Wireshark Monitor Mode Not Available: Understanding the Implementation Challenges

Libpcap, a library that implements packet capture functionality, is responsible for putting an interface into monitor mode. This process involves setting the link-layer header type to one that provides 802.11 headers. However, the implementation of monitor mode varies across platforms, making it challenging for Wireshark and other applications using libpcap/Npcap.

On macOS, for instance, setting the link-layer header type is done at the user-kernel boundary by specifying an 802.11 header type. In contrast, WinPcap does not support monitor mode, which means that applications must use libpcap/Npcap instead.

When Wireshark attempts to put an interface into monitor mode, it may encounter challenges depending on the platform being used. For example, if the device is already in monitor mode, Wireshark's ability to handle this scenario may vary based on the platform's implementation.

The process of activating a network interface for packet capture involves several steps, including:

1. Getting the list of data link layers supported by calling pcap_list_datalinks().

2. Determining the default data link type using pcap_datalink().

3. Activating the device using pcap_activate() and checking if it fails.

4. If the device supports monitor mode, turning on monitor mode.

5. Checking whether the device is a Linux bonding device and failing if it's not.

6. Calling pcap_can_set_rfmon() to determine whether the device supports monitor mode and failing if there's an error.

In the 2.6 Windows version of Wireshark, the get_if_capabilities() routine in caputils/capture-pcap-util.c is responsible for retrieving the interface's capabilities. This routine can return any of the header types required for monitor mode, including IEEE802_11_RADIO and IEEE802_11_RADIO_AVS.

In summary, while Wireshark can successfully put an interface into monitor mode on some platforms, challenges arise due to platform-dependent implementation variations. Understanding these complexities is crucial for developing effective packet capture applications that work seamlessly across different environments.

Wireshark monitor mode not available