public void SetHardwareAddress(EthernetAddress ea)
{
hlen = 6;
htype = (byte)HType.Ethernet;
chaddr = new byte[HardwareAddressLength];
ea.CopyOut(chaddr, 0);
}
// 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);
}
// Write an Ethernet header assuming that the header begins at offset 0
public static void Write(Bytes header,
EthernetAddress src,
EthernetAddress dst,
ushort type)
{
dst.CopyOut(header.Array, header.Start);
src.CopyOut(header.Array, header.Start + EthernetAddress.Length);
header[12] = (byte)(type >> 8);
header[13] = (byte)(type & 0xff);
}
// Write an Ethernet header to "pkt", starting at position "start".
public static int Write(byte[] !pkt,
int start,
EthernetAddress src,
EthernetAddress dst,
ushort type)
{
dst.CopyOut(pkt, start);
src.CopyOut(pkt, start + EthernetAddress.Length);
pkt[start + 12] = (byte)(type >> 8);
pkt[start + 13] = (byte)(type & 0xff);
return(start + 14);
}
// 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);
}