[FFmpeg-devel] [PATCH 1/3] avformat/rtsp: Fix floating point exception for low min/max port range

["zhilizhao(赵志立)"]

> On Apr 4, 2021, at 11:36 PM, Andriy Gelman <andriy.gelman at gmail.com> wrote:
> 
> From: Andriy Gelman <andriy.gelman at gmail.com>
> 
> Fixed by setting port offset to zero when it cannot be computed.
> 
> To reproduce:
> $ ffmpeg -min_port 32000 -max_port 32001 -i rtsp://wowzaec2demo.streamlock.net/vod/mp4:BigBuckBunny_115k.mov -f null -
> [1]    303871 floating point exception (core dumped)
> 
> Signed-off-by: Andriy Gelman <andriy.gelman at gmail.com>
> ---
> libavformat/rtsp.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> index 25bdf475b3..76efbf42cd 100644
> --- a/libavformat/rtsp.c
> +++ b/libavformat/rtsp.c
> @@ -1446,7 +1446,7 @@ int ff_rtsp_make_setup_request(AVFormatContext *s, const char *host, int port,
>                               int lower_transport, const char *real_challenge)
> {
>     RTSPState *rt = s->priv_data;
> -    int rtx = 0, j, i, err, interleave = 0, port_off;
> +    int rtx = 0, j, i, err, interleave = 0, port_off = 0;
>     RTSPStream *rtsp_st;
>     RTSPMessageHeader reply1, *reply = &reply1;
>     char cmd[MAX_URL_SIZE];
> @@ -1465,9 +1465,11 @@ int ff_rtsp_make_setup_request(AVFormatContext *s, const char *host, int port,
>     /* Choose a random starting offset within the first half of the
>      * port range, to allow for a number of ports to try even if the offset
>      * happens to be at the end of the random range. */
> +    if (rt->rtp_port_max - rt->rtp_port_min > 1) {
>     port_off = av_get_random_seed() % ((rt->rtp_port_max - rt->rtp_port_min)/2);
>     /* even random offset */
>     port_off -= port_off & 0x01;
> +    }

(rt->rtp_port_max - rt->rtp_port_min)/2 should larger than one, otherwise port_off is always zero.

So how about `if (rt->rtp_port_max - rt->rtp_port_min >= 4)`? 


> 
>     for (j = rt->rtp_port_min + port_off, i = 0; i < rt->nb_rtsp_streams; ++i) {
>         char transport[MAX_URL_SIZE];
> -- 
> 2.31.0
> 
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