How do I get the currently connected network interface name using Cocoa or Foundation?

Question

I need to know the network interface name of the currently connected network interface, as in en0, lo0 and so on.

Is there a Cocoa/Foundation function that is going to give me this information?

Answer 1

You can cycle through network interfaces and get their names, IP addresses, etc.

#include <ifaddrs.h>
// you may need to include other headers

struct ifaddrs* interfaces = NULL;
struct ifaddrs* temp_addr = NULL;

// retrieve the current interfaces - returns 0 on success
NSInteger success = getifaddrs(&interfaces);
if (success == 0)
{
    // Loop through linked list of interfaces
    temp_addr = interfaces;
    while (temp_addr != NULL)
    {
      if (temp_addr->ifa_addr->sa_family == AF_INET) // internetwork only
      {
        NSString* name = [NSString stringWithUTF8String:temp_addr->ifa_name];
        NSString* address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
        NSLog(@"interface name: %@; address: %@", name, address);
      }

      temp_addr = temp_addr->ifa_next;
    }
}

// Free memory
freeifaddrs(interfaces);

There are many other flags and data in the above structures, I hope you will find what you are looking for.

Answer 2

Since iOS works slightly differently to OSX, we had luck using the following code based on Davyd's answer to see the names of all available network interfaces on an iPhone: (also see here for full documentation on ifaddrs)

#include <ifaddrs.h>

struct ifaddrs* interfaces = NULL;
struct ifaddrs* temp_addr = NULL;

// retrieve the current interfaces - returns 0 on success
NSInteger success = getifaddrs(&interfaces);
if (success == 0)
{
    // Loop through linked list of interfaces
    temp_addr = interfaces;
    while (temp_addr != NULL)
    {
            NSString* name = [NSString stringWithUTF8String:temp_addr->ifa_name];
            NSLog(@"interface name: %@", name);

        temp_addr = temp_addr->ifa_next;
    }
}

// Free memory
freeifaddrs(interfaces);

Answer 3

Alternatively you can also utilize if_indextoname() to get available interface names. Here is how Swift implementation would look like:

public func interfaceNames() -> [String] {

    let MAX_INTERFACES = 128;

    var interfaceNames = [String]()
    let interfaceNamePtr = UnsafeMutablePointer<Int8>.alloc(Int(IF_NAMESIZE))
    for interfaceIndex in 1...MAX_INTERFACES {
        if (if_indextoname(UInt32(interfaceIndex), interfaceNamePtr) != nil){
            if let interfaceName = String.fromCString(interfaceNamePtr) {
                interfaceNames.append(interfaceName)
            }
        } else {
            break
        }
    }

    interfaceNamePtr.dealloc(Int(IF_NAMESIZE))
    return interfaceNames
}