[Asterisk-bugs] [Asterisk 0007755]: [patch] workaround for race condition with disconnect supervision

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The RELATED issue 0007612 has been RESOLVED. 
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http://bugs.digium.com/view.php?id=7755 
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Reported By:                rbraun
Assigned To:                mattf
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Project:                    Asterisk
Issue ID:                   7755
Category:                   Core/General
Reproducibility:            N/A
Severity:                   tweak
Priority:                   normal
Status:                     assigned
Asterisk Version:           1.4.5 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Disclaimer on File?:        Yes 
Request Review:              
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Date Submitted:             08-18-2006 17:46 CDT
Last Modified:              03-09-2007 04:49 CST
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Summary:                    [patch] workaround for race condition with
disconnect supervision
Description: 
We have an asterisk installation at a customer site connected to an adit
600 channel bank which feeds a legacy pbx (comdial) with analog lines.
Working through issues reported by this customer we have found numerous
ways in which the comdial pbx does not behave according to spec or even
consistent with its own documentation. One is that it expects at least 1
second of disconnect supervision (ZT_KEWLTIME) while 500 ms is documented.
Even this is insufficient to make it recognize that a call has terminated
if the call terminates at just the right time before it picks up; it does
not recognize the battery drop if it has not yet seized the line.

We have successfully solved this problem with the attached patch, which
changes the behavior of kewlstart so that if the line is picked up remotely
during the ZT_KEWLTIME or during the guard time (ZT_AFTERKEWLTIME) after
the battery drop, zaptel will respond by repeating the battery drop after
the guard time completes. This behavior is only triggered when the line was
on hook but is taken off hook during the battery drop or the guard time.
The main adjustment to make after this patch is applied is to set the
AFTERKEWLTIME to an appropriate value to eliminate the race condition; we
use 1.5 seconds for KEWLTIME (actually a bit less in practice on the adit)
and 2.5 seconds for AFTERKEWLTIME which sums to 4 seconds, the amount of
time between rings.
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Relationships       ID      Summary
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parent of           0007612 [patch] Zaptel misreports channel in ba...
parent of           0007754 [patch] chan_zap plays dialtone even if...
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 jmls - 03-09-07 04:49  
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ping ping 

Issue History 
Date Modified   Username       Field                    Change               
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03-09-07 04:49  jmls           Note Added: 0060648                          
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