channel.c: Resolve issue with receiving SIP INFO packets for DTMF

The problem is essentially the same as in ASTERISK~28245. Besides
the direct media scenario we have an additional scenario where a
special client is involved. This device mutes audio by default in
transmit direction (no rtp frames) and activates audio only by a
foot switch. In this situation dtmf input (pin for conferences,
transfer features codes , etc) using SIP INFO mode is not
understood properly especially when SIP INFO messages are sent
quickly.

This patch ensures that SIP INFO frames are properly queued and
processed in the above scenario. The patch also corrects situations
where successive dtmf events are received quicker than the
signalled event duration (plus minimum gap/pause) allows, i.e. DTMF
events have to be buffered in the ast channel read queue and
emulation has to be processed asynchronously at slower speed.

Reported by: Thomas Arimont
patches:
  trigger_dtmf_emulation.patch submitted by Thomas Arimont (license 5525)

Change-Id: I309bf61dd065c9978c8e48f5b9a936ab47de64c2

diff --git a/main/channel.c b/main/channel.c
index f09608731596712ee19e76212e326a40a9a8b2c8..c350177dbcc0ed9c497fda164b3478c1e7e72013 100644 (file)
--- a/main/channel.c
+++ b/main/channel.c
@@ -2819,6 +2819,33 @@ int ast_channel_get_up_time(struct ast_channel *chan)
        return (ast_channel_get_up_time_ms(chan) / 1000);
 }
 
+/*!
+ * \brief Determine whether or not we have to trigger dtmf emulating using 50 fps timer events
+ * especially when no voice frames are received during dtmf processing (direct media or muted
+ * sender case using SIP INFO)
+ */
+static inline int should_trigger_dtmf_emulating(struct ast_channel *chan)
+{
+       if (ast_test_flag(ast_channel_flags(chan), AST_FLAG_DEFER_DTMF | AST_FLAG_EMULATE_DTMF)) {
+               /* We're in the middle of emulating a digit, or DTMF has been
+                * explicitly deferred. Trigger dtmf with periodic 50 pfs timer events, then. */
+               return 1;
+       }
+
+       if (!ast_tvzero(*ast_channel_dtmf_tv(chan)) &&
+                       ast_tvdiff_ms(ast_tvnow(), *ast_channel_dtmf_tv(chan)) < 2*AST_MIN_DTMF_GAP) {
+               /*
+                * We're not in the middle of a digit, but it hasn't been long enough
+                * since the last digit, so we'll have to trigger DTMF furtheron.
+                * Using 2 times AST_MIN_DTMF_GAP to trigger readq reading for possible
+                * buffered next dtmf event
+                */
+               return 1;
+       }
+
+       return 0;
+}
+
 static void deactivate_generator_nolock(struct ast_channel *chan)
 {
        if (ast_channel_generatordata(chan)) {
@@ -2839,6 +2866,10 @@ void ast_deactivate_generator(struct ast_channel *chan)
 {
        ast_channel_lock(chan);
        deactivate_generator_nolock(chan);
+       if (should_trigger_dtmf_emulating(chan)) {
+               /* if in the middle of dtmf emulation keep 50 tick per sec timer on rolling */
+               ast_timer_set_rate(ast_channel_timer(chan), 50);
+       }
        ast_channel_unlock(chan);
 }
 
@@ -3508,6 +3539,7 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
 
        if (ast_channel_timingfd(chan) > -1 && ast_channel_fdno(chan) == AST_TIMING_FD) {
                enum ast_timer_event res;
+               int trigger_dtmf_emulating = should_trigger_dtmf_emulating(chan);
 
                ast_clear_flag(ast_channel_flags(chan), AST_FLAG_EXCEPTION);
 
@@ -3535,10 +3567,26 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
                                if (got_ref) {
                                        ao2_ref(data, -1);
                                }
+
+                               if (trigger_dtmf_emulating) {
+                                       /*
+                                        * Since we're breaking out of this switch block and not
+                                        * returning, we need to re-lock the channel.
+                                        */
+                                       ast_channel_lock(chan);
+                                       /* generate null frame to trigger dtmf emulating */
+                                       f = &ast_null_frame;
+                                       break;
+                               }
+                       } else if (trigger_dtmf_emulating) {
+                               /* generate null frame to trigger dtmf emualating */
+                               f = &ast_null_frame;
+                               break;
                        } else {
                                ast_timer_set_rate(ast_channel_timer(chan), 0);
-                               ast_channel_fdno_set(chan, -1);
-                               ast_channel_unlock(chan);
+                               /* generate very last null frame to trigger dtmf emulating */
+                               f = &ast_null_frame;
+                               break;
                        }
 
