How to retrieve current city name using wifi/3g ip address with iPhone/iOS programming (Objective-c)?

I want to retrieve the current "city name" of the iPhone using ip address of device (wifi/3g). Is there any way to do it? please help me out.

Following is the place where I want the current location.

-(BOOL)fetchAndParseRss{

NSString * CurrentLocation = <I want the retrieved Location here!!>;
NSString * URLrss = [NSString stringWithFormat:@"http://news.google.com/news?q=location:%@&output=rss", CurrentLocation];

NSURL *url = [NSURL URLWithString:URLrss]; 
NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:url];
}
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Actually i am developing an app for myself that displays the news of current city.

You can use CLLocationManager and MKReverseGeocoder to get users city.

First add CLLocationManager and start updating user location

- (void)startLocationManager 
{    
    if (locManager==nil)
        locManager = [[CLLocationManager alloc] init];
    if (locManager.locationServicesEnabled)
    {
        NSLog(@"User has opted out of service on it error");
    } else {
        locManager.delegate = self;
        locManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
        [locManager startUpdatingLocation];
    }
}

Then add location manager delegate methods to use MKReverseGeocoder.

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
    NSLog(@"Manager error: %@", [error description]);
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    self.geocoder = [[MKReverseGeocoder alloc] initWithCoordinate:newLocation.coordinate];
    [geocoder release];
    geocoder.delegate = self;
    [geocoder start];
    [manager stopUpdatingLocation];
}

and of course you have to implement MKReverseGeocoder Delegate methods

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error
{
    NSLog(@"reverseGeocoder:%@ didFailWithError:%@", geocoder, error);
}

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark
{   
    // with the placemark you can now retrieve the city name
    NSString *city = [placemark.addressDictionary objectForKey:@"City"];
    NSLog(@"City is %@", city);
}

This method can be use if user gives permission to your application for location manager.

One option would be to make an HTTP request to a website like geoiptool.com and scrape the city information from the response. I'm unsure how much success you'll have when using mobile phone networks, though—wifi worked when I tried it on my phone, but 3G didn't.