SRT listen on IPv6 fails

[Sesse]

How to reproduce:

% ./ffmpeg -i 'srt://[::]:9710?mode=listener' foo.mp4
ffmpeg version N-111830-gc48ec95ba3 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 13 (Debian 13.2.0-1)
  configuration: --enable-libsrt
  libavutil      58. 17.100 / 58. 17.100
  libavcodec     60. 23.100 / 60. 23.100
  libavformat    60. 10.101 / 60. 10.101
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 11.100 /  9. 11.100
  libswscale      7.  3.100 /  7.  3.100
  libswresample   4. 11.100 /  4. 11.100
[srt @ 0x557d57e23600] Operation not supported: Bad parameters
[in#0 @ 0x557d57e22cc0] Error opening input: Unknown error occurred
Error opening input file srt://[::]:9710?mode=listener.
Error opening input files: Unknown error occurred

It seems this broke with libsrt 1.5.0, cf.: ​https://github.com/Haivision/srt/issues/2764

Seemingly FFmpeg needs to add a setsockopt call to SRTO_IPV6ONLY (preferably to zero, so that one can listen on IPv4+IPv6), or listening is forever restricted to legacy IP.

[Erik Tews]

I can confirm the bug, but there is a workaround. When you specify a specific IP address, then it works.

./ffmpeg -i 'srt://[::1]:9710?mode=listener' foo.mp4

However in this example it will listen only on the loopback interface.

[Romain Beauxis <romain.beauxis@gmail.com>]

In bce8d61d/ffmpeg:

avformat/libsrt: fix ipv6 wildcard listener

For now it fails on srt://[::]:1234?mode=listener

This modification makes it accept a new option "ipv6only"

Reference:
​https://github.com/Haivision/srt/pull/2608
​https://github.com/Haivision/srt/blob/master/docs/API/API-socket-options.md#SRTO_IPV6ONLY

fix #10539

[toots]

Fixed in ​https://code.ffmpeg.org/FFmpeg/FFmpeg/commit/bce8d61d123602272db312eeed333a0063afc95e