[asterisk-dev] media watchdog for res_fax

Steve Underwood steveu at coppice.org
Mon Jan 3 10:41:46 CST 2011

On 01/03/2011 10:03 PM, Kevin P. Fleming wrote:
> On 01/03/2011 07:02 AM, Kristijan Vrban wrote:
>> In https://issues.asterisk.org/view.php?id=18557 i noticed that
>> app_fax has a watchdog to
>> identify a media (T.30) timeout. But res_fax not. The question: Should
>> res_fax also have this
>> watchdog, would a patch be merged ?
>>  From app_fax.c
>> /* Watchdog. I have seen situations when remote fax disconnects
>> (because of poor line
>>     quality) while SpanDSP continues staying in T30_STATE_IV_CTC 
>> state forever.
>>     To avoid this, we terminate when we see that T30 state does not
>> change for 5 minutes.
>>     We also terminate application when more than 30 minutes passed 
>> regardless of
>>     state changes. This is just a precaution measure - no fax should
>> take that long */
>> #define WATCHDOG_TOTAL_TIMEOUT    30 * 60
>> #define WATCHDOG_STATE_TIMEOUT    5 * 60
> I would expect the T.30 stack in the res_fax_* module to handle such 
> loss of media... but it doesn't sound like it would be a bad idea for 
> res_fax to do this as well.
All timing in the spandsp FAX engine is derived from the media. If the 
media stops, so does the timing. In at least some versions of app_fax we 
picked up a lack of media (something like a one second timeout), and 
went into a separately timed mode. I guess the res_fax module isn't 
doing that.


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