WPAD(8)

WPA and WPA2 protocol daemon

• usr/src/cmd/cmd-inet/usr.lib/wpad/wpa_supplicant.c
• usr/src/cmd/cmd-inet/usr.lib/wpad/eloop.c

Uses the Static File Descriptor pattern.

The wpa_supplicant_door_destroy function logs a message if a door fails to be revoked or detached. Not all door servers do this.

In main, we infer the path of the door file from the name of the wifi link device, as provided on the command line by smf(7):

    /*
     * Get the device name of the link, which will be used as the door
     * file name used to communicate with the driver. Note that different
     * links use different doors.
     */
    if (dladm_phys_info(handle, linkid, &dpa, DLADM_OPT_ACTIVE) !=
        DLADM_STATUS_OK) {
        wpa_printf(MSG_ERROR,
            "Failed to get device name of link '%s'.", link);
        dladm_close(handle);
        dlpi_close(dh);
        return (-1);
    }
    (void) snprintf(door_file, MAXPATHLEN, "%s_%s", WPA_DOOR, dpa.dp_dev);

Presumably, each driver also knows this convention, and will use this path to open a door into the appropriate wpad daemon.

Cookies are used here! A wpa_supplicant struct is created by main (on its stack??) and its address is used as a cookie when the door is created. This struct is then used in the wpa_event_handler function whenever the server procedure is invoked (by the driver?).

The main function initializes some event loop data with this WPA supplicant struct by calling eloop_init. When the main function that calls the eloop_run function to hang out in the event loop, that's what keeps the process from terminating (and this what keeps the wpa_s struct alive in the stack). This also allows event loop handling to reference the same struct that is available to the server procedure.

The cleanup for an fattach failure is interesting. It will detach the door from the filesystem only if fattach returns an error other than EBUSY. So can fattach succeed (associate the door with a filesystem path) but still claim to be busy?

    if (fattach(door_id, doorname) < 0) {
        if ((errno != EBUSY) || (fdetach(doorname) < 0) ||
            (fattach(door_id, doorname) < 0)) {
            (void) door_revoke(door_id);
            door_id = -1;
            error = -1;

            goto out;
        }
    }

out:
    return (error);