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UdpPacket.cs
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UdpPacket.cs
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/*
This file is part of PacketDotNet
PacketDotNet is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
PacketDotNet is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with PacketDotNet. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* Copyright 2009 Chris Morgan <[email protected]>
*/
using System;
using System.Collections.Generic;
using System.Text;
using PacketDotNet.Utils;
using PacketDotNet.Utils.Converters;
#if DEBUG
using log4net;
using System.Reflection;
#endif
namespace PacketDotNet
{
/// <summary>
/// User datagram protocol
/// See http://en.wikipedia.org/wiki/Udp
/// </summary>
public sealed class UdpPacket : TransportPacket
{
#if DEBUG
private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
#else
// NOTE: No need to warn about lack of use, the compiler won't
// put any calls to 'log' here but we need 'log' to exist to compile
#pragma warning disable 0169, 0649
private static readonly ILogInactive Log;
#pragma warning restore 0169, 0649
#endif
/// <summary>
/// Create from values
/// </summary>
/// <param name="sourcePort">
/// A <see cref="ushort" />
/// </param>
/// <param name="destinationPort">
/// A <see cref="ushort" />
/// </param>
public UdpPacket(ushort sourcePort, ushort destinationPort)
{
Log.Debug("");
// allocate memory for this packet
var length = UdpFields.HeaderLength;
var headerBytes = new byte[length];
Header = new ByteArraySegment(headerBytes, 0, length);
// set instance values
SourcePort = sourcePort;
DestinationPort = destinationPort;
}
/// <summary>
/// Constructor
/// </summary>
/// <param name="byteArraySegment">
/// A <see cref="ByteArraySegment" />
/// </param>
public UdpPacket(ByteArraySegment byteArraySegment)
{
Log.DebugFormat("ByteArraySegment {0}", byteArraySegment);
// set the header field, header field values are retrieved from this byte array
Header = new ByteArraySegment(byteArraySegment)
{
Length = UdpFields.HeaderLength
};
PayloadPacketOrData = new LazySlim<PacketOrByteArraySegment>(() =>
{
const int wakeOnLanPort0 = 0;
const int wakeOnLanPort7 = 7;
const int wakeOnLanPort9 = 9;
var result = new PacketOrByteArraySegment();
var destinationPort = DestinationPort;
var sourcePort = SourcePort;
var payload = Header.NextSegment();
// If this packet is going to port 0, 7 or 9, then it might be a WakeOnLan packet.
if (destinationPort == wakeOnLanPort0 || destinationPort == wakeOnLanPort7 || destinationPort == wakeOnLanPort9)
{
if (WakeOnLanPacket.IsValid(payload))
{
result.Packet = new WakeOnLanPacket(payload);
return result;
}
}
if (destinationPort == L2tpFields.Port || sourcePort == L2tpFields.Port)
{
result.Packet = new L2tpPacket(payload, this);
return result;
}
if ((sourcePort == DhcpV4Fields.ClientPort || sourcePort == DhcpV4Fields.ServerPort) &&
(destinationPort == DhcpV4Fields.ClientPort || destinationPort == DhcpV4Fields.ServerPort))
{
var nextSegmentLength = byteArraySegment.Length - Header.Length;
if (nextSegmentLength >= DhcpV4Fields.MinimumSize)
{
var nextSegment = new ByteArraySegment(byteArraySegment.Bytes, byteArraySegment.Offset + Header.Length, nextSegmentLength);
var magicNumber = EndianBitConverter.Big.ToUInt32(nextSegment.Bytes, nextSegment.Offset + DhcpV4Fields.MagicNumberPosition);
if (magicNumber == DhcpV4Fields.MagicNumber)
{
result.Packet = new DhcpV4Packet(nextSegment, this);
return result;
}
}
}
// Teredo encapsulates IPv6 traffic into UDP packets, parse out the bytes in the payload into packets.
// If it contains a IPV6 packet, it to this current packet as a payload.
// https://tools.ietf.org/html/rfc4380#section-5.1.1
if (destinationPort == IPv6Fields.TeredoPort || sourcePort == IPv6Fields.TeredoPort)
{
if (ContainsIPv6Packet(payload))
{
result.Packet = new IPv6Packet(payload);
return result;
}
}
// store the payload bytes
result.ByteArraySegment = payload;
return result;
});
}
/// <summary>
/// Constructor
/// </summary>
/// <param name="byteArraySegment">
/// A <see cref="ByteArraySegment" />
/// </param>
/// <param name="parentPacket">
/// A <see cref="Packet" />
/// </param>
public UdpPacket
(
ByteArraySegment byteArraySegment,
Packet parentPacket) :
this(byteArraySegment)
{
ParentPacket = parentPacket;
}
/// <summary>Fetch the header checksum.</summary>
public override ushort Checksum
{
get => EndianBitConverter.Big.ToUInt16(Header.Bytes,
Header.Offset + UdpFields.ChecksumPosition);
set
{
var val = value;
EndianBitConverter.Big.CopyBytes(val,
Header.Bytes,
Header.Offset + UdpFields.ChecksumPosition);
}
}
/// <summary>Fetch ascii escape sequence of the color associated with this packet type.</summary>
public override string Color => AnsiEscapeSequences.LightGreen;
/// <summary>Fetch the port number on the target host.</summary>
public override ushort DestinationPort
{
get => EndianBitConverter.Big.ToUInt16(Header.Bytes,
Header.Offset + UdpFields.DestinationPortPosition);
set
{
var val = value;
EndianBitConverter.Big.CopyBytes(val,
Header.Bytes,
Header.Offset + UdpFields.DestinationPortPosition);
}
}
/// <value>
/// Length in bytes of the header and payload, minimum size of 8,
/// the size of the Udp header
/// </value>
public int Length
{
get => EndianBitConverter.Big.ToInt16(Header.Bytes,
Header.Offset + UdpFields.HeaderLengthPosition);
internal set
{
// Internal because it is updated based on the payload when its bytes are retrieved.
