IFMCSTAT(8)

💅 IFMCSTAT(8) — like, the multicast group management tea, per interface

okay so bestie, welcome to the System Manager's Manual page for ifmcstat 🎀 this is the one that spills the multicast group management stats, interface by interface. get comfy, it's giving very demure, very mindful kernel inspection ✨

✨ NAME ✨

ifmcstat — dump multicast group management statistics per interface 🦋

🌸 SYNOPSIS 🌸

ifmcstat [-i interface] [-f address-family] [-v] [-K] [-M core]
         [-N system]

💖 DESCRIPTION 💖

the ifmcstat command dumps multicast group information from the kernel. like literally straight from the kernel, no cap 👑

here's the options it supports, bestie:

• -i interface — specifies the interface to be displayed 🌈
• -f address-family — specifies the address family to be displayed; inet, inet6 and link are supported 💫
• -v — specifies that link-layer memberships should be printed; they are suppressed by default. it may not be specified for -f link. source lists for each group will also be printed 🫶

also, if you specify it twice, and kvm(3) is in use, the control plane timers for each interface and the source list counters for each group will also be printed 👀 twice the -v, twice the lore.

the following options are only available if ifmcstat has been built with support for kvm(3):

• -K — attempts to use kvm(3) to retrieve the multicast group information 🔥
• -M core — extracts values associated with the name list from the specified core, instead of the default /dev/kmem 💀
• -N system — extracts the name list from the specified kernel instead of the default, which is the kernel image the system has booted from 🌟

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🧚 IMPLEMENTATION NOTES 🧚

ifmcstat will always print the embedded scope IDs of IPv6 multicast group memberships. this is because memberships are always scoped to an interface — it's giving "bound to the interface, periodt" 💅

when run with the -v option, ifmcstat may print multicast MAC addresses twice if they are referenced by a layer 3 protocol. not a bug bestie, just double the slay 🙈

when run with kvm(3) support, the names of all interfaces configured in the system will be printed in the first column of output, even if no multicast group memberships are present on those interfaces 😭 (yes, even the boring empty ones, they're all main characters). the output may also be slightly different, as the kernel data structures are being traversed with minimal post-processing of the output.

when built without kvm(3) support, the information displayed by ifmcstat is more limited. this support is recommended for debugging purposes. it requires super-user privilege if used to inspect a running kernel 👑

⚠️ heads up: super-user privilege check is real — don't come for a running kernel without it.

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🦋 SEE ALSO 🦋

netstat(1), getifaddrs(3), getifmaddrs(3), kvm(3)

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and that's the whole vibe check bestie 💜 this page came from Debian, dated May 27, 2009 — kinda vintage, but she still ate, fr fr 🌸✨🎀