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				.Dd April 15, 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.
				In this case, 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 .