added some dhcp4 packet functions and generic byte reading functions

pkt.go

@@ -0,0 +1,148 @@
+package haza
+
+import "net"
+
+type Dhcp4Op = uint8
+type Dhcp4Htype = uint8
+type Dhcp4Msg = uint8
+
+const (
+	_ Dhcp4Op = iota
+	DHCP4_OP_BOOTREQUEST = 1
+	DHCP4_OP_BOOTREPLY = 2
+)
+
+const (
+	_ Dhcp4Htype = iota
+	DHCP4_HTYPE_ETHER = 1
+	DHCP4_HTYPE_IEEE802 = 6
+	DHCP4_HTYPE_ARCNET = 7
+	DHCP4_HTYPE_APPLETALK = 8
+	DHCP4_HTYPE_HDLC = 17
+	DHCP4_HTYPE_ATM = 19
+	DHCP4_HTYPE_ARPSEC = 30
+	DHCP4_HTYPE_IPSEC = 31
+	DHCP4_HTYPE_INFINIBAND = 32
+	DHCP4_HTYPE_PUREIP = 35
+)
+
+const (
+	_ Dhcp4Msg = iota
+
+	DHCP4_MSG_DISCOVER = 1
+	DHCP4_MSG_OFFER = 2
+	DHCP4_MSG_REQUEST = 3
+	DHCP4_MSG_DECLINE = 4
+	DHCP4_MSG_ACK = 5
+	DHCP4_MSG_NAK = 6
+	DHCP4_MSG_RELEASE = 7
+	DHCP4_MSG_INFORM = 8
+
+	DHCP4_MSG_FORCE_RENEW = 9
+
+	DHCP4_MSG_LEASE_QUERY = 10
+	DHCP4_MSG_LEASE_UNASSIGNED = 11
+	DHCP4_MSG_LEASE_UNKNOWN = 12
+	DHCP4_MSG_LEASE_ACTIVE = 13
+
+	DHCP4_MSG_BULK_LEASE_QUERY = 14
+	DHCP4_MSG_LEASE_QUERY_DONE = 15
+	DHCP4_MSG_ACTIVE_LEASE_QUERY = 16
+	DHCP4_MSG_LEASE_QUERY_STATUS = 17
+	DHCP4_MSG_TLS = 18
+)
+
+type Dhcp4Pkt struct {
+	Op    Dhcp4Op
+	Htype Dhcp4Htype
+	Hlen uint8 // length of Chaddr
+
+	Hops uint8
+	Xid uint32
+	Secs uint16
+	Flags uint16
+
+	Ciaddr net.IP // uint32
+	Yiaddr net.IP // uint32
+	Siaddr net.IP // uint32
+	Gwaddr net.IP // uint32
+	Chaddr [16]byte
+
+	Sname  [64]byte // server host name
+	File   [128]byte // boot file name
+
+	// options are placed after the header.
+	// the first four bytes of the options compose a magic cookie  
+	// 0x63 0x82 0x53 0x63 
+}
+
+func (pkt *Dhcp4Pkt) Decode(b []byte) error {
+	// fill the packet with data from the bytes
+	var r *ByteReader
+	var u8 byte
+	var u16 uint16
+	var u32 uint32
+	var p Dhcp4Pkt
+	var err error
+
+	r = NewByteReader(b)	
+	
+	u8, err = r.ReadByte()	
+	if err != nil { return err }
+	p.Op = Dhcp4Op(u8)
+
+	u8, err = r.ReadByte()
+	if err != nil { return err }
+	p.Htype = Dhcp4Htype(u8)
+
+	u8, err = r.ReadByte()
+	if err != nil { return err }
+	p.Hlen = u8
+
+	u8, err = r.ReadByte()
+	if err != nil { return err }
+	p.Hops = u8
+
+	u32, err = r.ReadUint32()
+	if err != nil { return err }
+	p.Xid = u32
+
+	u16, err = r.ReadUint16()
+	if err != nil { return err }
+	p.Secs = u16
+
+	u16, err = r.ReadUint16()
+	if err != nil { return err }
+	p.Flags = u16
+
+	p.Ciaddr, err = r.ReadIp4()
+	if err != nil { return err }
+
+	p.Yiaddr, err = r.ReadIp4()
+	if err != nil { return err }
+
+	p.Siaddr, err = r.ReadIp4()
+	if err != nil { return err }
+
+	p.Gwaddr, err = r.ReadIp4()
+	if err != nil { return err }
+
+	err = r.ReadAllBytes(p.Chaddr[:])
+	if err != nil { return err }
+
+	err = r.ReadAllBytes(p.Sname[:])
+	if err != nil { return err }
+	
+	err = r.ReadAllBytes(p.File[:])
+	if err != nil { return err }
+	
+// magic
+// options..
+
+	*pkt = p
+	return nil
+}
+
+func (pkt *Dhcp4Pkt) Encode() []byte {
+	return nil
+}