On 10/2/20 4:48 AM, Martin Storsjö wrote:
On Thu, 1 Oct 2020, Andriy Gelman wrote:
On Thu, 01. Oct 22:00, Zhao Zhili wrote:
On 10/1/20 4:15 AM, Martin Storsjö wrote:
> On Wed, 30 Sep 2020, Zhao Zhili wrote:
> > > Hi Martin,
> > > > On 9/30/20 5:41 PM, Martin Storsjö wrote:
> > > In listen mode with UDP transport, once the sender has sent
> > > the TEARDOWN and closed the connection, poll will indicate that
> > > one can read from the connection (indicating that the socket has
> > > reached EOF and should be closed by the receiver as well). In
this
> > > case, parse_rtsp_message won't try to parse the command (because
> > > it's no longer in state STREAMING), but previously just returned
> > > zero.
> > > > > > Prior to f6161fccf8c5720ceac1ed1df8ba60ff8fed69f5, this
caused
> > > udp_read_packet to return zero, which is treated as EOF by
> > > read_packet. But after that commit, udp_read_packet would
continue
> > > if parse_rtsp_message didn't return an explicit error code.
> > > > > > To keep the original behaviour from before that commit,
more
> > > explicitly return an error in parse_rtsp_message when in the
wrong
> > > state.
> > > > > > Fixes: #8840
> > > ---
> > > libavformat/rtsp.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> > > index 5d8491b74b..ad12f2ae98 100644
> > > --- a/libavformat/rtsp.c
> > > +++ b/libavformat/rtsp.c
> > > @@ -1970,7 +1970,7 @@ static int
parse_rtsp_message(AVFormatContext *s)
> > > av_log(s, AV_LOG_WARNING,
> > > "Unable to answer to TEARDOWN\n");
> > > } else
> > > - return 0;
> > > + return AVERROR_EOF;
> > > > Does the else part needs the same fix?
> > Which else part do you refer to? The else above (with the
warning)? Yes
> that bit looks a bit odd to me as well - your patch 2/2 looks like a
> good fix for that.
I mean the else below, especially
/* XXX: parse message */
if (rt->state != RTSP_STATE_STREAMING)
return 0;
I did some tests with the rtsp server from:
https://github.com/revmischa/rtsp-server
This point can be reached with rt->state = RTSP_STATE_IDLE when the
initial_pause option is set:
./ffmpeg -initial_pause 1 -i rtsp://127.0.0.1/abc -f null -
Then it seems changing the return value in the above code would lead to
unintended results.
Thanks for testing this.
Indeed, I'd rather treat that as a separate case. The listen mode is
not very widely used, and this issue can be traced back to a
regression, so that can be easily fixed in that context.
For the other case you're pointing out, I don't have a concrete bug
(the UDP mode seems to require waiting for a long timeout at the end
though, but changing this return statement to return an error doesn't
seem to help), and the normal non-listen mode code can be used in a
huge variety of cases, many that aren't very easy to test (e.g. the
code used to support RealRTSP, but I'm not sure if there's any
publicly available test clips/servers for that any longer -
multimediawiki used to list some, but I tested them last time close to
a decade ago, and then there might have been zero or one of them still
responding). So for that code, I'd tread much more carefully...
Understood. Use cases are complex than what the simple code shows.
// Martin
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