public EthernetAddress GetHardwareAddress()
{
if (htype != (byte)HType.Ethernet)
{
// XXX Throw some nasty exception
}
return(EthernetAddress.ParseBytes(chaddr, 0));
}
// parse "pkt" from "start" bytes in, and return the
// "src" and "dst" Ethernet addresses, and the protocol
// "type" Returns the byte offset of the next layer's
// header.
public static int Read(byte [] !pkt,
int start,
out EthernetAddress src,
out EthernetAddress dst,
out ushort type)
{
dst = EthernetAddress.ParseBytes(pkt, start);
src = EthernetAddress.ParseBytes(pkt, start + 6);
type = (ushort)((pkt[start + 12] << 8) | (pkt[start + 13]));
return(start + 14);
}
public bool ReadEthernetAddress(out EthernetAddress address)
{
try {
address = EthernetAddress.ParseBytes(data, position);
position += EthernetAddress.Length;
}
catch (ArgumentException) {
address = EthernetAddress.Zero;
return(false);
}
return(true);
}
public ArpHeader(Bytes packet, ushort index)
{
//since this is already known to be an arp request
//we skip the sanity checks...
VTable.Assert(packet.Length - index >= 96);
// check hardware type == 0x0001 (Ethernet)
htype = NetworkBitConverter.ToUInt16(packet, index);
DebugStub.Assert(htype == 0x001);
index += 2;
// check protocol type == 0x0800 (IP)
ptype = NetworkBitConverter.ToUInt16(packet, index);
DebugStub.Assert(ptype == 0x0800);
index += 2;
// check hardware address len is 6 bytes
hlen = packet[index++];
DebugStub.Assert(hlen == 6);
// check IP address len is 4 bytes
plen = packet[index++];
DebugStub.Assert(plen == 4);
op = NetworkBitConverter.ToUInt16(packet, index);
index += 2;
senderEthernetAddr = EthernetAddress.ParseBytes(packet.Array, packet.Start + index);
index += EthernetAddress.Length;
uint addr = NetworkBitConverter.ToUInt32(packet, index);
index += 4;
senderIPAddr = new IPv4(addr);
destEthernetAddr = EthernetAddress.ParseBytes(packet.Array, packet.Start + index);
index += EthernetAddress.Length;
addr = NetworkBitConverter.ToUInt32(packet, index);
index += 4;
destIPAddr = new IPv4(addr);
//sgc complains
pad0 = 0;
pad1 = 0;
}
// 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);
}