fix(dhcp): can not renew an ip address

The dhcp server is systemd-networkd, and the dhcp
plugin can request an ip but can not renew it.
The systemd-networkd just ignore the renew request.

```
2024/09/14 21:46:00 no DHCP packet received within 10s
2024/09/14 21:46:00 retrying in 31.529038 seconds
2024/09/14 21:46:42 no DHCP packet received within 10s
2024/09/14 21:46:42 retrying in 63.150490 seconds
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: no more tries
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: renewal time expired, rebinding
2024/09/14 21:47:45 Link "eth1" down. Attempting to set up
2024/09/14 21:47:45 98184616c91f15419f5cacd012697f85afaa2daeb5d3233e28b0ec21589fb45a/iot/eth1: lease rebound, expiration is 2024-09-14 22:47:45.309270751 +0800 CST m=+11730.048516519
```

Follow the https://datatracker.ietf.org/doc/html/rfc2131#section-4.3.6,
following options must not be sent in renew

- Requested IP Address
- Server Identifier

Since the upstream code has been inactive for 6 years,
we should switch to another dhcpv4 library.
The new selected one is https://github.com/insomniacslk/dhcp.

Signed-off-by: Songmin Li <lisongmin@protonmail.com>

vendor/github.com/insomniacslk/dhcp/CONTRIBUTORS.md

@@ -0,0 +1,10 @@
+## Contributors
+
+* Andrea Barberio (main author)
+* Pablo Mazzini (tons of fixes and new options)
+* Sean Karlage (BSDP package, and of tons of improvements to the DHCPv4 package)
+* Owen Mooney (several option fixes and modifiers)
+* Mikolaj Walczak (asynchronous DHCPv6 client)
+* Chris Koch (tons of improvements in DHCPv4 and DHCPv6 internals and interface)
+* Akshay Navale, Brandon Bennett and Chris Gorham (ZTPv6 and ZTPv4 packages)
+* Anatole Denis (tons of fixes and new options)

vendor/github.com/insomniacslk/dhcp/LICENSE

@@ -0,0 +1,29 @@
+BSD 3-Clause License
+
+Copyright (c) 2018, Andrea Barberio
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+* Neither the name of the copyright holder nor the names of its
+  contributors may be used to endorse or promote products derived from
+  this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/github.com/insomniacslk/dhcp/dhcpv4/bindtointerface.go

@@ -0,0 +1,10 @@
+package dhcpv4
+
+import (
+	"github.com/insomniacslk/dhcp/interfaces"
+)
+
+// BindToInterface (deprecated) redirects to interfaces.BindToInterface
+func BindToInterface(fd int, ifname string) error {
+	return interfaces.BindToInterface(fd, ifname)
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/defaults.go

@@ -0,0 +1,6 @@
+package dhcpv4
+
+const (
+	ServerPort = 67
+	ClientPort = 68
+)

vendor/github.com/insomniacslk/dhcp/dhcpv4/dhcpv4.go

@@ -0,0 +1,856 @@
+// Package dhcpv4 provides encoding and decoding of DHCPv4 packets and options.
+//
+// Example Usage:
+//
+//   p, err := dhcpv4.New(
+//     dhcpv4.WithClientIP(net.IP{192, 168, 0, 1}),
+//     dhcpv4.WithMessageType(dhcpv4.MessageTypeInform),
+//   )
+//   p.UpdateOption(dhcpv4.OptServerIdentifier(net.IP{192, 110, 110, 110}))
+//
+//   // Retrieve the DHCP Message Type option.
+//   m := p.MessageType()
+//
+//   bytesOnTheWire := p.ToBytes()
+//   longSummary := p.Summary()
+package dhcpv4
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/insomniacslk/dhcp/rfc1035label"
+	"github.com/u-root/uio/rand"
+	"github.com/u-root/uio/uio"
+)
+
+const (
+	// minPacketLen is the minimum DHCP header length.
+	minPacketLen = 236
+
+	// MaxHWAddrLen is the maximum hardware address length of the ClientHWAddr
+	// (client hardware address) according to RFC 2131, Section 2. This is the
+	// link-layer destination a server must send responses to.
+	MaxHWAddrLen = 16
+
+	// MaxMessageSize is the maximum size in bytes that a DHCPv4 packet can hold.
+	MaxMessageSize = 576
+
+	// Per RFC 951, the minimum length of a packet is 300 bytes.
+	bootpMinLen = 300
+)
+
+// RandomTimeout is the amount of time to wait until random number generation
+// is canceled.
+var RandomTimeout = 2 * time.Minute
+
+// magicCookie is the magic 4-byte value at the beginning of the list of options
+// in a DHCPv4 packet.
+var magicCookie = [4]byte{99, 130, 83, 99}
+
+// DHCPv4 represents a DHCPv4 packet header and options. See the New* functions
+// to build DHCPv4 packets.
+type DHCPv4 struct {
+	OpCode         OpcodeType
+	HWType         iana.HWType
+	HopCount       uint8
+	TransactionID  TransactionID
+	NumSeconds     uint16
+	Flags          uint16
+	ClientIPAddr   net.IP
+	YourIPAddr     net.IP
+	ServerIPAddr   net.IP
+	GatewayIPAddr  net.IP
+	ClientHWAddr   net.HardwareAddr
+	ServerHostName string
+	BootFileName   string
+	Options        Options
+}
+
+// Modifier defines the signature for functions that can modify DHCPv4
+// structures. This is used to simplify packet manipulation
+type Modifier func(d *DHCPv4)
+
+// IPv4AddrsForInterface obtains the currently-configured, non-loopback IPv4
+// addresses for iface.
+func IPv4AddrsForInterface(iface *net.Interface) ([]net.IP, error) {
+	if iface == nil {
+		return nil, errors.New("IPv4AddrsForInterface: iface cannot be nil")
+	}
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return nil, err
+	}
+	return GetExternalIPv4Addrs(addrs)
+}
+
+// GetExternalIPv4Addrs obtains the currently-configured, non-loopback IPv4
+// addresses from `addrs` coming from a particular interface (e.g.
+// net.Interface.Addrs).
+func GetExternalIPv4Addrs(addrs []net.Addr) ([]net.IP, error) {
+	var v4addrs []net.IP
+	for _, addr := range addrs {
+		var ip net.IP
+		switch v := addr.(type) {
+		case *net.IPAddr:
+			ip = v.IP
+		case *net.IPNet:
+			ip = v.IP
+		}
+
+		if ip == nil || ip.IsLoopback() {
+			continue
+		}
+		ip = ip.To4()
+		if ip == nil {
+			continue
+		}
+		v4addrs = append(v4addrs, ip)
+	}
+	return v4addrs, nil
+}
+
+// GenerateTransactionID generates a random 32-bits number suitable for use as
+// TransactionID
+func GenerateTransactionID() (TransactionID, error) {
+	var xid TransactionID
+	ctx, cancel := context.WithTimeout(context.Background(), RandomTimeout)
+	defer cancel()
+	n, err := rand.ReadContext(ctx, xid[:])
+	if err != nil {
+		return xid, fmt.Errorf("could not get random number: %v", err)
+	}
+	if n != 4 {
+		return xid, errors.New("invalid random sequence for transaction ID: smaller than 32 bits")
+	}
+	return xid, err
+}
+
+// New creates a new DHCPv4 structure and fill it up with default values. It
+// won't be a valid DHCPv4 message so you will need to adjust its fields.
+// See also NewDiscovery, NewRequest, NewAcknowledge, NewInform and NewRelease.
+func New(modifiers ...Modifier) (*DHCPv4, error) {
+	xid, err := GenerateTransactionID()
+	if err != nil {
+		return nil, err
+	}
+	d := DHCPv4{
+		OpCode:        OpcodeBootRequest,
+		HWType:        iana.HWTypeEthernet,
+		ClientHWAddr:  make(net.HardwareAddr, 6),
+		HopCount:      0,
+		TransactionID: xid,
+		NumSeconds:    0,
+		Flags:         0,
+		ClientIPAddr:  net.IPv4zero,
+		YourIPAddr:    net.IPv4zero,
+		ServerIPAddr:  net.IPv4zero,
+		GatewayIPAddr: net.IPv4zero,
+		Options:       make(Options),
+	}
+	for _, mod := range modifiers {
+		mod(&d)
+	}
+	return &d, nil
+}
+
+// NewDiscoveryForInterface builds a new DHCPv4 Discovery message, with a default
+// Ethernet HW type and the hardware address obtained from the specified
+// interface.
+func NewDiscoveryForInterface(ifname string, modifiers ...Modifier) (*DHCPv4, error) {
+	iface, err := net.InterfaceByName(ifname)
+	if err != nil {
+		return nil, err
+	}
+	return NewDiscovery(iface.HardwareAddr, modifiers...)
+}
+
+// NewDiscovery builds a new DHCPv4 Discovery message, with a default Ethernet
+// HW type and specified hardware address.
+func NewDiscovery(hwaddr net.HardwareAddr, modifiers ...Modifier) (*DHCPv4, error) {
+	return New(PrependModifiers(modifiers,
+		WithHwAddr(hwaddr),
+		WithRequestedOptions(
+			OptionSubnetMask,
+			OptionRouter,
+			OptionDomainName,
+			OptionDomainNameServer,
+		),
+		WithMessageType(MessageTypeDiscover),
+	)...)
+}
+
+// NewInformForInterface builds a new DHCPv4 Informational message with default
+// Ethernet HW type and the hardware address obtained from the specified
+// interface.
+func NewInformForInterface(ifname string, needsBroadcast bool) (*DHCPv4, error) {
+	// get hw addr
+	iface, err := net.InterfaceByName(ifname)
+	if err != nil {
+		return nil, err
+	}
+
+	// Set Client IP as iface's currently-configured IP.
+	localIPs, err := IPv4AddrsForInterface(iface)
+	if err != nil || len(localIPs) == 0 {
+		return nil, fmt.Errorf("could not get local IPs for iface %s", ifname)
+	}
+	pkt, err := NewInform(iface.HardwareAddr, localIPs[0])
+	if err != nil {
+		return nil, err
+	}
+
+	if needsBroadcast {
+		pkt.SetBroadcast()
+	} else {
+		pkt.SetUnicast()
+	}
+	return pkt, nil
+}
+
+// PrependModifiers prepends other to m.
+func PrependModifiers(m []Modifier, other ...Modifier) []Modifier {
+	return append(other, m...)
+}
+
+// NewInform builds a new DHCPv4 Informational message with the specified
+// hardware address.
+func NewInform(hwaddr net.HardwareAddr, localIP net.IP, modifiers ...Modifier) (*DHCPv4, error) {
+	return New(PrependModifiers(modifiers,
+		WithHwAddr(hwaddr),
+		WithMessageType(MessageTypeInform),
+		WithClientIP(localIP),
+	)...)
+}
+
+// NewRequestFromOffer builds a DHCPv4 request from an offer.
+// It assumes the SELECTING state by default, see Section 4.3.2 in RFC 2131 for more details.
+func NewRequestFromOffer(offer *DHCPv4, modifiers ...Modifier) (*DHCPv4, error) {
+	return New(PrependModifiers(modifiers,
+		WithReply(offer),
+		WithMessageType(MessageTypeRequest),
+		WithClientIP(offer.ClientIPAddr),
+		WithOption(OptRequestedIPAddress(offer.YourIPAddr)),
+		// This is usually the server IP.
+		WithOptionCopied(offer, OptionServerIdentifier),
+		WithRequestedOptions(
+			OptionSubnetMask,
+			OptionRouter,
+			OptionDomainName,
+			OptionDomainNameServer,
+		),
+	)...)
+}
+
+// NewRenewFromAck builds a DHCPv4 RENEW-style request from the ACK of a lease. RENEW requests have
+// minor changes to their options compared to SELECT requests as specified by RFC 2131, section 4.3.2.
+func NewRenewFromAck(ack *DHCPv4, modifiers ...Modifier) (*DHCPv4, error) {
+	return New(PrependModifiers(modifiers,
+		WithReply(ack),
+		WithMessageType(MessageTypeRequest),
+		// The client IP must be filled in with the IP offered to the client
+		WithClientIP(ack.YourIPAddr),
+		// The renewal request must use unicast
+		WithBroadcast(false),
+		WithRequestedOptions(
+			OptionSubnetMask,
+			OptionRouter,
+			OptionDomainName,
+			OptionDomainNameServer,
+		),
+	)...)
+}
+
+// NewReplyFromRequest builds a DHCPv4 reply from a request.
+func NewReplyFromRequest(request *DHCPv4, modifiers ...Modifier) (*DHCPv4, error) {
+	return New(PrependModifiers(modifiers,
+		WithReply(request),
+		WithGatewayIP(request.GatewayIPAddr),
+		WithOptionCopied(request, OptionRelayAgentInformation),
+
+		// RFC 6842 states the Client Identifier option must be copied
+		// from the request if a client specified it.
+		WithOptionCopied(request, OptionClientIdentifier),
+	)...)
+}
+
+// NewReleaseFromACK creates a DHCPv4 Release message from ACK.
+// default Release message without any Modifer is created as following:
+//  - option Message Type is Release
+//  - ClientIP is set to ack.YourIPAddr
+//  - ClientHWAddr is set to ack.ClientHWAddr
+//  - Unicast
+//  - option Server Identifier is set to ack's ServerIdentifier
+func NewReleaseFromACK(ack *DHCPv4, modifiers ...Modifier) (*DHCPv4, error) {
+	return New(PrependModifiers(modifiers,
+		WithMessageType(MessageTypeRelease),
+		WithClientIP(ack.YourIPAddr),
+		WithHwAddr(ack.ClientHWAddr),
+		WithBroadcast(false),
+		WithOptionCopied(ack, OptionServerIdentifier),
+	)...)
+}
+
+// FromBytes decodes a DHCPv4 packet from a sequence of bytes, and returns an
+// error if the packet is not valid.
+func FromBytes(q []byte) (*DHCPv4, error) {
+	var p DHCPv4
+	buf := uio.NewBigEndianBuffer(q)
+
+	p.OpCode = OpcodeType(buf.Read8())
+	p.HWType = iana.HWType(buf.Read8())
+
+	hwAddrLen := buf.Read8()
+
+	p.HopCount = buf.Read8()
+	buf.ReadBytes(p.TransactionID[:])
+	p.NumSeconds = buf.Read16()
+	p.Flags = buf.Read16()
+
+	p.ClientIPAddr = net.IP(buf.CopyN(net.IPv4len))
+	p.YourIPAddr = net.IP(buf.CopyN(net.IPv4len))
+	p.ServerIPAddr = net.IP(buf.CopyN(net.IPv4len))
+	p.GatewayIPAddr = net.IP(buf.CopyN(net.IPv4len))
+
+	if hwAddrLen > 16 {
+		hwAddrLen = 16
+	}
+	// Always read 16 bytes, but only use hwaddrlen of them.
+	p.ClientHWAddr = make(net.HardwareAddr, 16)
+	buf.ReadBytes(p.ClientHWAddr)
+	p.ClientHWAddr = p.ClientHWAddr[:hwAddrLen]
+
+	var sname [64]byte
+	buf.ReadBytes(sname[:])
+	length := strings.Index(string(sname[:]), "\x00")
+	if length == -1 {
+		length = 64
+	}
+	p.ServerHostName = string(sname[:length])
+
+	var file [128]byte
+	buf.ReadBytes(file[:])
+	length = strings.Index(string(file[:]), "\x00")
+	if length == -1 {
+		length = 128
+	}
+	p.BootFileName = string(file[:length])
+
+	var cookie [4]byte
+	buf.ReadBytes(cookie[:])
+
+	if err := buf.Error(); err != nil {
+		return nil, err
+	}
+	if cookie != magicCookie {
+		return nil, fmt.Errorf("malformed DHCP packet: got magic cookie %v, want %v", cookie[:], magicCookie[:])
+	}
+
+	p.Options = make(Options)
+	if err := p.Options.fromBytesCheckEnd(buf.Data(), true); err != nil {
+		return nil, err
+	}
+	return &p, nil
+}
+
+// FlagsToString returns a human-readable representation of the flags field.
+func (d *DHCPv4) FlagsToString() string {
+	flags := ""
+	if d.IsBroadcast() {
+		flags += "Broadcast"
+	} else {
+		flags += "Unicast"
+	}
+	if d.Flags&0xfe != 0 {
+		flags += " (reserved bits not zeroed)"
+	}
+	return flags
+}
+
+// IsBroadcast indicates whether the packet is a broadcast packet.
+func (d *DHCPv4) IsBroadcast() bool {
+	return d.Flags&0x8000 == 0x8000
+}
+
+// SetBroadcast sets the packet to be a broadcast packet.
+func (d *DHCPv4) SetBroadcast() {
+	d.Flags |= 0x8000
+}
+
+// IsUnicast indicates whether the packet is a unicast packet.
+func (d *DHCPv4) IsUnicast() bool {
+	return d.Flags&0x8000 == 0
+}
+
+// SetUnicast sets the packet to be a unicast packet.
+func (d *DHCPv4) SetUnicast() {
+	d.Flags &= ^uint16(0x8000)
+}
+
+// GetOneOption returns the option that matches the given option code.
+//
+// According to RFC 3396, options that are specified more than once are
+// concatenated, and hence this should always just return one option.
+func (d *DHCPv4) GetOneOption(code OptionCode) []byte {
+	return d.Options.Get(code)
+}
+
+// DeleteOption deletes an existing option with the given option code.
+func (d *DHCPv4) DeleteOption(code OptionCode) {
+	if d.Options != nil {
+		d.Options.Del(code)
+	}
+}
+
+// UpdateOption replaces an existing option with the same option code with the
+// given one, adding it if not already present.
+func (d *DHCPv4) UpdateOption(opt Option) {
+	if d.Options == nil {
+		d.Options = make(Options)
+	}
+	d.Options.Update(opt)
+}
+
+// String implements fmt.Stringer.
+func (d *DHCPv4) String() string {
+	return fmt.Sprintf("DHCPv4(xid=%s hwaddr=%s msg_type=%s, your_ip=%s, server_ip=%s)",
+		d.TransactionID, d.ClientHWAddr, d.MessageType(), d.YourIPAddr, d.ServerIPAddr)
+}
+
+// SummaryWithVendor prints a summary of the packet, interpreting the
+// vendor-specific info option using the given parser (can be nil).
+func (d *DHCPv4) SummaryWithVendor(vendorDecoder OptionDecoder) string {
+	ret := fmt.Sprintf(
+		"DHCPv4 Message\n"+
+			"  opcode: %s\n"+
+			"  hwtype: %s\n"+
+			"  hopcount: %v\n"+
+			"  transaction ID: %s\n"+
+			"  num seconds: %v\n"+
+			"  flags: %v (0x%02x)\n"+
+			"  client IP: %s\n"+
+			"  your IP: %s\n"+
+			"  server IP: %s\n"+
+			"  gateway IP: %s\n"+
+			"  client MAC: %s\n"+
+			"  server hostname: %s\n"+
+			"  bootfile name: %s\n",
+		d.OpCode,
+		d.HWType,
+		d.HopCount,
+		d.TransactionID,
+		d.NumSeconds,
+		d.FlagsToString(),
+		d.Flags,
+		d.ClientIPAddr,
+		d.YourIPAddr,
+		d.ServerIPAddr,
+		d.GatewayIPAddr,
+		d.ClientHWAddr,
+		d.ServerHostName,
+		d.BootFileName,
+	)
+	ret += "  options:\n"
+	ret += d.Options.Summary(vendorDecoder)
+	return ret
+}
+
+// Summary prints detailed information about the packet.
+func (d *DHCPv4) Summary() string {
+	return d.SummaryWithVendor(nil)
+}
+
+// IsOptionRequested returns true if that option is within the requested
+// options of the DHCPv4 message.
+func (d *DHCPv4) IsOptionRequested(requested OptionCode) bool {
+	rq := d.ParameterRequestList()
+	if rq == nil {
+		// RFC2131§3.5
+		// Not all clients require initialization of all parameters [...]
+		// Two techniques are used to reduce the number of parameters transmitted from
+		// the server to the client. [...] Second, in its initial DHCPDISCOVER or
+		// DHCPREQUEST message, a client may provide the server with a list of specific
+		// parameters the client is interested in.
+		// We interpret this to say that all available parameters should be sent if
+		// the parameter request list is not sent at all.
+		return true
+	}
+
+	for _, o := range rq {
+		if o.Code() == requested.Code() {
+			return true
+		}
+	}
+	return false
+}
+
+// In case somebody forgets to set an IP, just write 0s as default values.
+func writeIP(b *uio.Lexer, ip net.IP) {
+	var zeros [net.IPv4len]byte
+	if ip == nil {
+		b.WriteBytes(zeros[:])
+	} else {
+		// Converting IP to 4 byte format
+		ip = ip.To4()
+		b.WriteBytes(ip[:net.IPv4len])
+	}
+}
+
+// ToBytes writes the packet to binary.
+func (d *DHCPv4) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(make([]byte, 0, minPacketLen))
+	buf.Write8(uint8(d.OpCode))
+	buf.Write8(uint8(d.HWType))
+
+	// HwAddrLen
+	hlen := uint8(len(d.ClientHWAddr))
+	buf.Write8(hlen)
+	buf.Write8(d.HopCount)
+	buf.WriteBytes(d.TransactionID[:])
+	buf.Write16(d.NumSeconds)
+	buf.Write16(d.Flags)
+
+	writeIP(buf, d.ClientIPAddr)
+	writeIP(buf, d.YourIPAddr)
+	writeIP(buf, d.ServerIPAddr)
+	writeIP(buf, d.GatewayIPAddr)
+	copy(buf.WriteN(16), d.ClientHWAddr)
+
+	var sname [64]byte
+	copy(sname[:63], []byte(d.ServerHostName))
+	buf.WriteBytes(sname[:])
+
+	var file [128]byte
+	copy(file[:127], []byte(d.BootFileName))
+	buf.WriteBytes(file[:])
+
+	// The magic cookie.
+	buf.WriteBytes(magicCookie[:])
+
+	// Write all options.
+	d.Options.Marshal(buf)
+
+	// Finish the options.
+	buf.Write8(OptionEnd.Code())
+
+	// DHCP is based on BOOTP, and BOOTP messages have a minimum length of
+	// 300 bytes per RFC 951. This not stated explicitly, but if you sum up
+	// all the bytes in the message layout, you'll get 300 bytes.
+	//
+	// Some DHCP servers and relay agents care about this BOOTP legacy B.S.
+	// and "conveniently" drop messages that are less than 300 bytes long.
+	if buf.Len() < bootpMinLen {
+		buf.WriteBytes(bytes.Repeat([]byte{OptionPad.Code()}, bootpMinLen-buf.Len()))
+	}
+
+	return buf.Data()
+}
+
+// GetBroadcastAddress returns the DHCPv4 Broadcast Address value in d.
+//
+// The broadcast address option is described in RFC 2132, Section 5.3.
+func (d *DHCPv4) BroadcastAddress() net.IP {
+	return GetIP(OptionBroadcastAddress, d.Options)
+}
+
+// RequestedIPAddress returns the DHCPv4 Requested IP Address value in d.
+//
+// The requested IP address option is described by RFC 2132, Section 9.1.
+func (d *DHCPv4) RequestedIPAddress() net.IP {
+	return GetIP(OptionRequestedIPAddress, d.Options)
+}
+
+// ServerIdentifier returns the DHCPv4 Server Identifier value in d.
+//
+// The server identifier option is described by RFC 2132, Section 9.7.
+func (d *DHCPv4) ServerIdentifier() net.IP {
+	return GetIP(OptionServerIdentifier, d.Options)
+}
+
+// Router parses the DHCPv4 Router option if present.
+//
+// The Router option is described by RFC 2132, Section 3.5.
+func (d *DHCPv4) Router() []net.IP {
+	return GetIPs(OptionRouter, d.Options)
+}
+
+// ClasslessStaticRoute parses the DHCPv4 Classless Static Route option if present.
+//
+// The Classless Static Route option is described by RFC 3442.
+func (d *DHCPv4) ClasslessStaticRoute() []*Route {
+	v := d.Options.Get(OptionClasslessStaticRoute)
+	if v == nil {
+		return nil
+	}
+	var routes Routes
+	if err := routes.FromBytes(v); err != nil {
+		return nil
+	}
+	return routes
+}
+
+// NTPServers parses the DHCPv4 NTP Servers option if present.
+//
+// The NTP servers option is described by RFC 2132, Section 8.3.
+func (d *DHCPv4) NTPServers() []net.IP {
+	return GetIPs(OptionNTPServers, d.Options)
+}
+
+// DNS parses the DHCPv4 Domain Name Server option if present.
+//
+// The DNS server option is described by RFC 2132, Section 3.8.
+func (d *DHCPv4) DNS() []net.IP {
+	return GetIPs(OptionDomainNameServer, d.Options)
+}
+
+// DomainName parses the DHCPv4 Domain Name option if present.
+//
+// The Domain Name option is described by RFC 2132, Section 3.17.
+func (d *DHCPv4) DomainName() string {
+	return GetString(OptionDomainName, d.Options)
+}
+
+// HostName parses the DHCPv4 Host Name option if present.
+//
+// The Host Name option is described by RFC 2132, Section 3.14.
+func (d *DHCPv4) HostName() string {
+	name := GetString(OptionHostName, d.Options)
+	return strings.TrimRight(name, "\x00")
+}
+
+// RootPath parses the DHCPv4 Root Path option if present.
+//
+// The Root Path option is described by RFC 2132, Section 3.19.
+func (d *DHCPv4) RootPath() string {
+	return GetString(OptionRootPath, d.Options)
+}
+
+// BootFileNameOption parses the DHCPv4 Bootfile Name option if present.
+//
+// The Bootfile Name option is described by RFC 2132, Section 9.5.
+func (d *DHCPv4) BootFileNameOption() string {
+	name := GetString(OptionBootfileName, d.Options)
+	return strings.TrimRight(name, "\x00")
+}
+
+// TFTPServerName parses the DHCPv4 TFTP Server Name option if present.
+//
+// The TFTP Server Name option is described by RFC 2132, Section 9.4.
+func (d *DHCPv4) TFTPServerName() string {
+	name := GetString(OptionTFTPServerName, d.Options)
+	return strings.TrimRight(name, "\x00")
+}
+
+// ClassIdentifier parses the DHCPv4 Class Identifier option if present.
+//
+// The Vendor Class Identifier option is described by RFC 2132, Section 9.13.
+func (d *DHCPv4) ClassIdentifier() string {
+	return GetString(OptionClassIdentifier, d.Options)
+}
+
+// ClientArch returns the Client System Architecture Type option.
+func (d *DHCPv4) ClientArch() []iana.Arch {
+	v := d.Options.Get(OptionClientSystemArchitectureType)
+	if v == nil {
+		return nil
+	}
+	var archs iana.Archs
+	if err := archs.FromBytes(v); err != nil {
+		return nil
+	}
+	return archs
+}
+
+// DomainSearch returns the domain search list if present.
+//
+// The domain search option is described by RFC 3397, Section 2.
+func (d *DHCPv4) DomainSearch() *rfc1035label.Labels {
+	v := d.Options.Get(OptionDNSDomainSearchList)
+	if v == nil {
+		return nil
+	}
+	labels, err := rfc1035label.FromBytes(v)
+	if err != nil {
+		return nil
+	}
+	return labels
+}
+
+// IPAddressLeaseTime returns the IP address lease time or the given
+// default duration if not present.
+//
+// The IP address lease time option is described by RFC 2132, Section 9.2.
+func (d *DHCPv4) IPAddressLeaseTime(def time.Duration) time.Duration {
+	v := d.Options.Get(OptionIPAddressLeaseTime)
+	if v == nil {
+		return def
+	}
+	var dur Duration
+	if err := dur.FromBytes(v); err != nil {
+		return def
+	}
+	return time.Duration(dur)
+}
+
+// IPAddressRenewalTime returns the IP address renewal time or the given
+// default duration if not present.
+//
+// The IP address renewal time option is described by RFC 2132, Section 9.11.
+func (d *DHCPv4) IPAddressRenewalTime(def time.Duration) time.Duration {
+	v := d.Options.Get(OptionRenewTimeValue)
+	if v == nil {
+		return def
+	}
+	var dur Duration
+	if err := dur.FromBytes(v); err != nil {
+		return def
+	}
+	return time.Duration(dur)
+}
+
+// IPAddressRebindingTime returns the IP address rebinding time or the given
+// default duration if not present.
+//
+// The IP address rebinding time option is described by RFC 2132, Section 9.12.
+func (d *DHCPv4) IPAddressRebindingTime(def time.Duration) time.Duration {
+	v := d.Options.Get(OptionRebindingTimeValue)
+	if v == nil {
+		return def
+	}
+	var dur Duration
+	if err := dur.FromBytes(v); err != nil {
+		return def
+	}
+	return time.Duration(dur)
+}
+
+// IPv6OnlyPreferred returns the V6ONLY_WAIT duration, and a boolean
+// indicating whether this option was present.
+//
+// The IPv6-Only Preferred option is described by RFC 8925, Section 3.1.
+func (d *DHCPv4) IPv6OnlyPreferred() (time.Duration, bool) {
+	v := d.Options.Get(OptionIPv6OnlyPreferred)
+	if v == nil {
+		return 0, false
+	}
+	var dur Duration
+	if err := dur.FromBytes(v); err != nil {
+		return 0, false
+	}
+	return time.Duration(dur), true
+}
+
+// MaxMessageSize returns the DHCP Maximum Message Size if present.
+//
+// The Maximum DHCP Message Size option is described by RFC 2132, Section 9.10.
+func (d *DHCPv4) MaxMessageSize() (uint16, error) {
+	return GetUint16(OptionMaximumDHCPMessageSize, d.Options)
+}
+
+// AutoConfigure returns the value of the AutoConfigure option, and a
+// boolean indicating if it was present.
+//
+// The AutoConfigure option is described by RFC 2563, Section 2.
+func (d *DHCPv4) AutoConfigure() (AutoConfiguration, bool) {
+	v, err := GetByte(OptionAutoConfigure, d.Options)
+	return AutoConfiguration(v), err == nil
+}
+
+// MessageType returns the DHCPv4 Message Type option.
+func (d *DHCPv4) MessageType() MessageType {
+	v := d.Options.Get(OptionDHCPMessageType)
+	if v == nil {
+		return MessageTypeNone
+	}
+	var m MessageType
+	if err := m.FromBytes(v); err != nil {
+		return MessageTypeNone
+	}
+	return m
+}
+
+// Message returns the DHCPv4 (Error) Message option.
+//
+// The message options is described in RFC 2132, Section 9.9.
+func (d *DHCPv4) Message() string {
+	return GetString(OptionMessage, d.Options)
+}
+
+// ParameterRequestList returns the DHCPv4 Parameter Request List.
+//
+// The parameter request list option is described by RFC 2132, Section 9.8.
+func (d *DHCPv4) ParameterRequestList() OptionCodeList {
+	v := d.Options.Get(OptionParameterRequestList)
+	if v == nil {
+		return nil
+	}
+	var codes OptionCodeList
+	if err := codes.FromBytes(v); err != nil {
+		return nil
+	}
+	return codes
+}
+
+// RelayAgentInfo returns options embedded by the relay agent.
+//
+// The relay agent info option is described by RFC 3046.
+func (d *DHCPv4) RelayAgentInfo() *RelayOptions {
+	v := d.Options.Get(OptionRelayAgentInformation)
+	if v == nil {
+		return nil
+	}
+	var relayOptions RelayOptions
+	if err := relayOptions.FromBytes(v); err != nil {
+		return nil
+	}
+	return &relayOptions
+}
+
+// SubnetMask returns a subnet mask option contained if present.
+//
+// The subnet mask option is described by RFC 2132, Section 3.3.
+func (d *DHCPv4) SubnetMask() net.IPMask {
+	v := d.Options.Get(OptionSubnetMask)
+	if v == nil {
+		return nil
+	}
+	var im IPMask
+	if err := im.FromBytes(v); err != nil {
+		return nil
+	}
+	return net.IPMask(im)
+}
+
+// UserClass returns the user class if present.
+//
+// The user class information option is defined by RFC 3004.
+func (d *DHCPv4) UserClass() []string {
+	v := d.Options.Get(OptionUserClassInformation)
+	if v == nil {
+		return nil
+	}
+	var uc Strings
+	if err := uc.FromBytes(v); err != nil {
+		return []string{GetString(OptionUserClassInformation, d.Options)}
+	}
+	return uc
+}
+
+// VIVC returns the vendor-identifying vendor class option if present.
+func (d *DHCPv4) VIVC() VIVCIdentifiers {
+	v := d.Options.Get(OptionVendorIdentifyingVendorClass)
+	if v == nil {
+		return nil
+	}
+	var ids VIVCIdentifiers
+	if err := ids.FromBytes(v); err != nil {
+		return nil
+	}
+	return ids
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/modifiers.go

