private Kavprot.Packets.Packet BuildRequest(System.Net.IPAddress destinationIP,
PhysicalAddress localMac,
System.Net.IPAddress localIP)
{
// an arp packet is inside of an ethernet packet
var ethernetPacket = new Kavprot.Packets.EthernetPacket(localMac,
PhysicalAddress.Parse("FF-FF-FF-FF-FF-FF"),
Kavprot.Packets.EthernetPacketType.Arp);
var arpPacket = new Kavprot.Packets.ARPPacket(Kavprot.Packets.ARPOperation.Request,
PhysicalAddress.Parse("00-00-00-00-00-00"),
destinationIP,
localMac,
localIP);
// the arp packet is the payload of the ethernet packet
ethernetPacket.PayloadPacket = arpPacket;
return(ethernetPacket);
}
/// <summary>
/// Resolves the MAC address of the specified IP address
/// </summary>
/// <param name="destIP">The IP address to resolve</param>
/// <param name="deviceName">The local network device name on which to send the ARP request</param>
/// <returns>The MAC address that matches to the given IP address or
/// null if there was a timeout</returns>
public PhysicalAddress Resolve(System.Net.IPAddress destIP, string deviceName)
{
PhysicalAddress localMAC = LocalMAC;
System.Net.IPAddress localIP = LocalIP;
var device = LibPcap.LibPcapLiveDeviceList.Instance[DeviceName];
// if no local ip address is specified attempt to find one from the adapter
if (localIP == null)
{
if (device.Addresses.Count > 0)
{
foreach (var address in device.Addresses)
{
if (address.Addr.type == LibPcap.Sockaddr.Type.AF_INET_AF_INET6)
{
localIP = address.Addr.ipAddress;
break; // break out of the foreach
}
}
if (localIP == null)
{
localIP = System.Net.IPAddress.Parse("127.0.0.1");
}
}
}
// if no local mac address is specified attempt to find one from the device
if (localMAC == null)
{
foreach (var address in device.Addresses)
{
if (address.Addr.type == LibPcap.Sockaddr.Type.HARDWARE)
{
localMAC = address.Addr.hardwareAddress;
}
}
}
if (localIP == null)
{
throw new System.InvalidOperationException("Unable to find local ip address");
}
if (localMAC == null)
{
throw new System.InvalidOperationException("Unable to find local mac address");
}
//Build a new ARP request packet
var request = BuildRequest(destIP, localMAC, localIP);
//create a "tcpdump" filter for allowing only arp replies to be read
String arpFilter = "arp and ether dst " + localMAC.ToString();
//open the device with 20ms timeout
device.Open(DeviceMode.Promiscuous, 20);
//set the filter
device.Filter = arpFilter;
// set a last request time that will trigger sending the
// arp request immediately
var lastRequestTime = DateTime.FromBinary(0);
var requestInterval = new TimeSpan(0, 0, 1);
Kavprot.Packets.ARPPacket arpPacket = null;
// attempt to resolve the address with the current timeout
var timeoutDateTime = DateTime.Now + Timeout;
while (DateTime.Now < timeoutDateTime)
{
if (requestInterval < (DateTime.Now - lastRequestTime))
{
// inject the packet to the wire
device.SendPacket(request);
lastRequestTime = DateTime.Now;
}
//read the next packet from the network
var reply = device.GetNextPacket();
if (reply == null)
{
continue;
}
// parse the packet
var packet = Kavprot.Packets.Packet.ParsePacket(reply);
// is this an arp packet?
arpPacket = Kavprot.Packets.ARPPacket.GetEncapsulated(packet);
if (arpPacket == null)
{
continue;
}
//if this is the reply we're looking for, stop
if (arpPacket.SenderProtocolAddress.Equals(destIP))
{
break;
}
}
// free the device
device.Close();
// the timeout happened
if (DateTime.Now >= timeoutDateTime)
{
return(null);
}
else
{
//return the resolved MAC address
return(arpPacket.SenderHardwareAddress);
}
}
