have set accounting interval to 10 minutes, and even after waiting an hour, the old session does not get timeout. The stoptime is still set to NULL.

Now the new session entry has the same acctstarttime as the old one. Even the acctinputoctets/acctoutputoctets values are carried on from the old one. And during each interval, it gets updated. So the problem is, during accounting, am having to calculate duplicate usages from the user. The old session + the new session, but they have overlapping data usage.

What could be the problem?