Improve handling of T.38 re-INVITEs that arrive before a T.38-capable

application is executing on a channel.

This patch addresses an issue found during working with end-users
using res_fax. If an incoming call is answered in the dialplan, or
jumps to the 'fax' extension due to reception of a CNG tone (with
faxdetect enabled), and then the remote endpoint sends a T.38
re-INVITE, it is possible for the channel's T.38 state to be
'T38_STATE_NEGOTIATING' when the application starts up. Unfortunately,
even if the application wants to use T.38, it can't respond to the
peer's negotiation request, because the AST_CONTROL_T38_PARAMETERS
control frame that chan_sip sent originally has been lost, and the
application needs the content of that frame to be able to formulate a
reply.

This patch adds a new 'request' type to AST_CONTROL_T38_PARAMETERS,
AST_T38_REQUEST_PARMS. If the application sends this request, chan_sip
will re-send the original control frame (with
AST_T38_REQUEST_NEGOTIATE as the request type), and the application
can respond as normal. If this occurs within the five second timeout
in chan_sip, the automatic cancellation of the peer reinvite will be
stopped, and the application will 'own' the negotiation process from
that point onwards.

This also improves the code path in chan_sip to allow sip_indicate(),
when called for AST_CONTROL_T38_PARAMETERS, to be able to return a
non-zero response, which should have been in place before since the
control frame *can* fail to be processed properly. It also modifies
ast_indicate() to return whatever result the channel driver returned
for this control frame, rather than converting all non-zero results
into '-1'. Finally, the new request type intentionally returns a
positive value, so that an application that sends
AST_T38_REQUEST_PARMS can know for certain whether the channel driver
accepted it and will be replying with a control frame of its own, or
whether it was ignored (if the sip_indicate()/ast_indicate() path had
properly supported failure responses before, this would not be
necessary).

This patch also modifies res_fax to take advantage of the new request.

In addition, this patch makes sip_t38_abort() actually lock the
private structure before doing its work... bad programmer, no donut.

This patch also enhances chan_sip's 'faxdetect' support to allow
triggering on T.38 re-INVITEs received as well as CNG tone detection.

Review: https://reviewboard.asterisk.org/r/556/



git-svn-id: http://svn.digium.com/svn/asterisk/trunk@254450 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 41 insertions, 37 deletions

