Why do "arp -a" doesn't show names on -CURRENT?

[Masachika ISHIZUKA]

>  On -CURRENT (r334027)  "arp -a" can not resolve addresses to names. DNS
> working, as "drill -x" shows:
> 
> % arp -a
> ? (192.168.136.1) at 00:22:4d:9d:e0:97 on ubnt permanent [vlan]
> ? (192.168.136.2) at f0:9f:c2:f3:3d:b7 on ubnt expires in 1192 seconds
> [vlan]

  Hi.

  I'm using 12-current and it shows names as follows.

% uname -a
FreeBSD carrot.ish.org 12.0-CURRENT FreeBSD 12.0-CURRENT #15 r334511: Sat Jun  2 13:26:19 JST 2018     ishizuka at carrot.ish.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC  amd64
% arp -a
sv3c.ish.org (xxx.xxx.xxx.xxx) at yy:yy:yy:yy:yy:yy on lagg0 permanent [ethernet]
carrot.ish.org (xxx.xxx.xxx.xxx) at yy:yy:yy:yy:yy:yy on lagg0 permanent [ethernet]
gw1.ish.org (xxx.xxx.xxx.xxx) at yy:yy:yy:yy:yy:yy on lagg0 expires in 1199 seconds [ethernet]
onion.ish.org (xxx.xxx.xxx.xxx) at yy:yy:yy:yy:yy:yy on lagg0 expires in 772 seconds [ethernet]

  I don't know why you cannot resolv names.

# I don't use /etc/hosts and use local_unbound to resolv names.
-- 
Masachika ISHIZUKA