Where did "from <__automatic_43ce223_0> come from?

From: Dave Horsfall <dave_at_horsfall.org>
Date: Sat, 25 Feb 2023 20:09:24 UTC
FreeBSD aneurin.horsfall.org 10.4-RELEASE-p13 FreeBSD 10.4-RELEASE-p13 #0: Thu Sep 27 09:21:23 UTC 2018     root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  i386

(Yeah, I'll update soon, when I find a newer box)

Seen in my daily security run output:

    +block drop in quick inet from <__automatic_43ce223_0> to any [ Evaluations: 7333 Packets: 4 Bytes: 240 States: 0 ]

Obviously something created automatically (I don't have anything faintly 
resembling that in my pf.conf), but how?

Thanks.

-- Dave