[Bug 769979] New: Possible race condition when fetching rtp info

["GStreamer" (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=769979

Bug ID: 769979
Summary: Possible race condition when fetching rtp info
Classification: Platform
Product: GStreamer
Version: git master
OS: Linux
Status: NEW
Severity: normal
Priority: Normal
Component: gst-rtsp-server
Assignee: gstreamer-***@lists.freedesktop.org
Reporter: ***@axis.com
QA Contact: gstreamer-***@lists.freedesktop.org
GNOME version: ---

If the application do not send pause before a new play request then is there a
possibility for a race condition to occur when fetching the RTP-Info.

This is easily triggered by adding a short sleep just before
/* grab RTPInfo from the media now */
rtpinfo = gst_rtsp_session_media_get_rtpinfo (sessmedia);

in rtsp-client, handle_play_request and then execute two Play requests without
a Pause in between.

Running a test case executing 10 Play requests with 1s delay between each other
triggers this problem 80% of the times (without short sleep) and since the test
case is checking the D-bit in the extension header is it mandatory that the RTP
Info finds the absolute first rtp package after the play command.

The solution is to perform a forced pause if the application have not send a
Pause command before the Play command.

["GStreamer" (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=769979

Joakim Johansson <***@axis.com> changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |***@axis.com

--- Comment #1 from Joakim Johansson <***@axis.com> ---
Created attachment 333408
--> https://bugzilla.gnome.org/attachment.cgi?id=333408&action=edit
Solution for race condition

["GStreamer" (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=769979

--- Comment #2 from Joakim Johansson <***@axis.com> ---
This patch however violates the RTSP protocol:

"A PLAY request without a Range header is legal. It starts playing a stream
from the beginning unless the stream has been paused. If a stream has been
paused via PAUSE, stream delivery resumes at the pause point. If a stream is
playing, such a PLAY request causes no further action and can be used by the
client to test server liveness.

Ongoing with a new solution that does not violate the protocol.

["GStreamer" (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=769979

GStreamer system administrator <***@gstreamer.net> changed:

What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |OBSOLETE

--- Comment #3 from GStreamer system administrator <***@gstreamer.net> ---
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been
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https://gitlab.freedesktop.org/gstreamer/gst-rtsp-server/issues/24.