diff --git a/channels/sip/include/sip.h b/channels/sip/include/sip.h
index 57fac84ca..ce87f0f23 100644
--- a/channels/sip/include/sip.h
+++ b/channels/sip/include/sip.h
@@ -302,43 +302,47 @@
 	a second page of flags (for flags[1] */
 /*@{*/
 /* realtime flags */
-#define SIP_PAGE2_RTCACHEFRIENDS        (1 << 0)    /*!< GP: Should we keep RT objects in memory for extended time? */
-#define SIP_PAGE2_RTAUTOCLEAR           (1 << 2)    /*!< GP: Should we clean memory from peers after expiry? */
-#define SIP_PAGE2_RPID_UPDATE           (1 << 3)
-#define SIP_PAGE2_Q850_REASON           (1 << 4)    /*!< DP: Get/send cause code via Reason header */
-
-/* Space for addition of other realtime flags in the future */
-#define SIP_PAGE2_SYMMETRICRTP          (1 << 8)    /*!< GDP: Whether symmetric RTP is enabled or not */
-#define SIP_PAGE2_STATECHANGEQUEUE      (1 << 9)    /*!< D: Unsent state pending change exists */
-
-#define SIP_PAGE2_CONNECTLINEUPDATE_PEND (1 << 10)
-#define SIP_PAGE2_RPID_IMMEDIATE         (1 << 11)
-#define SIP_PAGE2_RPORT_PRESENT         (1 << 12)   /*!< Was rport received in the Via header? */
-#define SIP_PAGE2_PREFERRED_CODEC	(1 << 13)   /*!< GDP: Only respond with single most preferred joint codec */
-#define SIP_PAGE2_VIDEOSUPPORT		(1 << 14)   /*!< DP: Video supported if offered? */
-#define SIP_PAGE2_TEXTSUPPORT		(1 << 15)   /*!< GDP: Global text enable */
-#define SIP_PAGE2_ALLOWSUBSCRIBE	(1 << 16)   /*!< GP: Allow subscriptions from this peer? */
-#define SIP_PAGE2_ALLOWOVERLAP		(1 << 17)   /*!< DP: Allow overlap dialing ? */
-#define SIP_PAGE2_SUBSCRIBEMWIONLY	(1 << 18)   /*!< GP: Only issue MWI notification if subscribed to */
-#define SIP_PAGE2_IGNORESDPVERSION	(1 << 19)   /*!< GDP: Ignore the SDP session version number we receive and treat all sessions as new */
-
-#define SIP_PAGE2_T38SUPPORT                   (3 << 20)    /*!< GDP: T.38 Fax Support */
-#define SIP_PAGE2_T38SUPPORT_UDPTL             (1 << 20)    /*!< GDP: T.38 Fax Support (no error correction) */
-#define SIP_PAGE2_T38SUPPORT_UDPTL_FEC         (2 << 20)    /*!< GDP: T.38 Fax Support (FEC error correction) */
-#define SIP_PAGE2_T38SUPPORT_UDPTL_REDUNDANCY  (3 << 20)    /*!< GDP: T.38 Fax Support (redundancy error correction) */
-
-#define SIP_PAGE2_CALL_ONHOLD           (3 << 23)  /*!< D: Call hold states: */
-#define SIP_PAGE2_CALL_ONHOLD_ACTIVE    (1 << 23)  /*!< D: Active hold */
-#define SIP_PAGE2_CALL_ONHOLD_ONEDIR    (2 << 23)  /*!< D: One directional hold */
-#define SIP_PAGE2_CALL_ONHOLD_INACTIVE  (3 << 23)  /*!< D: Inactive hold */
-
-#define SIP_PAGE2_RFC2833_COMPENSATE    (1 << 25)  /*!< DP: Compensate for buggy RFC2833 implementations */
-#define SIP_PAGE2_BUGGY_MWI             (1 << 26)  /*!< DP: Buggy CISCO MWI fix */
-#define SIP_PAGE2_DIALOG_ESTABLISHED    (1 << 27)  /*!< 29: Has a dialog been established? */
-#define SIP_PAGE2_FAX_DETECT            (1 << 28)  /*!< DP: Fax Detection support */
-#define SIP_PAGE2_REGISTERTRYING        (1 << 29)  /*!< DP: Send 100 Trying on REGISTER attempts */
-#define SIP_PAGE2_UDPTL_DESTINATION     (1 << 30)  /*!< DP: Use source IP of RTP as destination if NAT is enabled */
-#define SIP_PAGE2_VIDEOSUPPORT_ALWAYS   (1 << 31)  /*!< DP: Always set up video, even if endpoints don't support it */
