How to determine netmask of active interface in Objective-C on a Mac?

Question

I\'m trying to determine the network segment my Macbook is in, because I then want to scan this segment for active hosts (basic IP scanner) by using the CFHost class. Therefore

Answer 1

Martin had given a nice answer.
And his code in a ARC version is here:

+ (NSDictionary *)primaryIPv4AddressInfoFromSystemConfiguration
{
    SCDynamicStoreRef storeRef = SCDynamicStoreCreate(NULL, (CFStringRef)@"FindCurrentInterfaceIpMac", NULL, NULL);
    if (!storeRef)
    {
        return nil;
    }

    NSDictionary *IPv4Dictionary = nil;
    CFPropertyListRef global = SCDynamicStoreCopyValue(storeRef, CFSTR("State:/Network/Global/IPv4"));
    id primaryInterface = [(NSDictionary *)CFBridgingRelease(global) valueForKey:@"PrimaryInterface"];
    if (primaryInterface)
    {
        NSString *interfaceState = @"State:/Network/Interface/";
        interfaceState = [[interfaceState stringByAppendingString:(NSString *)primaryInterface] stringByAppendingString:@"/IPv4"];
        CFPropertyListRef IPv4PropertyList = SCDynamicStoreCopyValue(storeRef, (__bridge CFStringRef)interfaceState);
        IPv4Dictionary = (NSDictionary *)CFBridgingRelease(IPv4PropertyList);
    }

    CFRelease(storeRef);
    return IPv4Dictionary;
}

+ (NSDictionary *)primaryIPv6AddressInfoFromSystemConfiguration
{
    SCDynamicStoreRef storeRef = SCDynamicStoreCreate(NULL, (CFStringRef)@"FindCurrentInterfaceIpMac", NULL, NULL);
    if (!storeRef)
    {
        return nil;
    }

    NSDictionary *IPv6Dictionary = nil;
    CFPropertyListRef global = SCDynamicStoreCopyValue(storeRef, CFSTR("State:/Network/Global/IPv6"));
    id primaryInterface = [(NSDictionary *)CFBridgingRelease(global) valueForKey:@"PrimaryInterface"];
    if (primaryInterface)
    {
        NSString *interfaceState = @"State:/Network/Interface/";
        interfaceState = [[interfaceState stringByAppendingString:(NSString *)primaryInterface] stringByAppendingString:@"/IPv6"];
        CFPropertyListRef IPv6PropertyList = SCDynamicStoreCopyValue(storeRef, (__bridge CFStringRef)interfaceState);
        IPv6Dictionary = (NSDictionary *)CFBridgingRelease(IPv6PropertyList);
    }

    CFRelease(storeRef);
    return IPv6Dictionary;
}