I have a Pi Zero W running Raspbian 11. It is connected via WiFi. I am using dhcpcd to configure my interfaces (the official method IIUC) with the default config file. I have a DHCPv4 and v6 server available. SLAAC should also work.
I get messages every 5-10s along the lines of:
kernel: ICMPv6: NA: <MAC address> advertised our address <IPv6 address> on <iface>!
IIUC that normally means there is an IPv6 address conflict but in this case the MAC address is for the Pi's wlan0 interface and the IPv6 address is the IPv6 address for that interface. So something on the Pi is presumably seeing these NAs and the kernel thinks they come from someone else?
Who is supposed to be responsible for sending NAs under Raspbian? The kernel or a process?