var val = (short) value;
EndianBitConverter.Big.CopyBytes(val,
Header.Bytes,
Header.Offset + UdpFields.HeaderLengthPosition);
}
}
/// <summary>Fetch the port number on the source host.</summary>
public override ushort SourcePort
{
get => EndianBitConverter.Big.ToUInt16(Header.Bytes, Header.Offset + UdpFields.SourcePortPosition);
set
{
var val = value;
EndianBitConverter.Big.CopyBytes(val, Header.Bytes, Header.Offset + UdpFields.SourcePortPosition);
}
}
/// <summary>Check if the UDP packet is valid, checksum-wise.</summary>
public bool ValidChecksum
{
get
{
// IPv6 has no checksum so only the TCP checksum needs evaluation
if (ParentPacket is IPv6Packet)
return ValidUdpChecksum;
// For IPv4 both the IP layer and the TCP layer contain checksums
return ((IPv4Packet) ParentPacket).ValidIPChecksum && ValidUdpChecksum;
}
}
/// <value>
/// True if the UDP checksum is valid
/// </value>
public bool ValidUdpChecksum
{
get
{
Log.Debug("ValidUdpChecksum");
var result = IsValidChecksum(TransportChecksumOption.IncludePseudoIPHeader);
Log.DebugFormat("ValidUdpChecksum {0}", result);
return result;
}
}
/// <summary>
/// Update the Udp length
/// </summary>
public override void UpdateCalculatedValues()
{
// update the length field based on the length of this packet header
// plus the length of all of the packets it contains
Length = TotalPacketLength;
}
/// <summary>
/// Calculates the UDP checksum, optionally updating the UDP checksum header.
/// </summary>
/// <returns>The calculated UDP checksum.</returns>
public ushort CalculateUdpChecksum()
{
return (ushort) CalculateChecksum(TransportChecksumOption.IncludePseudoIPHeader);
}
/// <summary>
/// Update the checksum value.
/// </summary>
public void UpdateUdpChecksum()
{
Checksum = CalculateUdpChecksum();
}
/// <summary cref="Packet.ToString(StringOutputType)" />
public override string ToString(StringOutputType outputFormat)
{
var buffer = new StringBuilder();
var color = "";
var colorEscape = "";
if ((outputFormat == StringOutputType.Colored) || (outputFormat == StringOutputType.VerboseColored))
{
color = Color;
colorEscape = AnsiEscapeSequences.Reset;
}
if ((outputFormat == StringOutputType.Normal) || (outputFormat == StringOutputType.Colored))
buffer.AppendFormat("{0}[UDPPacket: SourcePort={2}, DestinationPort={3}]{1}",
color,
colorEscape,
SourcePort,
DestinationPort);
if ((outputFormat == StringOutputType.Verbose) || (outputFormat == StringOutputType.VerboseColored))
{
// collect the properties and their value
var properties = new Dictionary<string, string>
{
{ "source", SourcePort.ToString() },
{ "destination", DestinationPort.ToString() },
{ "length", Length.ToString() },
{ "checksum", "0x" + Checksum.ToString("x") + " [" + (ValidUdpChecksum ? "valid" : "invalid") + "]" }
};
// calculate the padding needed to right-justify the property names
var padLength = RandomUtils.LongestStringLength(new List<string>(properties.Keys));
// build the output string
buffer.AppendLine("UDP: ******* UDP - \"User Datagram Protocol\" - offset=? length=" + TotalPacketLength);
buffer.AppendLine("UDP:");
foreach (var property in properties)
buffer.AppendLine("UDP: " + property.Key.PadLeft(padLength) + " = " + property.Value);
buffer.AppendLine("UDP:");
}
// append the base string output
buffer.Append(base.ToString(outputFormat));
return buffer.ToString();
}
/// <summary>
/// Generate a random packet
/// </summary>
/// <returns>
/// A <see cref="UdpPacket" />
/// </returns>
public static UdpPacket RandomPacket()
{
var rnd = new Random();
var sourcePort = (ushort) rnd.Next(UInt16.MinValue, UInt16.MaxValue);
var destinationPort = (ushort) rnd.Next(UInt16.MinValue, UInt16.MaxValue);
return new UdpPacket(sourcePort, destinationPort);
}
/// <summary>
/// Determines whether the specified byte array segment contains an IPv6 packet.
/// </summary>
/// <param name="packetBytes">The packet bytes.</param>
/// <returns>
/// <c>true</c> if it contains an IPv6 packet; otherwise, <c>false</c>.
/// </returns>
private static bool ContainsIPv6Packet(ByteArraySegment packetBytes)
{
// Packet bytes must be greater than or equal to the IPV6 header length, start with the version number,
// and be greater in length than the payload length + the header length.
return (packetBytes.Length >= IPv6Fields.HeaderLength) &&
(packetBytes.Bytes[packetBytes.Offset] >> 4 == (int) RawIPPacketProtocol.IPv6) &&
(packetBytes.Length >= IPv6Fields.HeaderLength + packetBytes.Bytes[packetBytes.Offset + IPv6Fields.PayloadLengthPosition]);
}
}
}