corrupt UDP packets sent to proxy (Alan DeKok)

Taylor, Graham GrahamTaylor at
Tue Jun 21 12:30:52 CEST 2005

Message: 2
Date: Fri, 17 Jun 2005 13:20:06 -0400
From: "Alan DeKok" <aland at>
Subject: Re: corrupt UDP packets sent to proxy 
To: FreeRadius users mailing list
	<freeradius-users at>>
Message-ID: <20050617172007.F3ED716FAB at>>

"Taylor, Graham" <GrahamTaylor at>> wrote:
>> Hi People, I hope you can shed some light on a problem I am having
>> freeradius acting as a proxy. As you can see the packet below has a
>> corrupt UDP header

>  The kernel creates the UDP header, including checksum.  If it's
>wrong, there's little FreeRADIUS can do.

	Alan I agree that the kernel creates the UDP header normally, I
am concerned that FreeRADIUS is forwarding the packet to the proxy
without re-calculating the UDP header. This would explain why the
behaviour is different when proxying than when using radtest.

>> If I use radtest then the packet is fine and I get authenticated, the
>> problem only occurs when the request is proxied out, all of the
>> forwarded to the secondary radius server have the UDP checksum error,

 > I've never seen that, and I'm not sure why it would happen.

  Alan DeKok.

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