Why does atop open a raw socket?

I install atop on Debian 9. It runs as a monitoring daemon. Why is it listening on a raw socket? Raw sockets are used to generate arbitrary IPv4 packets or capture all packets read all packets for a given IP sub-protocol! But I don't think my atop and its logs show any information from reading packets. I don't even use netatop - and that would require a kernel module, which is not included in Debian. And I would be extremely surprised if any of the atop features involve *sending* raw IP packets. $ sudo netstat -l --raw -ep Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State User Inode PID/Program name raw 0 0 0.0.0.0:255 0.0.0.0:* 7 root 2427667 7353/atop $ sudo ss -l --raw -p State Recv-Q Send-Q Local Address:Port Peer Address:Port UNCONN 0 0 *:ipproto-255 *:* users:(("atop",pid=7353,fd=4))