@@ -0,0 +1,176 @@
+package dhcpv4
+
+import (
+	"net"
+	"time"
+
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/insomniacslk/dhcp/rfc1035label"
+)
+
+// WithTransactionID sets the Transaction ID for the DHCPv4 packet
+func WithTransactionID(xid TransactionID) Modifier {
+	return func(d *DHCPv4) {
+		d.TransactionID = xid
+	}
+}
+
+// WithClientIP sets the Client IP for a DHCPv4 packet.
+func WithClientIP(ip net.IP) Modifier {
+	return func(d *DHCPv4) {
+		d.ClientIPAddr = ip
+	}
+}
+
+// WithYourIP sets the Your IP for a DHCPv4 packet.
+func WithYourIP(ip net.IP) Modifier {
+	return func(d *DHCPv4) {
+		d.YourIPAddr = ip
+	}
+}
+
+// WithServerIP sets the Server IP for a DHCPv4 packet.
+func WithServerIP(ip net.IP) Modifier {
+	return func(d *DHCPv4) {
+		d.ServerIPAddr = ip
+	}
+}
+
+// WithGatewayIP sets the Gateway IP for the DHCPv4 packet.
+func WithGatewayIP(ip net.IP) Modifier {
+	return func(d *DHCPv4) {
+		d.GatewayIPAddr = ip
+	}
+}
+
+// WithOptionCopied copies the value of option opt from request.
+func WithOptionCopied(request *DHCPv4, opt OptionCode) Modifier {
+	return func(d *DHCPv4) {
+		if val := request.Options.Get(opt); val != nil {
+			d.UpdateOption(OptGeneric(opt, val))
+		}
+	}
+}
+
+// WithReply fills in opcode, hwtype, xid, clienthwaddr, and flags from the given packet.
+func WithReply(request *DHCPv4) Modifier {
+	return func(d *DHCPv4) {
+		if request.OpCode == OpcodeBootRequest {
+			d.OpCode = OpcodeBootReply
+		} else {
+			d.OpCode = OpcodeBootRequest
+		}
+		d.HWType = request.HWType
+		d.TransactionID = request.TransactionID
+		d.ClientHWAddr = request.ClientHWAddr
+		d.Flags = request.Flags
+	}
+}
+
+// WithHWType sets the Hardware Type for a DHCPv4 packet.
+func WithHWType(hwt iana.HWType) Modifier {
+	return func(d *DHCPv4) {
+		d.HWType = hwt
+	}
+}
+
+// WithBroadcast sets the packet to be broadcast or unicast
+func WithBroadcast(broadcast bool) Modifier {
+	return func(d *DHCPv4) {
+		if broadcast {
+			d.SetBroadcast()
+		} else {
+			d.SetUnicast()
+		}
+	}
+}
+
+// WithHwAddr sets the hardware address for a packet
+func WithHwAddr(hwaddr net.HardwareAddr) Modifier {
+	return func(d *DHCPv4) {
+		d.ClientHWAddr = hwaddr
+	}
+}
+
+// WithOption appends a DHCPv4 option provided by the user
+func WithOption(opt Option) Modifier {
+	return func(d *DHCPv4) {
+		d.UpdateOption(opt)
+	}
+}
+
+// WithoutOption removes the DHCPv4 option with the given code
+func WithoutOption(code OptionCode) Modifier {
+	return func(d *DHCPv4) {
+		d.DeleteOption(code)
+	}
+}
+
+// WithUserClass adds a user class option to the packet.
+// The rfc parameter allows you to specify if the userclass should be
+// rfc compliant or not. More details in issue #113
+func WithUserClass(uc string, rfc bool) Modifier {
+	// TODO let the user specify multiple user classes
+	return func(d *DHCPv4) {
+		if rfc {
+			d.UpdateOption(OptRFC3004UserClass([]string{uc}))
+		} else {
+			d.UpdateOption(OptUserClass(uc))
+		}
+	}
+}
+
+// WithNetboot adds bootfile URL and bootfile param options to a DHCPv4 packet.
+func WithNetboot(d *DHCPv4) {
+	WithRequestedOptions(OptionTFTPServerName, OptionBootfileName)(d)
+}
+
+// WithMessageType adds the DHCPv4 message type m to a packet.
+func WithMessageType(m MessageType) Modifier {
+	return WithOption(OptMessageType(m))
+}
+
+// WithRequestedOptions adds requested options to the packet.
+func WithRequestedOptions(optionCodes ...OptionCode) Modifier {
+	return func(d *DHCPv4) {
+		cl := d.ParameterRequestList()
+		cl.Add(optionCodes...)
+		d.UpdateOption(OptParameterRequestList(cl...))
+	}
+}
+
+// WithRelay adds parameters required for DHCPv4 to be relayed by the relay
+// server with given ip
+func WithRelay(ip net.IP) Modifier {
+	return func(d *DHCPv4) {
+		d.SetUnicast()
+		d.GatewayIPAddr = ip
+		d.HopCount++
+	}
+}
+
+// WithNetmask adds or updates an OptSubnetMask
+func WithNetmask(mask net.IPMask) Modifier {
+	return WithOption(OptSubnetMask(mask))
+}
+
+// WithLeaseTime adds or updates an OptIPAddressLeaseTime
+func WithLeaseTime(leaseTime uint32) Modifier {
+	return WithOption(OptIPAddressLeaseTime(time.Duration(leaseTime) * time.Second))
+}
+
+// WithIPv6OnlyPreferred adds or updates an OptIPv6OnlyPreferred
+func WithIPv6OnlyPreferred(v6OnlyWait uint32) Modifier {
+	return WithOption(OptIPv6OnlyPreferred(time.Duration(v6OnlyWait) * time.Second))
+}
+
+// WithDomainSearchList adds or updates an OptionDomainSearch
+func WithDomainSearchList(searchList ...string) Modifier {
+	return WithOption(OptDomainSearch(&rfc1035label.Labels{
+		Labels: searchList,
+	}))
+}
+
+func WithGeneric(code OptionCode, value []byte) Modifier {
+	return WithOption(OptGeneric(code, value))
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/nclient4/client.go

