PortMapper.m

/*

File: PortMapper.m

Abstract: Objective-C class implementation using Bonjour port mapping

Version: 1.0

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*/


#import "PortMapper.h"
#import <dns_sd.h>
#import <sys/types.h>
#import <sys/socket.h>
#import <net/if.h>
#import <netinet/in.h>
#import <ifaddrs.h>


#ifndef Log
#define ENABLE_LOGGING 1                            /* Change value to 1 to enable logging. */
#define Log   if(!ENABLE_LOGGING) ; else NSLog
#endif


NSString* const PortMapperChangedNotification = @"PortMapperChanged";


/** Converts a raw IPv4 address to an NSString in dotted-quad notation */
static NSString* StringFromIPv4Addr( UInt32 ipv4Addr )
{
    if( ipv4Addr != 0 ) {
        const UInt8* addrBytes = (const UInt8*)&ipv4Addr;
        return [NSString stringWithFormat: @"%u.%u.%u.%u",
                (unsigned)addrBytes[0],(unsigned)addrBytes[1],
                (unsigned)addrBytes[2],(unsigned)addrBytes[3]];
    } else
        return nil;
}    


@interface PortMapper ()
// Redeclare these properties as settable, internally:
@property (readwrite) SInt32 error;
@property (readwrite) UInt32 rawPublicAddress;
@property (copy) NSString* publicAddress;
@property (readwrite) unsigned short publicPort;
// Private getter:
@property (readonly) void* _service;
- (void) priv_disconnect;
@end


@implementation PortMapper


- (id) initWithPort: (UInt16)port
{
    self = [super init];
    if (self != nil) {
        _port = port;
		_desiredPublicPort = port;
        _mapTCP = NO;
		_mapUDP = YES;
    }
    return self;
}


- (void) dealloc
{
    if( _service )
        [self priv_disconnect];
    [super dealloc];
}

- (void) finalize
{
    if( _service )
        [self priv_disconnect];
    [super finalize];
}


@synthesize publicAddress=_publicAddress, rawPublicAddress=_rawPublicAddress,
            publicPort=_publicPort, error=_error, _service=_service,
            mapTCP=_mapTCP, mapUDP=_mapUDP,
            desiredPublicPort=_desiredPublicPort;

- (void) setDesiredPublicPort:(UInt16) port
{
	_desiredPublicPort = port;
	_port = port;
}

- (BOOL) isMapped
{
    return _rawPublicAddress && _rawPublicAddress != [[self class] rawLocalAddress];
}


/** Called whenever the port mapping changes (see comment for callback, below.) */
- (void) priv_portMapStatus: (DNSServiceErrorType)errorCode 
              publicAddress: (UInt32)rawPublicAddress
                 publicPort: (UInt16)publicPort
{
    if( errorCode ) {
        Log(@"Port-mapping callback got error %i",errorCode);
    } else {
        if( publicPort == 0 && _desiredPublicPort != 0 ) {
            Log(@"Port-mapping callback reported no mapping available");
            errorCode = kDNSServiceErr_NATPortMappingUnsupported;
        }
    }
    if( errorCode != self.error )
        self.error = errorCode;
    if( rawPublicAddress != self.rawPublicAddress ) {
        self.rawPublicAddress = rawPublicAddress;
        self.publicAddress = StringFromIPv4Addr(rawPublicAddress);
    }
    if( publicPort != self.publicPort )
        self.publicPort = publicPort;
    
    if( ! errorCode ) {
        Log(@"PortMapper: Got %@ :%hu (mapped=%i)", self.publicAddress,self.publicPort,self.isMapped);
		if(self.publicAddress == nil && self.publicPort == 0) {
			Log(@"PortMapper: Error couldn't get the public address.");
			self.error = -1;
		}
    }
    [[NSNotificationCenter defaultCenter] postNotificationName: PortMapperChangedNotification
                                                        object: self];
}


/** Asynchronous callback from DNSServiceNATPortMappingCreate.
    This is invoked whenever the status of the port mapping changes.
    All it does is dispatch to the object's priv_portMapStatus:publicAddress:publicPort: method. */
static void portMapCallback (
                      DNSServiceRef                    sdRef,
                      DNSServiceFlags                  flags,
                      uint32_t                         interfaceIndex,
                      DNSServiceErrorType              errorCode,
                      uint32_t                         publicAddress,    /* four byte IPv4 address in network byte order */
                      DNSServiceProtocol               protocol,
                      uint16_t                         privatePort,
                      uint16_t                         publicPort,       /* may be different than the requested port */
                      uint32_t                         ttl,              /* may be different than the requested ttl */
                      void                             *context
                      )
{
    NSAutoreleasePool *pool = [NSAutoreleasePool new];
    @try{
        [(PortMapper*)context priv_portMapStatus: errorCode 
                                   publicAddress: publicAddress
                                      publicPort: ntohs(publicPort)];  // port #s in network byte order!
    }@catch( id x ) {
        NSLog(@"PortMapper caught exception: %@",x);
    }
    [pool drain];
}


/** CFSocket callback, informing us that _socket has data available, which means
    that the DNS service has an incoming result to be processed. This will end up invoking
    the portMapCallback. */
static void serviceCallback(CFSocketRef s, 
                            CFSocketCallBackType type,
                            CFDataRef address, const void *data, void *clientCallBackInfo)
{
    PortMapper *mapper = (PortMapper*)clientCallBackInfo;
    DNSServiceRef service = mapper._service;
    DNSServiceErrorType err = DNSServiceProcessResult(service);
    if( err ) {
        // An error here means the socket has failed and should be closed.
        [mapper priv_portMapStatus: err publicAddress: 0 publicPort: 0];
        [mapper priv_disconnect];
    }
}



