Phil Mayers wrote:
All,
I've just become aware of a rather annoying problem with our PPTP VPN
server. Sometimes, a client will connect, disconnect and reconnect in
quick succession. In these circumstances, there seems to be a window
which an IP can remain allocated to a live VPN session, but is marked as
free in the SQL table, causing subsequent clients to connect, be
allocated the IP, and fail to get any connectivity.
ACK!
Shortly after sending this email, we found the problem and it's truly
vile. It's nothing to do with FreeRadius at all, except tangentially -
what's actually happening is that the PPTP client is closing the PPP LCP
layer and re-opening it on the same PPTP control/data channel.
This results in a very rapid set of:
1. access-request
nas-port-id = 100
2. access-accept
framedipaddress = 192.168.1.100
3. acct-start
acctsessionid = 4B151C655A0000
nas-port-id = 100
framedipaddress = 192.168.1.100
4. acct-stop
nas-port-id = 100
framedipaddress = 192.168.1.100
acctterminatecause = user-request
5. access-request
nas-port-id = 100
6. access-accept
framedipaddress = 192.168.1.100
7. acct-start
acctsessionid = 4B151C685A0001
nas-port-id = 100
framedipaddress = 192.168.1.100
I am assuming the radius packet for #5 actually arrives before the
accounting stop in #4, thus the accounting-stop then marks the IP free,
and the problem occurs.
Bah.
I can probably work around this by unallocating the "allocate-clear"
query in rlm_sqlippool.
Sick..
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