add ntp.Client and begin adding dhcp.Client

lneto/dhcp/client.go

@@ -0,0 +1,56 @@
+package dhcp
+
+import (
+	"io"
+)
+
+type ClientV4 struct {
+	reqHostname []byte
+	hostname    []byte
+	offer       [4]byte
+	svip        [4]byte
+	reqIP       [4]byte
+	dns         [4]byte
+	router      [4]byte
+	subnet      [4]byte
+	broadcast   [4]byte
+	gateway     [4]byte
+	optbuf      [10]Option
+	currentXID  uint32
+	tRenew      uint32
+	tRebind     uint32
+	tIPLease    uint32
+	state       ClientState
+}
+
+type RequestConfig struct {
+	RequestedAddr [4]byte
+	// Optional hostname to request.
+	Hostname string
+}
+
+func (c *ClientV4) BeginRequest(xid uint32, cfg RequestConfig) error {
+	c.currentXID = xid
+	c.reqHostname = append(c.reqHostname[:0], cfg.Hostname...)
+	c.reqIP = cfg.RequestedAddr
+	return nil
+}
+
+func (c *ClientV4) Write(dst []byte) (int, error) {
+	if c.isClosed() {
+		return 0, io.EOF
+	}
+	frm, err := NewFrameV4(dst)
+	if err != nil {
+		return 0, err
+	}
+	// var options []Option
+	// var nextState ClientState
+	switch c.state {
+	case StateInit:
+		frm.MagicCookie()
+	}
+	return 0, nil
+}
+
+func (c *ClientV4) isClosed() bool { return c.state == 0 }

lneto/dhcp/definitions.go

@@ -5,7 +5,30 @@ import (
 	"fmt"
 )
 
-//go:generate stringer -type=OptNum,Op,MessageType -linecomment -output stringers.go
+//go:generate stringer -type=OptNum,Op,MessageType,ClientState -linecomment -output stringers.go
+
+type ClientState uint8
+
+// State transition table:
+//
+//	StateInit      -> | Send out Discover  | -> StateSelecting
+//	StateSelecting -> |Accept Offer+Request| -> StateRequesting
+//	StateRequesting-> |    Receive Ack     | -> StateBound
+const (
+	_ ClientState = iota
+	// On clean slate boot, abort, NAK or decline enter the INIT state.
+	StateInit // init
+	// After sending out a Discover enter SELECTING.
+	StateSelecting // selecting
+	// After receiving a worthy offer and sending out request for offer enter REQUESTING.
+	StateRequesting // requesting
+	// On ACK to Request enter BOUND.
+	StateBound      // bound
+	StateRenewing   // renewing
+	StateRebinding  // rebinding
+	StateInitReboot // init-reboot
+	StateRebooting  // rebooting
+)
 
 type Option struct {
 	Num  OptNum

lneto/dhcp/frame.go

@@ -20,8 +20,11 @@ const (
 	DefaultServerPort = 67
 )
 
-func NewFrameV4(buf []byte) FrameV4 {
-	return FrameV4{buf: buf}
+func NewFrameV4(buf []byte) (FrameV4, error) {
+	if len(buf) < sizeHeader {
+		return FrameV4{}, errors.New("DHCP short frame")
+	}
+	return FrameV4{buf: buf}, nil
 }
 
 // Frame encapsulates the raw data of a DHCP packet
@@ -94,6 +97,13 @@ func (frm FrameV4) MagicCookie() uint32 {
 	return binary.BigEndian.Uint32(frm.buf[magicCookieOffset:])
 }
 
+// ClearHeader zeros out the header contents.
+func (frm FrameV4) ClearHeader() {
+	for i := range frm.buf[:sizeHeader] {
+		frm.buf[i] = 0
+	}
+}
+
 func (frm FrameV4) ForEachOption(fn func(opt Option) error) error {
 	if fn == nil {
 		return errors.New("nil function to parse DHCP")

lneto/dhcp/stringers.go

@@ -1,4 +1,4 @@
-// Code generated by "stringer -type=OptNum,Op,MessageType -linecomment -output stringers.go"; DO NOT EDIT.
+// Code generated by "stringer -type=OptNum,Op,MessageType,ClientState -linecomment -output stringers.go"; DO NOT EDIT.
 
 package dhcp
 
@@ -126,3 +126,28 @@ func (i MessageType) String() string {
 	}
 	return _MessageType_name[_MessageType_index[i]:_MessageType_index[i+1]]
 }
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[StateInit-1]
+	_ = x[StateSelecting-2]
+	_ = x[StateRequesting-3]
+	_ = x[StateBound-4]
+	_ = x[StateRenewing-5]
+	_ = x[StateRebinding-6]
+	_ = x[StateInitReboot-7]
+	_ = x[StateRebooting-8]
+}
+
+const _ClientState_name = "initselectingrequestingboundrenewingrebindinginit-rebootrebooting"
+
+var _ClientState_index = [...]uint8{0, 4, 13, 23, 28, 36, 45, 56, 65}
+
+func (i ClientState) String() string {
+	i -= 1
+	if i >= ClientState(len(_ClientState_index)-1) {
+		return "ClientState(" + strconv.FormatInt(int64(i+1), 10) + ")"
+	}
+	return _ClientState_name[_ClientState_index[i]:_ClientState_index[i+1]]
+}

lneto/dns/definitions.go

@@ -97,6 +97,13 @@ func (frm Frame) SetARCount(arCount uint16) {
 	binary.BigEndian.PutUint16(frm.buf[10:12], arCount)
 }
 
