chan_iax2: Block unnecessary control frames to/from the wire.

Establishing an IAX2 call between Asterisk v1.4 and v1.8 (or later)
results in an unexpected call disconnect.  The problem happens because
newer values in the enum ast_control_frame_type are not consistent between
the branch versions of Asterisk.

For example:
1) v1.4 calls v1.8 (or later) using IAX2

2) v1.8 answers and sends a connected line update control frame.  (on v1.8
AST_CONTROL_CONNECTED_LINE = 22)

3) v1.4 receives the control frame as an end-of-q (on v1.4
AST_CONTROL_END_OF_Q = 22)

4) v1.4 disconnects the call once the receive queue becomes empty.

Several things are done by this patch to fix the problem and attempt to
prevent it from happening again in the future:

* Added a warning at the definition of enum ast_control_frame_type about
how to add new control frame values.

* Made block sending and receiving control frames that have no reason to
go over the wire.

* Extended the connectedline iax.conf parameter to also include the
redirecting information updates.

* Updated the connectedline iax.conf parameter documentation to include a
notice that the parameter must be "no" when the peer is an Asterisk v1.4
instance.

(closes issue AST-1302)

Review: https://reviewboard.asterisk.org/r/3174/
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Merged revisions 407678 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 407727 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 407729 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@407731 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 12 insertions, 8 deletions

diff --git a/configs/iax.conf.sample b/configs/iax.conf.sample
index a9841f0da..e17c7dfeb 100644
--- a/configs/iax.conf.sample
+++ b/configs/iax.conf.sample
@@ -610,14 +610,18 @@ description=Demo System At Digium    ; Description of this peer, as listed by
 ; IPs can also optionally be given but are not required.  Caller*ID can be
 ; suggested to the other side as well if it is for example a phone instead of
 ; another PBX.
-;connectedline=yes ; Set how connected line information is handled for this
-;                  ; peer. If set to "yes", both sending and receiving
-;                  ; connected line information will be enabled. If set to
-;                  ; "send", this peer will send connected line information
-;                  ; but will not process connected line updates. If set to
-;                  ; "receive", connected line updates will be processed
-;                  ; but not sent. If set to "no", connected line updates
-;                  ; will be disabled. Default is "no".
+;connectedline=yes ; Set if connected line and redirecting information updates
+;                  ; are passed between Asterisk servers for this peer.
+;                  ; yes - Sending and receiving updates are enabled.
+;                  ; send - Only send updates.
+;                  ; receive - Only process received updates.
+;                  ; no - Sending and receiving updates are disabled.
+;                  ; Default is "no".
+;                  ;
+;                  ; Note: Because of an incompatibility between Asterisk v1.4
+;                  ; and Asterisk v1.8 or later, this option must be set
+;                  ; to "no" toward the Asterisk v1.4 peer.  A symptom of the
+;                  ; incompatibility is the call gets disconnected unexpectedly.
 
 
 ;[dynamichost]