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using System;
using System.Collections.Generic;
using System.Net.Sockets;
using System.Net;
using System.Net.NetworkInformation;
namespace OpenSim.Framework
{
/// <summary>
/// Handles NAT translation in a 'manner of speaking'
/// Allows you to return multiple different external
/// hostnames depending on the requestors network
///
/// This enables standard port forwarding techniques
/// to work correctly with OpenSim.
/// </summary>
static class NetworkUtil
{
// IPv4Address, Subnet
static readonly Dictionary<IPAddress,IPAddress> m_subnets = new Dictionary<IPAddress, IPAddress>();
private static IPAddress GetExternalIPFor(IPAddress destination, string defaultHostname)
{
// Adds IPv6 Support (Not that any of the major protocols supports it...)
if (destination.AddressFamily == AddressFamily.InterNetworkV6)
{
foreach (IPAddress host in Dns.GetHostAddresses(defaultHostname))
{
if (host.AddressFamily == AddressFamily.InterNetworkV6)
return host;
}
}
if(destination.AddressFamily != AddressFamily.InterNetwork)
return null;
// Check if we're accessing localhost.
foreach (IPAddress host in Dns.GetHostAddresses(Dns.GetHostName()))
{
if (host.Equals(destination))
return destination;
}
// Check for same LAN segment
foreach (KeyValuePair<IPAddress, IPAddress> subnet in m_subnets)
{
byte[] subnetBytes = subnet.Value.GetAddressBytes();
byte[] localBytes = subnet.Key.GetAddressBytes();
byte[] destBytes = destination.GetAddressBytes();
if(subnetBytes.Length != destBytes.Length || subnetBytes.Length != localBytes.Length)
return null;
bool valid = true;
for(int i=0;i<subnetBytes.Length;i++)
{
if ((localBytes[i] & subnetBytes[i]) != (destBytes[i] & subnetBytes[i]))
{
valid = false;
break;
}
}
if (valid)
return subnet.Key;
}
// Check to see if we can find a IPv4 address.
foreach (IPAddress host in Dns.GetHostAddresses(defaultHostname))
{
if (host.AddressFamily == AddressFamily.InterNetwork)
return host;
}
// Unable to find anything.
throw new ArgumentException("[NetworkUtil] Unable to resolve defaultHostname to an IPv4 address for an IPv4 client");
}
static NetworkUtil()
{
foreach (NetworkInterface ni in NetworkInterface.GetAllNetworkInterfaces())
{
foreach (UnicastIPAddressInformation address in ni.GetIPProperties().UnicastAddresses)
{
if (address.Address.AddressFamily == AddressFamily.InterNetwork)
{
m_subnets.Add(address.Address, address.IPv4Mask);
}
}
}
}
public static IPAddress GetIPFor(IPEndPoint user, string defaultHostname)
{
// Try subnet matching
IPAddress rtn = GetExternalIPFor(user.Address, defaultHostname);
if (rtn != null)
return rtn;
// Otherwise use the old algorithm
IPAddress ia;
if (IPAddress.TryParse(defaultHostname, out ia))
return ia;
ia = null;
foreach (IPAddress Adr in Dns.GetHostAddresses(defaultHostname))
{
if (Adr.AddressFamily == AddressFamily.InterNetwork)
{
ia = Adr;
break;
}
}
return ia;
}
public static string GetHostFor(IPAddress user, string defaultHostname)
{
IPAddress rtn = GetExternalIPFor(user, defaultHostname);
if(rtn != null)
return rtn.ToString();
return defaultHostname;
}
}
}
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