+// ClearHeader zeros out the fixed(non-variable) header contents.
+func (frm Frame) ClearHeader() {
+	for i := range frm.buf[:SizeHeader] {
+		frm.buf[i] = 0
+	}
+}
+
 // HeaderFlags gathers the flags in bits 16..31 of the header.
 type HeaderFlags uint16
 

lneto/frames.go

@@ -125,6 +125,13 @@ func (efrm EthFrame) IsVLAN() bool {
 	return efrm.EtherTypeOrSize() == EtherTypeVLAN
 }
 
+// ClearHeader zeros out the fixed(non-variable) header contents.
+func (frm EthFrame) ClearHeader() {
+	for i := range frm.buf[:sizeHeaderEthNoVLAN] {
+		frm.buf[i] = 0
+	}
+}
+
 // ARPFrame encapsulates the raw data of an ARP packet
 // and provides methods for manipulating, validating and
 // retrieving fields and payload data. See [RFC826].
@@ -208,6 +215,13 @@ func (afrm ARPFrame) Target16() (hardwareAddr *[6]byte, proto *[16]byte) {
 	return (*[6]byte)(afrm.buf[30:36]), (*[16]byte)(afrm.buf[36:52])
 }
 
+// ClearHeader zeros out the fixed(non-variable) header contents.
+func (frm ARPFrame) ClearHeader() {
+	for i := range frm.buf[:8] {
+		frm.buf[i] = 0
+	}
+}
+
 // IPv4Frame encapsulates the raw data of an IPv4 packet
 // and provides methods for manipulating, validating and
 // retreiving fields and payload data. See [RFC791].
@@ -356,6 +370,13 @@ func (ifrm IPv4Frame) Payload() []byte {
 	return ifrm.buf[off:l]
 }
 
+// ClearHeader zeros out the fixed(non-variable) header contents.
+func (frm IPv4Frame) ClearHeader() {
+	for i := range frm.buf[:sizeHeaderIPv4] {
+		frm.buf[i] = 0
+	}
+}
+
 // IPv6Frame encapsulates the raw data of an IPv6 packet
 // and provides methods for manipulating, validating and
 // retrieving fields and payload data. See [RFC8200].
@@ -443,6 +464,13 @@ func (ifrm IPv6Frame) crcWritePseudo(crc *CRC791) {
 	crc.AddUint32(uint32(ifrm.NextHeader()))
 }
 
+// ClearHeader zeros out the header contents.
+func (frm IPv6Frame) ClearHeader() {
+	for i := range frm.buf[:sizeHeaderIPv6] {
+		frm.buf[i] = 0
+	}
+}
+
 // TCPFrame encapsulates the raw data of a TCP segment
 // and provides methods for manipulating, validating and
 // retrieving fields and payload data. See [RFC9293].
@@ -581,6 +609,13 @@ func (tfrm TCPFrame) Options() []byte {
 	return tfrm.buf[sizeHeaderTCP:tfrm.HeaderLength()]
 }
 
+// ClearHeader zeros out the fixed(non-variable) header contents.
+func (frm TCPFrame) ClearHeader() {
+	for i := range frm.buf[:sizeHeaderTCP] {
+		frm.buf[i] = 0
+	}
+}
+
 // UDPFrame encapsulates the raw data of a UDP datagram
 // and provides methods for manipulating, validating and
 // retrieving fields and payload data. See [RFC768].
@@ -662,3 +697,10 @@ func (ufrm UDPFrame) CalculateIPv6Checksum(ifrm IPv6Frame) uint16 {
 	crc.Write(ufrm.Payload())
 	return crc.Sum16()
 }
+
+// ClearHeader zeros out the header contents.
+func (frm UDPFrame) ClearHeader() {
+	for i := range frm.buf[:sizeHeaderUDP] {
+		frm.buf[i] = 0
+	}
+}

