/// <summary>
/// Modifies an existing ARP entry in the ARP table on the local computer.
/// </summary>
/// <param name="entry">
/// The entry to modify. All fields must be valid.
/// </param>
/// <returns>
/// Returns true for success, false otherwise.
/// </returns>
public bool SetArpEntry(ArpEntry entry)
{
bool ret = false;
// allocate 24 bytes for the entry
IntPtr pArpEntry = Marshal.AllocHGlobal (24);
Marshal.WriteInt32 (pArpEntry, entry.AdapterIndex);
Marshal.WriteInt32 (new IntPtr(pArpEntry.ToInt32() + 4), entry.MediaAccessControlAddress.Address.Length);
// write the MAC address
for (int i = 0; i < entry.MediaAccessControlAddress.Address.Length; i++)
{
Marshal.WriteByte (new IntPtr(pArpEntry.ToInt32() + 8 + i), entry.MediaAccessControlAddress.Address[i]);
}
// pad out the MAC address to 8 bytes
for (int i = 0; i < 8 - entry.MediaAccessControlAddress.Address.Length; i++)
{
Marshal.WriteByte (new IntPtr(pArpEntry.ToInt32() + 8 + i), 0);
}
// write the IP address
byte[] ip = entry.IPAddress.GetAddressBytes ();
for (int i = 0; i < ip.Length; i++)
{
Marshal.WriteByte (new IntPtr(pArpEntry.ToInt32() + 16 + i), ip[i]);
}
Marshal.WriteInt32 (new IntPtr(pArpEntry.ToInt32() + 20), (int)entry.EntryType);
// try to modify the entry
ret = SetIpNetEntry (pArpEntry) == 0;
// free the allocated memory
Marshal.FreeHGlobal (pArpEntry);
return ret;
}
/// <summary>
/// Read the ARP table. Returns null if reading failed.
/// </summary>
public ArpEntry[] ReadArpTable()
{
// pointer to the block of memory we will use
IntPtr pBuffer = IntPtr.Zero;
// size of the buffer
int bufferSize = 0;
// return value
int ret = 0;
// the table
ArpEntry[] entries;
// make an initial call to the method to recieve the correct buffer
// size
ret = GetIpNetTable (pBuffer, ref bufferSize, true);
// if an error other than insufficient buffer size occurs then return
// null
if (ret != ERROR_INSUFFICIENT_BUFFER)
{
Marshal.FreeHGlobal (pBuffer);
return null;
}
// now we know how much memory to allocate, allocate it
pBuffer = Marshal.AllocHGlobal (bufferSize);
// make the real call now
ret = GetIpNetTable (pBuffer, ref bufferSize, true);
// check for failure
if (ret != 0)
{
Marshal.FreeHGlobal (pBuffer);
return null;
}
// the first 4 bytes is the number of entries
int nEntries = Marshal.ReadInt32 (new IntPtr (pBuffer.ToInt32()));
// allocate space for each entry
entries = new ArpEntry[nEntries];
// loop through each entry
for (int i = 0; i < nEntries; i++)
{
entries[i] = new ArpEntry ();
// read the adapter index
entries[i].AdapterIndex = Marshal.ReadInt32 (new IntPtr (pBuffer.ToInt32() + (24*i) + 4));
// read the physical address
int addressLength = Marshal.ReadInt32 (new IntPtr (pBuffer.ToInt32() + (24*i) + 8));
byte[] macAddress = new byte[addressLength];
for (int j = 0; j < addressLength; j++)
{
macAddress[j] = Marshal.ReadByte (new IntPtr (pBuffer.ToInt32() + (24*i) + 12 + j));
}
entries[i].MediaAccessControlAddress = new MACAddress (macAddress);
// read the IP address
entries[i].IPAddress = new IPAddress (Marshal.ReadInt32 (new IntPtr (pBuffer.ToInt32() + (24*i) + 20)));
// read the entry type
entries[i].EntryType = (ArpEntryType)Marshal.ReadInt32 (new IntPtr (pBuffer.ToInt32() + (24*i) + 24));
}
// free the allocated memory
Marshal.FreeHGlobal (pBuffer);
return entries;
}
/// <summary>
/// Creates an Address Resolution Protocol (ARP) entry in the ARP table on
/// the local computer.