@@ -0,0 +1,669 @@
+// Copyright 2018 the u-root Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.12
+
+// Package nclient4 is a small, minimum-functionality client for DHCPv4.
+//
+// It only supports the 4-way DHCPv4 Discover-Offer-Request-Ack handshake as
+// well as the Request-Ack renewal process.
+package nclient4
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+)
+
+const (
+	defaultBufferCap = 5
+
+	// DefaultTimeout is the default value for read-timeout if option WithTimeout is not set
+	DefaultTimeout = 5 * time.Second
+
+	// DefaultRetries is amount of retries will be done if no answer was received within read-timeout amount of time
+	DefaultRetries = 3
+
+	// MaxMessageSize is the value to be used for DHCP option "MaxMessageSize".
+	MaxMessageSize = 1500
+
+	// ClientPort is the port that DHCP clients listen on.
+	ClientPort = 68
+
+	// ServerPort is the port that DHCP servers and relay agents listen on.
+	ServerPort = 67
+)
+
+var (
+	// DefaultServers is the address of all link-local DHCP servers and
+	// relay agents.
+	DefaultServers = &net.UDPAddr{
+		IP:   net.IPv4bcast,
+		Port: ServerPort,
+	}
+)
+
+var (
+	// ErrNoResponse is returned when no response packet is received.
+	ErrNoResponse = errors.New("no matching response packet received")
+
+	// ErrNoConn is returned when NewWithConn is called with nil-value as conn.
+	ErrNoConn = errors.New("conn is nil")
+
+	// ErrNoIfaceHWAddr is returned when NewWithConn is called with nil-value as ifaceHWAddr
+	ErrNoIfaceHWAddr = errors.New("ifaceHWAddr is nil")
+)
+
+// pendingCh is a channel associated with a pending TransactionID.
+type pendingCh struct {
+	// SendAndRead closes done to indicate that it wishes for no more
+	// messages for this particular XID.
+	done <-chan struct{}
+
+	// ch is used by the receive loop to distribute DHCP messages.
+	ch chan<- *dhcpv4.DHCPv4
+}
+
+// Logger is a handler which will be used to output logging messages
+type Logger interface {
+	// PrintMessage print _all_ DHCP messages
+	PrintMessage(prefix string, message *dhcpv4.DHCPv4)
+
+	// Printf is use to print the rest debugging information
+	Printf(format string, v ...interface{})
+}
+
+// EmptyLogger prints nothing
+type EmptyLogger struct{}
+
+// Printf is just a dummy function that does nothing
+func (e EmptyLogger) Printf(format string, v ...interface{}) {}
+
+// PrintMessage is just a dummy function that does nothing
+func (e EmptyLogger) PrintMessage(prefix string, message *dhcpv4.DHCPv4) {}
+
+// Printfer is used for actual output of the logger. For example *log.Logger is a Printfer.
+type Printfer interface {
+	// Printf is the function for logging output. Arguments are handled in the manner of fmt.Printf.
+	Printf(format string, v ...interface{})
+}
+
+// ShortSummaryLogger is a wrapper for Printfer to implement interface Logger.
+// DHCP messages are printed in the short format.
+type ShortSummaryLogger struct {
+	// Printfer is used for actual output of the logger
+	Printfer
+}
+
+// Printf prints a log message as-is via predefined Printfer
+func (s ShortSummaryLogger) Printf(format string, v ...interface{}) {
+	s.Printfer.Printf(format, v...)
+}
+
+// PrintMessage prints a DHCP message in the short format via predefined Printfer
+func (s ShortSummaryLogger) PrintMessage(prefix string, message *dhcpv4.DHCPv4) {
+	s.Printf("%s: %s", prefix, message)
+}
+
+// DebugLogger is a wrapper for Printfer to implement interface Logger.
+// DHCP messages are printed in the long format.
+type DebugLogger struct {
+	// Printfer is used for actual output of the logger
+	Printfer
+}
+
+// Printf prints a log message as-is via predefined Printfer
+func (d DebugLogger) Printf(format string, v ...interface{}) {
+	d.Printfer.Printf(format, v...)
+}
+
+// PrintMessage prints a DHCP message in the long format via predefined Printfer
+func (d DebugLogger) PrintMessage(prefix string, message *dhcpv4.DHCPv4) {
+	d.Printf("%s: %s", prefix, message.Summary())
+}
+
+// Client is an IPv4 DHCP client.
+type Client struct {
+	ifaceHWAddr net.HardwareAddr
+	conn        net.PacketConn
+	timeout     time.Duration
+	retry       int
+	logger      Logger
+
+	// bufferCap is the channel capacity for each TransactionID.
+	bufferCap int
+
+	// serverAddr is the UDP address to send all packets to.
+	//
+	// This may be an actual broadcast address, or a unicast address.
+	serverAddr *net.UDPAddr
+
+	// closed is an atomic bool set to 1 when done is closed.
+	closed uint32
+
+	// done is closed to unblock the receive loop.
+	done chan struct{}
+
+	// wg protects any spawned goroutines, namely the receiveLoop.
+	wg sync.WaitGroup
+
+	pendingMu sync.Mutex
+	// pending stores the distribution channels for each pending
+	// TransactionID. receiveLoop uses this map to determine which channel
+	// to send a new DHCP message to.
+	pending map[dhcpv4.TransactionID]*pendingCh
+}
+
+// New returns a client usable with an unconfigured interface.
+func New(iface string, opts ...ClientOpt) (*Client, error) {
+	return new(iface, nil, nil, opts...)
+}
+
+// NewWithConn creates a new DHCP client that sends and receives packets on the
+// given interface.
+func NewWithConn(conn net.PacketConn, ifaceHWAddr net.HardwareAddr, opts ...ClientOpt) (*Client, error) {
+	return new(``, conn, ifaceHWAddr, opts...)
+}
+
+func new(iface string, conn net.PacketConn, ifaceHWAddr net.HardwareAddr, opts ...ClientOpt) (*Client, error) {
+	c := &Client{
+		ifaceHWAddr: ifaceHWAddr,
+		timeout:     DefaultTimeout,
+		retry:       DefaultRetries,
+		serverAddr:  DefaultServers,
+		bufferCap:   defaultBufferCap,
+		conn:        conn,
+		logger:      EmptyLogger{},
+
+		done:    make(chan struct{}),
+		pending: make(map[dhcpv4.TransactionID]*pendingCh),
+	}
+
+	for _, opt := range opts {
+		err := opt(c)
+		if err != nil {
+			return nil, fmt.Errorf("unable to apply option: %w", err)
+		}
+	}
+
+	if c.ifaceHWAddr == nil {
+		if iface == `` {
+			return nil, ErrNoIfaceHWAddr
+		}
+
+		i, err := net.InterfaceByName(iface)
+		if err != nil {
+			return nil, fmt.Errorf("unable to get interface information: %w", err)
+		}
+
+		c.ifaceHWAddr = i.HardwareAddr
+	}
+
+	if c.conn == nil {
+		var err error
+		if iface == `` {
+			return nil, ErrNoConn
+		}
+		c.conn, err = NewRawUDPConn(iface, ClientPort) // broadcast
+		if err != nil {
+			return nil, fmt.Errorf("unable to open a broadcasting socket: %w", err)
+		}
+	}
+	c.wg.Add(1)
+	go c.receiveLoop()
+	return c, nil
+}
+
+// Close closes the underlying connection.
+func (c *Client) Close() error {
+	// Make sure not to close done twice.
+	if !atomic.CompareAndSwapUint32(&c.closed, 0, 1) {
+		return nil
+	}
+
+	err := c.conn.Close()
+
+	// Closing c.done sets off a chain reaction:
+	//
+	// Any SendAndRead unblocks trying to receive more messages, which
+	// means rem() gets called.
+	//
+	// rem() should be unblocking receiveLoop if it is blocked.
+	//
+	// receiveLoop should then exit gracefully.
+	close(c.done)
+
+	// Wait for receiveLoop to stop.
+	c.wg.Wait()
+
+	return err
+}
+
+func (c *Client) isClosed() bool {
+	return atomic.LoadUint32(&c.closed) != 0
+}
+
+func (c *Client) receiveLoop() {
+	defer c.wg.Done()
+	for {
+		// TODO: Clients can send a "max packet size" option in their
+		// packets, IIRC. Choose a reasonable size and set it.
+		b := make([]byte, MaxMessageSize)
+		n, _, err := c.conn.ReadFrom(b)
+		if err != nil {
+			if !c.isClosed() {
+				c.logger.Printf("error reading from UDP connection: %v", err)
+			}
+			return
+		}
+
+		msg, err := dhcpv4.FromBytes(b[:n])
+		if err != nil {
+			// Not a valid DHCP packet; keep listening.
+			continue
+		}
+
+		if msg.OpCode != dhcpv4.OpcodeBootReply {
+			// Not a response message.
+			continue
+		}
+
+		// This is a somewhat non-standard check, by the looks
+		// of RFC 2131. It should work as long as the DHCP
+		// server is spec-compliant for the HWAddr field.
+		if c.ifaceHWAddr != nil && !bytes.Equal(c.ifaceHWAddr, msg.ClientHWAddr) {
+			// Not for us.
+			continue
+		}
+
+		c.pendingMu.Lock()
+		p, ok := c.pending[msg.TransactionID]
+		if ok {
+			select {
+			case <-p.done:
+				close(p.ch)
+				delete(c.pending, msg.TransactionID)
+
+			// This send may block.
+			case p.ch <- msg:
+			}
+		}
+		c.pendingMu.Unlock()
+	}
+}
+
+// ClientOpt is a function that configures the Client.
+type ClientOpt func(c *Client) error
+
+// WithTimeout configures the retransmission timeout.
+//
+// Default is 5 seconds.
+func WithTimeout(d time.Duration) ClientOpt {
+	return func(c *Client) (err error) {
+		c.timeout = d
+		return
+	}
+}
+
+// WithSummaryLogger logs one-line DHCPv4 message summaries when sent & received.
+func WithSummaryLogger() ClientOpt {
+	return func(c *Client) (err error) {
+		c.logger = ShortSummaryLogger{
+			Printfer: log.New(os.Stderr, "[dhcpv4] ", log.LstdFlags),
+		}
+		return
+	}
+}
+
+// WithDebugLogger logs multi-line full DHCPv4 messages when sent & received.
+func WithDebugLogger() ClientOpt {
+	return func(c *Client) (err error) {
+		c.logger = DebugLogger{
+			Printfer: log.New(os.Stderr, "[dhcpv4] ", log.LstdFlags),
+		}
+		return
+	}
+}
+
+// WithLogger set the logger (see interface Logger).
+func WithLogger(newLogger Logger) ClientOpt {
+	return func(c *Client) (err error) {
+		c.logger = newLogger
+		return
+	}
+}
+
+// WithUnicast forces client to send messages as unicast frames.
+// By default client sends messages as broadcast frames even if server address is defined.
+//
+// srcAddr is both:
+// * The source address of outgoing frames.
+// * The address to be listened for incoming frames.
+func WithUnicast(srcAddr *net.UDPAddr) ClientOpt {
+	return func(c *Client) (err error) {
+		if srcAddr == nil {
+			srcAddr = &net.UDPAddr{Port: ClientPort}
+		}
+		c.conn, err = net.ListenUDP("udp4", srcAddr)
+		if err != nil {
+			err = fmt.Errorf("unable to start listening UDP port: %w", err)
+		}
+		return
+	}
+}
+
+// WithHWAddr tells to the Client to receive messages destinated to selected
+// hardware address
+func WithHWAddr(hwAddr net.HardwareAddr) ClientOpt {
+	return func(c *Client) (err error) {
+		c.ifaceHWAddr = hwAddr
+		return
+	}
+}
+
+func withBufferCap(n int) ClientOpt {
+	return func(c *Client) (err error) {
+		c.bufferCap = n
+		return
+	}
+}
+
+// WithRetry configures the number of retransmissions to attempt.
+//
+// Default is 3.
+func WithRetry(r int) ClientOpt {
+	return func(c *Client) (err error) {
+		c.retry = r
+		return
+	}
+}
+
+// WithServerAddr configures the address to send messages to.
+func WithServerAddr(n *net.UDPAddr) ClientOpt {
+	return func(c *Client) (err error) {
+		c.serverAddr = n
+		return
+	}
+}
+
+// Matcher matches DHCP packets.
+type Matcher func(*dhcpv4.DHCPv4) bool
+
+// IsMessageType returns a matcher that checks for the message types.
+func IsMessageType(t dhcpv4.MessageType, tt ...dhcpv4.MessageType) Matcher {
+	return func(p *dhcpv4.DHCPv4) bool {
+		if p.MessageType() == t {
+			return true
+		}
+		for _, mt := range tt {
+			if p.MessageType() == mt {
+				return true
+			}
+		}
+		return false
+	}
+}
+
+// IsCorrectServer returns a matcher that checks for the correct ServerAddress.
+func IsCorrectServer(s net.IP) Matcher {
+	return func(p *dhcpv4.DHCPv4) bool {
+		return p.ServerIdentifier().Equal(s)
+	}
+}
+
+// IsAll returns a matcher that checks for all given matchers to be true.
+func IsAll(ms ...Matcher) Matcher {
+	return func(p *dhcpv4.DHCPv4) bool {
+		for _, m := range ms {
+			if !m(p) {
+				return false
+			}
+		}
+		return true
+	}
+}
+
+// RemoteAddr is the default DHCP server address this client sends messages to.
+func (c *Client) RemoteAddr() *net.UDPAddr {
+	// Make a copy so the caller cannot modify the address once the client
+	// is running.
+	cop := *c.serverAddr
+	return &cop
+}
+
+// InterfaceAddr returns the MAC address of the client's interface.
+func (c *Client) InterfaceAddr() net.HardwareAddr {
+	b := make(net.HardwareAddr, len(c.ifaceHWAddr))
+	copy(b, c.ifaceHWAddr)
+	return b
+}
+
+// DiscoverOffer sends a DHCPDiscover message and returns the first valid offer
+// received.
+func (c *Client) DiscoverOffer(ctx context.Context, modifiers ...dhcpv4.Modifier) (offer *dhcpv4.DHCPv4, err error) {
+	// RFC 2131, Section 4.4.1, Table 5 details what a DISCOVER packet should
+	// contain.
+	discover, err := dhcpv4.NewDiscovery(c.ifaceHWAddr, dhcpv4.PrependModifiers(modifiers,
+		dhcpv4.WithOption(dhcpv4.OptMaxMessageSize(MaxMessageSize)))...)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create a discovery request: %w", err)
+	}
+
+	offer, err = c.SendAndRead(ctx, c.serverAddr, discover, IsMessageType(dhcpv4.MessageTypeOffer))
+	if err != nil {
+		return nil, fmt.Errorf("got an error while the discovery request: %w", err)
+	}
+	return offer, nil
+}
+
+// Request completes the 4-way Discover-Offer-Request-Ack handshake.
+//
+// Note that modifiers will be applied *both* to Discover and Request packets.
+func (c *Client) Request(ctx context.Context, modifiers ...dhcpv4.Modifier) (lease *Lease, err error) {
+	offer, err := c.DiscoverOffer(ctx, modifiers...)
+	if err != nil {
+		err = fmt.Errorf("unable to receive an offer: %w", err)
+		return
+	}
+	return c.RequestFromOffer(ctx, offer, modifiers...)
+}
+
+// Inform sends an INFORM request using the given local IP.
+// Returns the ACK response from the server on success.
+func (c *Client) Inform(ctx context.Context, localIP net.IP, modifiers ...dhcpv4.Modifier) (*dhcpv4.DHCPv4, error) {
+	request, err := dhcpv4.NewInform(c.ifaceHWAddr, localIP, modifiers...)
+	if err != nil {
+		return nil, err
+	}
+
+	// DHCP clients must not fill in the server identifier in an INFORM request as per RFC 2131 Section 4.4.1 Table 5,
+	// however, they may still unicast the request to the target server if the address is known (c.serverAddr), as per
+	// Section 4.4.3. The server must then respond with an ACK, as per Section 4.3.5.
+	response, err := c.SendAndRead(ctx, c.serverAddr, request, IsMessageType(dhcpv4.MessageTypeAck))
+	if err != nil {
+		return nil, fmt.Errorf("got an error while processing the request: %w", err)
+	}
+
+	return response, nil
+}
+
+// ErrNak is returned if a DHCP server rejected our Request.
+type ErrNak struct {
+	Offer *dhcpv4.DHCPv4
+	Nak   *dhcpv4.DHCPv4
+}
+
+// Error implements error.Error.
+func (e *ErrNak) Error() string {
+	if msg := e.Nak.Message(); len(msg) > 0 {
+		return fmt.Sprintf("server rejected request with Nak (msg: %s)", msg)
+	}
+	return "server rejected request with Nak"
+}
+
+// RequestFromOffer sends a Request message and waits for an response.
+// It assumes the SELECTING state by default, see Section 4.3.2 in RFC 2131 for more details.
+func (c *Client) RequestFromOffer(ctx context.Context, offer *dhcpv4.DHCPv4, modifiers ...dhcpv4.Modifier) (*Lease, error) {
+	// TODO(chrisko): should this be unicast to the server?
+	request, err := dhcpv4.NewRequestFromOffer(offer, dhcpv4.PrependModifiers(modifiers,
+		dhcpv4.WithOption(dhcpv4.OptMaxMessageSize(MaxMessageSize)))...)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create a request: %w", err)
+	}
+
+	// Servers are supposed to only respond to Requests containing their server identifier,
+	// but sometimes non-compliant servers respond anyway.
+	// Clients are not required to validate this field, but servers are required to
+	// include the server identifier in their Offer per RFC 2131 Section 4.3.1 Table 3.
+	response, err := c.SendAndRead(ctx, c.serverAddr, request, IsAll(
+		IsCorrectServer(offer.ServerIdentifier()),
+		IsMessageType(dhcpv4.MessageTypeAck, dhcpv4.MessageTypeNak)))
+	if err != nil {
+		return nil, fmt.Errorf("got an error while processing the request: %w", err)
+	}
+	if response.MessageType() == dhcpv4.MessageTypeNak {
+		return nil, &ErrNak{
+			Offer: offer,
+			Nak:   response,
+		}
+	}
+	lease := &Lease{}
+	lease.ACK = response
+	lease.Offer = offer
+	lease.CreationTime = time.Now()
+	return lease, nil
+}
+
+// ErrTransactionIDInUse is returned if there were an attempt to send a message
+// with the same TransactionID as we are already waiting an answer for.
+type ErrTransactionIDInUse struct {
+	// TransactionID is the transaction ID of the message which the error is related to.
+	TransactionID dhcpv4.TransactionID
+}
+
+// Error is just the method to comply interface "error".
+func (err *ErrTransactionIDInUse) Error() string {
+	return fmt.Sprintf("transaction ID %s already in use", err.TransactionID)
+}
+
+// send sends p to destination and returns a response channel.
+//
+// Responses will be matched by transaction ID and ClientHWAddr.
+//
+// The returned lambda function must be called after all desired responses have
+// been received in order to return the Transaction ID to the usable pool.
+func (c *Client) send(dest *net.UDPAddr, msg *dhcpv4.DHCPv4) (resp <-chan *dhcpv4.DHCPv4, cancel func(), err error) {
+	c.pendingMu.Lock()
+	if _, ok := c.pending[msg.TransactionID]; ok {
+		c.pendingMu.Unlock()
+		return nil, nil, &ErrTransactionIDInUse{msg.TransactionID}
+	}
+
+	ch := make(chan *dhcpv4.DHCPv4, c.bufferCap)
+	done := make(chan struct{})
+	c.pending[msg.TransactionID] = &pendingCh{done: done, ch: ch}
+	c.pendingMu.Unlock()
+
+	cancel = func() {
+		// Why can't we just close ch here?
+		//
+		// Because receiveLoop may potentially be blocked trying to
+		// send on ch. We gotta unblock it first, and then we can take
+		// the lock and remove the XID from the pending transaction
+		// map.
+		close(done)
+
+		c.pendingMu.Lock()
+		if p, ok := c.pending[msg.TransactionID]; ok {
+			close(p.ch)
+			delete(c.pending, msg.TransactionID)
+		}
+		c.pendingMu.Unlock()
+	}
+
+	if _, err := c.conn.WriteTo(msg.ToBytes(), dest); err != nil {
+		cancel()
+		return nil, nil, fmt.Errorf("error writing packet to connection: %w", err)
+	}
+	return ch, cancel, nil
+}
+
+// This error should never be visible to users.
+// It is used only to increase the timeout in retryFn.
+var errDeadlineExceeded = errors.New("INTERNAL ERROR: deadline exceeded")
+
+// SendAndRead sends a packet p to a destination dest and waits for the first
+// response matching `match` as well as its Transaction ID and ClientHWAddr.
+//
+// If match is nil, the first packet matching the Transaction ID and
+// ClientHWAddr is returned.
+func (c *Client) SendAndRead(ctx context.Context, dest *net.UDPAddr, p *dhcpv4.DHCPv4, match Matcher) (*dhcpv4.DHCPv4, error) {
+	var response *dhcpv4.DHCPv4
+	err := c.retryFn(func(timeout time.Duration) error {
+		ch, rem, err := c.send(dest, p)
+		if err != nil {
+			return err
+		}
+		c.logger.PrintMessage("sent message", p)
+		defer rem()
+
+		for {
+			select {
+			case <-c.done:
+				return ErrNoResponse
+
+			case <-time.After(timeout):
+				return errDeadlineExceeded
+
+			case <-ctx.Done():
+				return ctx.Err()
+
+			case packet := <-ch:
+				if match == nil || match(packet) {
+					c.logger.PrintMessage("received message", packet)
+					response = packet
+					return nil
+				}
+			}
+		}
+	})
+	if err == errDeadlineExceeded {
+		return nil, ErrNoResponse
+	}
+	if err != nil {
+		return nil, err
+	}
+	return response, nil
+}
+
+func (c *Client) retryFn(fn func(timeout time.Duration) error) error {
+	timeout := c.timeout
+
+	// Each retry takes the amount of timeout at worst.
+	for i := 0; i < c.retry || c.retry < 0; i++ { // TODO: why is this called "retry" if this is "tries" ("retries"+1)?
+		switch err := fn(timeout); err {
+		case nil:
+			// Got it!
+			return nil
+
+		case errDeadlineExceeded:
+			// Double timeout, then retry.
+			timeout *= 2
+
+		default:
+			return err
+		}
+	}
+
+	return errDeadlineExceeded
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/nclient4/conn_unix.go

