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Conectivity loss because gateway's arp entry is incomplete

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  Conectivity loss because gateway's arp entry is incomplete "Miguel A. Vallejo" <ea4eoz@gmail.com> - 2020-03-04 00:40 +0100
    Re: Conectivity loss because gateway's arp entry is incomplete Nektarios Katakis <nektarios@mail.nektarioskatakis.xyz> - 2020-03-04 01:50 +0100
      Re: Conectivity loss because gateway's arp entry is incomplete "Miguel A. Vallejo" <ea4eoz@gmail.com> - 2020-03-04 03:00 +0100
        Re: Conectivity loss because gateway's arp entry is incomplete Nektarios Katakis <nektarios@mail.nektarioskatakis.xyz> - 2020-03-04 11:20 +0100
          Re: Conectivity loss because gateway's arp entry is incomplete "Miguel A. Vallejo" <ea4eoz@gmail.com> - 2020-03-04 20:30 +0100
    Re: Conectivity loss because gateway's arp entry is incomplete Nemeth Gyorgy <lists@friczy.net> - 2020-03-07 11:00 +0100
      Re: Conectivity loss because gateway's arp entry is incomplete "Miguel A. Vallejo" <ea4eoz@gmail.com> - 2020-03-09 13:10 +0100

#219756 — Conectivity loss because gateway's arp entry is incomplete

Hello!

Diagnosing one of my several problems with WiFi in Debian I found a
problem this time not related to the WiFi connection itself, but I
don't know how to get the culprit... Anyone can point me in the right
direction?

Symptoms: From time to time I lost Internet connection for a period of
about 5 to 30 minutes. It happens at least two or three times a day.

Setup: Desktop computer (192.168.1.2) running Debian Buster amd64 with
current kernel 4.19.98-1 connected via WiFi to router / gateway
(192.168.1.1). Wifi Adapter is MT7612U from Mediatek.

While connection is lost:

- I can launch wavemon and I can confirm the WiFi adapter is still
connected and sending / receiving packets and beacons.

- Arp command shows the gateway HWaddress as incomplete.

- Launching Wireshark in the desktop computer I can see incoming
packets from other devices, but I can also see a "Who has 192.168.1.1?
Tell 192.168.1.2" ARP requests from my desktop every second. At first
glance it seems the gateway isn't responding to my arp requests,
but...

- I can see arp queries from the gateway to my desktop, and I can see
the responses, but they seem they never reach the gateway.

- Forcing network activity with my smartphone, I can see also arp
requests from the smartphone answered by the desktop, but a ping from
the smartphone to the desktop machine gives no response. Of course the
phone can use internet without any problem using the same gateway.

- If I unplug and replug the WiFi adapter everything works again. If I
left the WiFi adapter plugged, eventually I get an arp response from
the gateway, and everything works normally again. This may take up to
20-30 minutes. Only once the wifi connection crashed after several
minutes.

It seems that when I lost connectivity I can't sent arp messages but I
can receive them. They are sent, I can see them with Wireshark, but it
seems they will never get outside the machine. I searched for known
bugs but I wasn't able to find anything, only a message from an Ubuntu
user aparently having the same problem, but with a different WiFi
adapter and kernel version (4.18 I think):

https://askubuntu.com/questions/1122683/no-internet-access-after-random-intervals-in-ubuntu-18-04-2-lts

The problem is now I don't know how to get the culprit of this bug. Is
the kernel? Is the Mediatek kernel module?

Any help will be appreciated.

