jitterbuffer: Correct signed/unsigned mismatch causing assert

If the system time has stepped backwards because of a time
adjustment between the time a frame is timestamped and the
time we check the timestamps in abstract_jb:hook_event_cb(),
we get a negative interval, but we don't check for that there.
abstract_jb:hook_event_cb() then calls
fixedjitterbuffer:fixed_jb_get() (via abstract_jb:jb_get_fixed)
and the first thing that does is assert(interval >= 0).

There are several issues with this...

 * abstract_jb:hook_event_cb() saves the interval in a variable
   named "now" which is confusing in itself.

 * "now" is defined as an unsigned int which converts the negative
   value returned from ast_tvdiff_ms() to a large positive value.

 * fixed_jb_get()'s parameter is defined as a signed int so the
   interval gets converted back to a negative value.

 * fixed_jb_get()'s assert is NOT an ast_assert but a direct define
   that points to the system assert() so it triggers even in
   production mode.

So...

 * hook_event_cb()'s "now" was renamed to "relative_frame_start" and
   changed to an int64_t.
 * hook_event_cb() now checks for a negative value right after
   retrieving both the current and framedata timestamps and just
   returns the frame if the difference is negative.
 * fixed_jb_get()'s local define of ASSERT() was changed to call
   ast_assert() instead of the system assert().

ASTERISK-29480
Reported by: Dan Cropp

Change-Id: Ic469dec73c2edc3ba134cda6721a999a9714f3c9

diff --git a/main/abstract_jb.c b/main/abstract_jb.c
index 7549008cdae33905e1f8be8b352045e47c0f1a2c..083ff9efb683956e3c42ae4b20fe94f6ccd44ebe 100644 (file)
--- a/main/abstract_jb.c
+++ b/main/abstract_jb.c
@@ -954,7 +954,7 @@ static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_fram
 {
        struct jb_framedata *framedata = data;
        struct timeval now_tv;
-       unsigned long now;
+       int64_t relative_frame_start;
        int putframe = 0; /* signifies if audio frame was placed into the buffer or not */
 
        switch (event) {
@@ -1064,7 +1064,17 @@ static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_fram
        }
 
        now_tv = ast_tvnow();
-       now = ast_tvdiff_ms(now_tv, framedata->start_tv);
+       relative_frame_start = ast_tvdiff_ms(now_tv, framedata->start_tv);
+       if (relative_frame_start < 0) {
+               /*
+                * The only way for this to happen is if the system time has
+                * stepped backwards between the time framedata->start_tv was
+                * set and now.  Think an ntpd or systemd-timesyncd adjustment.
+                *
+                * Just pass the frame through.
+                */
+               return frame;
+       }
 
        if (frame->frametype == AST_FRAME_VOICE) {
                int res;
@@ -1084,9 +1094,9 @@ static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_fram
                }
                if (!framedata->first) {
                        framedata->first = 1;
-                       res = framedata->jb_impl->put_first(framedata->jb_obj, jbframe, now);
+                       res = framedata->jb_impl->put_first(framedata->jb_obj, jbframe, relative_frame_start);
                } else {
-                       res = framedata->jb_impl->put(framedata->jb_obj, jbframe, now);
+                       res = framedata->jb_impl->put(framedata->jb_obj, jbframe, relative_frame_start);
                }
 
                if (res == AST_JB_IMPL_OK) {
@@ -1104,7 +1114,7 @@ static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_fram
                int res;
                long next = framedata->jb_impl->next(framedata->jb_obj);
 
-               /* If now is earlier than the next expected output frame
+               /* If relative_frame_start is earlier than the next expected output frame
                 * from the jitterbuffer we may choose to pass on retrieving
                 * a frame during this read iteration.  The only exception
                 * to this rule is when an audio frame is placed into the buffer
@@ -1113,8 +1123,8 @@ static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_fram
                 * doing this we are able to feed off the timing of the input frames
                 * and only rely on our jitterbuffer timer when frames are dropped.
                 * During testing, this hybrid form of timing gave more reliable results. */
-               if (now < next) {
-                       long int diff = next - now;
+               if (relative_frame_start < next) {
+                       long int diff = next - relative_frame_start;
                        if (!putframe) {
                                return frame;
                        } else if (diff >= framedata->timer_interval) {
@@ -1124,7 +1134,7 @@ static struct ast_frame *hook_event_cb(struct ast_channel *chan, struct ast_fram
 
                ast_frfree(frame);
                frame = &ast_null_frame;
-               res = framedata->jb_impl->get(framedata->jb_obj, &frame, now, framedata->timer_interval);
+               res = framedata->jb_impl->get(framedata->jb_obj, &frame, relative_frame_start, framedata->timer_interval);
                switch (res) {
                case AST_JB_IMPL_OK:
                        /* got it, and pass it through */

diff --git a/main/fixedjitterbuf.c b/main/fixedjitterbuf.c
index 3c350b4bc45d037551f6c66b0f14ed6245ac1962..6c923296c74cc7d8a683644da94eb39239fdefec 100644 (file)
--- a/main/fixedjitterbuf.c
+++ b/main/fixedjitterbuf.c
@@ -41,7 +41,7 @@
 #ifdef FIXED_JB_DEBUG
 #define ASSERT(a)
 #else
-#define ASSERT(a) assert(a)
+#define ASSERT(a) ast_assert(a)
 #endif
 
 /*! \brief private fixed_jb structure */