1403495 - Firefox prevents using the macOS network location switching menu

Status: NEW

(Core :: Networking, defect, P3)

Description

[Thomas De Reyck]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:55.0) Gecko/20100101 Firefox/55.0
Build ID: 20170824053838

Steps to reproduce:

1) Open Firefox 55.0.3 on MacOS Sierra.
2) With Firefox as the active Window, click the Apple icon in the menu bar, then choose "Location" and select another network location.



Actual results:

One of 2 things happens:
- Either a new (invisible) firefox process is created and crashes immediately, triggering the mozilla bug reporter tool.
- Or a new (invisible) firefox process is created and gets stuck as a background process, using significant CPU resources. Each time when a location switch is attempted, a new process is launched, worsening the problem. The main Firefox process keeps working though (even though a bit slower because of the new background process(es)). When quitting Firefox the invisible background processes remain and keep consuming significant CPU resources until these are quite via e.g. Terminal or Activity Monitor.

Also, after either of these 2 scenario's, the network location is not switched. It remains as it was, which is very confusing for end users.

If you switch to another app first, and then switch the network location, everything works fine. The problem only exists while "Firefox" is the bold menu item in the menu bar, thus it only exists when Firefox is the active foreground application.

I have about +- 150 macs running into this problem in my company. The issue can be reproduced on unrelated Macs as well. This bug already existed in earlier versions of Firefox as well(I suspect it first appeared somewhere in the late 40's releases). OS version does not seem to be related at first glance.


Expected results:

The network location is switched.

Comment 1

[Thomas De Reyck]

As a side not, I think I saw an ancient ticket about this issue in this bug tracker a few months back, but even after extensive searching I can't find it anymore.

Comment 2

[--]

I found Bug 1116956 that refers to a crash when switching location, but that's suspected to be VPN reasons and will likely be closed soon since nobody responded to it in years.

I can't reproduce this and I tried now back and forth on my Firefox 56.0, although between two network locations that are both using wifi (since that's all my mac has right now). How does your locations differ, network setup wise between those that you try to switch between?

(The mere notion that an application can prevent the network location to be switched seems weird to me...)

Comment 3

[Thomas De Reyck]

Hi,

I will see if I can further analyze the network locations. In the mean time, I have checked "about:crashes" (neat, didn't know this existed before today!) and seem to have found a crash report related to this:

https://crash-stats.mozilla.com/report/index/ffba8935-c033-423b-acb5-6b8b90171011

If I'm not mistaken this is a crash report from the first case (where the bug reporter tool opened). In recent versions that case seems more difficult to reproduce than the second case (with the background processes).

Also, Bug 1116956 seems exactly like what I'm experiencing, even though you don't actually need to quit Firefox to work around the issue. Switching to another application and then changing the network location works just fine. However most of my users, at their own first assessment, also made the deduction that they should quit Firefox to do so. Therefor I really expect this to be the same issue.

As I'm typing out this issue, I've tried switching locations again. Once again it failed and spawned a background process. I will include screenshots of the location currently selected ("IT") and the location I was trying to switch to ("Other Cable").

I do agree that it is weird that an application prevents switching the network location, but from my own small experiences in Cocoa programming I've noticed that the menu bar usually seems to be managed and rendered by the foreground application. You also see this when an applications hangs (because the GUI thread is busy). In such a case the menu bar (even the Apple menu) becomes unresponsive while that application is the foreground application. If you switch to another application, you can use it just fine. If you switch back to a hanging application, it will stop working again. From an outsider's perspective, it seems any Cocoa application has a built-in ability (and responsibility) to relay some menu bar actions to the OS. So when you see it from that perspective, it seems possible that the network location menu might have issues only within Firefox's context. Perhaps Firefox (which to me, seems far from just a plain old Cocoa application) somehow doesn't signals these actions properly to the OS?

Please let me know if I can provide anything else for you!

Kind regards,
Thomas De Reyck

Comment 4

[Thomas De Reyck]

Hi again,

I can't seem to find any screenshot uploading functionality here, so I'm hosting the screenshots myself. These are the links:

https://media.manucharit.com/screenshot-IT.png
https://media.manucharit.com/screenshot-OtherCable.png

Kind regards,
Thomas De Reyck