/// </summary>
/// <param name="entry">
/// The entry to add. All fields must be valid.
/// </param>
/// <returns>
/// Returns true for success, false otherwise.
/// </returns>
public bool CreateArpEntry(ArpEntry entry)
{
bool ret = false;
// allocate 24 bytes for the entry
IntPtr pArpEntry = Marshal.AllocHGlobal(24);
Marshal.WriteInt32(pArpEntry, entry.AdapterIndex);
Marshal.WriteInt32(new IntPtr(pArpEntry.ToInt32() + 4), entry.MediaAccessControlAddress.Address.Length);
// write the MAC address
for (int i = 0; i < entry.MediaAccessControlAddress.Address.Length; i++)
{
Marshal.WriteByte(new IntPtr(pArpEntry.ToInt32() + 8 + i), entry.MediaAccessControlAddress.Address[i]);
}
// pad out the MAC address to 8 bytes
for (int i = 0; i < 8 - entry.MediaAccessControlAddress.Address.Length; i++)
{
Marshal.WriteByte(new IntPtr(pArpEntry.ToInt32() + 8 + i), 0);
}
// write the IP address
byte[] ip = entry.IPAddress.GetAddressBytes();
for (int i = 0; i < ip.Length; i++)
{
Marshal.WriteByte(new IntPtr(pArpEntry.ToInt32() + 16 + i), ip[i]);
}
Marshal.WriteInt32(new IntPtr(pArpEntry.ToInt32() + 20), (int)entry.EntryType);
// try to modify the entry
ret = CreateIpNetEntry(pArpEntry) == 0;
// free the allocated memory
Marshal.FreeHGlobal(pArpEntry);
return(ret);
}
/// <summary>
/// Read the ARP table. Returns null if reading failed.
/// </summary>
public ArpEntry[] ReadArpTable()
{
// pointer to the block of memory we will use
IntPtr pBuffer = IntPtr.Zero;
// size of the buffer
int bufferSize = 0;
// return value
int ret = 0;
// the table
ArpEntry[] entries;
// make an initial call to the method to recieve the correct buffer
// size
ret = GetIpNetTable(pBuffer, ref bufferSize, true);
// if an error other than insufficient buffer size occurs then return
// null
if (ret != ERROR_INSUFFICIENT_BUFFER)
{
Marshal.FreeHGlobal(pBuffer);
return(null);
}
// now we know how much memory to allocate, allocate it
pBuffer = Marshal.AllocHGlobal(bufferSize);
// make the real call now
ret = GetIpNetTable(pBuffer, ref bufferSize, true);
// check for failure
if (ret != 0)
{
Marshal.FreeHGlobal(pBuffer);
return(null);
}
// the first 4 bytes is the number of entries
int nEntries = Marshal.ReadInt32(new IntPtr(pBuffer.ToInt32()));
// allocate space for each entry
entries = new ArpEntry[nEntries];
// loop through each entry
for (int i = 0; i < nEntries; i++)
{
entries[i] = new ArpEntry();
// read the adapter index
entries[i].AdapterIndex = Marshal.ReadInt32(new IntPtr(pBuffer.ToInt32() + (24 * i) + 4));
// read the physical address
int addressLength = Marshal.ReadInt32(new IntPtr(pBuffer.ToInt32() + (24 * i) + 8));
byte[] macAddress = new byte[addressLength];
for (int j = 0; j < addressLength; j++)
{
macAddress[j] = Marshal.ReadByte(new IntPtr(pBuffer.ToInt32() + (24 * i) + 12 + j));
}
entries[i].MediaAccessControlAddress = new MACAddress(macAddress);
// read the IP address
entries[i].IPAddress = new IPAddress(Marshal.ReadInt32(new IntPtr(pBuffer.ToInt32() + (24 * i) + 20)));
// read the entry type
entries[i].EntryType = (ArpEntryType)Marshal.ReadInt32(new IntPtr(pBuffer.ToInt32() + (24 * i) + 24));
}
// free the allocated memory
Marshal.FreeHGlobal(pBuffer);
return(entries);
}
