/**
* <summary>Implements the ITranslator portion for ManagedAddress..., takes an
* IP Packet, based upon who the originating Brunet Sender was, changes who
* the packet was sent from and then switches the destination address to the
* local nodes address. Takes incomming packets only.</summary>
* <param name="packet">The IP Packet to translate.</param>
* <param name="from">The Brunet address the packet was sent from.</param>
* <returns>The translated IP Packet.</returns>
*/
public MemBlock Translate(MemBlock packet, Address from)
{
UpdateCounter(_rx_counters, from);
MemBlock source_ip = _addr_ip[from];
if (source_ip == null)
{
throw new Exception("Invalid mapping " + from + ".");
}
// Attempt to translate a packet
IPPacket ipp = new IPPacket(packet);
// hdr is everything in the packet up to the source IP, dest IP, "options"
// and data
MemBlock hdr = packet.Slice(0, 12);
// Pull the "fragment" info from the header. If it is not fragmented, we
// can deal with the packet. DNS packets should never be sent as fragments
bool fragment = ((hdr[6] & 0x1F) | hdr[7]) != 0;
//should there be a field in the IPPacket class for this?
MemBlock dest_ip = ipp.DestinationIP;
byte dest_ip_first_byte = dest_ip[0];
bool is_multicast = dest_ip_first_byte > 223 && dest_ip_first_byte < 240;
//multicast addresses are 224.0.0.0 through 239.255.255.255
if (ipp.Protocol == IPPacket.Protocols.Udp && !fragment) //simple UDP
{
UdpPacket udpp = new UdpPacket(ipp.Payload);
foreach (IProtocolTranslator <UdpPacket> i in _udp_translators)
{
if (i.MatchesProtocol(udpp))
{
udpp = i.Translate(udpp, source_ip,
ipp.SourceIP, ipp.DestinationIP);
return(new IPPacket(ipp.Protocol, source_ip,
is_multicast?
ipp.DestinationIP:
_local_ip,
hdr, udpp.ICPacket).Packet);
}
}
}
//fallback
return(IPPacket.Translate(packet, source_ip,
is_multicast?
ipp.DestinationIP:
_local_ip
));
}