On 30/06/2026 12:02, Yuyang Huang wrote:

RTM_GETMULTICAST has been part of the rtnetlink ABI for a long time
and already reports IPv4 multicast group membership through
IFA_MULTICAST and IFA_CACHEINFO. It does not report how many consumers
hold each membership, so userspace still has to parse /proc/net/igmp to
get the Users column.

Add IFA_MC_USERS as a u32 attribute carrying ip_mc_list::users in
RTM_GETMULTICAST replies and entry-lifecycle notifications.

This gives iproute2 enough information to migrate the IPv4 part of
"ip maddr show" from procfs parsing to rtnetlink.

Signed-off-by: Yuyang Huang <redacted>
---
  Documentation/netlink/specs/rt-addr.yaml | 4 ++++
  include/uapi/linux/if_addr.h             | 1 +
  net/ipv4/igmp.c                          | 2 ++
  3 files changed, 7 insertions(+)

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>