@@ -0,0 +1,154 @@
+// Copyright 2018 the u-root Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.12 && (darwin || freebsd || linux || netbsd || openbsd || dragonfly)
+// +build go1.12
+// +build darwin freebsd linux netbsd openbsd dragonfly
+
+package nclient4
+
+import (
+	"errors"
+	"io"
+	"net"
+
+	"github.com/mdlayher/packet"
+	"github.com/u-root/uio/uio"
+	"golang.org/x/sys/unix"
+)
+
+var (
+	// BroadcastMac is the broadcast MAC address.
+	//
+	// Any UDP packet sent to this address is broadcast on the subnet.
+	BroadcastMac = net.HardwareAddr([]byte{255, 255, 255, 255, 255, 255})
+)
+
+var (
+	// ErrUDPAddrIsRequired is an error used when a passed argument is not of type "*net.UDPAddr".
+	ErrUDPAddrIsRequired = errors.New("must supply UDPAddr")
+)
+
+// NewRawUDPConn returns a UDP connection bound to the interface and port
+// given based on a raw packet socket. All packets are broadcasted.
+//
+// The interface can be completely unconfigured.
+func NewRawUDPConn(iface string, port int) (net.PacketConn, error) {
+	ifc, err := net.InterfaceByName(iface)
+	if err != nil {
+		return nil, err
+	}
+	rawConn, err := packet.Listen(ifc, packet.Datagram, unix.ETH_P_IP, nil)
+	if err != nil {
+		return nil, err
+	}
+	return NewBroadcastUDPConn(rawConn, &net.UDPAddr{Port: port}), nil
+}
+
+// BroadcastRawUDPConn uses a raw socket to send UDP packets to the broadcast
+// MAC address.
+type BroadcastRawUDPConn struct {
+	// PacketConn is a raw DGRAM socket.
+	net.PacketConn
+
+	// boundAddr is the address this RawUDPConn is "bound" to.
+	//
+	// Calls to ReadFrom will only return packets destined to this address.
+	boundAddr *net.UDPAddr
+}
+
+// NewBroadcastUDPConn returns a PacketConn that marshals and unmarshals UDP
+// packets, sending them to the broadcast MAC at on rawPacketConn.
+//
+// Calls to ReadFrom will only return packets destined to boundAddr.
+func NewBroadcastUDPConn(rawPacketConn net.PacketConn, boundAddr *net.UDPAddr) net.PacketConn {
+	return &BroadcastRawUDPConn{
+		PacketConn: rawPacketConn,
+		boundAddr:  boundAddr,
+	}
+}
+
+func udpMatch(addr *net.UDPAddr, bound *net.UDPAddr) bool {
+	if bound == nil {
+		return true
+	}
+	if bound.IP != nil && !bound.IP.Equal(addr.IP) {
+		return false
+	}
+	return bound.Port == addr.Port
+}
+
+// ReadFrom implements net.PacketConn.ReadFrom.
+//
+// ReadFrom reads raw IP packets and will try to match them against
+// upc.boundAddr. Any matching packets are returned via the given buffer.
+func (upc *BroadcastRawUDPConn) ReadFrom(b []byte) (int, net.Addr, error) {
+	ipHdrMaxLen := ipv4MaximumHeaderSize
+	udpHdrLen := udpMinimumSize
+
+	for {
+		pkt := make([]byte, ipHdrMaxLen+udpHdrLen+len(b))
+		n, _, err := upc.PacketConn.ReadFrom(pkt)
+		if err != nil {
+			return 0, nil, err
+		}
+		if n == 0 {
+			return 0, nil, io.EOF
+		}
+		pkt = pkt[:n]
+		buf := uio.NewBigEndianBuffer(pkt)
+
+		ipHdr := ipv4(buf.Data())
+
+		if !ipHdr.isValid(n) {
+			continue
+		}
+
+		ipHdr = ipv4(buf.Consume(int(ipHdr.headerLength())))
+
+		if ipHdr.transportProtocol() != udpProtocolNumber {
+			continue
+		}
+
+		if !buf.Has(udpHdrLen) {
+			continue
+		}
+
+		udpHdr := udp(buf.Consume(udpHdrLen))
+
+		addr := &net.UDPAddr{
+			IP:   ipHdr.destinationAddress(),
+			Port: int(udpHdr.destinationPort()),
+		}
+		if !udpMatch(addr, upc.boundAddr) {
+			continue
+		}
+		srcAddr := &net.UDPAddr{
+			IP:   ipHdr.sourceAddress(),
+			Port: int(udpHdr.sourcePort()),
+		}
+		// Extra padding after end of IP packet should be ignored,
+		// if not dhcp option parsing will fail.
+		dhcpLen := int(ipHdr.payloadLength()) - udpHdrLen
+		return copy(b, buf.Consume(dhcpLen)), srcAddr, nil
+	}
+}
+
+// WriteTo implements net.PacketConn.WriteTo and broadcasts all packets at the
+// raw socket level.
+//
+// WriteTo wraps the given packet in the appropriate UDP and IP header before
+// sending it on the packet conn.
+func (upc *BroadcastRawUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
+	udpAddr, ok := addr.(*net.UDPAddr)
+	if !ok {
+		return 0, ErrUDPAddrIsRequired
+	}
+
+	// Using the boundAddr is not quite right here, but it works.
+	pkt := udp4pkt(b, udpAddr, upc.boundAddr)
+
+	// Broadcasting is not always right, but hell, what the ARP do I know.
+	return upc.PacketConn.WriteTo(pkt, &packet.Addr{HardwareAddr: BroadcastMac})
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/nclient4/ipv4.go

@@ -0,0 +1,360 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// This file contains code taken from gVisor.
+
+//go:build go1.12
+// +build go1.12
+
+package nclient4
+
+import (
+	"encoding/binary"
+	"net"
+
+	"github.com/u-root/uio/uio"
+)
+
+const (
+	versIHL     = 0
+	tos         = 1
+	totalLen    = 2
+	id          = 4
+	flagsFO     = 6
+	ttl         = 8
+	protocol    = 9
+	checksumOff = 10
+	srcAddr     = 12
+	dstAddr     = 16
+)
+
+// transportProtocolNumber is the number of a transport protocol.
+type transportProtocolNumber uint32
+
+// ipv4Fields contains the fields of an IPv4 packet. It is used to describe the
+// fields of a packet that needs to be encoded.
+type ipv4Fields struct {
+	// IHL is the "internet header length" field of an IPv4 packet.
+	IHL uint8
+
+	// TOS is the "type of service" field of an IPv4 packet.
+	TOS uint8
+
+	// TotalLength is the "total length" field of an IPv4 packet.
+	TotalLength uint16
+
+	// ID is the "identification" field of an IPv4 packet.
+	ID uint16
+
+	// Flags is the "flags" field of an IPv4 packet.
+	Flags uint8
+
+	// FragmentOffset is the "fragment offset" field of an IPv4 packet.
+	FragmentOffset uint16
+
+	// TTL is the "time to live" field of an IPv4 packet.
+	TTL uint8
+
+	// Protocol is the "protocol" field of an IPv4 packet.
+	Protocol uint8
+
+	// checksum is the "checksum" field of an IPv4 packet.
+	checksum uint16
+
+	// SrcAddr is the "source ip address" of an IPv4 packet.
+	SrcAddr net.IP
+
+	// DstAddr is the "destination ip address" of an IPv4 packet.
+	DstAddr net.IP
+}
+
+// ipv4 represents an ipv4 header stored in a byte array.
+// Most of the methods of IPv4 access to the underlying slice without
+// checking the boundaries and could panic because of 'index out of range'.
+// Always call IsValid() to validate an instance of IPv4 before using other methods.
+type ipv4 []byte
+
+const (
+	// ipv4MinimumSize is the minimum size of a valid IPv4 packet.
+	ipv4MinimumSize = 20
+
+	// ipv4MaximumHeaderSize is the maximum size of an IPv4 header. Given
+	// that there are only 4 bits to represents the header length in 32-bit
+	// units, the header cannot exceed 15*4 = 60 bytes.
+	ipv4MaximumHeaderSize = 60
+
+	// ipv4AddressSize is the size, in bytes, of an IPv4 address.
+	ipv4AddressSize = 4
+
+	// IPv4Version is the version of the IPv4 protocol.
+	ipv4Version = 4
+)
+
+// ipVersion returns the version of IP used in the given packet. It returns -1
+// if the packet is not large enough to contain the version field.
+func ipVersion(b []byte) int {
+	// Length must be at least offset+length of version field.
+	if len(b) < versIHL+1 {
+		return -1
+	}
+	return int(b[versIHL] >> ipVersionShift)
+}
+
+const (
+	ipVersionShift = 4
+)
+
+// headerLength returns the value of the "header length" field of the ipv4
+// header.
+func (b ipv4) headerLength() uint8 {
+	return (b[versIHL] & 0xf) * 4
+}
+
+// protocol returns the value of the protocol field of the ipv4 header.
+func (b ipv4) protocol() uint8 {
+	return b[protocol]
+}
+
+// sourceAddress returns the "source address" field of the ipv4 header.
+func (b ipv4) sourceAddress() net.IP {
+	return net.IP(b[srcAddr : srcAddr+ipv4AddressSize])
+}
+
+// destinationAddress returns the "destination address" field of the ipv4
+// header.
+func (b ipv4) destinationAddress() net.IP {
+	return net.IP(b[dstAddr : dstAddr+ipv4AddressSize])
+}
+
+// transportProtocol implements Network.transportProtocol.
+func (b ipv4) transportProtocol() transportProtocolNumber {
+	return transportProtocolNumber(b.protocol())
+}
+
+// payloadLength returns the length of the payload portion of the ipv4 packet.
+func (b ipv4) payloadLength() uint16 {
+	return b.totalLength() - uint16(b.headerLength())
+}
+
+// totalLength returns the "total length" field of the ipv4 header.
+func (b ipv4) totalLength() uint16 {
+	return binary.BigEndian.Uint16(b[totalLen:])
+}
+
+// setTotalLength sets the "total length" field of the ipv4 header.
+func (b ipv4) setTotalLength(totalLength uint16) {
+	binary.BigEndian.PutUint16(b[totalLen:], totalLength)
+}
+
+// setChecksum sets the checksum field of the ipv4 header.
+func (b ipv4) setChecksum(v uint16) {
+	binary.BigEndian.PutUint16(b[checksumOff:], v)
+}
+
+// setFlagsFragmentOffset sets the "flags" and "fragment offset" fields of the
+// ipv4 header.
+func (b ipv4) setFlagsFragmentOffset(flags uint8, offset uint16) {
+	v := (uint16(flags) << 13) | (offset >> 3)
+	binary.BigEndian.PutUint16(b[flagsFO:], v)
+}
+
+// calculateChecksum calculates the checksum of the ipv4 header.
+func (b ipv4) calculateChecksum() uint16 {
+	return checksum(b[:b.headerLength()], 0)
+}
+
+// encode encodes all the fields of the ipv4 header.
+func (b ipv4) encode(i *ipv4Fields) {
+	b[versIHL] = (4 << 4) | ((i.IHL / 4) & 0xf)
+	b[tos] = i.TOS
+	b.setTotalLength(i.TotalLength)
+	binary.BigEndian.PutUint16(b[id:], i.ID)
+	b.setFlagsFragmentOffset(i.Flags, i.FragmentOffset)
+	b[ttl] = i.TTL
+	b[protocol] = i.Protocol
+	b.setChecksum(i.checksum)
+	copy(b[srcAddr:srcAddr+ipv4AddressSize], i.SrcAddr)
+	copy(b[dstAddr:dstAddr+ipv4AddressSize], i.DstAddr)
+}
+
+// isValid performs basic validation on the packet.
+func (b ipv4) isValid(pktSize int) bool {
+	if len(b) < ipv4MinimumSize {
+		return false
+	}
+
+	hlen := int(b.headerLength())
+	tlen := int(b.totalLength())
+	if hlen < ipv4MinimumSize || hlen > tlen || tlen > pktSize {
+		return false
+	}
+
+	if ipVersion(b) != ipv4Version {
+		return false
+	}
+
+	return true
+}
+
+const (
+	udpSrcPort  = 0
+	udpDstPort  = 2
+	udpLength   = 4
+	udpchecksum = 6
+)
+
+// udpFields contains the fields of a udp packet. It is used to describe the
+// fields of a packet that needs to be encoded.
+type udpFields struct {
+	// SrcPort is the "source port" field of a udp packet.
+	SrcPort uint16
+
+	// DstPort is the "destination port" field of a UDP packet.
+	DstPort uint16
+
+	// Length is the "length" field of a UDP packet.
+	Length uint16
+
+	// checksum is the "checksum" field of a UDP packet.
+	checksum uint16
+}
+
+// udp represents a udp header stored in a byte array.
+type udp []byte
+
+const (
+	// udpMinimumSize is the minimum size of a valid udp packet.
+	udpMinimumSize = 8
+
+	// udpProtocolNumber is udp's transport protocol number.
+	udpProtocolNumber transportProtocolNumber = 17
+)
+
+// sourcePort returns the "source port" field of the udp header.
+func (b udp) sourcePort() uint16 {
+	return binary.BigEndian.Uint16(b[udpSrcPort:])
+}
+
+// DestinationPort returns the "destination port" field of the udp header.
+func (b udp) destinationPort() uint16 {
+	return binary.BigEndian.Uint16(b[udpDstPort:])
+}
+
+// Length returns the "length" field of the udp header.
+func (b udp) length() uint16 {
+	return binary.BigEndian.Uint16(b[udpLength:])
+}
+
+// setChecksum sets the "checksum" field of the udp header.
+func (b udp) setChecksum(checksum uint16) {
+	binary.BigEndian.PutUint16(b[udpchecksum:], checksum)
+}
+
+// calculateChecksum calculates the checksum of the udp packet, given the total
+// length of the packet and the checksum of the network-layer pseudo-header
+// (excluding the total length) and the checksum of the payload.
+func (b udp) calculateChecksum(partialchecksum uint16, totalLen uint16) uint16 {
+	// Add the length portion of the checksum to the pseudo-checksum.
+	tmp := make([]byte, 2)
+	binary.BigEndian.PutUint16(tmp, totalLen)
+	xsum := checksum(tmp, partialchecksum)
+
+	// Calculate the rest of the checksum.
+	return checksum(b[:udpMinimumSize], xsum)
+}
+
+// encode encodes all the fields of the udp header.
+func (b udp) encode(u *udpFields) {
+	binary.BigEndian.PutUint16(b[udpSrcPort:], u.SrcPort)
+	binary.BigEndian.PutUint16(b[udpDstPort:], u.DstPort)
+	binary.BigEndian.PutUint16(b[udpLength:], u.Length)
+	binary.BigEndian.PutUint16(b[udpchecksum:], u.checksum)
+}
+
+func calculateChecksum(buf []byte, initial uint32) uint16 {
+	v := initial
+
+	l := len(buf)
+	if l&1 != 0 {
+		l--
+		v += uint32(buf[l]) << 8
+	}
+
+	for i := 0; i < l; i += 2 {
+		v += (uint32(buf[i]) << 8) + uint32(buf[i+1])
+	}
+
+	return checksumCombine(uint16(v), uint16(v>>16))
+}
+
+// checksum calculates the checksum (as defined in RFC 1071) of the bytes in the
+// given byte array.
+//
+// The initial checksum must have been computed on an even number of bytes.
+func checksum(buf []byte, initial uint16) uint16 {
+	return calculateChecksum(buf, uint32(initial))
+}
+
+// checksumCombine combines the two uint16 to form their checksum. This is done
+// by adding them and the carry.
+//
+// Note that checksum a must have been computed on an even number of bytes.
+func checksumCombine(a, b uint16) uint16 {
+	v := uint32(a) + uint32(b)
+	return uint16(v + v>>16)
+}
+
+// pseudoHeaderchecksum calculates the pseudo-header checksum for the
+// given destination protocol and network address, ignoring the length
+// field. pseudo-headers are needed by transport layers when calculating
+// their own checksum.
+func pseudoHeaderchecksum(protocol transportProtocolNumber, srcAddr net.IP, dstAddr net.IP) uint16 {
+	xsum := checksum([]byte(srcAddr), 0)
+	xsum = checksum([]byte(dstAddr), xsum)
+	return checksum([]byte{0, uint8(protocol)}, xsum)
+}
+
+func udp4pkt(packet []byte, dest *net.UDPAddr, src *net.UDPAddr) []byte {
+	ipLen := ipv4MinimumSize
+	udpLen := udpMinimumSize
+
+	h := make([]byte, 0, ipLen+udpLen+len(packet))
+	hdr := uio.NewBigEndianBuffer(h)
+
+	ipv4fields := &ipv4Fields{
+		IHL:         ipv4MinimumSize,
+		TotalLength: uint16(ipLen + udpLen + len(packet)),
+		TTL:         64, // Per RFC 1700's recommendation for IP time to live
+		Protocol:    uint8(udpProtocolNumber),
+		SrcAddr:     src.IP.To4(),
+		DstAddr:     dest.IP.To4(),
+	}
+	ipv4hdr := ipv4(hdr.WriteN(ipLen))
+	ipv4hdr.encode(ipv4fields)
+	ipv4hdr.setChecksum(^ipv4hdr.calculateChecksum())
+
+	udphdr := udp(hdr.WriteN(udpLen))
+	udphdr.encode(&udpFields{
+		SrcPort: uint16(src.Port),
+		DstPort: uint16(dest.Port),
+		Length:  uint16(udpLen + len(packet)),
+	})
+
+	xsum := checksum(packet, pseudoHeaderchecksum(
+		ipv4hdr.transportProtocol(), ipv4fields.SrcAddr, ipv4fields.DstAddr))
+	udphdr.setChecksum(^udphdr.calculateChecksum(xsum, udphdr.length()))
+
+	hdr.WriteBytes(packet)
+	return hdr.Data()
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/nclient4/lease.go

@@ -0,0 +1,79 @@
+// This is lease support for nclient4
+
+package nclient4
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+)
+
+// Lease contains a DHCPv4 lease after DORA.
+// note: Lease doesn't include binding interface name
+type Lease struct {
+	Offer        *dhcpv4.DHCPv4
+	ACK          *dhcpv4.DHCPv4
+	CreationTime time.Time
+}
+
+// Release send DHCPv4 release messsage to server, based on specified lease.
+// release is sent as unicast per RFC2131, section 4.4.4.
+// Note: some DHCP server requries of using assigned IP address as source IP,
+// use nclient4.WithUnicast to create client for such case.
+func (c *Client) Release(lease *Lease, modifiers ...dhcpv4.Modifier) error {
+	if lease == nil {
+		return fmt.Errorf("lease is nil")
+	}
+	req, err := dhcpv4.NewReleaseFromACK(lease.ACK, modifiers...)
+	if err != nil {
+		return fmt.Errorf("fail to create release request,%w", err)
+	}
+	_, err = c.conn.WriteTo(req.ToBytes(), &net.UDPAddr{IP: lease.ACK.Options.Get(dhcpv4.OptionServerIdentifier), Port: ServerPort})
+	if err == nil {
+		c.logger.PrintMessage("sent message:", req)
+	}
+	return err
+}
+
+// Renew sends a DHCPv4 request to the server to renew the given lease. The renewal information is
+// sourced from the initial offer in the lease, and the ACK of the lease is updated to the ACK of
+// the latest renewal. This avoids issues with DHCP servers that omit information needed to build a
+// completely new lease from their renewal ACK (such as the Windows DHCP Server).
+func (c *Client) Renew(ctx context.Context, lease *Lease, modifiers ...dhcpv4.Modifier) (*Lease, error) {
+	if lease == nil {
+		return nil, fmt.Errorf("lease is nil")
+	}
+
+	request, err := dhcpv4.NewRenewFromAck(lease.ACK, dhcpv4.PrependModifiers(modifiers,
+		dhcpv4.WithOption(dhcpv4.OptMaxMessageSize(MaxMessageSize)))...)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create a request: %w", err)
+	}
+
+	// Servers are supposed to only respond to Requests containing their server identifier,
+	// but sometimes non-compliant servers respond anyway.
+	// Clients are not required to validate this field, but servers are required to
+	// include the server identifier in their Offer per RFC 2131 Section 4.3.1 Table 3.
+	response, err := c.SendAndRead(ctx, c.serverAddr, request, IsAll(
+		IsCorrectServer(lease.Offer.ServerIdentifier()),
+		IsMessageType(dhcpv4.MessageTypeAck, dhcpv4.MessageTypeNak)))
+	if err != nil {
+		return nil, fmt.Errorf("got an error while processing the request: %w", err)
+	}
+	if response.MessageType() == dhcpv4.MessageTypeNak {
+		return nil, &ErrNak{
+			Offer: lease.Offer,
+			Nak:   response,
+		}
+	}
+
+	// Return a new lease with the latest ACK and updated creation time
+	return &Lease{
+		Offer:        lease.Offer,
+		ACK:          response,
+		CreationTime: time.Now(),
+	}, nil
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_autoconfigure.go

@@ -0,0 +1,61 @@
+package dhcpv4
+
+import (
+	"fmt"
+)
+
+// AutoConfiguration implements encoding and decoding functions for a
+// byte enumeration as used in RFC 2563, Section 2.
+type AutoConfiguration byte
+
+const (
+	DoNotAutoConfigure AutoConfiguration = 0
+	AutoConfigure      AutoConfiguration = 1
+)
+
+var autoConfigureToString = map[AutoConfiguration]string{
+	DoNotAutoConfigure: "DoNotAutoConfigure",
+	AutoConfigure:      "AutoConfigure",
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (o AutoConfiguration) ToBytes() []byte {
+	return []byte{byte(o)}
+}
+
+// String returns a human-readable string for this option.
+func (o AutoConfiguration) String() string {
+	s := autoConfigureToString[o]
+	if s != "" {
+		return s
+	}
+	return fmt.Sprintf("UNKNOWN (%d)", byte(o))
+}
+
+// FromBytes parses a a single byte into AutoConfiguration
+func (o *AutoConfiguration) FromBytes(data []byte) error {
+	if len(data) == 1 {
+		*o = AutoConfiguration(data[0])
+		return nil
+	}
+	return fmt.Errorf("Invalid buffer length (%d)", len(data))
+}
+
+// GetByte parses any single-byte option
+func GetByte(code OptionCode, o Options) (byte, error) {
+	data := o.Get(code)
+	if data == nil {
+		return 0, fmt.Errorf("option not present")
+	}
+	if len(data) != 1 {
+		return 0, fmt.Errorf("Invalid buffer length (%d)", len(data))
+	}
+	return data[0], nil
+}
+
+// OptAutoConfigure returns a new AutoConfigure option.
+//
+// The AutoConfigure option is described by RFC 2563, Section 2.
+func OptAutoConfigure(autoconf AutoConfiguration) Option {
+	return Option{Code: OptionAutoConfigure, Value: autoconf}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_duration.go

