interface's MTU to the if_bridge(4) interface. This fixes a
bug that MTU value of "addm <interface>" is used even when it
is invalid for the if_bridge(4) member:
# ifconfig bridge0 create
# ifconfig bridge0
bridge0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
...
# ifconfig bridge0 addm lo0
ifconfig: BRDGADD lo0: Invalid argument
# ifconfig bridge0
bridge0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 16384
...
- Do not ignore MTU value of an interface even when if_type == IFT_GIF.
This fixes MTU mismatch when an if_bridge(4) interface has a
gif(4) interface and no other interface as the member, and it
is directly used for L2 communication with EtherIP tunneling
enabled.
- Implement SIOCSIFMTU ioctl. Changing the MTU is allowed only
when all members have the same MTU value.