Add ETSI Call Waiting support.

Add the ability to announce a call to an endpoint when there are no B
channels available.  A call waiting call is a SETUP message with no B
channel selected.

Relevant specification: EN 300 056, EN 300 057, EN 300 058

For DAHDI/ISDN channels, the CHANNEL() dialplan function now supports the
"no_media_path" option.
* Returns "0" if there is a B channel associated with the call.
* Returns "1" if no B channel is associated with the call.  The call is
either on hold or is a call waiting call.

If you are going to allow incoming call waiting calls then you need to use
CHANNEL(no_media_path) do determine if you must drop a call to accept the
new call.

Review:	https://reviewboard.asterisk.org/r/568/


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@267261 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 7 insertions, 0 deletions

diff --git a/CHANGES b/CHANGES
index 08d526d59..91df249f7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -205,6 +205,11 @@ Dialplan Functions
    prefixing the name of the hash at assignment with the appropriate number of
    underscores, just like variables.
  * GROUP_MATCH_COUNT has been improved to allow regex matching on category
+ * For DAHDI/ISDN channels, the CHANNEL() dialplan function now supports the
+   "no_media_path" option.
+   Returns "0" if there is a B channel associated with the call.
+   Returns "1" if no B channel is associated with the call.  The call is either
+   on hold or is a call waiting call.
 
 Dialplan Variables
 ------------------
@@ -339,6 +344,8 @@ libpri channel driver (chan_dahdi) DAHDI changes
    back into the same interface.  Tromboned calls happen because of call routing,
    call deflection, call forwarding, and call transfer.
  * Added the ability to send and receive ETSI Advice-Of-Charge messages. 
+ * Added the ability to support call waiting calls.  (The SETUP has no B channel
+   assigned.)
 
 Asterisk Manager Interface
 --------------------------