lneto/ntp/client.go

@@ -0,0 +1,135 @@
+package ntp
+
+import (
+	"errors"
+	"io"
+	"time"
+)
+
+type state uint8
+
+const (
+	stateClosed state = iota
+	stateSend1
+	stateAwait1
+	stateSend2
+	stateAwait2
+	stateDone
+)
+
+const sysprecRecalcNeeded int8 = 127
+
+func NewClient(now func() time.Time) *Client {
+	return &Client{
+		_now:     now,
+		_sysprec: sysprecRecalcNeeded,
+	}
+}
+
+type Client struct {
+	start time.Time
+	_now  func() time.Time
+	t     [4]Timestamp
+	// org      Timestamp
+	// rec      Timestamp
+	xmt      Timestamp
+	state    state
+	_sysprec int8
+}
+
+func (c *Client) Write(payload []byte) (int, error) {
+	if c.isDone() {
+		return 0, io.EOF
+	}
+	frm, err := NewFrame(payload)
+	if err != nil {
+		return 0, err
+	}
+
+	switch c.state {
+	case stateSend1:
+		c.start = c.now()
+		c.xmt = TimestampFromUint64(0)
+		c.state = stateAwait1
+	case stateSend2:
+		c.xmt = c.unsyncTimestamp(c.now())
+		c.state = stateDone
+	default:
+		return 0, nil // Nothing to handle.
+	}
+
+	for i := range payload[:SizeHeader] {
+		payload[i] = 0
+	}
+	sysprec := c.sysprec()
+	frm.ClearHeader()
+	frm.SetStratum(StratumUnsync)
+	frm.SetPoll(6)
+	frm.SetPrecision(sysprec)
+	frm.SetOriginTime(c.xmt)
+	frm.SetFlags(ModeClient, Version4, LeapNoWarning)
+	return SizeHeader, nil
+}
+
+func (c *Client) read(payload []byte) error {
+	if c.isDone() {
+		return io.EOF
+	}
+	frm, err := NewFrame(payload)
+	if err != nil {
+		return err
+	}
+	t := &c.t
+	switch c.state {
+	case stateAwait1:
+		tstx := frm.TransmitTime()
+		tsorig := frm.OriginTime()
+		if tstx == tsorig || tsorig == c.xmt {
+			return errors.New("bogus NTP packet")
+		}
+		t[0] = tsorig
+		t[1] = frm.ReceiveTime()
+		t[2] = tstx
+		t[3] = c.unsyncTimestamp(c.now())
+		c.state = stateDone
+	case stateAwait2:
+		c.state = stateAwait2
+	}
+	return nil
+}
+
+func (c *Client) isDone() bool {
+	return c.state == stateDone
+}
+
+func (c *Client) now() time.Time {
+	if c._now == nil {
+		return time.Now()
+	}
+	return c._now()
+}
+
+func (c *Client) unsyncTimestamp(now time.Time) Timestamp {
+	return TimestampFromUint64(0).Add(now.Sub(c.start))
+}
+
+func (c *Client) sysprec() int8 {
+	if c._sysprec == sysprecRecalcNeeded {
+		c._sysprec = CalculateSystemPrecision(c._now)
+	}
+	return c._sysprec
+}
+
+// Now returns the current time as corrected by NTP protocol.
+func (c *Client) Now() time.Time {
+	return c.now().Add(c.Offset())
+}
+
+// Offset returns the
+func (c *Client) Offset() time.Duration {
+	if c.isDone() {
+		t := &c.t
+		return t[1].Sub(t[0])/2 + t[2].Sub(t[3])/2
+	}
+	return 0
+}

lneto/ntp/ntp.go

@@ -24,10 +24,18 @@ const (
 	MinDispDiv = 200  // Minimum dispersion divisor 1/(200) == 0.005
 )
 
-func NewFrame(buf []byte) Frame {
-	return Frame{buf: buf}
+func NewFrame(buf []byte) (Frame, error) {
+	if len(buf) < SizeHeader {
+		return Frame{buf: nil}, errors.New("NTP frame too short")
+	}
+	return Frame{buf: buf}, nil
 }
 
+// Frame encapsulates the raw data of an NTP packet
+// and provides methods for manipulating, validating and
+// retrieving fields and payload data. See [RFC5905].
+//
+// [RFC5905]: https://tools.ietf.org/html/rfc5905
 type Frame struct {
 	buf []byte
 }
@@ -123,6 +131,13 @@ func (frm Frame) SetTransmitTime(rt Timestamp) {
 	rt.Put(frm.buf[40:48])
 }
 
+// ClearHeader zeros out the header contents.
+func (frm Frame) ClearHeader() {
+	for i := range frm.buf[:SizeHeader] {
+		frm.buf[i] = 0
+	}
+}
+
 type Short uint32
 
 var baseTime = time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC)
@@ -262,11 +277,23 @@ func SystemPrecision() int8 {
 }
 
 func recalculateSystemPrecision() {
+	sysPrec = CalculateSystemPrecision(nil)
+}
+
+// CalculateSystemPrecision calculates the NTP system precision for a time source.
+// If the time source is nil the default static call to [time.Now] is used.
+func CalculateSystemPrecision(now func() time.Time) int8 {
 	const maxIter = 16
 	var times [maxIter]time.Time
-	for i := 0; i < maxIter; i++ {
-		times[i] = time.Now()
+	if now == nil {
+		for i := 0; i < maxIter; i++ {
+			times[i] = time.Now()
+		}
+	} else {
+		for i := 0; i < maxIter; i++ {
+			times[i] = now()
+		}
 	}
 	avg := times[maxIter-1].Sub(times[0]) / maxIter
-	sysPrec = int8(math.Log2(avg.Seconds()))
+	return int8(math.Log2(avg.Seconds()))
 }