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

[Martin Storsjö]

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

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.

// Martin