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#219757

Στις 2020-03-03 23:34, Miguel A. Vallejo έγραψε:
> Hello!
> 
> Diagnosing one of my several problems with WiFi in Debian I found a
> problem this time not related to the WiFi connection itself, but I
> don't know how to get the culprit... Anyone can point me in the right
> direction?
> 
> Symptoms: From time to time I lost Internet connection for a period of
> about 5 to 30 minutes. It happens at least two or three times a day.
> 
> Setup: Desktop computer (192.168.1.2) running Debian Buster amd64 with
> current kernel 4.19.98-1 connected via WiFi to router / gateway
> (192.168.1.1). Wifi Adapter is MT7612U from Mediatek.
> 
> While connection is lost:
> 
> - I can launch wavemon and I can confirm the WiFi adapter is still
> connected and sending / receiving packets and beacons.
> 
> - Arp command shows the gateway HWaddress as incomplete.
> 
> - Launching Wireshark in the desktop computer I can see incoming
> packets from other devices, but I can also see a "Who has 192.168.1.1?
> Tell 192.168.1.2" ARP requests from my desktop every second. At first
> glance it seems the gateway isn't responding to my arp requests,
> but...
> 
> - I can see arp queries from the gateway to my desktop, and I can see
> the responses, but they seem they never reach the gateway.
> 
> - Forcing network activity with my smartphone, I can see also arp
> requests from the smartphone answered by the desktop, but a ping from
> the smartphone to the desktop machine gives no response. Of course the
> phone can use internet without any problem using the same gateway.
> 
> - If I unplug and replug the WiFi adapter everything works again. If I
> left the WiFi adapter plugged, eventually I get an arp response from
> the gateway, and everything works normally again. This may take up to
> 20-30 minutes. Only once the wifi connection crashed after several
> minutes.
> 
> It seems that when I lost connectivity I can't sent arp messages but I
> can receive them. They are sent, I can see them with Wireshark, but it
> seems they will never get outside the machine. I searched for known
> bugs but I wasn't able to find anything, only a message from an Ubuntu
> user aparently having the same problem, but with a different WiFi
> adapter and kernel version (4.18 I think):
> 
> https://askubuntu.com/questions/1122683/no-internet-access-after-random-intervals-in-ubuntu-18-04-2-lts
> 
> The problem is now I don't know how to get the culprit of this bug. Is
> the kernel? Is the Mediatek kernel module?

I would check the `dmesg` command output. If there are erros there then
they re coming from the kernel.

Have you made sure that the wifi is not the problem? Before going into
wild software investigation? For example have you tried in a Windows
laptop with the correct device drivers? Because you even might not be
using the correct device drivers!

> 
> Any help will be appreciated.

---
Regards,
Nektarios Katakis

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#219758

Nektarios Katakis wrote:

> I would check the `dmesg` command output. If there are erros there then
> they re coming from the kernel.

I forgot to mention not a single message in syslog, kern.log, or any
other log I could find. Nothing. Nada. Zero.

> Have you made sure that the wifi is not the problem? Before going into
> wild software investigation?

No, that's what I want to discover to fill an appropriate bug report
against the right component. I must admit MT7612u support is buggy as
hell. I suffer many other bugs with these devices, all of them related
to the inhability to follow AP frequency changes in the 5 GHz band,
but this one does not seems related to the wifi itself. When the bug
triggers I can send and receive packets. Only sending arp messages
seems to be missing.

> For example have you tried in a Windows
> laptop with the correct device drivers? Because you even might not be
> using the correct device drivers!

I can't test the devices in Windows because I have no Windows here,
but I have four dongles, from two different manufacturers, all of them
with the MT7612U chip in it and all of them load the mt76x2u module
when plugged, so I must conclude they are using the correct device
driver/module. The problem exists with all the four dongles.

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#219763

Στις 2020-03-04 01:54, Miguel A. Vallejo έγραψε:
> Nektarios Katakis wrote:
> 
>> I would check the `dmesg` command output. If there are erros there 
>> then
>> they re coming from the kernel.
> 
> I forgot to mention not a single message in syslog, kern.log, or any
> other log I could find. Nothing. Nada. Zero.
> 
>> Have you made sure that the wifi is not the problem? Before going into
>> wild software investigation?
> 
> No, that's what I want to discover to fill an appropriate bug report
> against the right component. I must admit MT7612u support is buggy as
> hell. I suffer many other bugs with these devices, all of them related
> to the inhability to follow AP frequency changes in the 5 GHz band,
> but this one does not seems related to the wifi itself. When the bug
> triggers I can send and receive packets. Only sending arp messages
> seems to be missing.
> 
>> For example have you tried in a Windows
>> laptop with the correct device drivers? Because you even might not be
>> using the correct device drivers!
> 
> I can't test the devices in Windows because I have no Windows here,

I dont use windows either. But most manufacturers give correct drivers
for them.

