IGMP default_version is ignored

[gurksaften]

Describe the bug

I have a home setup that works well except i am unable to get IPTV to work.
The reason is that i need IGMP to be version 2 on WAN for the ISP to start sending the multicast TV stream.

IGMP is always sent as v3 on the WAN interface. os-igmp-proxy relies on the kernel for IGMP client IP_ADD_MEMBERSHIP. All attempts to change the version used by the kernel is ignored.

To Reproduce

Steps to reproduce the behavior:

1. Setup OPNsense as a common WAN/LAN home router
2. Install os-igmp-proxy and configure according to WAN/LAN networks for upstream/downstream
3. Set FW to allow IGMP between WAN/LAN with IP options.
4. Set "Tunables": net.inet.igmp.default_version=2
5. Reboot
6. Start IPTV box and monitor WAN for IGMP traffic.

Expected behavior

The IPTV box sends IGMPv2 on LAN and expects it to remain that version on WAN. The ISP expects said version for it to enable the multicast stream. By inspecting the "old" router provided by the ISP i see that IGMPv2 is sent on WAN and the stream starts instantly without issues. FreeBSD kernel will always send IGMPv3 and thus no stream is received.

Describe alternatives you considered

Attempted all possible net.inet.igmp.* values according to man-pages in /boot/loader.conf.local, /etc/sysctl.conf, "Tunables" to no avail.

I am in the process of building my own kernel from sources with patches (first time) but would like to see associated patches merged and/or discussed in this repo for possible fix in the future.

Additional context

Patches related to this issue:

• https://lists.freebsd.org/archives/dev-commits-src-all/2025-May/054531.html
• freebsd/freebsd-src@b94ec00

Forum post where i found the second patch:

• https://forum.opnsense.org/index.php?topic=45711.0

Environment

OPNsense 26.1_4 (amd64)
Intel® Xeon™ E3-1230 3.2Ghz Quad Core with HT
TP-Link TG-3468 (Realtek), WAN IF, PCI passthrough
Running as VM in Proxmox 9.1 (with host CPU)
os-realtek-re