On 10/9/19 4:53 AM, Bjørn Mork wrote:

Adam Bennett <abennet...@gmail.com> writes:

I've been messing around with a Raspberry Pi Zero, in its ethernet
gadget mode.  This possible bug report is not against the Pi Zero
linux kernel, but rather the host computer's linux kernel.  I've been
able to reproduce the same host computer issue with my normal laptop,
and an embedded board (buildroot-based). Both run a newish version of
The issue is reported on the host, but it's really a problem with the
gadget.  You'll probably have the same issues with any host, including
hosts running something other than Linux.  They just won't be as verbose
about it.

That was my original assumption also.  But I tested the Pi Zero on Windows 10 (build 1903) and latest MacOS, and it works fine on those machines.
The bug report is that most of the time I cannot ping through the
local link, and I get a kernel debug message:  sometimes I can ping
the Pi Zero with no kernel message, most of the time I can't ping and
the message comes up, and occasionally I get the message right when I
plug in the Pi Zero, before I issue the ping command.

Here is the dmesg on my normal laptop (I've included the plug-in
sequence also):

[11728.029900] usb 1-1: new high-speed USB device number 10 using xhci_hcd
[11728.434200] usb 1-1: device descriptor read/64, error -71
First symptom of something wrong with the gadget...

[11728.669543] usb 1-1: New USB device found, idVendor=0525,
idProduct=a4a2, bcdDevice= 4.19
[11728.669548] usb 1-1: New USB device strings: Mfr=1, Product=2,
[11728.669551] usb 1-1: Product: RNDIS/Ethernet Gadget
[11728.669554] usb 1-1: Manufacturer: Linux 4.19.75+ with 20980000.usb
[11728.674528] cdc_ether 1-1:1.0 usb0: register 'cdc_ether' at
usb-0000:00:14.0-1, CDC Ethernet Device, 22:93:3a:1e:ac:5c
[11730.725278] cdc_ether 1-1:1.0 enp0s20f0u1: renamed from usb0
[11768.174915] ------------[ cut here ]------------
[11768.174921] NETDEV WATCHDOG: enp0s20f0u1 (cdc_ether): transmit
queue 0 timed out

This warning means that the gadget doesn't accept the packets we send
it.  There isn't much the host can do about that, except dropping
packets on the floor.  Which is why the warning is this loud.

Would a firewall on either the linux host or the Pi Zero cause the same problem (and message)?


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