Unknown AVPs

Alan DeKok aland at deployingradius.com
Sat Aug 30 08:23:28 CEST 2008

Jeffrey Sewell wrote:
> I've got a FreeRADIUS server that takes in Accounting data that is
> proxied to it from another server. In the Accounting packets I see AVPs
> that are tagged "Unknown-Attribute."

  Hm... unknown attributes should be printed as Vendor-123-Attr-456.

> I assume that's because either the
> originating server or the FreeRADIUS server is missing a dictionary
> file/entry to identify the Attribute.

  The proxying server is missing the dictionary entries.

> First question: is that assumption correct?


> If so, who sets that Attribute, the originator or the target?

  The originator sets the *number* of the attribute.  The proxy uses
that number to look up a name in the dictionaries.

> And more generally: as these are written to the MySQL DB I see that they
> are pulled off the packet and stored as variables that are accessible in
> the sql.conf file for example:
> AcctSessionTime = '%{Acct-Session-Time}'
> Is that variable pulled directly from the packet? So that whatever
> attribute is in the packet, it will be named %{whatever} ?

  It will look up the name in the dictionary, get the number, and then
look up the relevant numbered attribute from the packet.

> I've got other data coming in that I need to store in the SQL DB and
> suppose that I'll need to modify the sql.conf and the radacct table in
> order to get them in there.


  You may want to take a look at
raddb/sites-available/robust-proxy-accounting.  It documents a method of
proxying transparently when the home server is up, and writing to local
disk when it's not.  When the home server comes back up, the packets
written to disk are forwarded automagically.

  You may also want to look at raddb/sites-available/buffered-sql for
the "write to SQL" portion.  Some people have seen significant
performance improvements by using this method.  i.e. writing all packets
directly to SQL can often thrash the SQL server.

  Alan DeKok

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