Make SIOCSIFDSTMASK and SIOCSIFNETMASK fail if there is no previous address configured on the interface just like SIOCSIFBRDADDR does.
Make SIOCSIFDSTMASK and SIOCSIFNETMASK fail if there is no previous
address configured on the interface just like SIOCSIFBRDADDR does.

This prevent the global IPv4 address list and the per-interface list
to be out of sync until one of SIOCAIFADDR or SIOCSIFADDR ioctl(2)
is issued.

ok mikeb@, sthen@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars