vendor: add github.com/d2g

vendor/github.com/d2g/dhcp4/packet.go

@@ -0,0 +1,149 @@
+package dhcp4
+
+import (
+	"net"
+	"time"
+)
+
+// A DHCP packet
+type Packet []byte
+
+func (p Packet) OpCode() OpCode { return OpCode(p[0]) }
+func (p Packet) HType() byte    { return p[1] }
+func (p Packet) HLen() byte     { return p[2] }
+func (p Packet) Hops() byte     { return p[3] }
+func (p Packet) XId() []byte    { return p[4:8] }
+func (p Packet) Secs() []byte   { return p[8:10] } // Never Used?
+func (p Packet) Flags() []byte  { return p[10:12] }
+func (p Packet) CIAddr() net.IP { return net.IP(p[12:16]) }
+func (p Packet) YIAddr() net.IP { return net.IP(p[16:20]) }
+func (p Packet) SIAddr() net.IP { return net.IP(p[20:24]) }
+func (p Packet) GIAddr() net.IP { return net.IP(p[24:28]) }
+func (p Packet) CHAddr() net.HardwareAddr {
+	hLen := p.HLen()
+	if hLen > 16 { // Prevent chaddr exceeding p boundary
+		hLen = 16
+	}
+	return net.HardwareAddr(p[28 : 28+hLen]) // max endPos 44
+}
+
+// 192 bytes of zeros BOOTP legacy
+func (p Packet) Cookie() []byte { return p[236:240] }
+func (p Packet) Options() []byte {
+	if len(p) > 240 {
+		return p[240:]
+	}
+	return nil
+}
+
+func (p Packet) Broadcast() bool { return p.Flags()[0] > 127 }
+
+func (p Packet) SetBroadcast(broadcast bool) {
+	if p.Broadcast() != broadcast {
+		p.Flags()[0] ^= 128
+	}
+}
+
+func (p Packet) SetOpCode(c OpCode) { p[0] = byte(c) }
+func (p Packet) SetCHAddr(a net.HardwareAddr) {
+	copy(p[28:44], a)
+	p[2] = byte(len(a))
+}
+func (p Packet) SetHType(hType byte)     { p[1] = hType }
+func (p Packet) SetCookie(cookie []byte) { copy(p.Cookie(), cookie) }
+func (p Packet) SetHops(hops byte)       { p[3] = hops }
+func (p Packet) SetXId(xId []byte)       { copy(p.XId(), xId) }
+func (p Packet) SetSecs(secs []byte)     { copy(p.Secs(), secs) }
+func (p Packet) SetFlags(flags []byte)   { copy(p.Flags(), flags) }
+func (p Packet) SetCIAddr(ip net.IP)     { copy(p.CIAddr(), ip.To4()) }
+func (p Packet) SetYIAddr(ip net.IP)     { copy(p.YIAddr(), ip.To4()) }
+func (p Packet) SetSIAddr(ip net.IP)     { copy(p.SIAddr(), ip.To4()) }
+func (p Packet) SetGIAddr(ip net.IP)     { copy(p.GIAddr(), ip.To4()) }
+
+// Parses the packet's options into an Options map
+func (p Packet) ParseOptions() Options {
+	opts := p.Options()
+	options := make(Options, 10)
+	for len(opts) >= 2 && OptionCode(opts[0]) != End {
+		if OptionCode(opts[0]) == Pad {
+			opts = opts[1:]
+			continue
+		}
+		size := int(opts[1])
+		if len(opts) < 2+size {
+			break
+		}
+		options[OptionCode(opts[0])] = opts[2 : 2+size]
+		opts = opts[2+size:]
+	}
+	return options
+}
+
+func NewPacket(opCode OpCode) Packet {
+	p := make(Packet, 241)
+	p.SetOpCode(opCode)
+	p.SetHType(1) // Ethernet
+	p.SetCookie([]byte{99, 130, 83, 99})
+	p[240] = byte(End)
+	return p
+}
+
+// Appends a DHCP option to the end of a packet
+func (p *Packet) AddOption(o OptionCode, value []byte) {
+	*p = append((*p)[:len(*p)-1], []byte{byte(o), byte(len(value))}...) // Strip off End, Add OptionCode and Length
+	*p = append(*p, value...)                                           // Add Option Value
+	*p = append(*p, byte(End))                                          // Add on new End
+}
+
+// Removes all options from packet.
+func (p *Packet) StripOptions() {
+	*p = append((*p)[:240], byte(End))
+}
+
+// Creates a request packet that a Client would send to a server.
+func RequestPacket(mt MessageType, chAddr net.HardwareAddr, cIAddr net.IP, xId []byte, broadcast bool, options []Option) Packet {
+	p := NewPacket(BootRequest)
+	p.SetCHAddr(chAddr)
+	p.SetXId(xId)
+	if cIAddr != nil {
+		p.SetCIAddr(cIAddr)
+	}
+	p.SetBroadcast(broadcast)
+	p.AddOption(OptionDHCPMessageType, []byte{byte(mt)})
+	for _, o := range options {
+		p.AddOption(o.Code, o.Value)
+	}
+	p.PadToMinSize()
+	return p
+}
+
+// ReplyPacket creates a reply packet that a Server would send to a client.
+// It uses the req Packet param to copy across common/necessary fields to
+// associate the reply the request.
+func ReplyPacket(req Packet, mt MessageType, serverId, yIAddr net.IP, leaseDuration time.Duration, options []Option) Packet {
+	p := NewPacket(BootReply)
+	p.SetXId(req.XId())
+	p.SetFlags(req.Flags())
+	p.SetYIAddr(yIAddr)
+	p.SetGIAddr(req.GIAddr())
+	p.SetCHAddr(req.CHAddr())
+	p.SetSecs(req.Secs())
+	p.AddOption(OptionDHCPMessageType, []byte{byte(mt)})
+	p.AddOption(OptionServerIdentifier, []byte(serverId))
+	p.AddOption(OptionIPAddressLeaseTime, OptionsLeaseTime(leaseDuration))
+	for _, o := range options {
+		p.AddOption(o.Code, o.Value)
+	}
+	p.PadToMinSize()
+	return p
+}
+
+// PadToMinSize pads a packet so that when sent over UDP, the entire packet,
+// is 300 bytes (BOOTP min), to be compatible with really old devices.
+var padder [272]byte
+
+func (p *Packet) PadToMinSize() {
+	if n := len(*p); n < 272 {
+		*p = append(*p, padder[:272-n]...)
+	}
+}