Dummy WiFi Module

Overview

The Dummy WiFi Module is an example Linux kernel module for a Wi-Fi FullMAC driver. This module demonstrates how to create a wireless device, perform scans, and connect to a Wi-Fi network. Please note that this module is a simplified example for educational purposes and does not provide real Wi-Fi functionality.

Module Information

Author: Dr. -Ing. Ahmad Kamal Nasir dringakn@gmail.com
Version: 1.0
License: GPL v2

Description

The Dummy WiFi Module creates a wireless device with the following capabilities:

STA (Station) mode only.
Scanning for nearby networks (dummy network in this case).
Connecting to a Wi-Fi network (dummy network).

Module Structure

The module consists of the following key components:

dummy_wifi_context Structure: This structure holds various components and data related to the Dummy WiFi wireless network manager.
Work Queue Items:
- ws_connect: Work queue item for connection handling.
- ws_disconnect: Work queue item for disconnection handling.
- ws_scan: Work queue item for wireless scanning.
Private Context Structures:
- dummy_wifi_wiphy_priv_context: Structure to hold private context data related to a wireless PHY (wiphy) for the Dummy WiFi system.
- dummy_wifi_ndev_priv_context: Structure to hold private context data related to a network device (ndev) for the Dummy WiFi system.
cfg80211_ops: Structure defining a set of operations for interacting with the cfg80211 subsystem, including scanning, connecting, and disconnecting.

Functionality

Scanning

The module provides a "scan" routine that informs the Linux kernel about a "dummy" Basic Service Set (BSS). When the scan is done, it calls cfg80211_scan_done() to inform the kernel that the scan is finished.

Connecting

The module also offers a "connect" routine for the Dummy WiFi device. It checks if the connecting SSID is a dummy SSID and takes appropriate actions:

If the SSID is not a dummy, it triggers a connection timeout.
If the SSID is a dummy, it sends dummy BSS information to the kernel and notifies the kernel of a successful connection.

Disconnecting

The module handles disconnection events through a "disconnect" routine. It informs the wireless stack that the device has disconnected and provides a reason code for the disconnection.

Usage

To use the Dummy WiFi Module, follow these steps:

Download

git clone https://github.com/dringakn/DummyWiFi.git
cd DummyWiFi

Build and install the module:
```
make
sudo insmod dummywifi.ko
```

Check if the module is loaded:

lsmod | grep dummywifi

Sample output:

dummywifi              16384  0
cfg80211              970752  5 iwlmvm,mt7601u,iwlwifi,mac80211,dummywifi

To get wifi info and to perform a scan:

iw dummy info
iw dev dummy0 scan

Sample dummy info output using iw dummy info:

Wiphy dummy
max # scan SSIDs: 69
max scan IEs length: 0 bytes
max # sched scan SSIDs: 0
max # match sets: 0
Retry short limit: 7
Retry long limit: 4
Coverage class: 0 (up to 0m)
Available Antennas: TX 0 RX 0
Supported interface modes:
	 * managed
Band 1:
	Bitrates (non-HT):
		* 1.0 Mbps
		* 2.0 Mbps
		* 5.5 Mbps
		* 11.0 Mbps
	Frequencies:
		* 2437 MHz [6] (20.0 dBm)
Supported commands:
	 * connect
	 * disconnect
software interface modes (can always be added):
interface combinations are not supported
Device supports scan flush.
max # scan plans: 1
max scan plan interval: -1
max scan plan iterations: 0
Supported extended features:

Sample scan output using iw dev dummy0 scan:

BSS aa:bb:cc:dd:ee:ff(on dummy0)
TSF: 0 usec (0d, 00:00:00)
freq: 2437
beacon interval: 100 TUs
capability: ESS (0x0001)
last seen: 0 ms ago
SSID: MyAwesomeWiFi

To connect to the dummy network:
```
iw dev dummy0 link
iw dev dummy0 connect MyAwesomeWiFi [2437]
```
The sample output of the dummy device before connection using iw dev dummy0 link:
```
Not connected.
```
The sample output of the iwconfig dummy0 after connection:
```
dummy0   IEEE 802.11  ESSID:"MyAwesomeWiFi"
         Mode:Managed  Frequency:2.437 GHz  Access Point: AA:BB:CC:DD:EE:FF
         Retry short limit:7   RTS thr:off   Fragment thr:off
         Power Management:on
```
Note Since only one channel (6, 2.437GHz) is implemented, therefore connection will not be established if diffrent frequency is specified. Error might states command failed: Invalid argument (-22). If there is already a conneciton the error might states command failed: Operation already in progress (-114) The frequency or channel information can be obtained as follows iwlist dummy0 freq, here is the sample output:
```
dummy0   1 channels in total; available frequencies :
         Channel 06 : 2.437 GHz
         Current Frequency:2.437 GHz (Channel 6)
```

To disconnect from the network:

iw dev dummy0 disconnect

The sample output of the iwconfig dummy0 after disconnection:

dummy0   IEEE 802.11  ESSID:off/any
         Mode:Managed  Access Point: Not-Associated
         Retry short limit:7   RTS thr:off   Fragment thr:off
         Power Management:on

Unload the module when done:
```
sudo rmmod dummywifi
```
Cleanup: To remove the module and clean up the build artifacts:
```
make clean
```

Disclaimer

This module is a simplified example for educational purposes and does not provide real Wi-Fi functionality. It serves as a starting point for developing FullMAC Wi-Fi drivers for the Linux kernel.

License

This module is released under the GPL v2 license. See the LICENSE file for details.