/// <summary> Fetch the urgent pointer.</summary>
public virtual int getUrgentPointer()
{
if (!_urgentPointerSet)
{
_urgentPointer = ArrayHelper.extractInteger(Bytes, _ipOffset + TCPFields_Fields.TCP_URG_POS, TCPFields_Fields.TCP_URG_LEN);
_urgentPointerSet = true;
}
return(_urgentPointer);
}
/// <summary> Convert captured packet data into an object.</summary>
public static Packet dataToPacket(int linkType, byte[] bytes, Timeval tv)
{
int ethProtocol;
// retrieve the length of the headers associated with this link layer type.
// this length is the offset to the header embedded in the packet.
int lLen = LinkLayer.getLinkLayerLength(linkType);
// extract the protocol code for the type of header embedded in the
// link-layer of the packet
int offset = LinkLayer.getProtoOffset(linkType);
if (offset == -1)
{
// if there is no embedded protocol, assume IP?
ethProtocol = EthernetPacket.EtherType.IP;
}
else
{
ethProtocol = ArrayHelper.extractInteger(bytes, offset, EthernetFields_Fields.ETH_CODE_LEN);
}
// try to recognize the ethernet type..
switch (ethProtocol)
{
// arp
case EthernetPacket.EtherType.ARP:
return(new ARPPacket(lLen, bytes, tv));
case EthernetPacket.EtherType.IPV6:
case EthernetPacket.EtherType.IP:
// ethernet level code is recognized as IP, figure out what kind..
int ipProtocol = IPProtocol.extractProtocol(lLen, bytes);
switch (ipProtocol)
{
case (int)IPProtocol.IPProtocolType.ICMP: return(new ICMPPacket(lLen, bytes, tv));
case (int)IPProtocol.IPProtocolType.IGMP: return(new IGMPPacket(lLen, bytes, tv));
case (int)IPProtocol.IPProtocolType.TCP: return(new TCPPacket(lLen, bytes, tv));
case (int)IPProtocol.IPProtocolType.UDP: return(new UDPPacket(lLen, bytes, tv));
// unidentified ip..
default:
return(new IPPacket(lLen, bytes, tv));
}
// ethernet level code not recognized, default to anonymous packet..
default:
return(new EthernetPacket(lLen, bytes, tv));
}
}
/// <summary>
/// Sets the data section of this udp packet
/// </summary>
/// <param name="data">the data bytes</param>
public void SetData(byte[] data)
{
if (IPVersion != IPVersions.IPv4)
{
throw new System.NotImplementedException("IPVersion of " + IPVersion + " is unrecognized");
}
byte[] headers = ArrayHelper.copy(Bytes, 0, UDPFields_Fields.UDP_HEADER_LEN + IPHeaderLength + EthernetHeaderLength);
byte[] newBytes = ArrayHelper.join(headers, data);
this.Bytes = newBytes;
UDPLength = Bytes.Length - IPHeaderLength - EthernetHeaderLength;
//update ip total length length
IPTotalLength = IPHeaderLength + UDPFields_Fields.UDP_HEADER_LEN + data.Length;
//update also offset and pcap header
OnOffsetChanged();
}
public int ComputeTransportLayerChecksum(int checksumOffset, bool update, bool pseudoIPHeader)
{
// copy the tcp section with data
byte[] dataToChecksum = IPData;
// reset the checksum field (checksum is calculated when this field is
// zeroed)
ArrayHelper.insertLong(dataToChecksum, 0, checksumOffset, 2);
if (pseudoIPHeader)
{
dataToChecksum = AttachPseudoIPHeader(dataToChecksum);
}
// compute the one's complement sum of the tcp header
int cs = ChecksumUtils.OnesComplementSum(dataToChecksum);
if (update)
{
SetTransportLayerChecksum(cs, checksumOffset);
}
return(cs);
}
/// <summary> Computes the UDP checksum, optionally updating the UDP checksum header.
///
/// </summary>
/// <param name="update">Specifies whether or not to update the UDP checksum header
/// after computing the checksum. A value of true indicates the
/// header should be updated, a value of false indicates it should
/// not be updated.
/// </param>
/// <returns> The computed UDP checksum.
