net/isoping: add isoping package

Signed-off-by: Simeng He <simeng@tailscale.com>

net/isoping/constants.go

@@ -0,0 +1,24 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package isoping
+
+const (
+	MAGIC                           = 0x424c4950
+	DEFAULT_PORT                    = ":4948"
+	DEFAULT_PACKETS_PER_SEC float64 = 10.0
+	USEC_PER_CYCLE                  = (10 * 1000 * 1000)
+)
+
+// DIV takes two int64 divides the two and returns a float64
+func DIV(x, y int64) float64 {
+	if y == 0 {
+		return 0
+	}
+	return float64(x) / float64(y)
+}
+
+// DIFF takes the difference between two uint32s and returns int32
+func DIFF(x, y uint32) int32 {
+	return int32(int64(x) - int64(y))
+}

net/isoping/isoping.go

@@ -0,0 +1,254 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// package isoping implements isoping in Go.
+package isoping
+
+import (
+	"bytes"
+	"encoding/binary"
+	"log"
+	"math"
+	"net"
+	"time"
+)
+
+type Packet struct {
+	Magic      uint32 // Magic number to reject bogus packets
+	Id         uint32 // Id is a sequential packet id number
+	Txtime     uint32 // Txtime is the transmitter's monotonic time when pkt was sent
+	Clockdiff  uint32 // Clockdiff is an estimate of (transmitter's clk) - (receiver's clk)
+	UsecPerPkt uint32 // Usec_per_pkt microseconds of delay between packets
+	NumLost    uint32 // Num_lost is the number of pkts transmitter expected to get but didn't
+	FirstAck   uint32 // First_ack is the starting index in acks[] circular buffer
+	Acks       [64]struct {
+		// txtime==0 for empty elements in this array.
+		Id     uint32 // Id field from a received packet
+		Rxtime uint32 // Rxtime is a receiver's monotonic time when pkt arrived
+	}
+}
+
+type Isoping struct {
+	ClockStartTime time.Time    // ClockStartTime is the time the program starts
+	IsServer       bool         // IsServer distinguishes if we are a server or client
+	Conn           *net.UDPConn // Conn is either the server or client's connection
+	Tx             Packet       // Tx is a Packet that will be sent
+	Rx             Packet       // Rx is a Packet that will be received
+	LastAckInfo    string       // LastAckInfo human readable format of latest ack
+	ListenAddr     *net.UDPAddr // ListenAddr is the address of the listener
+	RemoteAddr     *net.UDPAddr // RemtoteAddr remote UDP address we send to.
+	RxAddr         *net.UDPAddr // RxAddr keeps track of what address we are sending to
+	LastRxAddr     *net.UDPAddr // LastRxAddr keeps track of what we last used
+	Quiet          bool         // Option to show output or not
+
+	printsPerSec   float64
+	packetsPerSec  float64
+	usecPerPkt     int32
+	usecPerPrint   int32
+	nextTxId       uint32
+	nextRxId       uint32
+	nextRxackId    uint32
+	startRtxtime   uint32 // remote's txtime at startup
+	startRxtime    uint32 // local rxtime at startup
+	lastRxtime     uint32 // local rxtime of last received packet
+	minCycleRxdiff int32  // smallest packet delay seen this cycle
+	nextCycle      uint32 // time when next cycle begins
+	now            uint32 // current time
+	nextSend       uint32 // time when we'll send next pkt
+	numLost        uint32 // number of rx packets not received
+	nextTxackIndex int    // next array item to fill in tx.acks
+	lastPrint      uint32 // time of last packet printout
+	latTx          int64
+	latTxMin       int64
+	latTxMax       int64
+	latTxCount     int64
+	latTxSum       int64
+	latTxVarSum    int64
+
+	latRx       int64
+	latRxMin    int64
+	latRxMax    int64
+	latRxCount  int64
+	latRxSum    int64
+	latRxVarSum int64
+}
+
+// Incremental standard deviation calculation, without needing to know the
+// mean in advance.  See:
+// http://mathcentral.uregina.ca/QQ/database/QQ.09.02/carlos1.html
+func onePassStddev(sumsq, sum, count int64) float64 {
+	numer := (count * sumsq) - (sum * sum)
+	denom := count * (count - 1)
+	return math.Sqrt(DIV(numer, denom))
+}
+
+// UsecMonoTimeNow returns the monotonic number of microseconds since the program started.
+func (srv *Isoping) UsecMonoTimeNow() uint64 {
+	tn := time.Since(srv.ClockStartTime)
+	return uint64(tn.Microseconds())
+}
+