> but I have four dongles, from two different manufacturers, all of them
> with the MT7612U chip in it and all of them load the mt76x2u module
> when plugged, so I must conclude they are using the correct device
> driver/module. The problem exists with all the four dongles.

This is not necessarily true. I recently bought a (chinese) wifi
adapter (atheros chip) that was recognized as mediatek. The moment
I linked the correct drivers with the device it worked properly.

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#219801

> This is not necessarily true. I recently bought a (chinese) wifi
> adapter (atheros chip) that was recognized as mediatek. The moment
> I linked the correct drivers with the device it worked properly.

Not my case. They all have the same usbID (0e8d:7612) and I physically
opened them and I saw the MT7612U chip in the four devices.

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#219930

2020. 03. 04. 0:34 keltezéssel, Miguel A. Vallejo írta:
> Hello!
>
> Diagnosing one of my several problems with WiFi in Debian I found a
> problem this time not related to the WiFi connection itself, but I
> don't know how to get the culprit... Anyone can point me in the right
> direction?
>
> Symptoms: From time to time I lost Internet connection for a period of
> about 5 to 30 minutes. It happens at least two or three times a day.
>
> Setup: Desktop computer (192.168.1.2) running Debian Buster amd64 with
> current kernel 4.19.98-1 connected via WiFi to router / gateway
> (192.168.1.1). Wifi Adapter is MT7612U from Mediatek.
>
> While connection is lost:
>
> - I can launch wavemon and I can confirm the WiFi adapter is still
> connected and sending / receiving packets and beacons.
>
> - Arp command shows the gateway HWaddress as incomplete.
>
> - Launching Wireshark in the desktop computer I can see incoming
> packets from other devices, but I can also see a "Who has 192.168.1.1?
> Tell 192.168.1.2" ARP requests from my desktop every second. At first
> glance it seems the gateway isn't responding to my arp requests,
> but...
>
> - I can see arp queries from the gateway to my desktop, and I can see
> the responses, but they seem they never reach the gateway.
>
> - Forcing network activity with my smartphone, I can see also arp
> requests from the smartphone answered by the desktop, but a ping from
> the smartphone to the desktop machine gives no response. Of course the
> phone can use internet without any problem using the same gateway.
>
> - If I unplug and replug the WiFi adapter everything works again. If I
> left the WiFi adapter plugged, eventually I get an arp response from
> the gateway, and everything works normally again. This may take up to
> 20-30 minutes. Only once the wifi connection crashed after several
> minutes.
>
> It seems that when I lost connectivity I can't sent arp messages but I
> can receive them. They are sent, I can see them with Wireshark, but it
> seems they will never get outside the machine. I searched for known
> bugs but I wasn't able to find anything, only a message from an Ubuntu
> user aparently having the same problem, but with a different WiFi
> adapter and kernel version (4.18 I think):
>
> https://askubuntu.com/questions/1122683/no-internet-access-after-random-intervals-in-ubuntu-18-04-2-lts
>
> The problem is now I don't know how to get the culprit of this bug. Is
> the kernel? Is the Mediatek kernel module?
>
> Any help will be appreciated.
>
Try to add your gateway arp with static arp entry and check whether the
problem persists.

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#219996

> Try to add your gateway arp with static arp entry and check whether the
> problem persists.

It does not work because the desktop machine still is not able to
answer gateway's arp requests. Well actually it answer the request but
they do not get outside the machine.

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