Allow ast_safe_sleep to defer specific frames until after the sleep has concluded.

From reviewboard

Background:
A Digium customer discovered a somewhat odd bug. The setup is that parties A
and B are bridged, and party A places party B on hold. While party B is 
listening to hold music, he mashes a bunch of DTMF. Party A takes party
B off hold while this is happening, but party B continues to hear hold
music. I could reproduce this about 1 in 5 times.

The issue:
When DTMF features are enabled and a user presses keys, the channel that
the DTMF is streamed to is placed in an ast_safe_sleep for 100 ms, the
duration of the emulated tone. If an AST_CONTROL_UNHOLD frame is read
from the channel during the sleep, the frame is dropped. Thus the
unhold indication is never made to the channel that was originally placed
on hold.

The fix:
Originally, I discussed with Kevin possible ways of fixing the specific
problem reported. However, we determined that the same type of problem
could happen in other situations where ast_safe_sleep() is used. Using
autoservice as a model, I modified ast_safe_sleep_conditional() to
defer specific frame types so they can be re-queued once the sleep has
finished. I made a common function for determining if a frame should
be deferred so that there are not two identical switch blocks to
maintain.

Review: https://reviewboard.asterisk.org/r/674/



git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@264996 f38db490-d61c-443f-a65b-d21fe96a405b

2 files changed, 57 insertions, 27 deletions

diff --git a/main/autoservice.c b/main/autoservice.c
index bccee43f8..e82998a44 100644
--- a/main/autoservice.c
+++ b/main/autoservice.c
@@ -133,32 +133,8 @@ static void *autoservice_run(void *ign)
 			 * thread in charge of this channel will know. */
 
 			defer_frame = &hangup_frame;
-		} else {
-
-			/* Do not add a default entry in this switch statement.  Each new
-			 * frame type should be addressed directly as to whether it should
-			 * be queued up or not. */
-
-			switch (f->frametype) {
-			/* Save these frames */
-			case AST_FRAME_DTMF_END:
-			case AST_FRAME_CONTROL:
-			case AST_FRAME_TEXT:
-			case AST_FRAME_IMAGE:
-			case AST_FRAME_HTML:
-				defer_frame = f;
-				break;
-
-			/* Throw these frames away */
-			case AST_FRAME_DTMF_BEGIN:
-			case AST_FRAME_VOICE:
-			case AST_FRAME_VIDEO:
-			case AST_FRAME_NULL:
-			case AST_FRAME_IAX:
-			case AST_FRAME_CNG:
-			case AST_FRAME_MODEM:
-				break;
-			}
+		} else if (ast_is_deferrable_frame(f)) {
+			defer_frame = f;
 		}
 
 		if (defer_frame) {
diff --git a/main/channel.c b/main/channel.c
index f7c122feb..15dba8684 100644
--- a/main/channel.c
+++ b/main/channel.c
@@ -1206,12 +1206,41 @@ struct ast_channel *ast_walk_channel_by_exten_locked(const struct ast_channel *c
 	return channel_find_locked(chan, NULL, 0, context, exten);
 }
 
+int ast_is_deferrable_frame(const struct ast_frame *frame)
+{
+	/* Do not add a default entry in this switch statement.  Each new
+	 * frame type should be addressed directly as to whether it should
+	 * be queued up or not.
+	 */
+	switch (frame->frametype) {
+	case AST_FRAME_DTMF_END:
+	case AST_FRAME_CONTROL:
+	case AST_FRAME_TEXT:
+	case AST_FRAME_IMAGE:
+	case AST_FRAME_HTML:
+		return 1;
+
+	case AST_FRAME_DTMF_BEGIN:
+	case AST_FRAME_VOICE:
+	case AST_FRAME_VIDEO:
+	case AST_FRAME_NULL:
+	case AST_FRAME_IAX:
+	case AST_FRAME_CNG:
+	case AST_FRAME_MODEM:
+		return 0;
+	}
+	return 0;
+}
+
 /*! \brief Wait, look for hangups and condition arg */
 int ast_safe_sleep_conditional(struct ast_channel *chan, int ms, int (*cond)(void*), void *data)
 {
 	struct ast_frame *f;
 	struct ast_silence_generator *silgen = NULL;
 	int res = 0;
+	AST_LIST_HEAD_NOLOCK(, ast_frame) deferred_frames;
+
+	AST_LIST_HEAD_INIT_NOLOCK(&deferred_frames);
 
 	/* If no other generator is present, start silencegen while waiting */
 	if (ast_opt_transmit_silence && !chan->generatordata) {
@@ -1219,6 +1248,7 @@ int ast_safe_sleep_conditional(struct ast_channel *chan, int ms, int (*cond)(voi
 	}
 
 	while (ms > 0) {
+		struct ast_frame *dup_f = NULL;
 		if (cond && ((*cond)(data) == 0)) {
 			break;
 		}
@@ -1233,7 +1263,18 @@ int ast_safe_sleep_conditional(struct ast_channel *chan, int ms, int (*cond)(voi
 				res = -1;
 				break;
 			}
-			ast_frfree(f);
+
+			if (!ast_is_deferrable_frame(f)) {
+				ast_frfree(f);
+				continue;
+			}
+			
+			if ((dup_f = ast_frisolate(f))) {
+				if (dup_f != f) {
+					ast_frfree(f);
+				}
+				AST_LIST_INSERT_HEAD(&deferred_frames, dup_f, frame_list);
+			}
 		}
 	}
 
@@ -1242,6 +1283,19 @@ int ast_safe_sleep_conditional(struct ast_channel *chan, int ms, int (*cond)(voi
 		ast_channel_stop_silence_generator(chan, silgen);
 	}
 
+	/* We need to free all the deferred frames, but we only need to
+	 * queue the deferred frames if there was no error and no
+	 * hangup was received
+	 */
+	ast_channel_lock(chan);
+	while ((f = AST_LIST_REMOVE_HEAD(&deferred_frames, frame_list))) {
+		if (!res) {
+			ast_queue_frame_head(chan, f);
+		}
+		ast_frfree(f);
+	}
+	ast_channel_unlock(chan);
+
 	return res;
 }