Wifi NetworkManager

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Wireless

DART-MX8M Overview

The DART-MX8M supports the following WiFi modules:

Module	Chipset	Features	Network Interface(s)
Sterling LWB	Cypress CYW4343W	802.11 b/g/n	wlan0
Sterling LWB5	Cypress CYW43353	802.11 ac/a/b/g/n,	wlan0

This guide demonstrates how to configure WiFi using NetworkManager. It is important to use the correct network interface for the module assembled on your DART-MX8M.

Managing WiFi using NetworkManager

NetworkManager is a program for providing detection and configuration for systems to automatically connect to network.
NetworkManager's functionality can be useful for both wireless and wired networks.
This guide describes how to use NetworkManager to configure wireless networks.

Enabling and disabling WiFi

To check if WiFi is enabled by NetworkManager run

# nmcli dev show wlan0

and check the GENERAL.STATE line. If WiFi is enabled, the state is either connected or disconnected. If WiFi is disabled the state is unavailable.

To enable WiFi run

# nmcli radio wifi on

or if you need to disable it you can run

# nmcli radio wifi off

Configuring WiFi Client

Scanning for available WiFi APs

If WiFi is enabled you can get the list of available APs by running

# nmcli dev wifi list

Connecting to an open WiFi network

To connect to an open WiFi network run

# nmcli dev wifi connect <SSID> ifname wlan0

To connect to an open hidden WiFi network run

# nmcli dev wifi connect <SSID> hidden yes ifname wlan0

To check connection status run

# nmcli con show <SSID>

To check WiFi device status run

# nmcli dev show wlan0

Connecting to a protected WiFi network

To connect to a protected WiFi network run

# nmcli dev wifi connect <SSID> password <password> ifname wlan0

To connect to a protected hidden WiFi network run

# nmcli dev wifi connect <SSID> password <password> hidden yes ifname wlan0

To check connection status run

# nmcli con show <SSID>

To check WiFi device status run

# nmcli dev show wlan0

Managing existing connections

Once established, the connection is preserved across reboots unless deleted explicitly.

To show existing connections, run

# nmcli con show

To disconnect from a WiFi network, run

# nmcli con down <SSID>

To reconnect to a WiFi network, run

# nmcli con up <SSID>

To permanently delete a connection, run

# nmcli con delete <SSID>

Configuring WiFi Access Point

NetworkManager can also be used to turn WiFi interface into Access Point.
The benefit of using NetworkManager in this scenario is the complete automation of WiFi, DHCP server and NAT configuration.

Disabling standalone dnsmasq service

Dnsmasq is a lightweight DNS forwarder and DHCP server.
By default dnsmasq runs as a standalone service and will conflict with dnsmasq instance launched by NetworkManager.
To prevent the conflict, disable dnsmasq service by running the following commands:

# systemctl disable dnsmasq
# systemctl stop dnsmasq

For NetworkManager to run dnsmasq as a local caching DNS server, edit/create /etc/NetworkManager/NetworkManager.conf and add the following

[main]
dns=dnsmasq

Creating WiFi AP

Use the following commands to create the initial AP setup

# nmcli con add type wifi ifname <device> mode ap con-name <name> ssid <ssid> && \
  nmcli con modify <name> 802-11-wireless.band <band> && \
  nmcli con modify <name> 802-11-wireless.channel <channel> && \
  nmcli con modify <name> 802-11-wireless-security.key-mgmt <key-mgmt> && \
  nmcli con modify <name> 802-11-wireless-security.proto <proto> && \
  nmcli con modify <name> 802-11-wireless-security.group <group> && \
  nmcli con modify <name> 802-11-wireless-security.pairwise <pairwise> && \
  nmcli con modify <name> 802-11-wireless-security.psk <passphrase> && \
  nmcli con modify <name> ipv4.method shared && \
  nmcli con up <name>

For example, the following commands will create AP configuration named WIFI_AP on wlan0, with SSID MY_AP, 2.4GHz band, channel 1, WPA2-PSK security, CCMP encryption, and passphrase 11223344 for the Sterling LWB/LWB5.

# nmcli con add type wifi ifname wlan0 mode ap con-name WIFI_AP ssid MY_AP && \
  nmcli con modify WIFI_AP 802-11-wireless.band bg && \
  nmcli con modify WIFI_AP 802-11-wireless.channel 1 && \
  nmcli con modify WIFI_AP 802-11-wireless-security.key-mgmt wpa-psk && \
  nmcli con modify WIFI_AP 802-11-wireless-security.proto rsn && \
  nmcli con modify WIFI_AP 802-11-wireless-security.group ccmp && \
  nmcli con modify WIFI_AP 802-11-wireless-security.pairwise ccmp && \
  nmcli con modify WIFI_AP 802-11-wireless-security.psk 11223344 && \
  nmcli con modify WIFI_AP ipv4.method shared && \
  nmcli con up WIFI_AP

If you are planning to use the 5 GHz band and channel 36, you can partially change the above commands as follow

...
# nmcli con modify WIFI_AP 802-11-wireless.band a
# nmcli con modify WIFI_AP 802-11-wireless.channel 36
...