@@ -0,0 +1,56 @@
+package dhcpv4
+
+import (
+	"math"
+	"time"
+
+	"github.com/u-root/uio/uio"
+)
+
+// MaxLeaseTime is the maximum lease time that can be encoded.
+var MaxLeaseTime = math.MaxUint32 * time.Second
+
+// Duration implements the IP address lease time option described by RFC 2132,
+// Section 9.2.
+type Duration time.Duration
+
+// FromBytes parses a duration from a byte stream according to RFC 2132, Section 9.2.
+func (d *Duration) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	*d = Duration(time.Duration(buf.Read32()) * time.Second)
+	return buf.FinError()
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (d Duration) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write32(uint32(time.Duration(d) / time.Second))
+	return buf.Data()
+}
+
+// String returns a human-readable string for this option.
+func (d Duration) String() string {
+	return time.Duration(d).String()
+}
+
+// OptIPAddressLeaseTime returns a new IP address lease time option.
+//
+// The IP address lease time option is described by RFC 2132, Section 9.2.
+func OptIPAddressLeaseTime(d time.Duration) Option {
+	return Option{Code: OptionIPAddressLeaseTime, Value: Duration(d)}
+}
+
+// The IP address renew time option as described by RFC 2132, Section 9.11.
+func OptRenewTimeValue(d time.Duration) Option {
+	return Option{Code: OptionRenewTimeValue, Value: Duration(d)}
+}
+
+// The IP address rebinding time option as described by RFC 2132, Section 9.12.
+func OptRebindingTimeValue(d time.Duration) Option {
+	return Option{Code: OptionRebindingTimeValue, Value: Duration(d)}
+}
+
+// The IPv6-Only Preferred option is described by RFC 8925, Section 3.1
+func OptIPv6OnlyPreferred(d time.Duration) Option {
+	return Option{Code: OptionIPv6OnlyPreferred, Value: Duration(d)}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_generic.go

@@ -0,0 +1,27 @@
+package dhcpv4
+
+import (
+	"fmt"
+)
+
+// OptionGeneric is an option that only contains the option code and associated
+// data. Every option that does not have a specific implementation will fall
+// back to this option.
+type OptionGeneric struct {
+	Data []byte
+}
+
+// ToBytes returns a serialized generic option as a slice of bytes.
+func (o OptionGeneric) ToBytes() []byte {
+	return o.Data
+}
+
+// String returns a human-readable representation of a generic option.
+func (o OptionGeneric) String() string {
+	return fmt.Sprintf("%v", o.Data)
+}
+
+// OptGeneric returns a generic option.
+func OptGeneric(code OptionCode, value []byte) Option {
+	return Option{Code: code, Value: OptionGeneric{value}}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_ip.go

@@ -0,0 +1,62 @@
+package dhcpv4
+
+import (
+	"net"
+
+	"github.com/u-root/uio/uio"
+)
+
+// IP implements DHCPv4 IP option marshaling and unmarshaling as described by
+// RFC 2132, Sections 5.3, 9.1, 9.7, and others.
+type IP net.IP
+
+// FromBytes parses an IP from data in binary form.
+func (i *IP) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	*i = IP(buf.CopyN(net.IPv4len))
+	return buf.FinError()
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (i IP) ToBytes() []byte {
+	return []byte(net.IP(i).To4())
+}
+
+// String returns a human-readable IP.
+func (i IP) String() string {
+	return net.IP(i).String()
+}
+
+// GetIP returns code out of o parsed as an IP.
+func GetIP(code OptionCode, o Options) net.IP {
+	v := o.Get(code)
+	if v == nil {
+		return nil
+	}
+	var ip IP
+	if err := ip.FromBytes(v); err != nil {
+		return nil
+	}
+	return net.IP(ip)
+}
+
+// OptBroadcastAddress returns a new DHCPv4 Broadcast Address option.
+//
+// The broadcast address option is described in RFC 2132, Section 5.3.
+func OptBroadcastAddress(ip net.IP) Option {
+	return Option{Code: OptionBroadcastAddress, Value: IP(ip)}
+}
+
+// OptRequestedIPAddress returns a new DHCPv4 Requested IP Address option.
+//
+// The requested IP address option is described by RFC 2132, Section 9.1.
+func OptRequestedIPAddress(ip net.IP) Option {
+	return Option{Code: OptionRequestedIPAddress, Value: IP(ip)}
+}
+
+// OptServerIdentifier returns a new DHCPv4 Server Identifier option.
+//
+// The server identifier option is described by RFC 2132, Section 9.7.
+func OptServerIdentifier(ip net.IP) Option {
+	return Option{Code: OptionServerIdentifier, Value: IP(ip)}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_ips.go

@@ -0,0 +1,103 @@
+package dhcpv4
+
+import (
+	"fmt"
+	"net"
+	"strings"
+
+	"github.com/u-root/uio/uio"
+)
+
+// IPs are IPv4 addresses from a DHCP packet as used and specified by options
+// in RFC 2132, Sections 3.5 through 3.13, 8.2, 8.3, 8.5, 8.6, 8.9, and 8.10.
+//
+// IPs implements the OptionValue type.
+type IPs []net.IP
+
+// FromBytes parses an IPv4 address from a DHCP packet as used and specified by
+// options in RFC 2132, Sections 3.5 through 3.13, 8.2, 8.3, 8.5, 8.6, 8.9, and
+// 8.10.
+func (i *IPs) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	if buf.Len() == 0 {
+		return fmt.Errorf("IP DHCP options must always list at least one IP")
+	}
+
+	*i = make(IPs, 0, buf.Len()/net.IPv4len)
+	for buf.Has(net.IPv4len) {
+		*i = append(*i, net.IP(buf.CopyN(net.IPv4len)))
+	}
+	return buf.FinError()
+}
+
+// ToBytes marshals IPv4 addresses to a DHCP packet as specified by RFC 2132,
+// Section 3.5 et al.
+func (i IPs) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, ip := range i {
+		buf.WriteBytes(ip.To4())
+	}
+	return buf.Data()
+}
+
+// String returns a human-readable representation of a list of IPs.
+func (i IPs) String() string {
+	s := make([]string, 0, len(i))
+	for _, ip := range i {
+		s = append(s, ip.String())
+	}
+	return strings.Join(s, ", ")
+}
+
+// GetIPs parses a list of IPs from code in o.
+func GetIPs(code OptionCode, o Options) []net.IP {
+	v := o.Get(code)
+	if v == nil {
+		return nil
+	}
+	var ips IPs
+	if err := ips.FromBytes(v); err != nil {
+		return nil
+	}
+	return []net.IP(ips)
+}
+
+// OptRouter returns a new DHCPv4 Router option.
+//
+// The Router option is described by RFC 2132, Section 3.5.
+func OptRouter(routers ...net.IP) Option {
+	return Option{
+		Code:  OptionRouter,
+		Value: IPs(routers),
+	}
+}
+
+// WithRouter updates a packet with the DHCPv4 Router option.
+func WithRouter(routers ...net.IP) Modifier {
+	return WithOption(OptRouter(routers...))
+}
+
+// OptNTPServers returns a new DHCPv4 NTP Server option.
+//
+// The NTP servers option is described by RFC 2132, Section 8.3.
+func OptNTPServers(ntpServers ...net.IP) Option {
+	return Option{
+		Code:  OptionNTPServers,
+		Value: IPs(ntpServers),
+	}
+}
+
+// OptDNS returns a new DHCPv4 Domain Name Server option.
+//
+// The DNS server option is described by RFC 2132, Section 3.8.
+func OptDNS(servers ...net.IP) Option {
+	return Option{
+		Code:  OptionDomainNameServer,
+		Value: IPs(servers),
+	}
+}
+
+// WithDNS modifies a packet with the DHCPv4 Domain Name Server option.
+func WithDNS(servers ...net.IP) Modifier {
+	return WithOption(OptDNS(servers...))
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_maximum_dhcp_message_size.go

@@ -0,0 +1,50 @@
+package dhcpv4
+
+import (
+	"fmt"
+
+	"github.com/u-root/uio/uio"
+)
+
+// Uint16 implements encoding and decoding functions for a uint16 as used in
+// RFC 2132, Section 9.10.
+type Uint16 uint16
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (o Uint16) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(o))
+	return buf.Data()
+}
+
+// String returns a human-readable string for this option.
+func (o Uint16) String() string {
+	return fmt.Sprintf("%d", uint16(o))
+}
+
+// FromBytes decodes data into o as per RFC 2132, Section 9.10.
+func (o *Uint16) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	*o = Uint16(buf.Read16())
+	return buf.FinError()
+}
+
+// GetUint16 parses a uint16 from code in o.
+func GetUint16(code OptionCode, o Options) (uint16, error) {
+	v := o.Get(code)
+	if v == nil {
+		return 0, fmt.Errorf("option not present")
+	}
+	var u Uint16
+	if err := u.FromBytes(v); err != nil {
+		return 0, err
+	}
+	return uint16(u), nil
+}
+
+// OptMaxMessageSize returns a new DHCP Maximum Message Size option.
+//
+// The Maximum DHCP Message Size option is described by RFC 2132, Section 9.10.
+func OptMaxMessageSize(size uint16) Option {
+	return Option{Code: OptionMaximumDHCPMessageSize, Value: Uint16(size)}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_message_type.go

@@ -0,0 +1,6 @@
+package dhcpv4
+
+// OptMessageType returns a new DHCPv4 Message Type option.
+func OptMessageType(m MessageType) Option {
+	return Option{Code: OptionDHCPMessageType, Value: m}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_misc.go

@@ -0,0 +1,23 @@
+package dhcpv4
+
+import (
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/insomniacslk/dhcp/rfc1035label"
+)
+
+// OptDomainSearch returns a new domain search option.
+//
+// The domain search option is described by RFC 3397, Section 2.
+func OptDomainSearch(labels *rfc1035label.Labels) Option {
+	return Option{Code: OptionDNSDomainSearchList, Value: labels}
+}
+
+// OptClientArch returns a new Client System Architecture Type option.
+func OptClientArch(archs ...iana.Arch) Option {
+	return Option{Code: OptionClientSystemArchitectureType, Value: iana.Archs(archs)}
+}
+
+// OptClientIdentifier returns a new Client Identifier option.
+func OptClientIdentifier(ident []byte) Option {
+	return OptGeneric(OptionClientIdentifier, ident)
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_parameter_request_list.go

@@ -0,0 +1,72 @@
+package dhcpv4
+
+import (
+	"sort"
+	"strings"
+
+	"github.com/u-root/uio/uio"
+)
+
+// OptionCodeList is a list of DHCP option codes.
+type OptionCodeList []OptionCode
+
+// Has returns whether c is in the list.
+func (ol OptionCodeList) Has(c OptionCode) bool {
+	for _, code := range ol {
+		if code == c {
+			return true
+		}
+	}
+	return false
+}
+
+// Add adds option codes in cs to ol.
+func (ol *OptionCodeList) Add(cs ...OptionCode) {
+	for _, c := range cs {
+		if !ol.Has(c) {
+			*ol = append(*ol, c)
+		}
+	}
+}
+
+func (ol OptionCodeList) sort() {
+	sort.Slice(ol, func(i, j int) bool { return ol[i].Code() < ol[j].Code() })
+}
+
+// String returns a human-readable string for the option names.
+func (ol OptionCodeList) String() string {
+	var names []string
+	ol.sort()
+	for _, code := range ol {
+		names = append(names, code.String())
+	}
+	return strings.Join(names, ", ")
+}
+
+// ToBytes returns a serialized stream of bytes for this option as defined by
+// RFC 2132, Section 9.8.
+func (ol OptionCodeList) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, req := range ol {
+		buf.Write8(req.Code())
+	}
+	return buf.Data()
+}
+
+// FromBytes parses a byte stream for this option as described by RFC 2132,
+// Section 9.8.
+func (ol *OptionCodeList) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	*ol = make(OptionCodeList, 0, buf.Len())
+	for buf.Has(1) {
+		*ol = append(*ol, optionCode(buf.Read8()))
+	}
+	return buf.FinError()
+}
+
+// OptParameterRequestList returns a new DHCPv4 Parameter Request List.
+//
+// The parameter request list option is described by RFC 2132, Section 9.8.
+func OptParameterRequestList(codes ...OptionCode) Option {
+	return Option{Code: OptionParameterRequestList, Value: OptionCodeList(codes)}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_relay_agent_information.go

@@ -0,0 +1,100 @@
+package dhcpv4
+
+import (
+	"fmt"
+)
+
+// RelayOptions is like Options, but stringifies using the Relay Agent Specific
+// option space.
+type RelayOptions struct {
+	Options
+}
+
+var relayHumanizer = OptionHumanizer{
+	ValueHumanizer: func(code OptionCode, data []byte) fmt.Stringer {
+		var d OptionDecoder
+		switch code {
+		case LinkSelectionSubOption, ServerIdentifierOverrideSubOption:
+			d = &IPs{}
+		}
+		if d != nil && d.FromBytes(data) == nil {
+			return d
+		}
+		return raiSubOptionValue{data}
+	},
+	CodeHumanizer: func(c uint8) OptionCode {
+		return raiSubOptionCode(c)
+	},
+}
+
+// String prints the contained options using Relay Agent-specific option code parsing.
+func (r RelayOptions) String() string {
+	return "\n" + r.Options.ToString(relayHumanizer)
+}
+
+// FromBytes parses relay agent options from data.
+func (r *RelayOptions) FromBytes(data []byte) error {
+	r.Options = make(Options)
+	return r.Options.FromBytes(data)
+}
+
+// OptRelayAgentInfo returns a new DHCP Relay Agent Info option.
+//
+// The relay agent info option is described by RFC 3046.
+func OptRelayAgentInfo(o ...Option) Option {
+	return Option{Code: OptionRelayAgentInformation, Value: RelayOptions{OptionsFromList(o...)}}
+}
+
+type raiSubOptionValue struct {
+	val []byte
+}
+
+func (rv raiSubOptionValue) String() string {
+	return fmt.Sprintf("%q (%v)", string(rv.val), rv.val)
+}
+
+type raiSubOptionCode uint8
+
+func (o raiSubOptionCode) Code() uint8 {
+	return uint8(o)
+}
+
+func (o raiSubOptionCode) String() string {
+	if s, ok := raiSubOptionCodeToString[o]; ok {
+		return s
+	}
+	return fmt.Sprintf("unknown (%d)", o)
+}
+
+// Option 82 Relay Agention Information Sub Options
+const (
+	AgentCircuitIDSubOption                raiSubOptionCode = 1   // RFC 3046
+	AgentRemoteIDSubOption                 raiSubOptionCode = 2   // RFC 3046
+	DOCSISDeviceClassSubOption             raiSubOptionCode = 4   // RFC 3256
+	LinkSelectionSubOption                 raiSubOptionCode = 5   // RFC 3527
+	SubscriberIDSubOption                  raiSubOptionCode = 6   // RFC 3993
+	RADIUSAttributesSubOption              raiSubOptionCode = 7   // RFC 4014
+	AuthenticationSubOption                raiSubOptionCode = 8   // RFC 4030
+	VendorSpecificInformationSubOption     raiSubOptionCode = 9   // RFC 4243
+	RelayAgentFlagsSubOption               raiSubOptionCode = 10  // RFC 5010
+	ServerIdentifierOverrideSubOption      raiSubOptionCode = 11  // RFC 5107
+	RelaySourcePortSubOption               raiSubOptionCode = 19  // RFC 8357
+	VirtualSubnetSelectionSubOption        raiSubOptionCode = 151 // RFC 6607
+	VirtualSubnetSelectionControlSubOption raiSubOptionCode = 152 // RFC 6607
+)
+
+var raiSubOptionCodeToString = map[raiSubOptionCode]string{
+	AgentCircuitIDSubOption:                "Agent Circuit ID Sub-option",
+	AgentRemoteIDSubOption:                 "Agent Remote ID Sub-option",
+	DOCSISDeviceClassSubOption:             "DOCSIS Device Class Sub-option",
+	LinkSelectionSubOption:                 "Link Selection Sub-option",
+	SubscriberIDSubOption:                  "Subscriber ID Sub-option",
+	RADIUSAttributesSubOption:              "RADIUS Attributes Sub-option",
+	AuthenticationSubOption:                "Authentication Sub-option",
+	VendorSpecificInformationSubOption:     "Vendor Specific Sub-option",
+	RelayAgentFlagsSubOption:               "Relay Agent Flags Sub-option",
+	ServerIdentifierOverrideSubOption:      "Server Identifier Override Sub-option",
+	RelaySourcePortSubOption:               "Relay Source Port Sub-option",
+	VirtualSubnetSelectionSubOption:        "Virtual Subnet Selection Sub-option",
+	VirtualSubnetSelectionControlSubOption: "Virtual Subnet Selection Control Sub-option",
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_routes.go

@@ -0,0 +1,104 @@
+package dhcpv4
+
+import (
+	"fmt"
+	"net"
+	"strings"
+
+	"github.com/u-root/uio/uio"
+)
+
+// Route is a classless static route as per RFC 3442.
+type Route struct {
+	// Dest is the destination network.
+	Dest *net.IPNet
+
+	// Router is the router to use for the given destination network.
+	Router net.IP
+}
+
+// Marshal implements uio.Marshaler.
+//
+// Format described in RFC 3442:
+//
+// <size of mask in number of bits>
+// <destination address, omitting octets that must be zero per mask>
+// <route IP>
+func (r Route) Marshal(buf *uio.Lexer) {
+	ones, _ := r.Dest.Mask.Size()
+	buf.Write8(uint8(ones))
+
+	// Only write the non-zero octets.
+	dstLen := (ones + 7) / 8
+	buf.WriteBytes(r.Dest.IP.To4()[:dstLen])
+
+	buf.WriteBytes(r.Router.To4())
+}
+
+// Unmarshal implements uio.Unmarshaler.
+func (r *Route) Unmarshal(buf *uio.Lexer) error {
+	maskSize := buf.Read8()
+	if maskSize > 32 {
+		return fmt.Errorf("invalid mask length %d in route option", maskSize)
+	}
+	r.Dest = &net.IPNet{
+		IP:   make([]byte, net.IPv4len),
+		Mask: net.CIDRMask(int(maskSize), 32),
+	}
+
+	dstLen := (maskSize + 7) / 8
+	buf.ReadBytes(r.Dest.IP[:dstLen])
+
+	r.Router = buf.CopyN(net.IPv4len)
+	return buf.Error()
+}
+
+// String prints the destination network and router IP.
+func (r *Route) String() string {
+	return fmt.Sprintf("route to %s via %s", r.Dest, r.Router)
+}
+
+// Routes is a collection of network routes.
+type Routes []*Route
+
+// FromBytes parses routes from a set of bytes as described by RFC 3442.
+func (r *Routes) FromBytes(p []byte) error {
+	buf := uio.NewBigEndianBuffer(p)
+	for buf.Has(1) {
+		var route Route
+		if err := route.Unmarshal(buf); err != nil {
+			return err
+		}
+		*r = append(*r, &route)
+	}
+	return buf.FinError()
+}
+
+// ToBytes marshals a set of routes as described by RFC 3442.
+func (r Routes) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, route := range r {
+		route.Marshal(buf)
+	}
+	return buf.Data()
+}
+
+// String prints all routes.
+func (r Routes) String() string {
+	s := make([]string, 0, len(r))
+	for _, route := range r {
+		s = append(s, route.String())
+	}
+	return strings.Join(s, "; ")
+}
+
+// OptClasslessStaticRoute returns a new DHCPv4 Classless Static Route
+// option.
+//
+// The Classless Static Route option is described by RFC 3442.
+func OptClasslessStaticRoute(routes ...*Route) Option {
+	return Option{
+		Code:  OptionClasslessStaticRoute,
+		Value: Routes(routes),
+	}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_string.go

@@ -0,0 +1,84 @@
+package dhcpv4
+
+// String represents an option encapsulating a string in IPv4 DHCP.
+//
+// This representation is shared by multiple options specified by RFC 2132,
+// Sections 3.14, 3.16, 3.17, 3.19, and 3.20.
+type String string
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (o String) ToBytes() []byte {
+	return []byte(o)
+}
+
+// String returns a human-readable string.
+func (o String) String() string {
+	return string(o)
+}
+
+// FromBytes parses a serialized stream of bytes into o.
+func (o *String) FromBytes(data []byte) error {
+	*o = String(string(data))
+	return nil
+}
+
+// GetString parses an RFC 2132 string from o[code].
+func GetString(code OptionCode, o Options) string {
+	v := o.Get(code)
+	if v == nil {
+		return ""
+	}
+	return string(v)
+}
+
+// OptDomainName returns a new DHCPv4 Domain Name option.
+//
+// The Domain Name option is described by RFC 2132, Section 3.17.
+func OptDomainName(name string) Option {
+	return Option{Code: OptionDomainName, Value: String(name)}
+}
+
+// OptHostName returns a new DHCPv4 Host Name option.
+//
+// The Host Name option is described by RFC 2132, Section 3.14.
+func OptHostName(name string) Option {
+	return Option{Code: OptionHostName, Value: String(name)}
+}
+
+// OptRootPath returns a new DHCPv4 Root Path option.
+//
+// The Root Path option is described by RFC 2132, Section 3.19.
+func OptRootPath(name string) Option {
+	return Option{Code: OptionRootPath, Value: String(name)}
+}
+
+// OptBootFileName returns a new DHCPv4 Boot File Name option.
+//
+// The Bootfile Name option is described by RFC 2132, Section 9.5.
+func OptBootFileName(name string) Option {
+	return Option{Code: OptionBootfileName, Value: String(name)}
+}
+
+// OptTFTPServerName returns a new DHCPv4 TFTP Server Name option.
+//
+// The TFTP Server Name option is described by RFC 2132, Section 9.4.
+func OptTFTPServerName(name string) Option {
+	return Option{Code: OptionTFTPServerName, Value: String(name)}
+}
+
+// OptClassIdentifier returns a new DHCPv4 Class Identifier option.
+//
+// The Vendor Class Identifier option is described by RFC 2132, Section 9.13.
+func OptClassIdentifier(name string) Option {
+	return Option{Code: OptionClassIdentifier, Value: String(name)}
+}
+
+// OptUserClass returns a new DHCPv4 User Class option.
+func OptUserClass(name string) Option {
+	return Option{Code: OptionUserClassInformation, Value: String(name)}
+}
+
+// OptMessage returns a new DHCPv4 (Error) Message option.
+func OptMessage(msg string) Option {
+	return Option{Code: OptionMessage, Value: String(msg)}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_strings.go

