Network connections have gone erratic

[Jeffrey Walton]

On Wed, Nov 22, 2023 at 10:28 AM Bret Busby <bret at busby.net> wrote:
>
> On one of my computers running Linux Mint Mate 21.2, I, yesterday or the
> day before, did a system update that included an update of avahi, which
> is apparently, a networking utility.
>
> Afterward, the computer, which I have had connected by wifi to a wifi
> modem, and, by USB tethering, to my cellphone for Internet access, both
> devices using 4G cellphone networks with different carriers, to access
> the Internet, with the USB tethering involving "hot plugging" (?), can
> no longer use the USB tethering, which, whilst I set the USB tethering
> to "On", on the cellphone, is automatically severed, with no data shown
> as being transferred, and, the NetworkManager Applet shows the wifi
> connection to the wifi modem, to be in an endless loop of dropping out
> and reconnecting.
>
> I can send and receive data, but, it is erratic.
>
> I do not know whether the networking connections failing, is due to the
> avahi upgrade, or just coincides with the timing, but, it is worrying.
>
> Prior to the avahi update, I had not encountered this problem, and, the
> networking connections had been stable.
>
> I had performed an orderly shutdown and reboot, to find whether that
> might fix this, but, it did not fix the problem.
>
> How do I find what is causing this, and, how do I fix it?

I _think_ I encountered a similar issue about a year or so ago. When
my Pixel was tethered to my Desktop, the desktop would try to use the
network connection from the phone rather than wired ethernet. The
pixel used wifi, and wifi was outside my internal wired network. So my
desktop (using the Pixel) could no longer talk to other hosts on my
internal (wired ethernet) network.

I filed a bug report about it. I don't think it was fixed. I
eventually installed a new distro for this machine. The problem went
away. I _think_ changing network costs or priorities could have fixed
the issue.

I don't think Avahi has anything to do with it. Avahi is just mDNS.

Jeff