Kurento gets confused when addIceCandidate is called before gatherCandidates

[makkarpov]

Prerequisites

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• [X] I have read the Troubleshooting Guide and Support Instructions.

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Issue description

When addIceCandidates is called before gatherCandidates (e.g. because of async race conditions), Kurento gets confused.

1. Kurento response is returned only after 10-20s, causing timeouts on client side
2. First ICE candidates are sent after ~10s (Wireshark'ed, there are literally 10 seconds of silence).
3. ICE negotiation slows down too due to lack of candidates. Eventually it succeeds, but takes 20s instead of 2s.

Context

Pipeline that is being run is a simple RTP-to-WebRTC converter, just two blocks attached together. WebRTC is operating in send-only mode.

No logs shows up, so debugging that may be tricky.

How to reproduce?

My tests shows that it's sufficient to send ICE candidates before gatherCandidates call.

Expected & current behavior

Kurento should start sending ICE candidates immediately after gatherCandidates call, but it stucks for ~10-20s instead.

INFO about Kurento Media Server

• Kurento version: 6.14.0, image ID sha256:c195eb150fced18b05edc1aea963f3d0546fa83961d0d81aa7f12084a094326f
• Server OS: Fedora 32
• Installation method: Docker

INFO about your Application Server

• Programming Language: Java, but issue is unrelated to client
• Kurento Client version: 6.14.0, but unrelated

INFO about end-user clients

Any clients, Chrome on Linux to be specific.

INFO about your environment

Docker container uses host networking.

Kurento is configured with a static IP address and has an explicitly specified network interface. Kurento is directly reachable in the network, so no NAT traversal is required. Because of that, no STUN/TURN servers are specified in the config file.

Run these commands

cat: /etc/lsb-release: No such file or directory

Kurento Media Server version: 6.14.0
Found modules:
	'core' version 6.14.0
	'elements' version 6.14.0
	'filters' version 6.14.0

ii  gstreamer1.5-alsa:amd64              1.8.1-1kurento2.16.04                    amd64        GStreamer plugin for ALSA
ii  gstreamer1.5-libav:amd64             1.8.1-1kurento1.16.04                    amd64        libav plugin for GStreamer
ii  gstreamer1.5-libav-dbg:amd64         1.8.1-1kurento1.16.04                    amd64        libav plugin for GStreamer (debug symbols)
ii  gstreamer1.5-nice:amd64              0.1.17-0kurento1.16.04                   amd64        ICE library (GStreamer 1.5 plugin)
ii  gstreamer1.5-nice-dbgsym:amd64       0.1.17-0kurento1.16.04                   amd64        debug symbols for package gstreamer1.5-nice
ii  gstreamer1.5-plugins-bad:amd64       1.8.1-1kurento4.16.04                    amd64        GStreamer plugins from the "bad" set
ii  gstreamer1.5-plugins-bad-dbg:amd64   1.8.1-1kurento4.16.04                    amd64        GStreamer plugins from the "bad" set (debug symbols)
ii  gstreamer1.5-plugins-base:amd64      1.8.1-1kurento2.16.04                    amd64        GStreamer plugins from the "base" set
ii  gstreamer1.5-plugins-base-dbg:amd64  1.8.1-1kurento2.16.04                    amd64        GStreamer plugins from the "base" set
ii  gstreamer1.5-plugins-good:amd64      1.8.1-1kurento4.16.04                    amd64        GStreamer plugins from the "good" set
ii  gstreamer1.5-plugins-good-dbg:amd64  1.8.1-1kurento4.16.04                    amd64        GStreamer plugins from the "good" set
ii  gstreamer1.5-plugins-ugly:amd64      1.8.1-1kurento1.16.04                    amd64        GStreamer plugins from the "ugly" set
ii  gstreamer1.5-plugins-ugly-dbg:amd64  1.8.1-1kurento1.16.04                    amd64        GStreamer plugins from the "ugly" set (debug symbols)
ii  gstreamer1.5-pulseaudio:amd64        1.8.1-1kurento4.16.04                    amd64        GStreamer plugin for PulseAudio
ii  gstreamer1.5-x:amd64                 1.8.1-1kurento2.16.04                    amd64        GStreamer plugins for X11 and Pango
ii  kms-core                             6.14.0-0kurento1.16.04                   amd64        Kurento Core module
ii  kms-core-dbg                         6.14.0-0kurento1.16.04                   amd64        Kurento Core module
ii  kms-elements                         6.14.0-0kurento1.16.04                   amd64        Kurento Elements module
ii  kms-elements-dbg                     6.14.0-0kurento1.16.04                   amd64        Kurento Elements module
ii  kms-filters                          6.14.0-0kurento1.16.04                   amd64        Kurento Filters module
ii  kms-filters-dbg                      6.14.0-0kurento1.16.04                   amd64        Kurento Filters module
ii  kms-jsonrpc                          6.14.0-0kurento1.16.04                   amd64        Kurento JSON-RPC library
ii  kms-jsonrpc-dbg                      6.14.0-0kurento1.16.04                   amd64        Kurento JSON-RPC library
ii  kmsjsoncpp                           1.6.3-1kurento1.16.04                    amd64        Kurento jsoncpp library
ii  kmsjsoncpp-dbg                       1.6.3-1kurento1.16.04                    amd64        Kurento jsoncpp library
ii  kurento-dbg                          6.14.0-0kurento1.16.04                   amd64        Meta-package that installs debug symbols
ii  kurento-media-server                 6.14.0-0kurento1.16.04                   amd64        Kurento Media Server
ii  kurento-media-server-dbg             6.14.0-0kurento1.16.04                   amd64        Kurento Media Server
ii  libgstreamer-plugins-bad1.5-0:amd64  1.8.1-1kurento4.16.04                    amd64        GStreamer development files for libraries from the "bad" set
ii  libgstreamer-plugins-base1.5-0:amd64 1.8.1-1kurento2.16.04                    amd64        GStreamer libraries from the "base" set
ii  libgstreamer1.5-0:amd64              1.8.1-1kurento2.16.04                    amd64        Core GStreamer libraries and elements
ii  libgstreamer1.5-0-dbg:amd64          1.8.1-1kurento2.16.04                    amd64        Core GStreamer libraries and elements
ii  libnice10:amd64                      0.1.17-0kurento1.16.04                   amd64        ICE library (shared library)
ii  libnice10-dbgsym:amd64               0.1.17-0kurento1.16.04                   amd64        debug symbols for package libnice10
ii  libsrtp0:amd64                       1.6.0-0kurento1.16.04                    amd64        Secure RTP (SRTP) and UST Reference Implementations - shared library
ii  libusrsctp                           0.9.2-1kurento1.16.04                    amd64        sctp-refimpl library
ii  openh264                             1.4.0-1kurento1.16.04                    amd64        OpenH264 library
ii  openh264-gst-plugins-bad-1.5:amd64   1.8.1-1kurento4.16.04                    amd64        GStreamer plugins from openh264
ii  openwebrtc-gst-plugins               0.10.0-1kurento1.16.04                   amd64        OpenWebRTC specific GStreamer plugins
ii  openwebrtc-gst-plugins-dbg           0.10.0-1kurento1.16.04                   amd64        OpenWebRTC specific GStreamer plugins

[github-actions[bot]]

Hello @makkarpov! :wave: we're sorry you found a bug... so first of all, thank you very much for reporting it.

To know about progress, check in Triage. All issues are considered Backlog Candidates until work priorities align and the issue is selected for development. It will then become part of our official Backlog.

[j1elo]

Sorry for the bot issue. It checks the prerequisites. Otherwise people just write a line like "doesn't work, fix please".

Now about the issue: could it happen due to too many async calls happening at the same time? i.e. does it happen if only one WebRtcEndpoint is operating on the pipeline?

[makkarpov]

Yes, it happens with just single client and otherwise unoccupied server. When I removed browser-to-server ICE trickling (i.e. it's sendonly anyway) everything started to work flawlessly.