336 lines
11 KiB
C#
336 lines
11 KiB
C#
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///////////////////////////////////////////////////////////////////////////////
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//
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// Microsoft Research Singularity
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//
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///////////////////////////////////////////////////////////////////////////////
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/**
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* Microsoft Research, Cambridge
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* author: Yaron Weinsberg, Richard Black
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*/
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using NetStack.Common;
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using System;
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using System.Diagnostics;
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#if !SINGULARITY
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using System.Net;
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// using System.Net.Sockets; // for AddressFamily
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#endif
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using System.Net.IP;
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using Drivers.Net;
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namespace NetStack.Protocols
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{
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public class IPFormat
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{
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// size of minimum IP header (wo options)
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public const int Size = 20;
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// all header fields are given in host endianness
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public class IPHeader
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{
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public byte verLen; // 0:3 Version, 4:7 Header length in DWORDs.
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public byte tos;
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public ushort totalLength;
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public ushort id;
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public ushort offset;
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public byte ttl;
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public byte protocol;
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public ushort checksum;
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internal IPv4 srcAddr;
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internal IPv4 destAddr;
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// some wrappers
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public IPv4 Source
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{
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get { return srcAddr; }
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set { srcAddr = value; }
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}
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public IPv4 Destination
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{
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get { return destAddr; }
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set { destAddr = value; }
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}
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public Protocol Protocol
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{
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get { return (Protocol) protocol; }
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set { protocol = (byte) value; }
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}
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// set default values
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public void SetDefaults(Protocol type)
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{
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verLen = 0x45; // version=4, header_len=5
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tos = 0;
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totalLength = 0;
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id = 0;
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offset = 0;
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ttl = DefaultTTL;
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protocol = (byte)type;
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checksum = 0;
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srcAddr = IPv4.Zero;
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destAddr = IPv4.Zero;
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}
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}
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// construct an IP header from a packet
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// if something is wrong, return the same start value
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public static bool ReadIPHeader(IBuffer! buf, out IPHeader! iphdr)
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{
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// initialize an IPHeader struct
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iphdr = new IPHeader();
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bool b;
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uint addr;
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b = buf.Read8(out iphdr.verLen);
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b &= buf.Read8(out iphdr.tos);
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b &= buf.ReadNet16(out iphdr.totalLength);
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b &= buf.ReadNet16(out iphdr.id);
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b &= buf.ReadNet16(out iphdr.offset);
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b &= buf.Read8(out iphdr.ttl);
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b &= buf.Read8(out iphdr.protocol);
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b &= buf.ReadNet16(out iphdr.checksum);
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b &= buf.ReadNet32(out addr);
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iphdr.srcAddr = new IPv4(addr);
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b &= buf.ReadNet32(out addr);
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iphdr.destAddr = new IPv4(addr);
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return b;
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}
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// TTL default value
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public const byte DefaultTTL = 128;
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// IP protocols identifiers
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public enum Protocol : byte
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{
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ICMP = 1,
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IGMP = 2,
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TCP = 6,
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IGRP = 9,
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UDP = 17,
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GRE = 47,
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ESP = 50,
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AH = 51,
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SKIP = 57,
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EIGRP = 88,
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OSPF = 89,
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L2TP = 115
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}
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// some getters...
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public static ushort GetVersion(IPHeader! hdr)
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{
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return (ushort)(hdr.verLen & 0xF0);
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}
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// minimum value is 20, if it is 60 bytes, then
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// Options field is valid.
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public static uint GetHeaderLength(IPHeader! hdr)
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{
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return ((uint)(hdr.verLen & 0xF));
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}
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public static bool IsMoreFragSet(IPHeader! hdr)
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{
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ushort flags = (ushort)(((ushort)hdr.offset) >> 13);
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return ((flags & 0x01)==0x01);
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}
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public static bool IsDontFragSet(IPHeader! hdr)
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{
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ushort flags = (ushort)(((ushort)hdr.offset) >> 13);
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return ((flags & 0x02)==0x02);
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}
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public static void SetDontFragBit(IPHeader! hdr)
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{
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hdr.offset=(ushort)(hdr.offset|0x4000);
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}
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public static ushort GetFragOffset(IPHeader! hdr)
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{
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return (ushort)(hdr.offset & 0x1FFF);
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}
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// calculate's one's complement
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public static ushort SumShortValues(byte[]! buffer,
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int offset,
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int length)
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{
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//generate an IP checksum based on a given data buffer
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uint chksum = 0;
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int end = offset + (length & ~1);
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int i = offset;
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while (i != end)
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{
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chksum += (uint)((((ushort)buffer[i++]) << 8) +
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(ushort)buffer[i++]);
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}
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if (i != offset + length)
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{
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// padding at the end!