                        /* cannot 'goto done' because the channel is already unlocked */
@@ -3576,6 +3624,7 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
 
        /* Check for pending read queue */
        if (!AST_LIST_EMPTY(ast_channel_readq(chan))) {
+               int skipped_dtmf_frame = 0;
                int skip_dtmf = should_skip_dtmf(chan);
 
                AST_LIST_TRAVERSE_SAFE_BEGIN(ast_channel_readq(chan), f, frame_list) {
@@ -3584,6 +3633,7 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
                         * some later time. */
 
                        if ( (f->frametype == AST_FRAME_DTMF_BEGIN || f->frametype == AST_FRAME_DTMF_END) && skip_dtmf) {
+                               skipped_dtmf_frame = 1;
                                continue;
                        }
 
@@ -3595,7 +3645,19 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
                if (!f) {
                        /* There were no acceptable frames on the readq. */
                        f = &ast_null_frame;
-                       ast_channel_alert_write(chan);
+                       if (!skipped_dtmf_frame) {
+                               /*
+                                * Do not trigger alert pipe if only buffered dtmf begin or end frames
+                                * are left in the readq.
+                                */
+                               ast_channel_alert_write(chan);
+                       } else {
+                               /*
+                                * Safely disable continous timer events if only buffered dtmf begin or end
+                                * frames are left in the readq.
+                                */
+                               ast_timer_disable_continuous(ast_channel_timer(chan));
+                       }
                }
 
                /* Interpret hangup and end-of-Q frames to return NULL */
@@ -3801,6 +3863,16 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
                                        } else
                                                ast_channel_emulate_dtmf_duration_set(chan, AST_DEFAULT_EMULATE_DTMF_DURATION);
                                        ast_log(LOG_DTMF, "DTMF begin emulation of '%c' with duration %u queued on %s\n", f->subclass.integer, ast_channel_emulate_dtmf_duration(chan), ast_channel_name(chan));
+
+                                       /*
+                                        * Start generating 50 fps timer events (null frames) for dtmf emulating
+                                        * independently from any existing incoming voice frames.
+                                        * If channel generator is already activated in regular mode use these
+                                        * timer events to generate null frames.
+                                        */
+                                       if (!ast_channel_generator(chan)) {
+                                               ast_timer_set_rate(ast_channel_timer(chan), 50);
+                                       }
                                }
                                if (ast_channel_audiohooks(chan)) {
                                        struct ast_frame *old_frame = f;
@@ -3842,12 +3914,30 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
                                        ast_channel_emulate_dtmf_duration_set(chan, option_dtmfminduration - f->len);
                                        ast_frfree(f);
                                        f = &ast_null_frame;
+
+                                       /* Start generating 50 fps timer events (null frames) for dtmf emulating
+                                        * independently from any existing incoming voice frames.
+                                        * If channel generator is already activated in regular mode use these
+                                        * timer events to generate null frames.
+                                        */
+                                       if (!ast_channel_generator(chan)) {
+                                               ast_timer_set_rate(ast_channel_timer(chan), 50);
+                                       }
                                } else {
                                        ast_log(LOG_DTMF, "DTMF end passthrough '%c' on %s\n", f->subclass.integer, ast_channel_name(chan));
                                        if (f->len < option_dtmfminduration) {
                                                f->len = option_dtmfminduration;
                                        }
                                        ast_channel_dtmf_tv_set(chan, &now);
+
+                                       /* Start generating 50 fps timer events (null frames) for dtmf emulating
+                                        * independently from any existing incoming voice frames.
+                                        * If channel generator is already activated in regular mode use these
+                                        * timer events to generate null frames.
+                                        */
+                                       if (!ast_channel_generator(chan)) {
+                                               ast_timer_set_rate(ast_channel_timer(chan), 50);
+                                       }
                                }
                                if (ast_channel_audiohooks(chan)) {
                                        struct ast_frame *old_frame = f;
@@ -3901,6 +3991,15 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio, int
                                                        ast_frfree(old_frame);
                                                }
                                        }
+
+                                       /* Start generating 50 fps timer events (null frames) for dtmf emulating
+                                        * independently from any existing incoming voice frames.
+                                        * If channel generator is already activated in regular mode use these
+                                        * timer events to generate null frames.
+                                        */
+                                       if (!ast_channel_generator(chan)) {
+                                               ast_timer_set_rate(ast_channel_timer(chan), 50);
+                                       }
                                }
                        }
                        break;