+// UsecMonoTime returns the monotonic number of microseconds since the program started, as a uint32.
+func (srv *Isoping) UsecMonoTime() uint32 {
+	return uint32(srv.UsecMonoTimeNow())
+}
+
+// initClock keeps track of when the server/client starts.
+// keeps the exact time and we can subtract from the time
+// to get monotonicClock values
+func (srv *Isoping) initClock() {
+	srv.ClockStartTime = time.Now()
+}
+
+// initClient sets the Isoping.Conn, to the address string otherwise
+// uses [::]:4948 as the default
+func (srv *Isoping) initClient(address string) {
+	srv.initClock()
+	srv.IsServer = false
+	udpaddr, err := net.ResolveUDPAddr("udp", address)
+	if err != nil {
+		log.Println(err)
+		addr := DEFAULT_PORT
+		udpaddr, err = net.ResolveUDPAddr("udp", addr)
+		if err != nil {
+			log.Println(err)
+			return
+		}
+		log.Printf("Address %v failed to resolve\n", address)
+	}
+
+	conn, err := net.DialUDP("udp", nil, udpaddr)
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	srv.RemoteAddr = udpaddr
+	srv.Conn = conn
+}
+
+// initServer sets the Conn field of Isoping, for the listener side.
+func (srv *Isoping) initServer(port string) {
+	srv.initClock()
+	srv.IsServer = true
+	addr, err := net.ResolveUDPAddr("udp", port)
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	srv.ListenAddr = addr
+	srv.Conn, err = net.ListenUDP("udp", addr)
+	if err != nil {
+		log.Printf("%v\n", err)
+		return
+	}
+}
+
+func NewInstance() *Isoping {
+	clockStartTime := time.Now()
+
+	packetsPerSec := DEFAULT_PACKETS_PER_SEC
+	printsPerSec := -1
+
+	usecPerPkt := int32(1e6 / packetsPerSec)
+	usecPerPrint := int32(0)
+	if usecPerPrint > 0 {
+		usecPerPrint = int32(1e6 / printsPerSec)
+	}
+	log.Println("UsecPerPkt : ", usecPerPkt)
+	log.Println("UsecPerPrint : ", usecPerPrint)
+
+	nextTxId := 1
+	nextRxId := 0
+
+	nextRxackId := 0
+	startRtxtime := 0
+	startRxtime := 0
+	lastRxtime := 0
+
+	minCycleRxdiff := 0
+	nextCycle := 0
+	nextSend := 0
+	nextTxackIndex := 0
+
+	LastAckInfo := ""
+	inst := &Isoping{
+		packetsPerSec:  packetsPerSec,
+		printsPerSec:   float64(printsPerSec),
+		usecPerPkt:     int32(1e6 / DEFAULT_PACKETS_PER_SEC),
+		usecPerPrint:   usecPerPrint,
+		nextTxId:       uint32(nextTxId),
+		nextRxId:       uint32(nextRxId),
+		nextRxackId:    uint32(nextRxackId),
+		startRtxtime:   uint32(startRtxtime),
+		startRxtime:    uint32(startRxtime),
+		lastRxtime:     uint32(lastRxtime),
+		minCycleRxdiff: int32(minCycleRxdiff),
+		nextCycle:      uint32(nextCycle),
+		nextSend:       uint32(nextSend),
+		nextTxackIndex: nextTxackIndex,
+		Tx:             Packet{},
+		Rx:             Packet{},
+		LastAckInfo:    LastAckInfo,
+		ClockStartTime: clockStartTime,
+
+		latTx:       0,
+		latTxMin:    0x7fffffff,
+		latTxMax:    0,
+		latTxCount:  0,
+		latTxSum:    0,
+		latTxVarSum: 0,
+		latRx:       0,
+		latRxMin:    0x7fffffff,
+		latRxMax:    0,
+		latRxCount:  0,
+		latRxSum:    0,
+		latRxVarSum: 0,
+	}
+
+	// Setup the clock functions after creating the fields
+	inst.now = inst.UsecMonoTime()
+	inst.lastPrint = inst.now - uint32(inst.usecPerPkt)
+	return inst
+}
+
+// generateInitialPacket generates the inital packet Tx
+func (srv *Isoping) generateInitialPacket() (*bytes.Buffer, error) {
+	srv.Tx.Magic = MAGIC
+	srv.Tx.Id = srv.nextTxId
+	srv.nextTxId++
+	srv.Tx.Txtime = srv.nextSend
+	srv.Tx.UsecPerPkt = uint32(srv.usecPerPkt)
+	srv.Tx.Clockdiff = 0
+	if srv.startRtxtime > 0 {
+		srv.Rx.Clockdiff = srv.startRtxtime - srv.startRxtime
+	}
+	srv.Tx.NumLost = srv.numLost
+	srv.Tx.FirstAck = uint32(srv.nextTxackIndex)
+
+	// Setup the Tx to be sent from either server of client
+	buf := new(bytes.Buffer)
+	return buf, binary.Write(buf, binary.BigEndian, srv.Tx)
+}
+
+// StartServer starts the Isoping Server with port
+// If no port is given, then starts with DEFAULT_PORT
+func (srv *Isoping) StartServer(port string) {
+	if port != "" {
+		srv.initServer(port)
+	} else {
+		srv.initServer(DEFAULT_PORT)
+	}
+}
+
+// StartServer starts the Isoping Client with port
+// If no port is given, then starts with DEFAULT_PORT
+func (srv *Isoping) StartClient(port string) {
+	if port != "" {
+		srv.initClient(port)
+	} else {
+		srv.initClient(DEFAULT_PORT)
+	}
+}

