So in fairness, this doesn't actually use UDP at all (SOCK_DGRAM does not mean UDP!).

The actual protocol in use, and what's supported, it matched by all of the address family (IPV4), the socket type (DGRAM), and the protocol (ICMP). The match structure for IPV4 is here in Linux at least: https://elixir.bootlin.com/linux/v6.18/source/net/ipv4/af_in...

So ultimately, it's not even UDP, it's just creating a standard ICMP socket.