@@ -0,0 +1,55 @@
+package dhcpv4
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/u-root/uio/uio"
+)
+
+// Strings represents an option encapsulating a list of strings in IPv4 DHCP as
+// specified in RFC 3004
+//
+// Strings implements the OptionValue type.
+type Strings []string
+
+// FromBytes parses Strings from a DHCP packet as specified by RFC 3004.
+func (o *Strings) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	if buf.Len() == 0 {
+		return fmt.Errorf("Strings DHCP option must always list at least one String")
+	}
+
+	*o = make(Strings, 0)
+	for buf.Has(1) {
+		ucLen := buf.Read8()
+		if ucLen == 0 {
+			return fmt.Errorf("DHCP Strings must have length greater than 0")
+		}
+		*o = append(*o, string(buf.CopyN(int(ucLen))))
+	}
+	return buf.FinError()
+}
+
+// ToBytes marshals Strings to a DHCP packet as specified by RFC 3004.
+func (o Strings) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, uc := range o {
+		buf.Write8(uint8(len(uc)))
+		buf.WriteBytes([]byte(uc))
+	}
+	return buf.Data()
+}
+
+// String returns a human-readable representation of a list of Strings.
+func (o Strings) String() string {
+	return strings.Join(o, ", ")
+}
+
+// OptRFC3004UserClass returns a new user class option according to RFC 3004.
+func OptRFC3004UserClass(v []string) Option {
+	return Option{
+		Code:  OptionUserClassInformation,
+		Value: Strings(v),
+	}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_subnet_mask.go

@@ -0,0 +1,40 @@
+package dhcpv4
+
+import (
+	"net"
+
+	"github.com/u-root/uio/uio"
+)
+
+// IPMask represents an option encapsulating the subnet mask.
+//
+// This option implements the subnet mask option in RFC 2132, Section 3.3.
+type IPMask net.IPMask
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (im IPMask) ToBytes() []byte {
+	if len(im) > net.IPv4len {
+		return im[:net.IPv4len]
+	}
+	return im
+}
+
+// String returns a human-readable string.
+func (im IPMask) String() string {
+	return net.IPMask(im).String()
+}
+
+// FromBytes parses im from data per RFC 2132.
+func (im *IPMask) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	*im = IPMask(buf.CopyN(net.IPv4len))
+	return buf.FinError()
+}
+
+// OptSubnetMask returns a new DHCPv4 SubnetMask option per RFC 2132, Section 3.3.
+func OptSubnetMask(mask net.IPMask) Option {
+	return Option{
+		Code:  OptionSubnetMask,
+		Value: IPMask(mask),
+	}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/option_vivc.go

@@ -0,0 +1,65 @@
+package dhcpv4
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/u-root/uio/uio"
+)
+
+// VIVCIdentifier implements the vendor-identifying vendor class option
+// described by RFC 3925.
+type VIVCIdentifier struct {
+	// EntID is the enterprise ID.
+	EntID iana.EnterpriseID
+	Data  []byte
+}
+
+// OptVIVC returns a new vendor-identifying vendor class option.
+//
+// The option is described by RFC 3925.
+func OptVIVC(identifiers ...VIVCIdentifier) Option {
+	return Option{
+		Code:  OptionVendorIdentifyingVendorClass,
+		Value: VIVCIdentifiers(identifiers),
+	}
+}
+
+// VIVCIdentifiers implements encoding and decoding methods for a DHCP option
+// described in RFC 3925.
+type VIVCIdentifiers []VIVCIdentifier
+
+// FromBytes parses data into ids per RFC 3925.
+func (ids *VIVCIdentifiers) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	for buf.Has(5) {
+		entID := iana.EnterpriseID(buf.Read32())
+		idLen := int(buf.Read8())
+		*ids = append(*ids, VIVCIdentifier{EntID: entID, Data: buf.CopyN(idLen)})
+	}
+	return buf.FinError()
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (ids VIVCIdentifiers) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, id := range ids {
+		buf.Write32(uint32(id.EntID))
+		buf.Write8(uint8(len(id.Data)))
+		buf.WriteBytes(id.Data)
+	}
+	return buf.Data()
+}
+
+// String returns a human-readable string for this option.
+func (ids VIVCIdentifiers) String() string {
+	if len(ids) == 0 {
+		return ""
+	}
+	buf := bytes.Buffer{}
+	for _, id := range ids {
+		fmt.Fprintf(&buf, " %d:'%s',", id.EntID, id.Data)
+	}
+	return buf.String()[1 : buf.Len()-1]
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/options.go

@@ -0,0 +1,380 @@
+package dhcpv4
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"math"
+	"sort"
+	"strings"
+
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/insomniacslk/dhcp/rfc1035label"
+	"github.com/u-root/uio/uio"
+)
+
+var (
+	// ErrShortByteStream is an error that is thrown any time a short byte stream is
+	// detected during option parsing.
+	ErrShortByteStream = errors.New("short byte stream")
+
+	// ErrZeroLengthByteStream is an error that is thrown any time a zero-length
+	// byte stream is encountered.
+	ErrZeroLengthByteStream = errors.New("zero-length byte stream")
+)
+
+// OptionValue is an interface that all DHCP v4 options adhere to.
+type OptionValue interface {
+	ToBytes() []byte
+	String() string
+}
+
+// Option is a DHCPv4 option and consists of a 1-byte option code and a value
+// stream of bytes.
+//
+// The value is to be interpreted based on the option code.
+type Option struct {
+	Code  OptionCode
+	Value OptionValue
+}
+
+// String returns a human-readable version of this option.
+func (o Option) String() string {
+	v := o.Value.String()
+	if strings.Contains(v, "\n") {
+		return fmt.Sprintf("%s:\n%s", o.Code, v)
+	}
+	return fmt.Sprintf("%s: %s", o.Code, v)
+}
+
+// Options is a collection of options.
+type Options map[uint8][]byte
+
+// OptionsFromList adds all given options to an options map.
+func OptionsFromList(o ...Option) Options {
+	opts := make(Options)
+	for _, opt := range o {
+		opts.Update(opt)
+	}
+	return opts
+}
+
+// Get will attempt to get all options that match a DHCPv4 option
+// from its OptionCode.  If the option was not found it will return an
+// empty list.
+//
+// According to RFC 3396, options that are specified more than once are
+// concatenated, and hence this should always just return one option. This
+// currently returns a list to be API compatible.
+func (o Options) Get(code OptionCode) []byte {
+	return o[code.Code()]
+}
+
+// Has checks whether o has the given opcode.
+func (o Options) Has(opcode OptionCode) bool {
+	_, ok := o[opcode.Code()]
+	return ok
+}
+
+// Del deletes the option matching the option code.
+func (o Options) Del(opcode OptionCode) {
+	delete(o, opcode.Code())
+}
+
+// Update updates the existing options with the passed option, adding it
+// at the end if not present already
+func (o Options) Update(option Option) {
+	o[option.Code.Code()] = option.Value.ToBytes()
+}
+
+// ToBytes makes Options usable as an OptionValue as well.
+//
+// Used in the case of vendor-specific and relay agent options.
+func (o Options) ToBytes() []byte {
+	return uio.ToBigEndian(o)
+}
+
+// FromBytes parses a sequence of bytes until the end and builds a list of
+// options from it.
+//
+// The sequence should not contain the DHCP magic cookie.
+//
+// Returns an error if any invalid option or length is found.
+func (o Options) FromBytes(data []byte) error {
+	return o.fromBytesCheckEnd(data, false)
+}
+
+const (
+	optPad       = 0
+	optAgentInfo = 82
+	optEnd       = 255
+)
+
+// FromBytesCheckEnd parses Options from byte sequences using the
+// parsing function that is passed in as a paremeter
+func (o Options) fromBytesCheckEnd(data []byte, checkEndOption bool) error {
+	if len(data) == 0 {
+		return nil
+	}
+	buf := uio.NewBigEndianBuffer(data)
+
+	var end bool
+	for buf.Len() >= 1 {
+		// 1 byte: option code
+		// 1 byte: option length n
+		// n bytes: data
+		code := buf.Read8()
+
+		if code == optPad {
+			continue
+		} else if code == optEnd {
+			end = true
+			break
+		}
+		length := int(buf.Read8())
+
+		// N bytes: option data
+		data := buf.Consume(length)
+		if data == nil {
+			return fmt.Errorf("error collecting options: %v", buf.Error())
+		}
+		data = data[:length:length]
+
+		// RFC 2131, Section 4.1 "Options may appear only once, [...].
+		// The client concatenates the values of multiple instances of
+		// the same option into a single parameter list for
+		// configuration."
+		//
+		// See also RFC 3396 for concatenation order and options longer
+		// than 255 bytes.
+		o[code] = append(o[code], data...)
+	}
+
+	// If we never read the End option, the sender of this packet screwed
+	// up.
+	if !end && checkEndOption {
+		return io.ErrUnexpectedEOF
+	}
+
+	return nil
+}
+
+// sortedKeys returns an ordered slice of option keys from the Options map, for
+// use in serializing options to binary.
+func (o Options) sortedKeys() []int {
+	// Send all values for a given key
+	var codes []int
+	var hasOptAgentInfo, hasOptEnd bool
+	for k := range o {
+		// RFC 3046 section 2.1 states that option 82 SHALL come last (ignoring End).
+		if k == optAgentInfo {
+			hasOptAgentInfo = true
+			continue
+		}
+		if k == optEnd {
+			hasOptEnd = true
+			continue
+		}
+		codes = append(codes, int(k))
+	}
+
+	sort.Ints(codes)
+
+	if hasOptAgentInfo {
+		codes = append(codes, optAgentInfo)
+	}
+	if hasOptEnd {
+		codes = append(codes, optEnd)
+	}
+	return codes
+}
+
+// Marshal writes options binary representations to b.
+func (o Options) Marshal(b *uio.Lexer) {
+	for _, c := range o.sortedKeys() {
+		code := uint8(c)
+		// Even if the End option is in there, don't marshal it until
+		// the end.
+		// Don't write padding either, since the options are sorted
+		// it would always be written first which isn't useful
+		if code == optEnd || code == optPad {
+			continue
+		}
+
+		data := o[code]
+
+		// Ensure even 0-length options are written out
+		if len(data) == 0 {
+			b.Write8(code)
+			b.Write8(0)
+			continue
+		}
+		// RFC 3396: If more than 256 bytes of data are given, the
+		// option is simply listed multiple times.
+		for len(data) > 0 {
+			// 1 byte: option code
+			b.Write8(code)
+
+			n := len(data)
+			if n > math.MaxUint8 {
+				n = math.MaxUint8
+			}
+
+			// 1 byte: option length
+			b.Write8(uint8(n))
+
+			// N bytes: option data
+			b.WriteBytes(data[:n])
+			data = data[n:]
+		}
+	}
+}
+
+// String prints options using DHCP-specified option codes.
+func (o Options) String() string {
+	return o.ToString(dhcpHumanizer)
+}
+
+// Summary prints options in human-readable values.
+//
+// Summary uses vendorParser to interpret the OptionVendorSpecificInformation option.
+func (o Options) Summary(vendorDecoder OptionDecoder) string {
+	return o.ToString(OptionHumanizer{
+		ValueHumanizer: parserFor(vendorDecoder),
+		CodeHumanizer: func(c uint8) OptionCode {
+			return optionCode(c)
+		},
+	})
+}
+
+// OptionParser gives a human-legible interpretation of data for the given option code.
+type OptionParser func(code OptionCode, data []byte) fmt.Stringer
+
+// OptionHumanizer is used to interpret a set of Options for their option code
+// name and values.
+//
+// There should be separate OptionHumanizers for each Option "space": DHCP,
+// BSDP, Relay Agent Info, and others.
+type OptionHumanizer struct {
+	ValueHumanizer OptionParser
+	CodeHumanizer  func(code uint8) OptionCode
+}
+
+// Stringify returns a human-readable interpretation of the option code and its
+// associated data.
+func (oh OptionHumanizer) Stringify(code uint8, data []byte) string {
+	c := oh.CodeHumanizer(code)
+	val := oh.ValueHumanizer(c, data)
+	return fmt.Sprintf("%s: %s", c, val)
+}
+
+// dhcpHumanizer humanizes the set of DHCP option codes.
+var dhcpHumanizer = OptionHumanizer{
+	ValueHumanizer: parseOption,
+	CodeHumanizer: func(c uint8) OptionCode {
+		return optionCode(c)
+	},
+}
+
+// ToString uses parse to parse options into human-readable values.
+func (o Options) ToString(humanizer OptionHumanizer) string {
+	var ret string
+	for _, c := range o.sortedKeys() {
+		code := uint8(c)
+		v := o[code]
+		optString := humanizer.Stringify(code, v)
+		// If this option has sub structures, offset them accordingly.
+		if strings.Contains(optString, "\n") {
+			optString = strings.Replace(optString, "\n  ", "\n      ", -1)
+		}
+		ret += fmt.Sprintf("    %v\n", optString)
+	}
+	return ret
+}
+
+func parseOption(code OptionCode, data []byte) fmt.Stringer {
+	return parserFor(nil)(code, data)
+}
+
+func parserFor(vendorParser OptionDecoder) OptionParser {
+	return func(code OptionCode, data []byte) fmt.Stringer {
+		return getOption(code, data, vendorParser)
+	}
+}
+
+// OptionDecoder can decode a byte stream into a human-readable option.
+type OptionDecoder interface {
+	fmt.Stringer
+	FromBytes([]byte) error
+}
+
+func getOption(code OptionCode, data []byte, vendorDecoder OptionDecoder) fmt.Stringer {
+	var d OptionDecoder
+	switch code {
+	case OptionRouter, OptionDomainNameServer, OptionNTPServers, OptionServerIdentifier:
+		d = &IPs{}
+
+	case OptionBroadcastAddress, OptionRequestedIPAddress:
+		d = &IP{}
+
+	case OptionClientSystemArchitectureType:
+		d = &iana.Archs{}
+
+	case OptionSubnetMask:
+		d = &IPMask{}
+
+	case OptionDHCPMessageType:
+		var mt MessageType
+		d = &mt
+
+	case OptionParameterRequestList:
+		d = &OptionCodeList{}
+
+	case OptionHostName, OptionDomainName, OptionRootPath,
+		OptionClassIdentifier, OptionTFTPServerName, OptionBootfileName,
+		OptionMessage, OptionReferenceToTZDatabase:
+		var s String
+		d = &s
+
+	case OptionRelayAgentInformation:
+		d = &RelayOptions{}
+
+	case OptionDNSDomainSearchList:
+		d = &rfc1035label.Labels{}
+
+	case OptionIPAddressLeaseTime, OptionRenewTimeValue,
+		OptionRebindingTimeValue, OptionIPv6OnlyPreferred, OptionArpCacheTimeout,
+		OptionTimeOffset:
+		var dur Duration
+		d = &dur
+
+	case OptionMaximumDHCPMessageSize:
+		var u Uint16
+		d = &u
+
+	case OptionUserClassInformation:
+		var s Strings
+		d = &s
+		if s.FromBytes(data) != nil {
+			var s String
+			d = &s
+		}
+
+	case OptionAutoConfigure:
+		var a AutoConfiguration
+		d = &a
+
+	case OptionVendorIdentifyingVendorClass:
+		d = &VIVCIdentifiers{}
+
+	case OptionVendorSpecificInformation:
+		d = vendorDecoder
+
+	case OptionClasslessStaticRoute:
+		d = &Routes{}
+	}
+	if d != nil && d.FromBytes(data) == nil {
+		return d
+	}
+	return OptionGeneric{data}
+}

