wpa_action

wpa_action interface command

interface
    The name of the network interface for which the event occurred (e.g., wlan0, wlp2s0).

command
    The type of event or state change reported by wpa_supplicant. Common commands include CONNECTED, DISCONNECTED, BSSID-CHANGE, ASSOC-CHANGE, SCAN-RESULTS, TERMINATE, CTRL-REQ, EAP-AUTH, REASON.

wpa_action is a crucial helper utility, typically a shell script or a small binary, utilized by the wpa_supplicant daemon. It is not intended for direct user invocation. Instead, wpa_supplicant executes wpa_action automatically when significant events or state changes occur on a wireless interface, such as connecting to an access point, disconnecting, or roaming between BSSIDs.

Its primary role is to serve as an event hook manager. Upon execution, wpa_action usually interprets the passed arguments (interface and event type) and then triggers predefined scripts or actions located in specific directories (e.g., /etc/wpa_supplicant/actions.d/ or /etc/network/if-up.d/, /etc/network/if-down.d/). This mechanism enables flexible automation for network configuration, like initiating DHCP requests, setting up routing, or running custom post-connection scripts, making the Wi-Fi connection process seamless and configurable without modifying wpa_supplicant's core logic.

The exact implementation and location of wpa_action can vary significantly across different Linux distributions (e.g., a shell script in /sbin/ or /etc/wpa_supplicant/, or a compiled binary). Users should generally avoid running wpa_action directly as it relies on wpa_supplicant to set up the appropriate environment variables and context for its operation. Its primary purpose is to act as an internal wpa_supplicant event handler.

wpa_action often receives additional context via environment variables set by wpa_supplicant. Important variables can include WPA_ID, WPA_IFNAME, WPA_EVENT, WPA_BSSID, WPA_SSID, WPA_MODE, and others, providing detailed information about the network state change. These variables allow the triggered action scripts to react intelligently to specific connection details.

When wpa_action is invoked, it typically initiates actions like:
• Network Interface Management: Bringing the network interface up (ifup) or down (ifdown).
• IP Address Configuration: Running DHCP clients (dhclient or dhcpcd) to obtain an IP address, subnet mask, gateway, and DNS servers.
• Custom Script Execution: Executing user-defined scripts in specific directories (e.g., /etc/wpa_supplicant/actions.d/, /etc/network/if-up.d/, /etc/network/if-down.d/) to handle post-connection tasks, such as mounting network shares or starting applications.

wpa_action has been an integral part of the wpa_supplicant ecosystem since its early development. It was introduced to provide a flexible and extensible mechanism for handling network state changes without embedding distribution-specific network configuration logic directly into the wpa_supplicant daemon. Its design allows system administrators to customize network behaviors through external scripts, adapting to diverse network environments and configuration needs, which has been crucial for its long-term utility and adoption in various Linux distributions.

wpa_supplicant(8), wpa_cli(8), ifup(8), ifdown(8), dhclient(8)