From ebff14be20c3f2c0fbfa2da3321e3043a0ff8650 Mon Sep 17 00:00:00 2001 From: Yuyang Huang Date: Mon, 12 Oct 2026 10:17:05 +0900 Subject: net: add AF_PACKET multicast dumps RTM_GETMULTICAST dumps IPv4 and IPv6 multicast group memberships, but the device multicast list (dev->mc) is only available through /proc/net/dev_mcast, so "ip maddr show" still has to parse procfs for its link-layer entries. Handle RTM_GETMULTICAST dumps with ifa_family set to AF_PACKET next to the dev->mc helpers in dev_addr_lists.c and report every entry of dev->mc in the existing ifaddrmsg format: - IFA_MULTICAST carries the raw link-layer address - IFA_MC_USERS carries the entry reference count - IFA_F_GLOBAL in IFA_FLAGS reports netdev_hw_addr::global_use, set by dev_mc_add_global() (SIOCADDMULTI) and dev_mc_add_excl() ("bridge fdb add ... self"), i.e. entries added explicitly rather than by a protocol join. This is the static column of /proc/net/dev_mcast - ifa_scope is RT_SCOPE_LINK This covers every column of /proc/net/dev_mcast. AF_PACKET is the family iproute2 already uses for link-layer addresses ("ip -0"). The default FDB dump also walks dev->mc, but only for Ethernet devices and only if the driver uses it, vxlan for example does not, and it has no users count or global_use bit. Extending it would change "bridge fdb show" output and add NDA_* attributes. Requests are always validated, there are no legacy users: prefixlen, flags and scope must be zero, ifa_index selects one device and IFA_TARGET_NETNSID is the only attribute accepted. The dump runs under RCU and netif_addr_lock_bh() without RTNL. cb->seq is set from the dev->mc generation counter and dev_base_seq before each round and checked after it, so an entry added or removed since the previous round sets NLM_F_DUMP_INTR. A round without a message skips the check and cb->seq is set once more after the round, so the NLMSG_DONE check reports a change made during the last round or before an empty one. Signed-off-by: Yuyang Huang Reviewed-by: Nicolas Dichtel Link: https://patch.msgid.link/20261012011707.3378-5-sigefriedhyy@gmail.com Signed-off-by: Paolo Abeni --- include/linux/netdevice.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index f52c46e28e3a..79f9ee0cf799 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -5181,6 +5181,7 @@ int dev_mc_sync_multiple(struct net_device *to, struct net_device *from); void dev_mc_unsync(struct net_device *to, struct net_device *from); void dev_mc_flush(struct net_device *dev); void dev_mc_init(struct net_device *dev); +int dev_mc_dump(struct sk_buff *skb, struct netlink_callback *cb); /** * __dev_mc_sync - Synchronize device's multicast list -- cgit v1.2.3