vendor/github.com/insomniacslk/dhcp/dhcpv4/types.go

@@ -0,0 +1,467 @@
+package dhcpv4
+
+import (
+	"fmt"
+
+	"github.com/u-root/uio/uio"
+)
+
+// values from http://www.networksorcery.com/enp/protocol/dhcp.htm and
+// http://www.networksorcery.com/enp/protocol/bootp/options.htm
+
+// TransactionID represents a 4-byte DHCP transaction ID as defined in RFC 951,
+// Section 3.
+//
+// The TransactionID is used to match DHCP replies to their original request.
+type TransactionID [4]byte
+
+// String prints a hex transaction ID.
+func (xid TransactionID) String() string {
+	return fmt.Sprintf("0x%x", xid[:])
+}
+
+// MessageType represents the possible DHCP message types - DISCOVER, OFFER, etc
+type MessageType byte
+
+// DHCP message types
+const (
+	// MessageTypeNone is not a real message type, it is used by certain
+	// functions to signal that no explicit message type is requested
+	MessageTypeNone     MessageType = 0
+	MessageTypeDiscover MessageType = 1
+	MessageTypeOffer    MessageType = 2
+	MessageTypeRequest  MessageType = 3
+	MessageTypeDecline  MessageType = 4
+	MessageTypeAck      MessageType = 5
+	MessageTypeNak      MessageType = 6
+	MessageTypeRelease  MessageType = 7
+	MessageTypeInform   MessageType = 8
+)
+
+// ToBytes returns the serialized version of this option described by RFC 2132,
+// Section 9.6.
+func (m MessageType) ToBytes() []byte {
+	return []byte{byte(m)}
+}
+
+// String prints a human-readable message type name.
+func (m MessageType) String() string {
+	if s, ok := messageTypeToString[m]; ok {
+		return s
+	}
+	return fmt.Sprintf("unknown (%d)", byte(m))
+}
+
+// FromBytes reads a message type from data as described by RFC 2132, Section
+// 9.6.
+func (m *MessageType) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	*m = MessageType(buf.Read8())
+	return buf.FinError()
+}
+
+var messageTypeToString = map[MessageType]string{
+	MessageTypeDiscover: "DISCOVER",
+	MessageTypeOffer:    "OFFER",
+	MessageTypeRequest:  "REQUEST",
+	MessageTypeDecline:  "DECLINE",
+	MessageTypeAck:      "ACK",
+	MessageTypeNak:      "NAK",
+	MessageTypeRelease:  "RELEASE",
+	MessageTypeInform:   "INFORM",
+}
+
+// OpcodeType represents a DHCPv4 opcode.
+type OpcodeType uint8
+
+// constants that represent valid values for OpcodeType
+const (
+	OpcodeBootRequest OpcodeType = 1
+	OpcodeBootReply   OpcodeType = 2
+)
+
+func (o OpcodeType) String() string {
+	if s, ok := opcodeToString[o]; ok {
+		return s
+	}
+	return fmt.Sprintf("unknown (%d)", uint8(o))
+}
+
+var opcodeToString = map[OpcodeType]string{
+	OpcodeBootRequest: "BootRequest",
+	OpcodeBootReply:   "BootReply",
+}
+
+// OptionCode is a single byte representing the code for a given Option.
+//
+// OptionCode is an interface purely to support different stringers on options
+// with the same Code value, as vendor-specific options use option codes that
+// have the same value, but mean a different thing.
+type OptionCode interface {
+	// Code is the 1 byte option code for the wire.
+	Code() uint8
+
+	// String returns the option's name.
+	String() string
+}
+
+// optionCode is a DHCP option code.
+type optionCode uint8
+
+// Code implements OptionCode.Code.
+func (o optionCode) Code() uint8 {
+	return uint8(o)
+}
+
+// String returns an option name.
+func (o optionCode) String() string {
+	if s, ok := optionCodeToString[o]; ok {
+		return s
+	}
+	return fmt.Sprintf("unknown (%d)", uint8(o))
+}
+
+// GenericOptionCode is an unnamed option code.
+type GenericOptionCode uint8
+
+// Code implements OptionCode.Code.
+func (o GenericOptionCode) Code() uint8 {
+	return uint8(o)
+}
+
+// String returns the option's name.
+func (o GenericOptionCode) String() string {
+	return fmt.Sprintf("unknown (%d)", uint8(o))
+}
+
+// DHCPv4 Options
+const (
+	OptionPad                                        optionCode = 0
+	OptionSubnetMask                                 optionCode = 1
+	OptionTimeOffset                                 optionCode = 2
+	OptionRouter                                     optionCode = 3
+	OptionTimeServer                                 optionCode = 4
+	OptionNameServer                                 optionCode = 5
+	OptionDomainNameServer                           optionCode = 6
+	OptionLogServer                                  optionCode = 7
+	OptionQuoteServer                                optionCode = 8
+	OptionLPRServer                                  optionCode = 9
+	OptionImpressServer                              optionCode = 10
+	OptionResourceLocationServer                     optionCode = 11
+	OptionHostName                                   optionCode = 12
+	OptionBootFileSize                               optionCode = 13
+	OptionMeritDumpFile                              optionCode = 14
+	OptionDomainName                                 optionCode = 15
+	OptionSwapServer                                 optionCode = 16
+	OptionRootPath                                   optionCode = 17
+	OptionExtensionsPath                             optionCode = 18
+	OptionIPForwarding                               optionCode = 19
+	OptionNonLocalSourceRouting                      optionCode = 20
+	OptionPolicyFilter                               optionCode = 21
+	OptionMaximumDatagramAssemblySize                optionCode = 22
+	OptionDefaultIPTTL                               optionCode = 23
+	OptionPathMTUAgingTimeout                        optionCode = 24
+	OptionPathMTUPlateauTable                        optionCode = 25
+	OptionInterfaceMTU                               optionCode = 26
+	OptionAllSubnetsAreLocal                         optionCode = 27
+	OptionBroadcastAddress                           optionCode = 28
+	OptionPerformMaskDiscovery                       optionCode = 29
+	OptionMaskSupplier                               optionCode = 30
+	OptionPerformRouterDiscovery                     optionCode = 31
+	OptionRouterSolicitationAddress                  optionCode = 32
+	OptionStaticRoutingTable                         optionCode = 33
+	OptionTrailerEncapsulation                       optionCode = 34
+	OptionArpCacheTimeout                            optionCode = 35
+	OptionEthernetEncapsulation                      optionCode = 36
+	OptionDefaulTCPTTL                               optionCode = 37
+	OptionTCPKeepaliveInterval                       optionCode = 38
+	OptionTCPKeepaliveGarbage                        optionCode = 39
+	OptionNetworkInformationServiceDomain            optionCode = 40
+	OptionNetworkInformationServers                  optionCode = 41
+	OptionNTPServers                                 optionCode = 42
+	OptionVendorSpecificInformation                  optionCode = 43
+	OptionNetBIOSOverTCPIPNameServer                 optionCode = 44
+	OptionNetBIOSOverTCPIPDatagramDistributionServer optionCode = 45
+	OptionNetBIOSOverTCPIPNodeType                   optionCode = 46
+	OptionNetBIOSOverTCPIPScope                      optionCode = 47
+	OptionXWindowSystemFontServer                    optionCode = 48
+	OptionXWindowSystemDisplayManger                 optionCode = 49
+	OptionRequestedIPAddress                         optionCode = 50
+	OptionIPAddressLeaseTime                         optionCode = 51
+	OptionOptionOverload                             optionCode = 52
+	OptionDHCPMessageType                            optionCode = 53
+	OptionServerIdentifier                           optionCode = 54
+	OptionParameterRequestList                       optionCode = 55
+	OptionMessage                                    optionCode = 56
+	OptionMaximumDHCPMessageSize                     optionCode = 57
+	OptionRenewTimeValue                             optionCode = 58
+	OptionRebindingTimeValue                         optionCode = 59
+	OptionClassIdentifier                            optionCode = 60
+	OptionClientIdentifier                           optionCode = 61
+	OptionNetWareIPDomainName                        optionCode = 62
+	OptionNetWareIPInformation                       optionCode = 63
+	OptionNetworkInformationServicePlusDomain        optionCode = 64
+	OptionNetworkInformationServicePlusServers       optionCode = 65
+	OptionTFTPServerName                             optionCode = 66
+	OptionBootfileName                               optionCode = 67
+	OptionMobileIPHomeAgent                          optionCode = 68
+	OptionSimpleMailTransportProtocolServer          optionCode = 69
+	OptionPostOfficeProtocolServer                   optionCode = 70
+	OptionNetworkNewsTransportProtocolServer         optionCode = 71
+	OptionDefaultWorldWideWebServer                  optionCode = 72
+	OptionDefaultFingerServer                        optionCode = 73
+	OptionDefaultInternetRelayChatServer             optionCode = 74
+	OptionStreetTalkServer                           optionCode = 75
+	OptionStreetTalkDirectoryAssistanceServer        optionCode = 76
+	OptionUserClassInformation                       optionCode = 77
+	OptionSLPDirectoryAgent                          optionCode = 78
+	OptionSLPServiceScope                            optionCode = 79
+	OptionRapidCommit                                optionCode = 80
+	OptionFQDN                                       optionCode = 81
+	OptionRelayAgentInformation                      optionCode = 82
+	OptionInternetStorageNameService                 optionCode = 83
+	// Option 84 returned in RFC 3679
+	OptionNDSServers                       optionCode = 85
+	OptionNDSTreeName                      optionCode = 86
+	OptionNDSContext                       optionCode = 87
+	OptionBCMCSControllerDomainNameList    optionCode = 88
+	OptionBCMCSControllerIPv4AddressList   optionCode = 89
+	OptionAuthentication                   optionCode = 90
+	OptionClientLastTransactionTime        optionCode = 91
+	OptionAssociatedIP                     optionCode = 92
+	OptionClientSystemArchitectureType     optionCode = 93
+	OptionClientNetworkInterfaceIdentifier optionCode = 94
+	OptionLDAP                             optionCode = 95
+	// Option 96 returned in RFC 3679
+	OptionClientMachineIdentifier     optionCode = 97
+	OptionOpenGroupUserAuthentication optionCode = 98
+	OptionGeoConfCivic                optionCode = 99
+	OptionIEEE10031TZString           optionCode = 100
+	OptionReferenceToTZDatabase       optionCode = 101
+	// Option 108 returned in RFC 8925
+	OptionIPv6OnlyPreferred optionCode = 108
+	// Options 102-111 returned in RFC 3679
+	OptionNetInfoParentServerAddress optionCode = 112
+	OptionNetInfoParentServerTag     optionCode = 113
+	OptionURL                        optionCode = 114
+	// Option 115 returned in RFC 3679
+	OptionAutoConfigure                   optionCode = 116
+	OptionNameServiceSearch               optionCode = 117
+	OptionSubnetSelection                 optionCode = 118
+	OptionDNSDomainSearchList             optionCode = 119
+	OptionSIPServers                      optionCode = 120
+	OptionClasslessStaticRoute            optionCode = 121
+	OptionCCC                             optionCode = 122
+	OptionGeoConf                         optionCode = 123
+	OptionVendorIdentifyingVendorClass    optionCode = 124
+	OptionVendorIdentifyingVendorSpecific optionCode = 125
+	// Options 126-127 returned in RFC 3679
+	OptionTFTPServerIPAddress                   optionCode = 128
+	OptionCallServerIPAddress                   optionCode = 129
+	OptionDiscriminationString                  optionCode = 130
+	OptionRemoteStatisticsServerIPAddress       optionCode = 131
+	Option8021PVLANID                           optionCode = 132
+	Option8021QL2Priority                       optionCode = 133
+	OptionDiffservCodePoint                     optionCode = 134
+	OptionHTTPProxyForPhoneSpecificApplications optionCode = 135
+	OptionPANAAuthenticationAgent               optionCode = 136
+	OptionLoSTServer                            optionCode = 137
+	OptionCAPWAPAccessControllerAddresses       optionCode = 138
+	OptionOPTIONIPv4AddressMoS                  optionCode = 139
+	OptionOPTIONIPv4FQDNMoS                     optionCode = 140
+	OptionSIPUAConfigurationServiceDomains      optionCode = 141
+	OptionOPTIONIPv4AddressANDSF                optionCode = 142
+	OptionOPTIONIPv6AddressANDSF                optionCode = 143
+	// Options 144-149 returned in RFC 3679
+	OptionTFTPServerAddress optionCode = 150
+	OptionStatusCode        optionCode = 151
+	OptionBaseTime          optionCode = 152
+	OptionStartTimeOfState  optionCode = 153
+	OptionQueryStartTime    optionCode = 154
+	OptionQueryEndTime      optionCode = 155
+	OptionDHCPState         optionCode = 156
+	OptionDataSource        optionCode = 157
+	// Options 158-174 returned in RFC 3679
+	OptionEtherboot                        optionCode = 175
+	OptionIPTelephone                      optionCode = 176
+	OptionEtherbootPacketCableAndCableHome optionCode = 177
+	// Options 178-207 returned in RFC 3679
+	OptionPXELinuxMagicString  optionCode = 208
+	OptionPXELinuxConfigFile   optionCode = 209
+	OptionPXELinuxPathPrefix   optionCode = 210
+	OptionPXELinuxRebootTime   optionCode = 211
+	OptionOPTION6RD            optionCode = 212
+	OptionOPTIONv4AccessDomain optionCode = 213
+	// Options 214-219 returned in RFC 3679
+	OptionSubnetAllocation        optionCode = 220
+	OptionVirtualSubnetAllocation optionCode = 221
+	// Options 222-223 returned in RFC 3679
+	// Options 224-254 are reserved for private use
+	OptionEnd optionCode = 255
+)
+
+var optionCodeToString = map[OptionCode]string{
+	OptionPad:                                        "Pad",
+	OptionSubnetMask:                                 "Subnet Mask",
+	OptionTimeOffset:                                 "Time Offset",
+	OptionRouter:                                     "Router",
+	OptionTimeServer:                                 "Time Server",
+	OptionNameServer:                                 "Name Server",
+	OptionDomainNameServer:                           "Domain Name Server",
+	OptionLogServer:                                  "Log Server",
+	OptionQuoteServer:                                "Quote Server",
+	OptionLPRServer:                                  "LPR Server",
+	OptionImpressServer:                              "Impress Server",
+	OptionResourceLocationServer:                     "Resource Location Server",
+	OptionHostName:                                   "Host Name",
+	OptionBootFileSize:                               "Boot File Size",
+	OptionMeritDumpFile:                              "Merit Dump File",
+	OptionDomainName:                                 "Domain Name",
+	OptionSwapServer:                                 "Swap Server",
+	OptionRootPath:                                   "Root Path",
+	OptionExtensionsPath:                             "Extensions Path",
+	OptionIPForwarding:                               "IP Forwarding enable/disable",
+	OptionNonLocalSourceRouting:                      "Non-local Source Routing enable/disable",
+	OptionPolicyFilter:                               "Policy Filter",
+	OptionMaximumDatagramAssemblySize:                "Maximum Datagram Reassembly Size",
+	OptionDefaultIPTTL:                               "Default IP Time-to-live",
+	OptionPathMTUAgingTimeout:                        "Path MTU Aging Timeout",
+	OptionPathMTUPlateauTable:                        "Path MTU Plateau Table",
+	OptionInterfaceMTU:                               "Interface MTU",
+	OptionAllSubnetsAreLocal:                         "All Subnets Are Local",
+	OptionBroadcastAddress:                           "Broadcast Address",
+	OptionPerformMaskDiscovery:                       "Perform Mask Discovery",
+	OptionMaskSupplier:                               "Mask Supplier",
+	OptionPerformRouterDiscovery:                     "Perform Router Discovery",
+	OptionRouterSolicitationAddress:                  "Router Solicitation Address",
+	OptionStaticRoutingTable:                         "Static Routing Table",
+	OptionTrailerEncapsulation:                       "Trailer Encapsulation",
+	OptionArpCacheTimeout:                            "ARP Cache Timeout",
+	OptionEthernetEncapsulation:                      "Ethernet Encapsulation",
+	OptionDefaulTCPTTL:                               "Default TCP TTL",
+	OptionTCPKeepaliveInterval:                       "TCP Keepalive Interval",
+	OptionTCPKeepaliveGarbage:                        "TCP Keepalive Garbage",
+	OptionNetworkInformationServiceDomain:            "Network Information Service Domain",
+	OptionNetworkInformationServers:                  "Network Information Servers",
+	OptionNTPServers:                                 "NTP Servers",
+	OptionVendorSpecificInformation:                  "Vendor Specific Information",
+	OptionNetBIOSOverTCPIPNameServer:                 "NetBIOS over TCP/IP Name Server",
+	OptionNetBIOSOverTCPIPDatagramDistributionServer: "NetBIOS over TCP/IP Datagram Distribution Server",
+	OptionNetBIOSOverTCPIPNodeType:                   "NetBIOS over TCP/IP Node Type",
+	OptionNetBIOSOverTCPIPScope:                      "NetBIOS over TCP/IP Scope",
+	OptionXWindowSystemFontServer:                    "X Window System Font Server",
+	OptionXWindowSystemDisplayManger:                 "X Window System Display Manager",
+	OptionRequestedIPAddress:                         "Requested IP Address",
+	OptionIPAddressLeaseTime:                         "IP Addresses Lease Time",
+	OptionOptionOverload:                             "Option Overload",
+	OptionDHCPMessageType:                            "DHCP Message Type",
+	OptionServerIdentifier:                           "Server Identifier",
+	OptionParameterRequestList:                       "Parameter Request List",
+	OptionMessage:                                    "Message",
+	OptionMaximumDHCPMessageSize:                     "Maximum DHCP Message Size",
+	OptionRenewTimeValue:                             "Renew Time Value",
+	OptionRebindingTimeValue:                         "Rebinding Time Value",
+	OptionClassIdentifier:                            "Class Identifier",
+	OptionClientIdentifier:                           "Client identifier",
+	OptionNetWareIPDomainName:                        "NetWare/IP Domain Name",
+	OptionNetWareIPInformation:                       "NetWare/IP Information",
+	OptionNetworkInformationServicePlusDomain:        "Network Information Service+ Domain",
+	OptionNetworkInformationServicePlusServers:       "Network Information Service+ Servers",
+	OptionTFTPServerName:                             "TFTP Server Name",
+	OptionBootfileName:                               "Bootfile Name",
+	OptionMobileIPHomeAgent:                          "Mobile IP Home Agent",
+	OptionSimpleMailTransportProtocolServer:          "SMTP Server",
+	OptionPostOfficeProtocolServer:                   "POP Server",
+	OptionNetworkNewsTransportProtocolServer:         "NNTP Server",
+	OptionDefaultWorldWideWebServer:                  "Default WWW Server",
+	OptionDefaultFingerServer:                        "Default Finger Server",
+	OptionDefaultInternetRelayChatServer:             "Default IRC Server",
+	OptionStreetTalkServer:                           "StreetTalk Server",
+	OptionStreetTalkDirectoryAssistanceServer:        "StreetTalk Directory Assistance Server",
+	OptionUserClassInformation:                       "User Class Information",
+	OptionSLPDirectoryAgent:                          "SLP DIrectory Agent",
+	OptionSLPServiceScope:                            "SLP Service Scope",
+	OptionRapidCommit:                                "Rapid Commit",
+	OptionFQDN:                                       "FQDN",
+	OptionRelayAgentInformation:                      "Relay Agent Information",
+	OptionInternetStorageNameService:                 "Internet Storage Name Service",
+	// Option 84 returned in RFC 3679
+	OptionNDSServers:                       "NDS Servers",
+	OptionNDSTreeName:                      "NDS Tree Name",
+	OptionNDSContext:                       "NDS Context",
+	OptionBCMCSControllerDomainNameList:    "BCMCS Controller Domain Name List",
+	OptionBCMCSControllerIPv4AddressList:   "BCMCS Controller IPv4 Address List",
+	OptionAuthentication:                   "Authentication",
+	OptionClientLastTransactionTime:        "Client Last Transaction Time",
+	OptionAssociatedIP:                     "Associated IP",
+	OptionClientSystemArchitectureType:     "Client System Architecture Type",
+	OptionClientNetworkInterfaceIdentifier: "Client Network Interface Identifier",
+	OptionLDAP:                             "LDAP",
+	// Option 96 returned in RFC 3679
+	OptionClientMachineIdentifier:     "Client Machine Identifier",
+	OptionOpenGroupUserAuthentication: "OpenGroup's User Authentication",
+	OptionGeoConfCivic:                "GEOCONF_CIVIC",
+	OptionIEEE10031TZString:           "IEEE 1003.1 TZ String",
+	OptionReferenceToTZDatabase:       "Reference to the TZ Database",
+	// Option 108 returned in RFC 8925
+	OptionIPv6OnlyPreferred: "IPv6-Only Preferred",
+	// Options 102-111 returned in RFC 3679
+	OptionNetInfoParentServerAddress: "NetInfo Parent Server Address",
+	OptionNetInfoParentServerTag:     "NetInfo Parent Server Tag",
+	OptionURL:                        "URL",
+	// Option 115 returned in RFC 3679
+	OptionAutoConfigure:                   "Auto-Configure",
+	OptionNameServiceSearch:               "Name Service Search",
+	OptionSubnetSelection:                 "Subnet Selection",
+	OptionDNSDomainSearchList:             "DNS Domain Search List",
+	OptionSIPServers:                      "SIP Servers",
+	OptionClasslessStaticRoute:            "Classless Static Route",
+	OptionCCC:                             "CCC, CableLabs Client Configuration",
+	OptionGeoConf:                         "GeoConf",
+	OptionVendorIdentifyingVendorClass:    "Vendor-Identifying Vendor Class",
+	OptionVendorIdentifyingVendorSpecific: "Vendor-Identifying Vendor-Specific",
+	// Options 126-127 returned in RFC 3679
+	OptionTFTPServerIPAddress:                   "TFTP Server IP Address",
+	OptionCallServerIPAddress:                   "Call Server IP Address",
+	OptionDiscriminationString:                  "Discrimination String",
+	OptionRemoteStatisticsServerIPAddress:       "RemoteStatistics Server IP Address",
+	Option8021PVLANID:                           "802.1P VLAN ID",
+	Option8021QL2Priority:                       "802.1Q L2 Priority",
+	OptionDiffservCodePoint:                     "Diffserv Code Point",
+	OptionHTTPProxyForPhoneSpecificApplications: "HTTP Proxy for phone-specific applications",
+	OptionPANAAuthenticationAgent:               "PANA Authentication Agent",
+	OptionLoSTServer:                            "LoST Server",
+	OptionCAPWAPAccessControllerAddresses:       "CAPWAP Access Controller Addresses",
+	OptionOPTIONIPv4AddressMoS:                  "OPTION-IPv4_Address-MoS",
+	OptionOPTIONIPv4FQDNMoS:                     "OPTION-IPv4_FQDN-MoS",
+	OptionSIPUAConfigurationServiceDomains:      "SIP UA Configuration Service Domains",
+	OptionOPTIONIPv4AddressANDSF:                "OPTION-IPv4_Address-ANDSF",
+	OptionOPTIONIPv6AddressANDSF:                "OPTION-IPv6_Address-ANDSF",
+	// Options 144-149 returned in RFC 3679
+	OptionTFTPServerAddress: "TFTP Server Address",
+	OptionStatusCode:        "Status Code",
+	OptionBaseTime:          "Base Time",
+	OptionStartTimeOfState:  "Start Time of State",
+	OptionQueryStartTime:    "Query Start Time",
+	OptionQueryEndTime:      "Query End Time",
+	OptionDHCPState:         "DHCP Staet",
+	OptionDataSource:        "Data Source",
+	// Options 158-174 returned in RFC 3679
+	OptionEtherboot:                        "Etherboot",
+	OptionIPTelephone:                      "IP Telephone",
+	OptionEtherbootPacketCableAndCableHome: "Etherboot / PacketCable and CableHome",
+	// Options 178-207 returned in RFC 3679
+	OptionPXELinuxMagicString:  "PXELinux Magic String",
+	OptionPXELinuxConfigFile:   "PXELinux Config File",
+	OptionPXELinuxPathPrefix:   "PXELinux Path Prefix",
+	OptionPXELinuxRebootTime:   "PXELinux Reboot Time",
+	OptionOPTION6RD:            "OPTION_6RD",
+	OptionOPTIONv4AccessDomain: "OPTION_V4_ACCESS_DOMAIN",
+	// Options 214-219 returned in RFC 3679
+	OptionSubnetAllocation:        "Subnet Allocation",
+	OptionVirtualSubnetAllocation: "Virtual Subnet Selection",
+	// Options 222-223 returned in RFC 3679
+	// Options 224-254 are reserved for private use
+
+	OptionEnd: "End",
+}

