iPhone USB disabled because another network is connected due to touchbar

I was offline due to an outage with my ISP. I disabled Wi-Fi and connected to my 2016 Macbook Pro running macOS (10.12.4-10.12.5) an iPhone to use its personal hotspot to connect, but when I did, the hotspot did not kick in as it has on past Macs. Instead, in the Network System Preferences, I see this message for iPhone USB:

Attached iPhone USB is disabled because another network is connected. Uncheck the box below to connect anyway [✓] Disable unless needed

If I uncheck the box, the interface changes to Connected, but I want the device to only be active when needed. The mac seems to be incorrectly detecting that I don't need it when I do.

I tried removing all of the Network devices and restarting the machine, but even after restarting, the problem persisted.

I did some spelunking and found using ifconfig that en8 was to blame. If I sudo ifconfig en8 down, it makes that interface inactive and then the mac enables the iPhone USB device.

The details on the en8 device aren't very helpful:

$ sudo ifconfig -v en8
en8: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500 index 4
    eflags=1000080<TXSTART,ECN_ENABLE>
    ether ac:de:48:00:11:22 
    inet6 fe80::aede:48ff:fe00:1122%en8 prefixlen 64 scopeid 0x4 
    nd6 options=281<PERFORMNUD,INSECURE,DAD>
    media: autoselect
    status: active
    type: Ethernet
    link quality: 100 (good)
    state availability: 0 (true)
    scheduler: QFQ 
    qosmarking enabled: no mode: none

The only identifying information there is the mac address, which resolves to a generic "private" space.

Using networksetup -listallnetworkservices gives no hint as to what that device might be and the device doesn't appear in the list from networksetup -listallhardwareports.

I persisted and found en8 listed in System Information:

The device is iBridge, which with a search reveals that iBridge is for the touch bar.

Even with en8 down, the touchbar appears to work, which makes me think the ethernet device is not in use at all.

I suspect this behavior is a bug and will need to be fixed in a future OS update, but I'm hopeful for some prospects.

Is it safe to leave en8 inactive, or what issues might I encounter with that device inactive? Is there another way to configure that interface such that it is still up and functioning as Apple intended, but without signaling to the OS that it's a viable connection to a network when it is not?

Solution 1:

One thing that stops working if you take down the en8 interface is the Touch ID, which fails to unlock the laptop or otherwise authorize the user unless the interface is active.