asterisk users - Sep 2006 - Problems with KG1000 voip gateway and DTMF

I have a problem with a really weird piece of hardware, the KG1000 voip
gateway. Information about this device is nonexistant, and I have been
able to get it to work through trial-and-error except for one issue: DTMF.
Basically, a call is initiated okay, but Asterisk ignores any DTMF signals
sent, no matter what combination of DTMF mode I use in sip.conf and
extensions.conf. What I noticed is that the device is sending the
following SIP packet when a button is pressed:

07:44:34.028573 IP (tos 0x0, ttl 107, id 29088, offset 0, flags [none],
proto: UDP (17), length: 366) 192.168.0.6.5566 > 192.168.0.2.5060: SIP,
length: 338
        INFO sip:192.168.0.2:5060 SIP/2.0
        Via: SIP/2.0/UDP 192.168.0.6:5566;branch=0
        From: "thaddock"<sip:100@192.168.0.2:5060;user=phone>
        To: <sip:0@192.168.0.2:5060;user=phone>;tag=as2bfb2f08
        Call-ID: 29@192.168.0.6
        CSeq: 3 INFO
        User-Agent: KG1000-S VOIP Gateway
        Content-Type: application/dtmf
        Content-Length: 17

        v=0
        t=255
        d=5

But asterisk responds with:

07:44:34.028675 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto:
UDP (17), length: 414) 192.168.0.2.5060 > 192.168.0.6.5566: SIP, length:
386
        SIP/2.0 403 Unauthorized
        Via: SIP/2.0/UDP 192.168.0.6:5566;branch=0;received=192.168.0.6
        From: "thaddock"<sip:100@192.168.0.2:5060;user=phone>
        To: <sip:0@192.168.0.2:5060;user=phone>;tag=as2bfb2f08
        Call-ID: 29@192.168.0.6
        CSeq: 3 INFO
        User-Agent: Asterisk PBX
        Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
        Contact: <sip:0@192.168.0.2>
        Content-Length: 0

It looks like the KG1000 is sending DTMF over INFO messages, but Asterisk
is ignoring (or not understanding) them. I have tried dtmfmode=info as
well as dtmfmode=inband in sip.conf, but nothing seems to help. Here is
the sip.conf entry for the KG1000:

[100]
type=friend
;secret=test123
username=100
;fromuser=phone
;fromdomain=192.168.0.2
host=dynamic
dtmfmode=info
sipdebug = yes

And my current extensions.conf for the context:

[default]
exten => s,1,Answer
exten => s,n,Wait,4                     ; Wait a second, just for fun
;exten => s,n,SIPDtmfMode(info)
exten => s,n,Background(thanks)          ; "Thanks for calling press 1
for
sales, 2 for support, ..."
exten => s,n,WaitExten
exten => 1,1,Dial(SIP/thaddock)
exten => 2,1,Dial(SIP/myra)
exten => 0,1,Goto(s,1)

It's a long story, but I have calling an extension from the KG1000
working, but only for the intial connection. After that, Asterisk ignores
any keypress and the KG1000 sends the INFO messages.

Has anyone run into anything like this before? Is there some configuration
parameters to allow Asterisk to understand those INFO messages? Are they
even valid INFO messages? Is there any more information I can give that
may help?

Any help would be greatly appreciated, except for this point, Asterisk is
working wonderfully for me.

Sincerely,
Terence Haddock