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chksum += (uint)(((ushort)buffer[i]) << 8);
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}
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// Double-wrap chksum
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chksum = (chksum & 0xFFFF) + (chksum >> 16);
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chksum = (chksum & 0xFFFF) + (chksum >> 16);
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return (ushort)chksum;
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}
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public static ushort SumShortValues(ushort currentChecksum,
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ushort valueToAdd)
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{
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uint chksum = currentChecksum;
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chksum += valueToAdd;
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// Double-wrap chksum
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chksum = (chksum & 0xFFFF) + (chksum >> 16);
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chksum = (chksum & 0xFFFF) + (chksum >> 16);
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return (ushort)chksum;
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}
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public static bool IsCheckSumOK(IPHeader! hdr)
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{
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ushort sum = (ushort) ((((int)hdr.verLen) << 8) + ((int)hdr.tos));
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sum = SumShortValues(sum, hdr.totalLength);
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sum = SumShortValues(sum, hdr.id);
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sum = SumShortValues(sum, hdr.offset);
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sum = SumShortValues(sum, (ushort) ((((int)hdr.ttl) << 8) + ((int)hdr.protocol)));
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sum = SumShortValues(sum, (ushort) (((uint)hdr.srcAddr) >> 16));
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sum = SumShortValues(sum, (ushort) (((uint)hdr.srcAddr) & 0xFFFFU));
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sum = SumShortValues(sum, (ushort) (((uint)hdr.destAddr) >> 16));
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sum = SumShortValues(sum, (ushort) (((uint)hdr.destAddr) & 0xFFFFU));
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sum = (ushort)~sum;
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if (sum != hdr.checksum)
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{
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Console.WriteLine("Bad IP Checksum {0:x4} != {1:x4}",
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hdr.checksum, sum);
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}
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return (sum == hdr.checksum);
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}
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// calculate the ip header checksum
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public static ushort Checksum(byte[]! buffer,
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int ipHeaderOffset,
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int ipHeaderLength)
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{
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return (ushort)~SumShortValues(buffer,
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ipHeaderOffset,
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ipHeaderLength);
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}
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// calc the sum of the 16bits pseudo header fields
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// (to be later used for transport level checksum calculation)
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// offset points to the start of the IP header
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// also return the protocolLength=header+data
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public static ushort SumPseudoHeader(byte[]! pkt,
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int offset,
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ref ushort protocolLength)
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{
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// source IP + destination IP
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uint sum = SumShortValues(pkt, offset + 12, 8);
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// add the protocol field (with zero MSB)
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sum += pkt[offset + 9];
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// add udp length = ip_total_length-ip_header_len
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ushort ipTotalLen = (ushort)(((ushort)(pkt[offset + 2] << 8)) |
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((ushort)pkt[offset + 3]));
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// ushort ipSize = (ushort)((pkt[offset] & 0x0f) * 4);
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protocolLength = (ushort)(ipTotalLen - IPFormat.Size);
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sum += protocolLength;
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// Double-wrap the sum
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sum = (sum & 0xFFFF) + (sum >> 16);
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sum = (sum & 0xFFFF) + (sum >> 16);
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return (ushort)sum;
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}
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public static ushort SumPseudoHeader(IPHeader! ipHeader)
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{
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uint sum = 0;
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uint origin = (uint)ipHeader.srcAddr;
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uint target = (uint)ipHeader.destAddr;
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sum = (origin & 0xffff) + ((origin >> 16) & 0xffff);
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sum += (target & 0xffff) + ((target >> 16) & 0xffff);
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sum += ipHeader.protocol;
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sum += (ipHeader.totalLength - (ipHeader.verLen & 0xfu) * 4u);
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// Double-wrap the sum
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sum = (sum & 0xFFFF) + (sum >> 16);
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sum = (sum & 0xFFFF) + (sum >> 16);
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return (ushort)sum;
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}
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// writes an IP header to a packet
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// return the next place to write to, fixes the checksum field
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public static int WriteIPHeader(byte[]! pkt, int offset, IPHeader! hdr)
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{
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// check we have enough packet space
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if (pkt.Length - offset < Size)
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return offset;
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int o = offset;
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pkt[o++] = hdr.verLen;
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pkt[o++] = hdr.tos;
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pkt[o++] = (byte) (((ushort)hdr.totalLength) >> 8);
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pkt[o++] = (byte) (((ushort)hdr.totalLength) & 0xff);
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pkt[o++] = (byte) (((ushort)hdr.id) >> 8);
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pkt[o++] = (byte) (((ushort)hdr.id) & 0xff);
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pkt[o++] = (byte) (((ushort)hdr.offset) >> 8);
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pkt[o++] = (byte) (((ushort)hdr.offset) & 0xff);
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pkt[o++] = hdr.ttl;
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pkt[o++] = hdr.protocol;
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pkt[o++] = 0;
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pkt[o++] = 0;
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// set the ip addresses
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hdr.srcAddr.CopyOut(pkt, o);
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o += IPv4.Length;
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hdr.destAddr.CopyOut(pkt, o);
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o += IPv4.Length;
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// calculate checksum
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ushort chk = Checksum(pkt, offset, Size);
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pkt[offset + 10] = (byte) (((ushort)chk) >> 8);
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pkt[offset + 11] = (byte) (((ushort)chk) & 0xff);
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// save the header checksum
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hdr.checksum = (ushort)chk;
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return o;
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}
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/// <summary>
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/// Update checksum when a 16-bit value that composed the original
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/// checksum changes. Useful for recomputing checksum when
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/// TTL changes when acting as a router.
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/// </summary>
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public static ushort UpdateChecksum(ushort checksum,
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ushort oldValue,
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ushort newValue)
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{
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// From RFC1624
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ushort newChecksum = (ushort)~checksum;
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newChecksum += (ushort)~oldValue;
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newChecksum += newValue;
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return (ushort)~newChecksum;
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}
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}
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}
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