kazulog@sv1:~$ cat /etc/os-release | head -2
PRETTY_NAME="Ubuntu 26.04 LTS"
NAME="Ubuntu"
kazulog@sv1:~$ ldd /usr/sbin/in.tftpd | grep libwrap
	libwrap.so.0 => /usr/lib/x86_64-linux-gnu/libwrap.so.0 (0x00007cfa15a18000)
kazulog@sv1:~$ cat /etc/hosts.deny
# /etc/hosts.deny: list of hosts that are _not_ allowed to access the system.
#                  See the manual pages hosts_access(5) and hosts_options(5).
#
# Example:    ALL: some.host.name, .some.domain
#             ALL EXCEPT in.fingerd: other.host.name, .other.domain
#
# If you're going to protect the portmapper use the name "rpcbind" for the
# daemon name. See rpcbind(8) and rpc.mountd(8) for further information.
#
# The PARANOID wildcard matches any host whose name does not match its
# address.
#
# You may wish to enable this to ensure any programs that don't
# validate looked up hostnames still leave understandable logs. In past
# versions of Debian this has been the default.
# ALL: PARANOID
# TFTP は 192.168.100.20 からの接続を拒否する
in.tftpd: 192.168.100.20