vendor/github.com/insomniacslk/dhcp/iana/archtype.go

@@ -0,0 +1,148 @@
+package iana
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/u-root/uio/uio"
+)
+
+// Arch encodes an architecture type per RFC 4578, Section 2.1.
+type Arch uint16
+
+// See RFC 4578, 5970, and http://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#processor-architecture
+const (
+	INTEL_X86PC       Arch = 0
+	NEC_PC98          Arch = 1
+	EFI_ITANIUM       Arch = 2
+	DEC_ALPHA         Arch = 3
+	ARC_X86           Arch = 4
+	INTEL_LEAN_CLIENT Arch = 5
+	EFI_IA32          Arch = 6
+	EFI_X86_64        Arch = 7
+	EFI_XSCALE        Arch = 8
+	EFI_BC            Arch = 9
+	EFI_ARM32         Arch = 10
+	EFI_ARM64         Arch = 11
+	PPC_OPEN_FIRMWARE Arch = 12
+	PPC_EPAPR         Arch = 13
+	PPC_OPAL          Arch = 14
+	EFI_X86_HTTP      Arch = 15
+	EFI_X86_64_HTTP   Arch = 16
+	EFI_BC_HTTP       Arch = 17
+	EFI_ARM32_HTTP    Arch = 18
+	EFI_ARM64_HTTP    Arch = 19
+	INTEL_X86PC_HTTP  Arch = 20
+	UBOOT_ARM32       Arch = 21
+	UBOOT_ARM64       Arch = 22
+	UBOOT_ARM32_HTTP  Arch = 23
+	UBOOT_ARM64_HTTP  Arch = 24
+	EFI_RISCV32       Arch = 25
+	EFI_RISCV32_HTTP  Arch = 26
+	EFI_RISCV64       Arch = 27
+	EFI_RISCV64_HTTP  Arch = 28
+	EFI_RISCV128      Arch = 29
+	EFI_RISCV128_HTTP Arch = 30
+	S390_BASIC        Arch = 31
+	S390_EXTENDED     Arch = 32
+	EFI_MIPS32        Arch = 33
+	EFI_MIPS64        Arch = 34
+	EFI_SUNWAY32      Arch = 35
+	EFI_SUNWAY64      Arch = 36
+)
+
+// archTypeToStringMap maps an Arch to a mnemonic name
+var archTypeToStringMap = map[Arch]string{
+	INTEL_X86PC:       "Intel x86PC",
+	NEC_PC98:          "NEC/PC98",
+	EFI_ITANIUM:       "EFI Itanium",
+	DEC_ALPHA:         "DEC Alpha",
+	ARC_X86:           "Arc x86",
+	INTEL_LEAN_CLIENT: "Intel Lean Client",
+	EFI_IA32:          "EFI IA32",
+	EFI_XSCALE:        "EFI Xscale",
+	EFI_X86_64:        "EFI x86-64",
+	EFI_BC:            "EFI BC",
+	EFI_ARM32:         "EFI ARM32",
+	EFI_ARM64:         "EFI ARM64",
+	PPC_OPEN_FIRMWARE: "PowerPC Open Firmware",
+	PPC_EPAPR:         "PowerPC ePAPR",
+	PPC_OPAL:          "POWER OPAL v3",
+	EFI_X86_HTTP:      "EFI x86 boot from HTTP",
+	EFI_X86_64_HTTP:   "EFI x86-64 boot from HTTP",
+	EFI_BC_HTTP:       "EFI BC boot from HTTP",
+	EFI_ARM32_HTTP:    "EFI ARM32 boot from HTTP",
+	EFI_ARM64_HTTP:    "EFI ARM64 boot from HTTP",
+	INTEL_X86PC_HTTP:  "Intel x86PC boot from HTTP",
+	UBOOT_ARM32:       "U-Boot ARM32",
+	UBOOT_ARM64:       "U-Boot ARM64",
+	UBOOT_ARM32_HTTP:  "U-boot ARM32 boot from HTTP",
+	UBOOT_ARM64_HTTP:  "U-Boot ARM64 boot from HTTP",
+	EFI_RISCV32:       "EFI RISC-V 32-bit",
+	EFI_RISCV32_HTTP:  "EFI RISC-V 32-bit boot from HTTP",
+	EFI_RISCV64:       "EFI RISC-V 64-bit",
+	EFI_RISCV64_HTTP:  "EFI RISC-V 64-bit boot from HTTP",
+	EFI_RISCV128:      "EFI RISC-V 128-bit",
+	EFI_RISCV128_HTTP: "EFI RISC-V 128-bit boot from HTTP",
+	S390_BASIC:        "s390 Basic",
+	S390_EXTENDED:     "s390 Extended",
+	EFI_MIPS32:        "EFI MIPS32",
+	EFI_MIPS64:        "EFI MIPS64",
+	EFI_SUNWAY32:      "EFI Sunway 32-bit",
+	EFI_SUNWAY64:      "EFI Sunway 64-bit",
+}
+
+// String returns a mnemonic name for a given architecture type.
+func (a Arch) String() string {
+	if at := archTypeToStringMap[a]; at != "" {
+		return at
+	}
+	return "unknown"
+}
+
+// Archs represents multiple Arch values.
+type Archs []Arch
+
+// Contains returns whether b is one of the Archs in a.
+func (a Archs) Contains(b Arch) bool {
+	for _, t := range a {
+		if t == b {
+			return true
+		}
+	}
+	return false
+}
+
+// ToBytes returns the serialized option defined by RFC 4578 (DHCPv4) and RFC
+// 5970 (DHCPv6) as the Client System Architecture Option.
+func (a Archs) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, at := range a {
+		buf.Write16(uint16(at))
+	}
+	return buf.Data()
+}
+
+// String returns the list of archs in a human-readable manner.
+func (a Archs) String() string {
+	s := make([]string, 0, len(a))
+	for _, arch := range a {
+		s = append(s, arch.String())
+	}
+	return strings.Join(s, ", ")
+}
+
+// FromBytes parses a DHCP list of architecture types as defined by RFC 4578
+// and RFC 5970.
+func (a *Archs) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	if buf.Len() == 0 {
+		return fmt.Errorf("must have at least one archtype if option is present")
+	}
+
+	*a = make([]Arch, 0, buf.Len()/2)
+	for buf.Has(2) {
+		*a = append(*a, Arch(buf.Read16()))
+	}
+	return buf.FinError()
+}

vendor/github.com/insomniacslk/dhcp/iana/entid.go

@@ -0,0 +1,25 @@
+package iana
+
+// EnterpriseID represents the Enterprise IDs as set by IANA
+type EnterpriseID int
+
+// See https://www.iana.org/assignments/enterprise-numbers/enterprise-numbers for values
+const (
+	EnterpriseIDCiscoSystems            EnterpriseID = 9
+	EnterpriseIDCienaCorporation        EnterpriseID = 1271
+	EnterpriseIDMellanoxTechnologiesLTD EnterpriseID = 33049
+)
+
+var enterpriseIDToStringMap = map[EnterpriseID]string{
+	EnterpriseIDCiscoSystems:            "Cisco Systems",
+	EnterpriseIDCienaCorporation:        "Ciena Corporation",
+	EnterpriseIDMellanoxTechnologiesLTD: "Mellanox Technologies LTD",
+}
+
+// String returns the vendor name for a given Enterprise ID
+func (e EnterpriseID) String() string {
+	if vendor := enterpriseIDToStringMap[e]; vendor != "" {
+		return vendor
+	}
+	return "Unknown"
+}

vendor/github.com/insomniacslk/dhcp/iana/hwtypes.go

@@ -0,0 +1,91 @@
+package iana
+
+// HWType is a hardware type as per RFC 2132 and defined by the IANA.
+type HWType uint16
+
+// See IANA for values.
+const (
+	_ HWType = iota // skip 0
+	HWTypeEthernet
+	HWTypeExperimentalEthernet
+	HWTypeAmateurRadioAX25
+	HWTypeProteonTokenRing
+	HWTypeChaos
+	HWTypeIEEE802
+	HWTypeARCNET
+	HWTypeHyperchannel
+	HWTypeLanstar
+	HWTypeAutonet
+	HWTypeLocalTalk
+	HWTypeLocalNet
+	HWTypeUltraLink
+	HWTypeSMDS
+	HWTypeFrameRelay
+	HWTypeATM
+	HWTypeHDLC
+	HWTypeFibreChannel
+	HWTypeATM2
+	HWTypeSerialLine
+	HWTypeATM3
+	HWTypeMILSTD188220
+	HWTypeMetricom
+	HWTypeIEEE1394
+	HWTypeMAPOS
+	HWTypeTwinaxial
+	HWTypeEUI64
+	HWTypeHIPARP
+	HWTypeISO7816
+	HWTypeARPSec
+	HWTypeIPsec
+	HWTypeInfiniband
+	HWTypeCAI
+	HWTypeWiegandInterface
+	HWTypePureIP
+)
+
+var hwTypeToString = map[HWType]string{
+	HWTypeEthernet:             "Ethernet",
+	HWTypeExperimentalEthernet: "Experimental Ethernet",
+	HWTypeAmateurRadioAX25:     "Amateur Radio AX.25",
+	HWTypeProteonTokenRing:     "Proteon ProNET Token Ring",
+	HWTypeChaos:                "Chaos",
+	HWTypeIEEE802:              "IEEE 802",
+	HWTypeARCNET:               "ARCNET",
+	HWTypeHyperchannel:         "Hyperchannel",
+	HWTypeLanstar:              "Lanstar",
+	HWTypeAutonet:              "Autonet Short Address",
+	HWTypeLocalTalk:            "LocalTalk",
+	HWTypeLocalNet:             "LocalNet",
+	HWTypeUltraLink:            "Ultra link",
+	HWTypeSMDS:                 "SMDS",
+	HWTypeFrameRelay:           "Frame Relay",
+	HWTypeATM:                  "ATM",
+	HWTypeHDLC:                 "HDLC",
+	HWTypeFibreChannel:         "Fibre Channel",
+	HWTypeATM2:                 "ATM 2",
+	HWTypeSerialLine:           "Serial Line",
+	HWTypeATM3:                 "ATM 3",
+	HWTypeMILSTD188220:         "MIL-STD-188-220",
+	HWTypeMetricom:             "Metricom",
+	HWTypeIEEE1394:             "IEEE 1394.1995",
+	HWTypeMAPOS:                "MAPOS",
+	HWTypeTwinaxial:            "Twinaxial",
+	HWTypeEUI64:                "EUI-64",
+	HWTypeHIPARP:               "HIPARP",
+	HWTypeISO7816:              "IP and ARP over ISO 7816-3",
+	HWTypeARPSec:               "ARPSec",
+	HWTypeIPsec:                "IPsec tunnel",
+	HWTypeInfiniband:           "Infiniband",
+	HWTypeCAI:                  "CAI, TIA-102 Project 125 Common Air Interface",
+	HWTypeWiegandInterface:     "Wiegand Interface",
+	HWTypePureIP:               "Pure IP",
+}
+
+// String implements fmt.Stringer.
+func (h HWType) String() string {
+	hwtype := hwTypeToString[h]
+	if hwtype == "" {
+		hwtype = "unknown"
+	}
+	return hwtype
+}

vendor/github.com/insomniacslk/dhcp/iana/iana.go

@@ -0,0 +1,2 @@
+// Package iana contains constants defined by IANA.
+package iana

vendor/github.com/insomniacslk/dhcp/iana/statuscodes.go

@@ -0,0 +1,77 @@
+package iana
+
+// StatusCode represents a IANA status code for DHCPv6
+//
+// IANA Status Codes for DHCPv6
+// https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#dhcpv6-parameters-5
+type StatusCode uint16
+
+// IANA status codes
+const (
+	// RFC 3315 par. 24..4
+	StatusSuccess       StatusCode = 0
+	StatusUnspecFail    StatusCode = 1
+	StatusNoAddrsAvail  StatusCode = 2
+	StatusNoBinding     StatusCode = 3
+	StatusNotOnLink     StatusCode = 4
+	StatusUseMulticast  StatusCode = 5
+	StatusNoPrefixAvail StatusCode = 6
+	// RFC 5007
+	StatusUnknownQueryType StatusCode = 7
+	StatusMalformedQuery   StatusCode = 8
+	StatusNotConfigured    StatusCode = 9
+	StatusNotAllowed       StatusCode = 10
+	// RFC 5460
+	StatusQueryTerminated StatusCode = 11
+	// RFC 7653
+	StatusDataMissing          StatusCode = 12
+	StatusCatchUpComplete      StatusCode = 13
+	StatusNotSupported         StatusCode = 14
+	StatusTLSConnectionRefused StatusCode = 15
+	// RFC 8156
+	StatusAddressInUse               StatusCode = 16
+	StatusConfigurationConflict      StatusCode = 17
+	StatusMissingBindingInformation  StatusCode = 18
+	StatusOutdatedBindingInformation StatusCode = 19
+	StatusServerShuttingDown         StatusCode = 20
+	StatusDNSUpdateNotSupported      StatusCode = 21
+	StatusExcessiveTimeSkew          StatusCode = 22
+)
+
+// String returns a mnemonic name for a given status code
+func (s StatusCode) String() string {
+	if sc := statusCodeToStringMap[s]; sc != "" {
+		return sc
+	}
+	return "Unknown"
+}
+
+var statusCodeToStringMap = map[StatusCode]string{
+	StatusSuccess:       "Success",
+	StatusUnspecFail:    "UnspecFail",
+	StatusNoAddrsAvail:  "NoAddrsAvail",
+	StatusNoBinding:     "NoBinding",
+	StatusNotOnLink:     "NotOnLink",
+	StatusUseMulticast:  "UseMulticast",
+	StatusNoPrefixAvail: "NoPrefixAvail",
+	// RFC 5007
+	StatusUnknownQueryType: "UnknownQueryType",
+	StatusMalformedQuery:   "MalformedQuery",
+	StatusNotConfigured:    "NotConfigured",
+	StatusNotAllowed:       "NotAllowed",
+	// RFC 5460
+	StatusQueryTerminated: "QueryTerminated",
+	// RFC 7653
+	StatusDataMissing:          "DataMissing",
+	StatusCatchUpComplete:      "CatchUpComplete",
+	StatusNotSupported:         "NotSupported",
+	StatusTLSConnectionRefused: "TLSConnectionRefused",
+	// RFC 8156
+	StatusAddressInUse:               "AddressInUse",
+	StatusConfigurationConflict:      "ConfigurationConflict",
+	StatusMissingBindingInformation:  "MissingBindingInformation",
+	StatusOutdatedBindingInformation: "OutdatedBindingInformation",
+	StatusServerShuttingDown:         "ServerShuttingDown",
+	StatusDNSUpdateNotSupported:      "DNSUpdateNotSupported",
+	StatusExcessiveTimeSkew:          "ExcessiveTimeSkew",
+}

vendor/github.com/insomniacslk/dhcp/interfaces/bindtodevice_bsd.go

@@ -0,0 +1,19 @@
+// +build aix freebsd openbsd netbsd dragonfly
+
+package interfaces
+
+import (
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+// BindToInterface emulates linux's SO_BINDTODEVICE option for a socket by using
+// IP_RECVIF.
+func BindToInterface(fd int, ifname string) error {
+	iface, err := net.InterfaceByName(ifname)
+	if err != nil {
+		return err
+	}
+	return unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_RECVIF, iface.Index)
+}

vendor/github.com/insomniacslk/dhcp/interfaces/bindtodevice_darwin.go

@@ -0,0 +1,19 @@
+// +build darwin
+
+package interfaces
+
+import (
+	"net"
+
+	"golang.org/x/sys/unix"
+)
+
+// BindToInterface emulates linux's SO_BINDTODEVICE option for a socket by using
+// IP_BOUND_IF.
+func BindToInterface(fd int, ifname string) error {
+	iface, err := net.InterfaceByName(ifname)
+	if err != nil {
+		return err
+	}
+	return unix.SetsockoptInt(fd, unix.IPPROTO_IP, unix.IP_BOUND_IF, iface.Index)
+}

vendor/github.com/insomniacslk/dhcp/interfaces/bindtodevice_linux.go

@@ -0,0 +1,9 @@
+// +build linux
+
+package interfaces
+
+import "golang.org/x/sys/unix"
+
+func BindToInterface(fd int, ifname string) error {
+	return unix.BindToDevice(fd, ifname)
+}

vendor/github.com/insomniacslk/dhcp/interfaces/bindtodevice_windows.go

@@ -0,0 +1,8 @@
+package interfaces
+
+import "errors"
+
+// BindToInterface fails on Windows.
+func BindToInterface(fd int, ifname string) error {
+	return errors.New("not implemented on Windows")
+}

vendor/github.com/insomniacslk/dhcp/interfaces/interfaces.go

@@ -0,0 +1,41 @@
+package interfaces
+
+import "net"
+
+// InterfaceMatcher is a function type used to match the interfaces we want. See
+// GetInterfacesFunc below for usage.
+type InterfaceMatcher func(net.Interface) bool
+
+// interfaceGetter is used for testing purposes
+var interfaceGetter = net.Interfaces
+
+// GetInterfacesFunc loops through the available network interfaces, and returns
+// a list of interfaces for which the passed InterfaceMatcher function returns
+// true.
+func GetInterfacesFunc(matcher InterfaceMatcher) ([]net.Interface, error) {
+	ifaces, err := interfaceGetter()
+	if err != nil {
+		return nil, err
+	}
+	ret := make([]net.Interface, 0)
+	for _, iface := range ifaces {
+		if matcher(iface) {
+			ret = append(ret, iface)
+		}
+	}
+	return ret, nil
+}
+
+// GetLoopbackInterfaces returns a list of loopback interfaces.
+func GetLoopbackInterfaces() ([]net.Interface, error) {
+	return GetInterfacesFunc(func(iface net.Interface) bool {
+		return iface.Flags&net.FlagLoopback != 0
+	})
+}
+
+// GetNonLoopbackInterfaces returns a list of non-loopback interfaces.
+func GetNonLoopbackInterfaces() ([]net.Interface, error) {
+	return GetInterfacesFunc(func(iface net.Interface) bool {
+		return iface.Flags&net.FlagLoopback == 0
+	})
+}

vendor/github.com/insomniacslk/dhcp/rfc1035label/label.go

@@ -0,0 +1,173 @@
+package rfc1035label
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// Labels represents RFC1035 labels
+//
+// This implements RFC 1035 labels, including compression.
+// https://tools.ietf.org/html/rfc1035#section-4.1.4
+type Labels struct {
+	// original contains the original bytes if the object was parsed from a byte
+	// sequence, or nil otherwise. The `original` field is necessary to deal
+	// with compressed labels. If the labels are further modified, the original
+	// content is invalidated and no compression will be used.
+	original []byte
+	// Labels contains the parsed labels. A change here invalidates the
+	// `original` object.
+	Labels []string
+}
+
+// same compares two string arrays
+func same(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := 0; i < len(a); i++ {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// String prints labels.
+func (l *Labels) String() string {
+	return fmt.Sprintf("%v", l.Labels)
+}
+
+// ToBytes returns a byte sequence representing the labels. If the original
+// sequence is modified, the labels are parsed again, otherwise the original
+// byte sequence is returned.
+func (l *Labels) ToBytes() []byte {
+	// if the original byte sequence has been modified, invalidate it and
+	// serialize again.
+	// NOTE: this function is not thread-safe. If multiple threads modify
+	// the `Labels` field, the result may be wrong.
+	originalLabels, err := labelsFromBytes(l.original)
+	// if the original object has not been modified, or we cannot parse it,
+	// return the original bytes.
+	if err != nil || (l.original != nil && same(originalLabels, l.Labels)) {
+		return l.original
+	}
+	return labelsToBytes(l.Labels)
+}
+
+// Length returns the length in bytes of the serialized labels
+func (l *Labels) Length() int {
+	return len(l.ToBytes())
+}
+
+// NewLabels returns an initialized Labels object.
+func NewLabels() *Labels {
+	return &Labels{
+		Labels: make([]string, 0),
+	}
+}
+
+// FromBytes reads labels from a bytes stream according to RFC 1035.
+func (l *Labels) FromBytes(data []byte) error {
+	labs, err := labelsFromBytes(data)
+	if err != nil {
+		return err
+	}
+	l.original = data
+	l.Labels = labs
+	return nil
+}
+
+// FromBytes returns a Labels object from the given byte sequence, or an error if
+// any.
+func FromBytes(data []byte) (*Labels, error) {
+	var l Labels
+	if err := l.FromBytes(data); err != nil {
+		return nil, err
+	}
+	return &l, nil
+}
+
+// ErrBufferTooShort is returned when the label cannot be parsed due to a wrong
+// length or missing bytes.
+var ErrBufferTooShort = errors.New("rfc1035label: buffer too short")
+
+// fromBytes decodes a serialized stream and returns a list of labels
+func labelsFromBytes(buf []byte) ([]string, error) {
+	var (
+		labels          = make([]string, 0)
+		pos, oldPos     int
+		label           string
+		handlingPointer bool
+	)
+
+	for {
+		if pos >= len(buf) {
+			// interpret label without trailing zero-length byte as a partial
+			// domain name field as per RFC 4704 Section 4.2
+			if label != "" {
+				labels = append(labels, label)
+			}
+
+			break
+		}
+		length := int(buf[pos])
+		pos++
+		var chunk string
+		if length == 0 {
+			labels = append(labels, label)
+			label = ""
+			if handlingPointer {
+				pos = oldPos
+				handlingPointer = false
+			}
+		} else if length&0xc0 == 0xc0 {
+			// compression pointer
+			if handlingPointer {
+				return nil, errors.New("rfc1035label: cannot handle nested pointers")
+			}
+			handlingPointer = true
+			if pos+1 > len(buf) {
+				return nil, errors.New("rfc1035label: pointer buffer too short")
+			}
+			off := int(buf[pos-1]&^0xc0)<<8 + int(buf[pos])
+			oldPos = pos + 1
+			pos = off
+		} else {
+			if pos+length > len(buf) {
+				return nil, ErrBufferTooShort
+			}
+			chunk = string(buf[pos : pos+length])
+			if label != "" {
+				label += "."
+			}
+			label += chunk
+			pos += length
+		}
+	}
+	return labels, nil
+}
+
+// labelToBytes encodes a label and returns a serialized stream of bytes
+func labelToBytes(label string) []byte {
+	var encodedLabel []byte
+	if len(label) == 0 {
+		return []byte{0}
+	}
+	for _, part := range strings.Split(label, ".") {
+		encodedLabel = append(encodedLabel, byte(len(part)))
+		encodedLabel = append(encodedLabel, []byte(part)...)
+	}
+	return append(encodedLabel, 0)
+}
+
+// labelsToBytes encodes a list of labels and returns a serialized stream of
+// bytes
+func labelsToBytes(labels []string) []byte {
+	var encodedLabels []byte
+	for _, label := range labels {
+		encodedLabels = append(encodedLabels, labelToBytes(label)...)
+	}
+	return encodedLabels
+}