Channel hopping issue

[ZdenekBak]

Hi, I'm using Raspberry Pi 3B+ with Raspbian Buster and Alfa AWUS1900 with this driver (branch 5.6.4.1). I'm having a problem with channel hopping during capture in monitor mode. I set wlan to monitor mode and set the channel I want to sniff on, then I start capturing traffic with tshark, wireshark, airodump-ng, or anything else (btw. Kismet is not working with this driver). It sniff on proper channel that I set, for a while, but then it starts hopping on 2,4 GHz channels (1-13). I know it can be caused by networkmanager so I tried:

pi@raspberrypi:~ $ sudo airmon-ng check

Found 6 processes that could cause trouble.
Kill them using 'airmon-ng check kill' before putting
the card in monitor mode, they will interfere by changing channels
and sometimes putting the interface back in managed mode

  PID Name
  316 avahi-daemon
  353 wpa_supplicant
  378 avahi-daemon
  387 dhcpcd
  439 wpa_supplicant
  468 wpa_supplicant

I tried to kill these processes but after that network just stop working and I can't caputer any traffic. So I tried to stop (or kill) these processes one by one with no result (can't capture anything after killing wpa_supplicant). So I don't know if I'm doing something wrong or it's just bug. Thanks.

[ghost]

use this as root user # to enable ip link set wlan0 down airmon-ng check kill iw wlan0 set monitor none iw wlan0 set txpower fixed 3000 macchanger -r wlan0 ip link set wlan0 up

      &

use this as root # to disable

ip link set wlan0 down iw wlan0 set type managed macchanger -r wlan0 ip link set wlan0 up service network-manager restart

macchanger option is optional your choice

[Johnny8Bit]

Had the same issue with RPi 4B and driver 5.6.4.2. It looks like one of the processes is initiating a channel scan, even though the channel is manually set. The result is that you get a capture from mostly the channel that you set, along with whatever is captured on the other channels during the scan.

After killing each process manually - in my case - it was the dhcpcd process that was the culprit. Excluding the USB adapter from the dhcpcd process solved the problem.

This can be done by editing the /etc/dhcpcd.conf file And adding the following line to the end:

denyinterfaces wlan1

Assuming wlan1 is the USB interface you are capturing with. dhcpcd needs to be restarted for this to take effect.

[ZdenekBak]

Thank you @Johnny8Bit . It seems to work :)

[DeityOfChaos]

I have this issue on Raspberry Pi 4 and still happens. Some of the connections found will be on the specified channel but ultimately you will find other channels as well.

What I did:

sudo ip link set wlan1 down sudo airmon-ng check kill sudo iw dev wlan1 set type monitor sudo ip link set wlan1 up sudo iw dev wlan1 set channel 6 sudo airodump-ng -c6 wlan1

sudo airmon-ng check - separated terminal (Shows blank lines)

I had the same processes OP had, I uninstalled avahi-daemon after unsuccessful attempts of permanently disabling it, believing it was the culprit.

I added to /etc/dhcpcd.conf but was unsucessful: interface wlan1 nohook wpa_supplicant denyinterfaces wlan1

I am also using RTL8812AU, my Wireless Card is AWUS036AC I believe this might be a driver problem.