Getting the Wi-Fi router BSSID from a Daemon.

Our macOS application (running as a LaunchDaemon) has been able to report the current Wi-Fi SSID and BSSID (if connected) using the airport command. Since airport has been removed from macOS, we have not been able to collect BSSID information.

First, I demonstrate that the BSSID exists: I can option-click the Wi-Fi status menu icon and see the following:

Wi-Fi
Interface Name: en0
Address: a8:8f:d9:52:10:7d
* * *
Enable Wi-Fi Logging
Create Diagnostics Report...
Open Wireless Diagnostics...
* * *
Known Network
    polymorphic
    IP Address: 192.168.86.50
    Router: 192.168.86.1
    Security: WPA2 Personal
    BSSID: 88:3d:24:ba:36:81
    Channel: 149 (5 GHz, 80 MHZ)
    Country Code: US
    RSSI: -60 dBm
    Noise: -89 dBm
    Tx Rate: 520 Mbps
    PHY Mode: 802.11ac
    MCS Index: 5
    NSS: 2
* * *
Other Networks
* * *
Wi-Fi Settings...

This says to me that:

1. The WiFi router I am connected to has SSID = polymorphic.
2. The WiFi router I am connected to has BSSID = 88:3d:24:ba:36:81.
3. My computer's Wi-Fi hardware has MAC address = a8:8f:d9:52:10:7d.
4. My computer's Wi-Fi interface name = en0.

To get this information now (from within an application), I have attempted to run:

/usr/sbin/networksetup -listallhardwareports

The output of that command includes the following

Hardware Port: Wi-Fi
Device: en0
Ethernet Address: a8:8f:d9:52:10:7d

To get the SSID, I can then execute:

$ /usr/sbin/networksetup -getairportnetwork en0
Current Wi-Fi Network: polymorphic

But I still can't get the router's BSSID.

So I try

$/usr/sbin/networksetup -getinfo 'Wi-Fi'
DHCP Configuration
IP address: 192.168.86.50
Subnet mask: 255.255.255.0
Router: 192.168.86.1
Client ID:
IPv6: Automatic
IPv6 IP address: none
IPv6 Router: none
Wi-Fi ID: a8:8f:d9:52:10:7d

Still no new information.

$ /usr/sbin/networksetup -getmacaddress en0
Ethernet Address: a8:8f:d9:52:10:7d (Device: en0)

This is not helpful either.

Let's try another approach:

$ /usr/sbin/netstat -nr -f inet | grep ^default
default    192.168.86.1   UGScg   en0

This tells me that my router's IP address is 192.168.86.1.

The arp tool should be able to translate

$ /usr/sbin/arp -a -n | grep "(192.168.86.1)"
? (192.168.86.1) at 88:3d:24:ba:36:7f on en0 ifscope [ethernet]

This tells me that the router's MAC address is "88:3d:24:ba:36:7f", but it is not the same value as the router's BSSID, which we know to be 88:3d:24:ba:36:81!

Another approach. I wrote the following Swift program:

import CoreWLAN
let c : CWWiFiClient = CWWiFiClient.shared()
if let ifs : [CWInterface] = c.interfaces() {
  for i in ifs {
    print(
      i.interfaceName ?? "<nil>",
      i.powerOn(),
      i.ssid() ?? "<nil>",
      i.bssid() ?? "<nil>")
  }
}

When executing it with swift, I got:

en0 true polymorphic <nil>

So for some reason, the CoreWLAN API is hiding the BSSID, but not the SSID.

When I use swiftc to compile before executing, I get:

en0 true <nil> <nil>

Why is the CoreWLAN API now hiding the SSID as well?

I even tried an Objective-C program:

// Link with:
//   -framework Foundation
//   -framework CoreWLAN
#include <stdio.h>
#include <CoreWLAN/CoreWLAN.h>
void printWifi() {
    NSArray<CWInterface*>* ifs = [[CWWiFiClient sharedWiFiClient] interfaces];
    for (CWInterface* i in ifs) {
        printf("%s %s %s %s\n",
             [i.interfaceName UTF8String],
             [i powerOn] ? "true" : "false",
             [[i ssid] UTF8String],
             [[i bssid] UTF8String]);
    }
}
int main() {
    printWifi();
    return 0;
}

It prints out:

en0 true (null) (null)

Based on <https://developer.apple.com/forums/thread/131636>, I tried

// Link with:
//   -framework Foundation
//   -framework CoreWLAN
//   -framework CoreLocation 
#include <stdio.h>
#include <CoreWLAN/CoreWLAN.h>
#include <CoreLocation/CoreLocation.h>
void printWifi() {
    NSArray<CWInterface*>* ifs = [[CWWiFiClient sharedWiFiClient] interfaces];
    for (CWInterface* i in ifs) {
        printf("%s %s %s %s\n",
             [i.interfaceName UTF8String],
             [i powerOn] ? "true" : "false",
             [[i ssid] UTF8String],
             [[i bssid] UTF8String]);
    }
}
CLLocationManager* startCoreLocation() {
    CLLocationManager* mgr = [[CLLocationManager alloc] init];
    [mgr requestAlwaysAuthorization];
    [mgr startUpdatingLocation];
    return mgr;
}
int main() {
    CLLocationManager* locMgr = startCoreLocation();
    printWifi();
    return 0;
}

That change did not seem to make a difference.

After more work, I found that I can not even figure out CLLocationManager authorization. So I attempted to create a minimal program that can get that: <https://github.com/HalCanary/location>.

I am not sure how to proceed here. What is wrong with my location code? Will our application need to get the com.apple.security.personal-information.location entitlement in order to get the BSSID?