When FreeBSD runs as a jail, with the security.jail.jailed sysctl set,
the loopback address behaves differently. jail(2) says:
All IP activity will be forced to happen to/from the IP number
specified, which should be an alias on one of the network interfaces.
All connections to/from the loopback address (127.0.0.1 for IPv4, ::1
for IPv6) will be changed to be to/from the primary address of the jail
for the given address family.