[FFmpeg-devel] [PATCH v3 1/2] avformat/rtsp: fix infinite loop with udp transport

[Andriy Gelman]

On Wed, 30. Sep 12:41, Martin Storsjö wrote:
> Hi,
> 
> On Sun, 27 Sep 2020, Zhao Zhili wrote:
> 
> > Fix #8840.
> > 
> > Steps to reproduce:
> > 1. sender:
> > ./ffmpeg -i test.mp4 -c copy -f rtsp -rtsp_transport udp  rtsp://localhost:12345/live.sdp
> > 2. receiver:
> > ./ffmpeg_g -y -rtsp_flags listen -timeout 100 -i rtsp://localhost:12345/live.sdp -c copy test.mp4
> > ---
> > v3: mention the ticket.
> > 
> > libavformat/rtsp.c    | 2 ++
> > libavformat/rtsp.h    | 1 +
> > libavformat/rtspdec.c | 2 +-
> > 3 files changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> > index 5d8491b74b..597413803f 100644
> > --- a/libavformat/rtsp.c
> > +++ b/libavformat/rtsp.c
> > @@ -2051,6 +2051,8 @@ static int udp_read_packet(AVFormatContext *s, RTSPStream **prtsp_st,
> >                 if ((ret = parse_rtsp_message(s)) < 0) {
> >                     return ret;
> >                 }
> > +                if (rt->state == RTSP_STATE_TEARDOWN)
> > +                    return AVERROR_EOF;
> >             }
> > #endif
> >         } else if (n == 0 && ++timeout_cnt >= MAX_TIMEOUTS) {
> > diff --git a/libavformat/rtsp.h b/libavformat/rtsp.h
> > index 54a9a30c16..481cc0c3ce 100644
> > --- a/libavformat/rtsp.h
> > +++ b/libavformat/rtsp.h
> > @@ -198,6 +198,7 @@ enum RTSPClientState {
> >     RTSP_STATE_STREAMING, /**< initialized and sending/receiving data */
> >     RTSP_STATE_PAUSED,  /**< initialized, but not receiving data */
> >     RTSP_STATE_SEEKING, /**< initialized, requesting a seek */
> > +    RTSP_STATE_TEARDOWN,/**< initialized, in teardown state */
> > };
> > 
> > /**
> > diff --git a/libavformat/rtspdec.c b/libavformat/rtspdec.c
> > index dfa29913bf..ec786a469a 100644
> > --- a/libavformat/rtspdec.c
> > +++ b/libavformat/rtspdec.c
> > @@ -494,7 +494,7 @@ int ff_rtsp_parse_streaming_commands(AVFormatContext *s)
> >                               "Public: ANNOUNCE, PAUSE, SETUP, TEARDOWN, "
> >                               "RECORD\r\n", request.seq);
> >     } else if (methodcode == TEARDOWN) {
> > -        rt->state = RTSP_STATE_IDLE;
> > +        rt->state = RTSP_STATE_TEARDOWN;
> >         ret       = rtsp_send_reply(s, RTSP_STATUS_OK, NULL , request.seq);
> >     }
> >     return ret;
> > -- 
> > 2.17.1

Martin, thanks for looking over the patch.

> 
> I think this approach to fixing it, adding a new state, is a bit of
> overkill. This usecase actually used to work originally, but I bisected it
> and it broke in f6161fccf8c5720ceac1ed1df8ba60ff8fed69f5. So with that in
> mind, it's pretty straightforward to fix it by retaining the original
> behaviour from before that commit. I'll send an alternative patch that does
> that.

I made the suggestion to add TEARDOWN state because I thought it's safer than
relying on the idle state, and it made the code more readable.

Looking at your patch, I think it's a clean/elegant solution, and also looks
good to me.

-- 
Andriy