/// <summary>
/// Whenever a new IP packet arrives it should be passed to this method.
/// If the packet is fragmented it will be buffered until all of the other
/// fragments have arrived, then it will be pieced back together into a whole
/// packet.
/// </summary>
/// <param name="packet">
/// The packet which has arrived.
/// </param>
public void HandleNewPacket(IpV4Packet packet)
{
#region Check for Packets we don't need to parse
// first thing we do is check if this packet is whole or not
if (packet.ControlFlags.Offset == 0 && !packet.ControlFlags.MoreFragments)
{
// it's whole so our job is done already. Just forward it on.
if (IpV4PacketArrived != null) IpV4PacketArrived (packet);
return;
}
#endregion
// at this point we know the packet is a fragment. Now what we want to do
// is check through the array list to see if it belongs to any other fragments.
// If so, we store the index in the array list of the other packets for further
// processing. If not, we add it to a new item in the array list and store the new
// index for further processing.
#region Get Packet Index
int index = -1;
for (int i = 0; i < m_packets.Count; i++)
{
IpV4Packet p = (IpV4Packet)((IpFragmentsType)m_packets[i]).Fragments[0];
// we check if fragments belong by comparing their identification field, the
// source and destination address, and the transport protocol
if (p.Identification == packet.Identification && p.TransportProtocol == packet.TransportProtocol &&
p.SourceAddress == packet.SourceAddress && p.DestinationAddress == packet.DestinationAddress)
{
index = i;
break;
}
}
// if the index is still -1 then this is a new fragment
if (index == -1)
{
// create and add a new fragments entry to the packets array
IpFragmentsType newFragment = new IpFragmentsType();
index = m_packets.Add (newFragment);
}
#endregion
// now we now need to add the new fragment to the packet array.
#region Add Fragment
IpFragmentsType currentPacket = (IpFragmentsType)m_packets[index];
currentPacket.Fragments.Add (packet);
#endregion
// now we check if this packet has the More Fragments bit not set.
// This indicates that it is the last fragment.
// HOWEVER, since ip packets may arrive out of order, this does not mean we have all
// the fragments yet. But since it is the last packet, it does let us know how much
// data we are waiting on so we can identify when we have all the fragments.
// so calculate how much data we are waiting on and check if we have recieved it all.
#region Calculate Total Packet Size and Check For Completion
// calculate data currently recieved
currentPacket.CurrentDataSize += packet.TotalLength - packet.HeaderLength;
if (!packet.ControlFlags.MoreFragments)
{
// the total length of all the data is caculated by adding the offset on to the data
// length of this packet, since it's the last one.
currentPacket.TotalDataSize = packet.ControlFlags.Offset + packet.TotalLength - packet.HeaderLength;
}
// if we have recieved all the data then bingo, we have all the fragments
// so reassemble them into a complete packet and remove these uneeded fragments
if (currentPacket.CurrentDataSize == currentPacket.TotalDataSize)
{
IpV4Packet[] fragments = new IpV4Packet[currentPacket.Fragments.Count];
for (int i = 0; i < fragments.Length; i++)
{
fragments[i] = (IpV4Packet)currentPacket.Fragments[i];
}
IpV4Packet WholePacket = new IpV4Packet (fragments);
if (IpV4PacketArrived != null) IpV4PacketArrived (WholePacket);
m_packets.RemoveAt (index);
}
#endregion
}
/// <summary>
/// Whenever a new IP packet arrives it should be passed to this method.
/// If the packet is fragmented it will be buffered until all of the other
/// fragments have arrived, then it will be pieced back together into a whole
/// packet.
/// </summary>
/// <param name="packet">
/// The packet which has arrived.
/// </param>
public void HandleNewPacket(IpV4Packet packet)
{
#region Check for Packets we don't need to parse
// first thing we do is check if this packet is whole or not
if (packet.ControlFlags.Offset == 0 && !packet.ControlFlags.MoreFragments)
{
// it's whole so our job is done already. Just forward it on.
if (IpV4PacketArrived != null)
{
IpV4PacketArrived(packet);
}
return;
}
#endregion
// at this point we know the packet is a fragment. Now what we want to do
// is check through the array list to see if it belongs to any other fragments.
// If so, we store the index in the array list of the other packets for further
// processing. If not, we add it to a new item in the array list and store the new
// index for further processing.
#region Get Packet Index
int index = -1;
for (int i = 0; i < m_packets.Count; i++)
{
IpV4Packet p = (IpV4Packet)((IpFragmentsType)m_packets[i]).Fragments[0];
// we check if fragments belong by comparing their identification field, the
// source and destination address, and the transport protocol
if (p.Identification == packet.Identification && p.TransportProtocol == packet.TransportProtocol &&
p.SourceAddress == packet.SourceAddress && p.DestinationAddress == packet.DestinationAddress)
{
index = i;
break;
}
}
// if the index is still -1 then this is a new fragment
if (index == -1)
{
// create and add a new fragments entry to the packets array
IpFragmentsType newFragment = new IpFragmentsType();
index = m_packets.Add(newFragment);
}
#endregion
// now we now need to add the new fragment to the packet array.
#region Add Fragment
IpFragmentsType currentPacket = (IpFragmentsType)m_packets[index];
currentPacket.Fragments.Add(packet);
#endregion
// now we check if this packet has the More Fragments bit not set.
// This indicates that it is the last fragment.
// HOWEVER, since ip packets may arrive out of order, this does not mean we have all
// the fragments yet. But since it is the last packet, it does let us know how much
// data we are waiting on so we can identify when we have all the fragments.
// so calculate how much data we are waiting on and check if we have recieved it all.
#region Calculate Total Packet Size and Check For Completion
// calculate data currently recieved
currentPacket.CurrentDataSize += packet.TotalLength - packet.HeaderLength;
if (!packet.ControlFlags.MoreFragments)
{
// the total length of all the data is caculated by adding the offset on to the data
// length of this packet, since it's the last one.
currentPacket.TotalDataSize = packet.ControlFlags.Offset + packet.TotalLength - packet.HeaderLength;
}
// if we have recieved all the data then bingo, we have all the fragments
// so reassemble them into a complete packet and remove these uneeded fragments
if (currentPacket.CurrentDataSize == currentPacket.TotalDataSize)
{
IpV4Packet[] fragments = new IpV4Packet[currentPacket.Fragments.Count];
for (int i = 0; i < fragments.Length; i++)
{
fragments[i] = (IpV4Packet)currentPacket.Fragments[i];
}
IpV4Packet WholePacket = new IpV4Packet(fragments);
if (IpV4PacketArrived != null)
{
IpV4PacketArrived(WholePacket);
}
m_packets.RemoveAt(index);
}
#endregion
}