/// </returns>
public int ComputeUDPChecksum(bool update)
{
if (IPVersion != IPVersions.IPv4)
{
throw new System.NotImplementedException("IPVersion of " + IPVersion + " is unrecognized");
}
// copy the udp section with data
byte[] udp = IPData;
// reset the checksum field (checksum is calculated when this field is
// zeroed)
ArrayHelper.insertLong(udp, 0, UDPFields_Fields.UDP_CSUM_POS, UDPFields_Fields.UDP_CSUM_LEN);
//pseudo ip header should be attached to the udp+data
udp = AttachPseudoIPHeader(udp);
// compute the one's complement sum of the udp header
int cs = ChecksumUtils.OnesComplementSum(udp);
if (update)
{
UDPChecksum = cs;
}
return(cs);
}
/// <summary> Sets the urgent pointer.
///
/// </summary>
/// <param name="pointer">The urgent pointer value.
/// </param>
public void setUrgentPointer(int pointer)
{
ArrayHelper.insertLong(Bytes, pointer, _ipOffset + TCPFields_Fields.TCP_URG_POS, TCPFields_Fields.TCP_URG_LEN);
_urgentPointerSet = false;
}
/// <summary> Sets the IP header checksum.</summary>
protected internal virtual void SetChecksum(int cs, int checkSumOffset)
{
ArrayHelper.insertLong(Bytes, cs, checkSumOffset, 2);
}
/// <summary> Fetch the header checksum.</summary>
public virtual int GetTransportLayerChecksum(int pos)
{
return(ArrayHelper.extractInteger(Bytes, pos, 2));
}
/// <summary> Convert captured packet data into an object.</summary>
public static Packet dataToPacket(LinkLayers linkType, byte[] bytes, Timeval tv)
{
EthernetPacketType ethProtocol;
// retrieve the length of the headers associated with this link layer type.
// this length is the offset to the header embedded in the packet.
int byteOffsetToEthernetPayload = LinkLayer.LinkLayerLength(linkType);
// extract the protocol code for the type of header embedded in the
// link-layer of the packet
int offset = LinkLayer.ProtocolOffset(linkType);
if (offset == -1)
{
// if there is no embedded protocol, assume IpV4
ethProtocol = EthernetPacketType.IPv4;
}
else
{
ethProtocol = (EthernetPacketType)ArrayHelper.extractInteger(bytes, offset, EthernetFields_Fields.ETH_CODE_LEN);
}
string errorString;
Packet parsedPacket = null;
try
{
// try to recognize the ethernet type..
switch (ethProtocol)
{
// arp
case EthernetPacketType.ARP:
parsedPacket = new ARPPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
case EthernetPacketType.IPv6:
case EthernetPacketType.IPv4:
try
{
// ethernet level code is recognized as IP, figure out what kind..
int ipProtocol = IPProtocol.extractProtocol(byteOffsetToEthernetPayload, bytes);
switch (ipProtocol)
{
case (int)IPProtocol.IPProtocolType.ICMP:
parsedPacket = new ICMPPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
case (int)IPProtocol.IPProtocolType.IGMP:
parsedPacket = new IGMPPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
case (int)IPProtocol.IPProtocolType.TCP:
parsedPacket = new TCPPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
case (int)IPProtocol.IPProtocolType.UDP:
parsedPacket = new UDPPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
// unidentified ip..
default:
parsedPacket = new IPPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
}
// check that the parsed packet is valid
if (!parsedPacket.IsValid(out errorString))
{
throw new PcapException(errorString);
}
else
{
return(parsedPacket);
}
}
catch
{
// error parsing the specific ip packet type, parse as a generic IPPacket
parsedPacket = new IPPacket(byteOffsetToEthernetPayload, bytes, tv);
// check that the parsed packet is valid
if (!parsedPacket.IsValid(out errorString))
{
throw new PcapException(errorString);
}
else
{
return(parsedPacket);
}
}
// ethernet level code not recognized, default to anonymous packet..
default:
parsedPacket = new EthernetPacket(byteOffsetToEthernetPayload, bytes, tv);
break;
}
return(parsedPacket);
}
catch
{
// we know we have at least an ethernet packet, so return that
return(new EthernetPacket(byteOffsetToEthernetPayload, bytes, tv));
}
}