- (BOOL) open
{
    NSAssert(!_service,@"Already open");
    // Create the DNSService:
    DNSServiceProtocol protocol = 0;
    if( _mapTCP ) protocol |= kDNSServiceProtocol_TCP;
    if( _mapUDP ) protocol |= kDNSServiceProtocol_UDP;
    self.error = DNSServiceNATPortMappingCreate((DNSServiceRef*)&_service, 
                                         0 /*flags*/, 
                                         0 /*interfaceIndex*/, 
                                         protocol,
                                         htons(_port),
                                         htons(_desiredPublicPort),
                                         0 /*ttl*/,
                                         &portMapCallback, 
                                         self);
    if( _error ) {
        Log(@"Error %i creating port mapping",_error);
        return NO;
    }
    
    // Wrap a CFSocket around the service's socket:
    CFSocketContext ctxt = { 0, self, CFRetain, CFRelease, NULL };
    _socket = CFSocketCreateWithNative(NULL, 
                                       DNSServiceRefSockFD(_service), 
                                       kCFSocketReadCallBack, 
                                       &serviceCallback, &ctxt);
    if( _socket ) {
        CFSocketSetSocketFlags(_socket, CFSocketGetSocketFlags(_socket) & ~kCFSocketCloseOnInvalidate);
        // Attach the socket to the runloop so the serviceCallback will be invoked:
        _socketSource = CFSocketCreateRunLoopSource(NULL, _socket, 0);
        if( _socketSource )
            CFRunLoopAddSource(CFRunLoopGetCurrent(), _socketSource, kCFRunLoopCommonModes);
    }
    if( _socketSource ) {
        Log(@"Opening PortMapper");
        return YES;
    } else {
        Log(@"Failed to open PortMapper");
        [self close];
        _error = kDNSServiceErr_Unknown;
        return NO;
    }
}


- (BOOL) waitTillOpened
{
    if( ! _socketSource )
        if( ! [self open] )
            return NO;
    // Run the runloop until there's either an error or a result:
    while( _error==0 && _publicAddress==nil )
        if( ! [[NSRunLoop currentRunLoop] runMode: NSDefaultRunLoopMode
                                       beforeDate: [NSDate distantFuture]] )
            break;
    return (_error==0);
}


// Close down, but _without_ clearing the 'error' property
- (void) priv_disconnect
{
    if( _socketSource ) {
        CFRunLoopSourceInvalidate(_socketSource);
        CFRelease(_socketSource);
        _socketSource = NULL;
    }
    if( _socket ) {
        CFSocketInvalidate(_socket);
        CFRelease(_socket);
        _socket = NULL;
    }
    if( _service ) {
        Log(@"Deleting port mapping");
        DNSServiceRefDeallocate(_service);
        _service = NULL;
        self.rawPublicAddress = 0;
        self.publicAddress = nil;
        self.publicPort = 0;
    }
}

- (void) close
{
    [self priv_disconnect];
    self.error = 0;
}


#pragma mark -
#pragma mark UTILITY CLASS METHODS:



+ (UInt32) rawLocalAddress
{
    // getifaddrs returns a linked list of interface entries;
    // find the first active non-loopback interface with IPv4:
    UInt32 address = 0;
    struct ifaddrs *interfaces;
    if( getifaddrs(&interfaces) == 0 ) {
        struct ifaddrs *interface;
        for( interface=interfaces; interface; interface=interface->ifa_next ) {
            if( (interface->ifa_flags & IFF_UP) && ! (interface->ifa_flags & IFF_LOOPBACK) ) {
                const struct sockaddr_in *addr = (const struct sockaddr_in*) interface->ifa_addr;
                if( addr && addr->sin_family==AF_INET ) {
                    address = addr->sin_addr.s_addr;
                    break;
                }
            }
        }
        freeifaddrs(interfaces);
    }
    return address;
}

+ (NSString*) localAddress
{
    return StringFromIPv4Addr( [self rawLocalAddress] );
}


// Private IP address ranges. See RFC 3330.
static const struct {UInt32 mask, value;} const kPrivateRanges[] = {
    {0xFF000000, 0x00000000},       //   0.x.x.x (hosts on "this" network)
    {0xFF000000, 0x0A000000},       //  10.x.x.x (private address range)
    {0xFF000000, 0x7F000000},       // 127.x.x.x (loopback)
    {0xFFFF0000, 0xA9FE0000},       // 169.254.x.x (link-local self-configured addresses)
    {0xFFF00000, 0xAC100000},       // 172.(16-31).x.x (private address range)
    {0xFFFF0000, 0xC0A80000},       // 192.168.x.x (private address range)
    {0,0}
};


+ (BOOL) localAddressIsPrivate
{
    UInt32 address = ntohl([self rawLocalAddress]);
    int i;
    for( i=0; kPrivateRanges[i].mask; i++ )
        if( (address & kPrivateRanges[i].mask) == kPrivateRanges[i].value )
            return YES;
    return NO;
}


+ (NSString*) findPublicAddress
{
    // To find our public IP address, open a PortMapper with no port or protocols.
    // This will cause the DNSService to look up our public address without creating a mapping.
    NSString *addr = nil;
    PortMapper *mapper = [[self alloc] initWithPort: 0];
    mapper.mapTCP = mapper.mapUDP = NO;
    if( [mapper waitTillOpened] )
        addr = mapper.publicAddress;
    [mapper close];
    [mapper release];
    return addr;
}


@end