Introduction
Coding drivers for different mode chipsets can be a challenging task, especially when it comes to supporting modes that are not initially supported by the hardware. This article will explore the possibility of allowing support for different modes on a driver, using the ALFA USB WiFi AWUS036NH as an example.
Understanding Chipset Modes
A chipset is a set of electronic components in an electronic system, designed to work together to perform a specific function. In the context of wireless networking, a chipset determines the modes that a wireless device can operate in. These modes include master mode, where the device can act as an access point, and managed mode, where the device can connect to an access point.
Non-supporting Monitor Mode Chipsets
Some chipsets, such as the one used in the ALFA USB WiFi AWUS036NH, do not support monitor mode out of the box. Monitor mode is a special mode that allows a wireless device to capture all traffic in the air, regardless of whether it is intended for that device or not. This mode is useful for tasks such as network monitoring and packet sniffing.
Adding Monitor Mode Support
Adding monitor mode support to a chipset that does not initially support it can be a complex task. It involves writing custom driver code that can manipulate the chipset to enter monitor mode. This code must be written in a low-level language such as C, and must be specifically tailored to the chipset in question.
The ALFA USB WiFi AWUS036NH Example
The ALFA USB WiFi AWUS036NH uses the RTL8187L chipset, which does not support monitor mode out of the box. However, it is possible to add monitor mode support to this chipset by writing a custom driver. This driver would need to use the RT2870 USB command set to put the chipset into monitor mode.
Code Sample
Here is an example of how the code for entering monitor mode might look:
#include <rt2870.h>
int enter_monitor_mode(struct net_device *dev)
{
struct rt2870_priv *priv = netdev_priv(dev);
u8 buf[32];
int ret;
/* Set the wireless mode to monitor mode */
buf[0] = RT2870_CMD_SET_WirelessMode;
buf[1] = 0x03; /* Monitor mode */
ret = rt2870_cmd(priv, buf, 2);
if (ret != 0)
return ret;
/* Enable monitor mode */
buf[0] = RT2870_CMD_SET_MonitorMode;
buf[1] = 0x01;
ret = rt2870_cmd(priv, buf, 2);
if (ret != 0)
return ret;
return 0;
}
Adding support for different modes to a driver for a chipset that does not initially support it can be a complex task. However, with the right knowledge and skills, it is possible to write custom driver code that can enable these modes. By understanding the underlying chipset and its command set, it is possible to manipulate the chipset to enter new modes, such as monitor mode.
References
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RT2870 USB command set documentation: https://github.com/kelebek333/rtl8188eu-driver/blob/master/rtl8188eufw.c
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ALFA USB WiFi AWUS036NH datasheet: https://www.alfa.com.tw/products/AWUS036NH