The MAC address reported by `ifconfig ${nic} ether' does not always match
the address in the hardware, as reported by the driver during attach. In
particular, NICs which are components of a lagg(4) interface all report the
same MAC.

When attaching, the NIC driver passes the MAC address it read from the
hardware as an argument to ether_ifattach(). Keep a second copy of it, and
create ioctl(SIOCGHWADDR) to return it. Teach `ifconfig' to report it along
with the active MAC address.

% ifconfig ix0 ether # both "ether" and "hwaddr" end in "3b"
ix0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
hwaddr 0c:c4:7a:7c:0d:3b
% ifconfig ix1 ether # both "ether" and "hwaddr" end in "3a"
ix1: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3a
hwaddr 0c:c4:7a:7c:0d:3a
% sudo ifconfig lagg0 create # Create a lagg device
% ifconfig lagg0 ether # "ether" is zeroed, and "hwaddr" does not exist
lagg0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=800000<>
ether 00:00:00:00:00:00
% sudo ifconfig lagg0 laggport ix0 # Add ix0 to lagg0
% ifconfig lagg0 ether # The lagg's "ether" is now the same as ix0's
lagg0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
% ifconfig ix0 ether # No change to ix0's "ether" or "hwaddr"
ix0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
hwaddr 0c:c4:7a:7c:0d:3b
% ifconfig ix1 ether # No change to ix1's "ether" or "hwaddr"
ix1: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3a
hwaddr 0c:c4:7a:7c:0d:3a
% sudo ifconfig lagg0 laggport ix1 # Add ix1 to lagg0
% ifconfig lagg0 ether # No change to lagg0's "ether"
lagg0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
% ifconfig ix0 ether # No change to ix0's "ether" or "hwaddr"
ix0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
hwaddr 0c:c4:7a:7c:0d:3b
% ifconfig ix1 ether # ix1's "ether" changed to match lagg0's ; "hwaddr" unchanged
ix1: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
hwaddr 0c:c4:7a:7c:0d:3a
% sudo ifconfig lagg0 destroy # Destroy lagg0
% ifconfig ix0 ether # No change to ix0's "ether" or "hwaddr"
ix0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3b
hwaddr 0c:c4:7a:7c:0d:3b
% ifconfig ix1 ether # ix1's "ether" returned to original "3a" value; "hwaddr" never changed
ix1: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=e407bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:7c:0d:3a
hwaddr 0c:c4:7a:7c:0d:3a