[asterisk-users] FAX detection in chan_dahdi 1.8.15

[Jeff LaCoursiere]

On 09/13/2012 03:20 AM, Olivier wrote:
>
>
> 2012/8/31 Jeff LaCoursiere <jeff at sunfone.com <mailto:jeff at sunfone.com>>
>
>     > -----Original Message-----
>     > From: asterisk-users-bounces at lists.digium.com
>     <mailto:asterisk-users-bounces at lists.digium.com>
>     > [mailto:asterisk-users-bounces at lists.digium.com
>     <mailto:asterisk-users-bounces at lists.digium.com>] On Behalf Of Jeff
>     > LaCoursiere
>     > Sent: Tuesday, August 28, 2012 3:24 PM
>     > To: asterisk-users at lists.digium.com
>     <mailto:asterisk-users at lists.digium.com>
>     > Subject: [asterisk-users] FAX detection in chan_dahdi 1.8.15
>     >
>     > Hi,
>     >
>     > I recently replaced a site that was using 1.4.[mumble] with
>     > hylafax/iaxmodem.  They have an RBS T1 and were using about half
>     of their 50
>     > DID numbers for "fax to email".  This all broke with the new
>     system :(
>     >
>     > The original chan_dahdi.conf had no mention of "faxdetect", so I
>     assume it
>     > was operating with whatever is the default.  Off?
>     >
>     > The new box originally had "faxdetect=no", and I found that all
>     my test
>     > faxes failed with negotiation errors.  When I finally tried
>     > "faxdetect=incoming" test faxes from another machine running
>     hylafax went
>     > through fine, and I thought I was done.
>     >
>     > The following week the customer reported that inbound faxes
>     weren't working.
>     > When I looked at the log, I saw lots of these:
>     >
>     > chan_dahdi.c:     -- Redirecting DAHDI/24-1 to fax extension
>     >
>     > Which in my FreePBX setup eventually goes to a "no service"
>     message and
>     > hangs up.  I've never defined a "fax" extension and don't really
>     know what
>     > that is about.  Turns out that any fax machine that calls ends
>     up following
>     > this path.  If my other hylafax server calls, it follows the
>     normal path and
>     > gets answered by my pool of iaxmodems. I don't really understand the
>     > difference between the two types of calls, first of all.
>     >
>     > So it seems from this experience and a recent thread on -users
>     that enabling
>     > faxdetection in chan_dahdi sets up some additional buffering
>     that at least
>     > in my case, in 1.8, seems to be required (without it all inbound
>     faxes fail
>     > from my hylafax server with negotiation problems).
>     > Unfortunately for me, this also seems to bypass normal DID
>     handling and
>     > sends calls to an undefined "fax extension".
>     >
>     > Can anyone shed some light?
>     >
>     > Thanks,
>     >
>     > j
>     >
>     > On Tue, 2012-08-28 at 15:28 -0500, Danny Nicholas wrote:
>     > IIRC correctly this is sort of like the "s" extension; you set
>     up your
>     fax
>     > handler in [default,fax,1].  Not sure how that is done in FreePBX.
>     >
>     >
>
>     I've managed to hack a fix for this... in chan_dahdi.c I found two
>     places where an "async goto" happens right after the message
>     "Redirecting to fax extension".  I simply commented it out in both
>     places.
>
>     While looking a the source I noticed that an attempt is made to
>     create a
>     new channel variable "FAXEXTEN" with a comment "save the DID number
>     before sending to the fax extension".  I created a "fax" context in
>     extensions.conf and tried to use ${FAXEXTEN} to properly route my
>     inbound fax to email calls, but it turns out that it is just set
>     to "s",
>     which isn't useful at all.  I spent some time trying to figure out
>     where
>     in the channel structure the actual DID information exists, as
>     properly
>     setting the "FAXEXTEN" variable is arguably the right "fix" for my
>     problem.  But I'm just not familiar enough with the internals :( I'm
>     surprised others haven't had this issue...
>
>     Anyway commenting out the redirection did the trick for me.
>
>     Cheers,
>
>     j
>
>
> Which Freepbx version are you using ?
> Have you installed Freepbx's "Fax Configuration" module ?
>
> Are you trying to attach fax-to-email service to incoming DIDs or to 
> SIP endpoints ?
>
>
FreePBX 2.10

Originally, just because I usually do an install and let FreePBX load 
all available modules, it did load that module.  Original advice was to 
remove that module, which had no effect on my problem.  It is removed 
now anyway.

The intention is individual DIDs go to specific fax email addresses.  I 
saw your explanation for what you are trying to accomplish, and it 
sounds interesting.  Curious to see if you get it working.

Cheers,

j
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