// methods:
public static int Write(byte [] !pkt,
int offset,
EthernetAddress srchw,
IPv4 srcip,
Type operation,
EthernetAddress targethw,
IPv4 targetip)
{
int o = offset;
pkt[o++] = 0x00; pkt[o++] = 0x01; // hardware type = 0x0001
pkt[o++] = 0x08; pkt[o++] = 0x00; // protocol type = 0x0800
pkt[o++] = 0x06; // hardware addr len (bytes)
pkt[o++] = 0x04; // protocol address len (bytes)
pkt[o++] = (byte)(((ushort)operation) >> 8);
pkt[o++] = (byte)(((ushort)operation) & 0xff);
srchw.CopyOut(pkt, o);
o += EthernetAddress.Length;
srcip.CopyOut(pkt, o);
o += IPv4.Length;
targethw.CopyOut(pkt, o);
o += EthernetAddress.Length;
targetip.CopyOut(pkt, o);
o += IPv4.Length;
return(o);
}
public static int Write(Bytes pkt,
EthernetAddress srchw,
IPv4 srcip,
ushort operation,
EthernetAddress targethw,
IPv4 targetip)
{
int o = 0;
pkt[o++] = 0x00; pkt[o++] = 0x01; // hardware type = 0x0001
pkt[o++] = 0x08; pkt[o++] = 0x00; // protocol type = 0x0800
pkt[o++] = 0x06; // hardware addr len (bytes)
pkt[o++] = 0x04; // protocol address len (bytes)
pkt[o++] = (byte)(operation >> 8);
pkt[o++] = (byte)(operation & 0xff);
srchw.CopyOut(pkt.Array, pkt.Start + o);
o += EthernetAddress.Length;
srcip.CopyOut(pkt.Array, pkt.Start + o);
o += IPv4.Length;
targethw.CopyOut(pkt.Array, pkt.Start + o);
o += EthernetAddress.Length;
targetip.CopyOut(pkt.Array, pkt.Start + o);
o += IPv4.Length;
return(o);
}
//assume ethernet
//we have to expose this for the DhcpClient
//Once we move the Dhcp client into an app this can be hidden again
public void WriteCompleteUDPHeader(Bytes header, Bytes data, int payloadLength)
{
int totalLength = IpHeader.Size + UDPHeader.Size + payloadLength;
//write ip header
int offset = EthernetHeader.Size;
int o = EthernetHeader.Size;
DebugStub.Assert(payloadLength < 0xffff);
header[o++] = 0x45; //default version 4, header_len 5
header[o++] = 0; //tos
header[o++] = (byte)(((ushort)totalLength) >> 8); //total length of the ip header
header[o++] = (byte)(((ushort)totalLength) & 0xff);
header[o++] = (byte)(((ushort)0) >> 8); //fragment id
header[o++] = (byte)(((ushort)0) & 0xff); //fragment id
header[o++] = (byte)(((ushort)0) >> 8); //fragment offset
header[o++] = (byte)(((ushort)0) & 0xff); //fragment offset
header[o++] = 128; //default ttl
header[o++] = 17; // protocol ID --> udp
header[o++] = 0; //ipchecksum (fill it in later)
header[o++] = 0; //ipchecksum
// set the ip addresses
localIPAddress.CopyOut(header.Array, header.Start + o);
o += IPv4.Length;
remoteIPAddress.CopyOut(header.Array, header.Start + o);
o += IPv4.Length;
// calculate checksum
ushort chk = IpHeader.CalculateChecksum(header, offset, IpHeader.Size);
header[offset + 10] = (byte)(((ushort)chk) >> 8);
header[offset + 11] = (byte)(((ushort)chk) & 0xff);
//write the udp header
header[o++] = (byte)(((ushort)localPort) >> 8);
header[o++] = (byte)(((ushort)localPort) & 0xff);
header[o++] = (byte)(((ushort)remotePort) >> 8);
header[o++] = (byte)(((ushort)remotePort) & 0xff);
ushort udpLength = (ushort)(UDPHeader.Size + payloadLength);
header[o++] = (byte)(((ushort)udpLength) >> 8);
header[o++] = (byte)(((ushort)udpLength) & 0xff);
// udp checksum (forget for now)
header[o++] = 0;
header[o++] = 0;
UDPHeader.SetUdpChecksum(header, data, EthernetHeader.Size, udpLength);
}
// creates an arp reply using the received packet
// the packet must be an arp request
// the responder should pass its own IP and MAC address
// we assume that we have the same hw type
// (return offset_arp size)
public static int CreateArpReply(ref byte[] !pkt,
IPv4 selfIP,
EthernetAddress selfMACAddr)
{
int offset = 14; // arp message starts here.
int o = offset;
// check we have enough packet
if (pkt.Length - offset < Size)
{
return(offset);
}
// check hardware type == 0x0001 (Ethernet)
if (pkt[o++] != 0x00 || pkt[o++] != 0x01)
{
return(offset);
}
// check protocol type == 0x0800 (IP)
if (pkt[o++] != 0x08 || pkt[o++] != 0x00)
{
return(offset); // error
}
// check addresses len
if (pkt[o++] != 0x06)
{
return(offset);
}
if (pkt[o++] != 0x04)
{
return(offset);
}
// operation code
Type opcode = (Type)(((int)pkt[o++] << 8) | (int)pkt[o++]);
// we need a request message.
if (opcode != Type.ARP_REQUEST)
{
return(offset);
}
// sender HW & IP
EthernetAddress senderhw = EthernetAddress.ParseBytes(pkt, o);
o += EthernetAddress.Length;
IPv4 senderIP = IPv4.ParseBytes(pkt, o);
o += IPv4.Length;
// target HW & IP
// EthernetAddress targethw = EthernetAddress.ParseBytes(pkt, o);
o += EthernetAddress.Length;
// IPv4 targetIP = IPv4.ParseBytes(pkt, o);
o += IPv4.Length;
// all is well, do our stuff...
// 1. set local hw address to arp's source ether address + fix dest addresses
// 2. set arp type = ARP_REPLY
// 3. set the destination's ethernet address to self
// and target is the source of the request.
o = offset + 6; // opcode entry
pkt[o++] = (byte)(((ushort)Type.ARP_REPLY) >> 8);
pkt[o++] = (byte)Type.ARP_REPLY;
// set hw and IP address
selfMACAddr.CopyOut(pkt, o);
o += EthernetAddress.Length;
selfIP.CopyOut(pkt, o);
o += IPv4.Length;
// setup dest address to the requesting host address
senderhw.CopyOut(pkt, o);
o += EthernetAddress.Length;
senderIP.CopyOut(pkt, o);
o += IPv4.Length;
// set ethernet level addresses
Array.Copy(pkt, 6, pkt, 0, 6); // src -> dest
selfMACAddr.CopyOut(pkt, 6); // self -> src
return(offset + Size);
}