net/isoping/isoping_test.go

@@ -0,0 +1,107 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+package isoping
+
+import (
+	"bytes"
+	"encoding/binary"
+	"math"
+	"net"
+	"strconv"
+	"testing"
+)
+
+// Tests if our stddev calculation is within reason
+// Must do some rounding to a certain significant digit
+// Currently only need 6 digits for the testing.
+func sigDigs(x float64, digs int) float64 {
+	return math.Round(x*math.Pow10(digs)) / math.Pow10(digs)
+}
+
+// TestOnepass_stddev tests if the function receives the same answer as in
+// the C implementation of this function.
+func TestOnepass_stddev(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name  string
+		input []int64
+		out   float64
+	}{
+
+		{
+			name:  "basic1",
+			input: []int64{12, 2, 3},
+			out:   2.309401,
+		},
+		{
+
+			name:  "basic2",
+			input: []int64{12023232232, 212, 321},
+			out:   6129.649279,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ttAns := sigDigs(onePassStddev(tt.input[0], tt.input[1], tt.input[2]), 6)
+			if ttAns != tt.out {
+				t.Errorf("got %v, expected %v", ttAns, tt.out)
+			}
+		})
+	}
+
+}
+
+// TestUstimeCast tests if casting was correct
+func TestUstimeCast(t *testing.T) {
+	t.Parallel()
+
+	var num uint64 = 11471851221
+	var expected uint32 = 2881916629
+	if uint32(num) != expected {
+		t.Errorf("expected %v, got : %v", expected, uint32(num))
+	}
+}
+
+// TestValidInitialPacket will send a packet via UDP, and check if it matches
+// The size and the Magic number field that needs to be equal.
+// This mocks the initial packet sent in Isoping.
+func TestValidInitialPacket(t *testing.T) {
+	t.Parallel()
+
+	server := NewInstance()
+	server.StartServer(":0")
+	defer server.Conn.Close()
+	serverPort := server.Conn.LocalAddr().(*net.UDPAddr).Port
+
+	client := NewInstance()
+	client.StartClient(":" + strconv.Itoa(serverPort))
+
+	buf, err := client.generateInitialPacket()
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Client writes to the server, server tries to read it.
+	p := make([]byte, binary.Size(server.Rx))
+	if _, err := client.Conn.Write(buf.Bytes()); err != nil {
+		t.Error(err)
+	}
+
+	got, _, err := server.Conn.ReadFromUDP(p)
+	if err != nil {
+		t.Error(err)
+	}
+
+	buffer := bytes.NewBuffer(p)
+	defer buffer.Reset()
+
+	err = binary.Read(buffer, binary.BigEndian, &server.Rx)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if got != binary.Size(server.Rx) || server.Rx.Magic != MAGIC {
+		t.Error("received Rx is not proper")
+	}
+}