The complete list of nmcli configuration parameters is described in https://developer.gnome.org/NetworkManager/stable/ref-settings.html

Configuring DHCP subnet

By default 10.42.0.x/24 subnet is used by NetworkManager DHCP server, with 10.42.0.1 address assigned to AP itself. To modify it use the following command

# nmcli con modify <name> ipv4.addr <ipaddress/prefix>

For example, the following command will set DHCP subnet to 192.168.5.x/24

# nmcli con modify WIFI_AP ipv4.addr 192.168.5.1/24

Editing AP configuration file

NetworkManager will create /etc/NetworkManager/system-connections/WIFI_AP configuration file.
In addition to executing nmcli commands one can also edit this file to modify the AP settings.

For changes in configuration file to take effect, restart NetworkManager by running

# systemctl restart NetworkManager

Managing existing connections

Once created, the AP configuration is preserved across reboots unless deleted explicitly.

To show existing connections, run

# nmcli con show

To temporarily disable AP configuration, run

# nmcli con down <name>

To enable AP configuration, run

# nmcli con up <name>

To permanently delete AP configuration, run

# nmcli con delete <name>

Sterling LWB/LWB5 WiFi STA/AP concurrency

To get the WiFi module to work in concurrent AP-STA mode on the Sterling LWB/LWB5, a virtual wireless interface is required.

This can be achieved creating a virtual wlan1 interface, running

# iw dev wlan0 interface add wlan1 type __ap

STA setup can be managed simply following the steps described in Configuring WiFi Client section.

AP setup can be managed following the steps described in Configuring WiFi Access Point section, but when creating the access point, be careful to use wlan1 instead of wlan0.

Notes

nmcli commands create a permanent setup, that does not require to be repeated at every boot.

However, the iw command (used to create the virtual wlan1 interface) does not create permanent changes: we suggest to introduce it in the variscite-wifi script (located in /etc/wifi for latest releases), when checking for the wlan0 existance, something like

if [ -d /sys/class/net/wlan0 ]; then
	# create wlan1 interface
	iw dev wlan0 interface add wlan1 type __ap
	return 0
else
	...

Also, in the same file, just before shutting down wlan0, you may want to delete this virtual interface, something like

...
# delete wlan1 interface
iw dev wlan1 del
# Down WIFI
wifi_down
...

Limitations

By HW design, Sterling-LWB/LWB5 WiFi modules provide a single channel tuner.

AP-STA operations are possible, but the local AP channel is actually the one negotiated between the local client and the remote AP.

Testing WiFi throughput

Establish connection to WiFi network and use iperf3 tool on target and another host:

iperf3 server (on Target/Host):

# iperf3 -s

iperf3 client (on Host/Target):

Run UDP test for 30 seconds
# iperf3 -c <IP_ADDRESS_OF_IPERF_SERVER> -t 30 -u -b 0

Run TCP test for 30 seconds
# iperf3 -c <IP_ADDRESS_OF_IPERF_SERVER> -t 30

Configuring WiFi Regulatory Domain

According the mounting option of the SoM in use, the kernel loads dedicated firmware files from the folder /lib/firmware/brcm:

mounting option	WiFi chip	firmware files
WB	Sterling LWB	brcmfmac43430-sdio.bin / brcmfmac43430-sdio.txt
WBD	Sterling LWB5	brcmfmac4339-sdio.bin / brcmfmac4339-sdio.txt

Each txt file contains the ccode parameter selecting the regulatory domain.

Additionally, for Sterling LWB5 only, the regrev parameter must change according the ccode (it's always zero for Sterling LWB).

By default, the BSP ships firmware configurations matching FCC Regulatory Domain, one of the most restrictive in terms of available channels.

For Sterling LWB5 and FCC you can read

ccode=US
regrev=911

The following table reports the valid options for ccode / regrev parameter.

regulatory authority	Sterling LWB		Sterling LWB5
	ccode	regrev	ccode	regrev
FCC	US	0	US	911
ETSI	EU	0	EU	116
ISED	US*	0	CA	938
MIC	JP	0	JP	101

* ISED for Sterling LWB is managed using ccode=US, it's not a typo.

Note on DART-MX8M WiFi Initialization

WiFi is initialized by /etc/wifi/variscite-wifi. During initialization, the Linux device tree model property is read from /sys/devices/soc0/machine and is used to determine the Variscite SOM model and configure the SoM GPIO pins.

Additionally, on the DART-MX8M, the WiFi and the SD card share the same SDIO controller and therefore cannot be used simultaneously. The WiFi script looks for a "WIFI" sub-string to determine whether or not the WiFi device tree was selected.

Therefore, customers who choose to modify the Linux device tree model property should only append to the string provided by Variscite.