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.Dd June 1, 2021
.Dt ETHER_GEN_ADDR 9
.Os
.Sh NAME
.Nm ether_gen_addr
.Nd "generate an arbitrary MAC address for use"
.Sh SYNOPSIS
.In sys/types.h
.In sys/socket.h
.In net/if.h
.In net/if_var.h
.In net/ethernet.h
.Ft void
.Fn ether_gen_addr "struct ifnet *ifp" "struct ether_addr *hwaddr"
.Sh DESCRIPTION
The
.Fn ether_gen_addr
function generates an arbitrary MAC address for use by an ethernet interface
that does not have an assigned address.
.Pp
By default,
.Nm
attempts to generate a stable MAC address using the hostid of the jail that
the
.Ar ifp
is being added to.
During early boot, the hostid may not be set on machines that haven't yet
populated
.Pa /etc/hostid ,
or on machines that do not use
.Xr loader 8 .
.Pp
.Nm
can fail to derive a MAC address due to memory allocation failure, or because
the hostid has not been populated.
In these cases, a locally-administered unicast MAC address will be randomly
generated and returned via the
.Ar hwaddr
parameter.
.Pp
If
.Nm
succeeds, then it will return a MAC address in the FreeBSD Foundation OUI,
.Dq 58:9c:fc ,
via the
.Ar hwaddr
parameter.
.Sh AUTHORS
This manual page was written by
.An Kyle Evans Aq Mt kevans@FreeBSD.org .