No IGMP report packets on multicast stream

Question

I'm trying to capture an multicast stream with ffmpeg behind a switch with IGMP Snooping enabled:

root [ /tmpfs/root ] $ ffmpeg -i rtp://239.0.0.1:5006 /tmp/stream.mp4

The stream always disconnects after the routers member port time runs out, so always after my configured 260 seconds.

In my tcdump capture, I can see the first join group packet:

6   0.004965    192.168.1.12    224.0.0.22  IGMPv3  54  Membership Report / Join group 239.0.0.1 for any sources
7   0.005046    192.168.1.31    239.0.0.1   UDP 1382    5006 → 5006 Len=1340
8   0.005390    192.168.1.31    239.0.0.1   UDP 1109    5006 → 5006 Len=1067
...

After that, no IGMP report packets are captured until the time runs out:

...
225360  279.883980  192.168.1.12    224.0.0.22  IGMPv3  54  Membership Report / Leave group 239.0.0.1

In my Linux 6.1.60 kernel, CONFIG_IP_MULTICAST=y and CONFIG_BRIDGE_IGMP_SNOOPING=y are enabled.

I tried to adjust the the interval for unsolicited report interval: echo "10000" > /proc/sys/net/ipv4/conf/eth1/igmpv3_unsolicited_report_interval

As I understand, IGMP reports should be answered to IGMP queries, but where should the IGMP queries come from? From the streaming camera or the switch? Can I force my kernel to send the reports without the queries?

Answer 1

I have found a solution for the problem.

I was missing a "multicast router" that is responsible for the IGMP query packets.

I had to enable CONFIG_IP_MROUTE=y in the kernel and configure the pimd daemon. The daemon queries the multicast members in the network.