Wifi

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Resources

This article describes the setup of a Wifi network device.

Wifi during installation

If a Wifi connection is needed while installing Gentoo, note that the Gentoo minimal install CD has a limited number of drivers available, and provides only wpa_cli (and not wpa_gui) for configuring for WPA/WPA2/Enterprise connections.

If the minimal install CD does not contain the required drivers or the graphical frontend to wpa_supplicant is preferred, choose a different live CD such as the System Rescue CD. Be aware that some special steps may be required when using a non-Gentoo live CD.

Hardware detection

First detect the Wifi controllers. lspci or lsusb are command-line tools that can be used for this task.

If a Linux (LiveCD/USB) is booted that makes a Wifi connection:

root #lspci -k

The driver will be identified with Kernel driver in use:.

If the booted system does not make a Wifi connection, then obtain a full list of hardware identifiers from the current system. This list can be used to identify the proper driver later:

root #lspci -n

Copy the list of PCIID's that the command produces and paste it at http://kmuto.jp/debian/hcl/.

For USB devices, a similar approach can be taken. First obtain the list of detected USB devices on the system:

user $lsusb

This command produces the PCI ID, manufacturer, make, model, and/or chipset of every USB device attached to the system. Of these, the chipset may be the most useful information. Googling linuxwireless.org <chipset> is often the shortest way to find a USB NIC driver and firmware name.

Alternatively, lshw can be used to obtain the necessary information:

root #lshw | grep -i driver

This command produces a list of all drivers, regardless of the device being PCI or USB based.

Kernel

With the drivers identified, it is time to configure the Linux kernel.

IEEE 802.11

Activate at least cfg80211 and mac80211. Some wireless drivers also require a rate control algorithm.

KERNEL linux-4.1
[*] Networking support  --->
    [*] Wireless  --->
        <*>   cfg80211 - wireless configuration API
        [ ]     nl80211 testmode command
        [ ]     enable developer warnings
        [ ]     cfg80211 regulatory debugging
        [ ]     cfg80211 certification onus
        [*]     enable powersave by default
        [ ]     cfg80211 DebugFS entries
        [ ]     use statically compiled regulatory rules database
        [ ]     cfg80211 wireless extensions compatibility
        <*>   Generic IEEE 802.11 Networking Stack (mac80211)
        [*]   Minstrel
        [*]     Minstrel 802.11n support
        [ ]       Minstrel 802.11ac support
              Default rate control algorithm (Minstrel)  --->
        [ ]   Enable mac80211 mesh networking (pre-802.11s) support
        -*-   Enable LED triggers
        [ ]   Export mac80211 internals in DebugFS
        [ ]   Trace all mac80211 debug messages
        [ ]   Select mac80211 debugging features  ----

Minstrel and its 802.11n support is a rate control algorithm.

WEXT

The "cfg80211 wireless extensions compatibility" option aka WEXT will support old wireless-tools & iwconfig.

KERNEL
[*] Networking support  --->
    [*] Wireless  --->
        [*]     cfg80211 wireless extensions compatibility

Device drivers

Next the right set of corresponding kernel options need to be enabled, based on the drivers and hardware detected previously. The recommendation is to build drivers as modules. Also be sure to enable AES cipher support in the kernel if the wireless network uses WPA or WPA2 encryption.

KERNEL
    Device Drivers  --->
    [*] Network device support  --->
        [*] Wireless LAN  --->
 
            Select the driver for your Wifi network device, e.g.:
            <M> Broadcom 43xx wireless support (mac80211 stack) (b43)
            [M]    Support for 802.11n (N-PHY) devices
            [M]    Support for low-power (LP-PHY) devices
            [M]    Support for HT-PHY (high throughput) devices
            <M> Intel Wireless WiFi Next Gen AGN - Wireless-N/Advanced-N/Ultimate-N (iwlwifi)
            <M>    Intel Wireless WiFi DVM Firmware support                             
            <M>    Intel Wireless WiFi MVM Firmware support
            <M> Intel Wireless WiFi 4965AGN (iwl4965)
            <M> Intel PRO/Wireless 3945ABG/BG Network Connection (iwl3945)
            <M> Ralink driver support  --->
                <M>   Ralink rt27xx/rt28xx/rt30xx (USB) support (rt2800usb)
 
-*- Cryptographic API --->
    -*- AES cipher algorithms
    -*- AES cipher algorithms (x86_64)
    <*> AES cipher algorithms (AES-NI)
Important
In case the driver is built into the kernel (<*>) instead of as a module (<M>), then the firmware needs to be built into the kernel as well.
Do not forget to rebuild the kernel after changing its configuration.

