.\" .\" SPDX-License-Identifier: BSD-2-Clause .\" .\" Copyright (C) 2021 Kyle Evans <kevans@FreeBSD.org> .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice(s), this list of conditions and the following disclaimer as .\" the first lines of this file unmodified other than the possible .\" addition of one or more copyright notices. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice(s), this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY .\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE .\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY .\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES .\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR .\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER .\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH .\" DAMAGE. .\" .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 .