I’m developing a Bluetooth application for an embedded device on Ubuntu. I’m using the sd-bus library to pair a Bluetooth device with a given MAC address. The code I’ve written successfully initiates the pairing process and prompts a passkey confirmation dialog.

Here’s my current code:

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <systemd/sd-bus.h>

#define _cleanup_(f) __attribute__((cleanup(f)))

#define DESTINATION   "org.bluez"
#define INTERFACE     "org.bluez.Device1"

static int log_error(int error, const char *message) {
    errno = -error;
    fprintf(stderr, "%s: %mn", message);
    return error;
}

int bt_conn_control(char* bt_dev_mac) {
    _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
    _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
    char *member_state = "Pair";
    char *path = NULL;
    int r;

    path = malloc(sizeof("/org/bluez/hci0/dev_00_00_00_00_00_00"));
    if (path == NULL) {
        perror("Memory allocation failed");
        return -1;
    }
    sprintf(path, "/org/bluez/hci0/dev_%c%c_%c%c_%c%c_%c%c_%c%c_%c%c",
            bt_dev_mac[0], bt_dev_mac[1], bt_dev_mac[3], bt_dev_mac[4], bt_dev_mac[6], bt_dev_mac[7],
            bt_dev_mac[9], bt_dev_mac[10], bt_dev_mac[12], bt_dev_mac[13], bt_dev_mac[15], bt_dev_mac[16]);

    r = sd_bus_open_system(&bus);
    if (r < 0) {  
        free(path);      
        return log_error(r, "Failed to acquire bus");
    }

    r = sd_bus_call_method(bus, DESTINATION, path, INTERFACE, member_state, &error, NULL, NULL, NULL);
    if (r < 0) {
        free(path);
        return log_error(r, "Method call failed");        
    }

    free(path);
    return 0;
}

int main() {
    bt_conn_control("3C:19:5E:F9:26:60");
    return 0;
}

When this code executes, a popup appears with the passkey and the device name. I want to handle the passkey confirmation programmatically within my application, instead of relying on the Ubuntu UI.

Additionally, how can I check for external pairing requests and manage them within the same application?