systemd-networkd keeps open that kind of socket for LLDP but apparently not for the DHCP client code. wpa_supplicant also keeps open this type of socket on my local system. and the dhcpd daemons on my routers have some of those too for each interface...

i wonder if the slow path here could be avoided by using separate network namespaces in a way these sockets don't even get to see the packets...