From bc973bd7195587c6a4be8da96bab26503f1cf8aa Mon Sep 17 00:00:00 2001 From: George Joseph Date: Thu, 17 Jun 2021 06:57:11 -0600 Subject: [PATCH] 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 --- main/abstract_jb.c | 26 ++++++++++++++++++-------- main/fixedjitterbuf.c | 2 +- 2 files changed, 19 insertions(+), 9 deletions(-) diff --git a/main/abstract_jb.c b/main/abstract_jb.c index 7549008cda..083ff9efb6 100644 --- 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 3c350b4bc4..6c923296c7 100644 --- 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 */