LED support

To enable LED triggers for different packet receive/transmit events, compile the kernel with the following options:

KERNEL
Device Drivers  --->
    [*] LED Support  --->
        <*>   LED Class Support
 
[*] Networking support  --->
    [*] Wireless  --->
        [*] Enable LED triggers

Firmware

In addition to the kernel driver, some chipsets also require firmware. If required, locate it on the following list and install it:

root #emerge --ask sys-kernel/linux-firmware
Wifi device Driver Firmware Note
Atheros AR9271 & AR7010 ath9k_htc sys-kernel/linux-firmware
Broadcom 43xx wireless support b43 / b43legacy sys-firmware/b43-firmware Aircrack-ng ready, most probably the best choice if your bcm43xx device is supported
Broadcom PCIe and SDIO/USB devices brcmsmac / brcmfmac sys-kernel/linux-firmware Lacks powersaving, LED support and other features
Broadcom 43xx wireless support wl net-wireless/broadcom-sta Proprietary, no AP or Monitor modes, Comparison of bcm43xx drivers
Intel PRO/Wireless 2200BG ipw2200 sys-firmware/ipw2200-firmware
Intel PRO/Wireless 3945ABG/BG iwlegacy sys-kernel/linux-firmware
Intel Wireless WiFi 4965AGN iwl4965 sys-kernel/linux-firmware
All other Intel Wireless devices iwlwifi sys-kernel/linux-firmware See the iwlwifi article for detailed instructions.
Ralink/MediaTek USB devices e.g. rt2800usb sys-kernel/linux-firmware
Realtek RTL8191SE & RTL8192SE rtl8192se sys-kernel/linux-firmware

If the driver requires firmware but does not appear on the list, it will be necessary to download it manually and place it in /lib/firmware.

WPA supplicant

If the wireless network is set up with WPA or WPA2, then wpa_supplicant needs to be used. For more information on configuring wireless networking in Gentoo Linux, please read the Wireless networking chapter in the Gentoo Handbook.


Testing

After a reboot with the new kernel or after loading the modules, the device can be checked for availability by using following methods:

  • Using the /sys file system
  • Using the ip command
  • Using the ifconfig command
  • Using the iw command

/sys file system

Get the device name by listing the /sys/class/net directory using ls -al or the tree command (app-text/tree):

user $tree /sys/class/net
/sys/class/net/
├── enp2s14 -> ../../devices/pci0000:00/0000:00:1e.0/0000:02:0e.0/net/enp2s14
├── lo -> ../../devices/virtual/net/lo
├── sit0 -> ../../devices/virtual/net/sit0
└── wlp8s0 -> ../../devices/pci0000:00/0000:00:1c.0/0000:08:00.0/net/wlp8s0

ip command

To obtain the device name and verify that the wireless card is detected, execute the following ip command:

user $ip addr
3: wlan0:   ...

ifconfig command

The ifconfig command is provided through the sys-apps/net-tools) package. Use ifconfig -a to list all detected network cards, even those that are not enabled/active yet:

user $ifconfig -a
wlan0     ...

A network card can be activated as follows:

root #ifconfig -v wlan0 up
SIOCSIFFLAGS: Operation not possible due to RF-kill
WARNING: at least one error occurred. (-1)

In this example, enabling the wireless card failed as a radio frequency kill state is set (usually to keep power consumption at bay and not connect by accident to a wireless network).

iw command

If the wireless network card driver supports the nl80211 stack, then the iw command as offered by the net-wireless/iw package can show the detected wireless cards:

root #iw dev
   phy#0
	Interface wlan0
		ifindex 4
		type managed

dmesg

If none of these methods work be sure to check dmesg output for errors. It is likely a kernel driver or module has not been loaded properly:

user $dmesg

Troubleshooting

See also

External resources