+#define SIP_PAGE2_RTCACHEFRIENDS		(1 <<  0)    /*!< GP: Should we keep RT objects in memory for extended time? */
+#define SIP_PAGE2_RTAUTOCLEAR			(1 <<  1)    /*!< GP: Should we clean memory from peers after expiry? */
+#define SIP_PAGE2_RPID_UPDATE			(1 <<  2)
+#define SIP_PAGE2_Q850_REASON			(1 <<  3)    /*!< DP: Get/send cause code via Reason header */
+
+#define SIP_PAGE2_SYMMETRICRTP			(1 <<  4)    /*!< GDP: Whether symmetric RTP is enabled or not */
+#define SIP_PAGE2_STATECHANGEQUEUE		(1 <<  5)    /*!< D: Unsent state pending change exists */
+
+#define SIP_PAGE2_CONNECTLINEUPDATE_PEND	(1 <<  6)
+#define SIP_PAGE2_RPID_IMMEDIATE		(1 <<  7)
+#define SIP_PAGE2_RPORT_PRESENT			(1 <<  8)   /*!< Was rport received in the Via header? */
+#define SIP_PAGE2_PREFERRED_CODEC		(1 <<  9)   /*!< GDP: Only respond with single most preferred joint codec */
+#define SIP_PAGE2_VIDEOSUPPORT			(1 << 10)   /*!< DP: Video supported if offered? */
+#define SIP_PAGE2_TEXTSUPPORT			(1 << 11)   /*!< GDP: Global text enable */
+#define SIP_PAGE2_ALLOWSUBSCRIBE		(1 << 12)   /*!< GP: Allow subscriptions from this peer? */
+#define SIP_PAGE2_ALLOWOVERLAP			(1 << 13)   /*!< DP: Allow overlap dialing ? */
+#define SIP_PAGE2_SUBSCRIBEMWIONLY		(1 << 14)   /*!< GP: Only issue MWI notification if subscribed to */
+#define SIP_PAGE2_IGNORESDPVERSION		(1 << 15)   /*!< GDP: Ignore the SDP session version number we receive and treat all sessions as new */
+
+#define SIP_PAGE2_T38SUPPORT			(3 << 16)    /*!< GDP: T.38 Fax Support */
+#define SIP_PAGE2_T38SUPPORT_UDPTL		(1 << 16)    /*!< GDP: T.38 Fax Support (no error correction) */
+#define SIP_PAGE2_T38SUPPORT_UDPTL_FEC		(2 << 16)    /*!< GDP: T.38 Fax Support (FEC error correction) */
+#define SIP_PAGE2_T38SUPPORT_UDPTL_REDUNDANCY	(3 << 16)    /*!< GDP: T.38 Fax Support (redundancy error correction) */
+
+#define SIP_PAGE2_CALL_ONHOLD			(3 << 18)  /*!< D: Call hold states: */
+#define SIP_PAGE2_CALL_ONHOLD_ACTIVE		(1 << 18)  /*!< D: Active hold */
+#define SIP_PAGE2_CALL_ONHOLD_ONEDIR		(2 << 18)  /*!< D: One directional hold */
+#define SIP_PAGE2_CALL_ONHOLD_INACTIVE		(3 << 18)  /*!< D: Inactive hold */
+
+#define SIP_PAGE2_RFC2833_COMPENSATE		(1 << 20)  /*!< DP: Compensate for buggy RFC2833 implementations */
+#define SIP_PAGE2_BUGGY_MWI			(1 << 21)  /*!< DP: Buggy CISCO MWI fix */
+#define SIP_PAGE2_DIALOG_ESTABLISHED		(1 << 22)  /*!< 29: Has a dialog been established? */
+
+#define SIP_PAGE2_FAX_DETECT			(3 << 23)  /*!< DP: Fax Detection support */
+#define SIP_PAGE2_FAX_DETECT_CNG		(1 << 23)  /*!< DP: Fax Detection support - detect CNG in audio */
+#define SIP_PAGE2_FAX_DETECT_T38		(2 << 23)  /*!< DP: Fax Detection support - detect T.38 reinvite from peer */
+#define SIP_PAGE2_FAX_DETECT_BOTH		(3 << 23)  /*!< DP: Fax Detection support - detect both */
+
+#define SIP_PAGE2_REGISTERTRYING		(1 << 24)  /*!< DP: Send 100 Trying on REGISTER attempts */
+#define SIP_PAGE2_UDPTL_DESTINATION		(1 << 25)  /*!< DP: Use source IP of RTP as destination if NAT is enabled */
+#define SIP_PAGE2_VIDEOSUPPORT_ALWAYS		(1 << 26)  /*!< DP: Always set up video, even if endpoints don't support it */
 
 #define SIP_PAGE2_FLAGS_TO_COPY \
 	(SIP_PAGE2_ALLOWSUBSCRIBE | SIP_PAGE2_ALLOWOVERLAP | SIP_PAGE2_IGNORESDPVERSION | \