asterisk users - Jun 2010 - Workaround for bug in Linksys Firmware 6.1.3(a) (or greater)

If you've used Linksys phones against recent Asterisk 1.4.x you may
have noticed
that they may drop registration for a quick bit and then go back to being ok
if your phone is behind NAT.
If you turn Asterisk's sip debug information on, you'll probably find
errors like these in your logs:

NOTICE[30179] chan_sip.c: Correct auth, but based on stale nonce
received from '"999911" <sip:999911 at 208.90.186.10>'

I believe I have determined that this is caused by a bug in the
Linksys firmware that is related to the NAT Keep-Alive packets.
Because recent Asterisk 1.4.x's do not establish a SIP dialog for
NOTIFY requests, the "489 Bad Event"
replies were going back to the wrong address if your phone was behind NAT.
This lack of reply would cause the next REGISTER message to use the
same nonce as the previous REGISTER,
resulting in the "stale nonce" errors and temporarily dropping
registration. I've also seen the lack of response to
the NAT keep-alive cause the phone to stop being able to register
completely as well.

Below I've posted a patch that responds with a 200 OK to these
keep-alive requests, and I believe
also solves the temporary loss of registration problem, though more
testing in different environments
for those who experience this problem would be greatly appreciated.

The patch is against 1.4.32.

-- James
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James Lamanna schrieb:
> If you've used Linksys phones against recent Asterisk 1.4.x you may
> have noticed
> that they may drop registration for a quick bit and then go back to being
ok
> if your phone is behind NAT.
> If you turn Asterisk's sip debug information on, you'll probably
find
> errors like these in your logs:
>
> NOTICE[30179] chan_sip.c: Correct auth, but based on stale nonce
> received from '"999911" <sip:999911 at
208.90.186.10>'
>
> I believe I have determined that this is caused by a bug in the
> Linksys firmware that is related to the NAT Keep-Alive packets.
> Because recent Asterisk 1.4.x's do not establish a SIP dialog for
> NOTIFY requests, the "489 Bad Event"
> replies were going back to the wrong address if your phone was behind NAT.
> This lack of reply would cause the next REGISTER message to use the
> same nonce as the previous REGISTER,
> resulting in the "stale nonce" errors and temporarily dropping
> registration. I've also seen the lack of response to
> the NAT keep-alive cause the phone to stop being able to register
> completely as well.
>
> Below I've posted a patch that responds with a 200 OK to these
> keep-alive requests, and I believe
> also solves the temporary loss of registration problem, though more
> testing in different environments
> for those who experience this problem would be greatly appreciated.
>
> The patch is against 1.4.32.
>
> -- James
>   
Hello,

you also just could set the NAT KEEP ALIVE MESSAGE on Ext 1 from $NOTIFY 
to $OPTIONS and make this extension in your default context:
exten => s,1,hangup

and you also would get a 200 ok for the keep alive package.

IMHO a stale nonce would only occur when a user tries to register faster 
than 3600s cause of the register timeout used in asterisk. Maybe you 
should also try to set a higher register timeout on your phones. but i 
dont have an 1.4 system running, only around 2k of linksys phones on a 
1.2.40 and 300 on 1.6.1.18 and i dont see this problem there.

best regards.

steve

> completely as well.
>
> Below I've posted a patch that responds with a 200 OK to these
> keep-alive requests, and I believe
> also solves the temporary loss of registration problem, though more
> testing in different environments
> for those who experience this problem would be greatly appreciated.
>
> The patch is against 1.4.32.
>
>    
A workaround we have used for a long time is to simply change the config 
on the Linksys phones to send an empty packet as a keep-alive.  There is 
obviously no response from asterisk but it keeps the NAT bindings alive 
and well on every router we have tested.

Andres
http://www.neuroredes.com
> -- James
>