I have set up a monitor interface using:

iw dev wlan0 interface add mon0 type monitor
ifconfig mon0 up

And I am using libpcap to capture and inspect 802.11 frames and radiotap headers. I was previously using the following Linux kernel:

Linux armada 3.10.103-marvell armv7l GNU/Linux

I am now using:

Linux armada 4.13.4-mvebu 2017 armv7l GNU/Linux

When using the older kernel I was able to monitor all RX and TX packets that were sent on the wlan0 interface. But on the new kernel only the RX packets are seen. I find the same when running tcpdump -e -i mon0 -Q out, no TX packets are seen.

Does anyone know how I can enable this functionality, can I rebuild the kernel with something to make it work?


The wifi module is an Azurewave, both these images were custom compiled for a Clearfog board using the Armbian build tools, Debian Jessie.

  • You have added neither the brand nor model, nor the kernel module you are using, nor the brand/model of your iOT. Out of curiosity, is the new kernel official, or you compiled it yourself? – Rui F Ribeiro Mar 2 '18 at 11:14
  • Custom compiled using the Armbian build tools script. See edit. – Ross MacArthur Mar 2 '18 at 11:36
  • Both of the kernels are custom compiled – Ross MacArthur Mar 2 '18 at 11:49

I also have dealt with iOTs on and off. The reality of the situation is that not all boards accept new kernels, and often some have hacks done by the vendor for a couple of specific versions, and usually you are tied to those versions for good.

The way I see it: Debian documentation clearly states the Clearfog pro is well supported by the mainline kernel nowadays, which clearly suggests there are some limitations for the non-pro version.

Furthermore, from the kernel versions you provide, it is easy to see your kernel 3.x was somewhat blessed/changed/hacked by the vendor, whilst the 4.x version you are using is not.

I would avise sticking with the 3.x kernel for now, and both filling a bug with the vendor, following their boards to see if some patch or a better supported version comes along.

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