new udp exchange

config/builder.go

@@ -10,6 +10,7 @@ import (
 	"mpbl3p/tcp"
 	"mpbl3p/udp"
 	"mpbl3p/udp/congestion"
+	"mpbl3p/udp/congestion/newreno"
 	"time"
 )
 
@@ -104,7 +105,7 @@ func buildUdp(ctx context.Context, p *proxy.Proxy, peer Peer, g func() proxy.Mac
 	default:
 		fallthrough
 	case "NewReno":
-		c = func() udp.Congestion { return congestion.NewNewReno() }
+		c = func() udp.Congestion { return newreno.NewNewReno() }
 	}
 
 	if peer.RemoteHost != "" {

proxy/exchange.go

@@ -1,7 +1,9 @@
 package proxy
 
+import "context"
+
 type Exchange interface {
+	Initial(ctx context.Context) (out []byte, err error)
+	Handle(ctx context.Context, in []byte) (out []byte, data []byte, err error)
 	Complete() bool
-	Initial() (out []byte, err error)
-	Handle(in []byte) (out []byte, data []byte, err error)
 }

shared/errors.go

@@ -5,3 +5,4 @@ import "errors"
 var ErrBadChecksum = errors.New("the packet had a bad checksum")
 var ErrDeadConnection = errors.New("the connection is dead")
 var ErrNotEnoughBytes = errors.New("not enough bytes")
+var ErrBadExchange = errors.New("bad exchange")

udp/congestion/newreno/exchange.go

@@ -0,0 +1,119 @@
+package newreno
+
+import (
+	"context"
+	"encoding/binary"
+	"math/rand"
+	"mpbl3p/shared"
+	"time"
+)
+
+func (c *NewReno) Initial(ctx context.Context) (out []byte, err error) {
+	c.alive = false
+	c.wasInitial = true
+	c.startSequenceLoop(ctx)
+
+	var s uint32
+	select {
+	case s = <-c.sequence:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+
+	b := make([]byte, 12)
+	binary.LittleEndian.PutUint32(b[8:12], s)
+
+	c.inFlight = []flightInfo{{time.Now(), s}}
+
+	return b, nil
+}
+
+func (c *NewReno) Handle(ctx context.Context, in []byte) (out []byte, data []byte, err error) {
+	if c.alive || c.stopSequence == nil {
+		// reset
+		c.alive = false
+		c.startSequenceLoop(ctx)
+	}
+
+	// receive
+	if len(in) != 12 {
+		return nil, nil, shared.ErrBadExchange
+	}
+
+	rcvAck := binary.LittleEndian.Uint32(in[0:4])
+	rcvNack := binary.LittleEndian.Uint32(in[4:8])
+	rcvSeq := binary.LittleEndian.Uint32(in[8:12])
+
+	// verify
+	var ack, seq uint32
+
+	if rcvNack != 0 {
+		return nil, nil, shared.ErrBadExchange
+	}
+
+	if c.wasInitial {
+		if rcvAck == c.inFlight[0].sequence {
+			ack = rcvSeq
+			c.alive = true
+		} else {
+			return nil, nil, shared.ErrBadExchange
+		}
+	} else { // if !c.wasInitial
+		if rcvAck == 0 {
+			// theirs is a syn packet
+			ack = rcvSeq
+			select {
+			case seq = <-c.sequence:
+			case <-ctx.Done():
+				return nil, nil, ctx.Err()
+			}
+
+			c.inFlight = []flightInfo{{time.Now(), seq}}
+		} else if len(c.inFlight) == 1 && rcvAck == c.inFlight[0].sequence {
+			ack = rcvSeq
+			c.alive = true
+		} else {
+			return nil, nil, shared.ErrBadExchange
+		}
+	}
+
+	// respond
+	b := make([]byte, 12)
+	binary.LittleEndian.PutUint32(b[0:4], ack)
+	binary.LittleEndian.PutUint32(b[8:12], seq)
+
+	return b, nil, nil
+}
+
+func (c *NewReno) Complete() bool {
+	return c.alive
+}
+
+func (c *NewReno) startSequenceLoop(ctx context.Context) {
+	if c.stopSequence != nil {
+		c.stopSequence()
+	}
+
+	var s uint32
+	for s == 0 {
+		s = rand.Uint32()
+	}
+
+	ctx, c.stopSequence = context.WithCancel(ctx)
+	go func() {
+		s := s
+		for {
+			if s == 0 {
+				s++
+				continue
+			}
+
+			select {
+			case c.sequence <- s:
+			case <-ctx.Done():
+				return
+			}
+			s++
+		}
+	}()
+}

udp/congestion/newreno/newreno.go

@@ -1,4 +1,4 @@
-package congestion
+package newreno
 
 import (
 	"context"
@@ -15,6 +15,8 @@ const RttLossDelay = 1.5
 
 type NewReno struct {
 	sequence          chan uint32
+	stopSequence      context.CancelFunc
+	wasInitial, alive bool
 
 	inFlight   []flightInfo
 	lastSent   time.Time
@@ -64,19 +66,6 @@ func NewNewReno() *NewReno {
 		slowStart:  true,
 	}
 
-	go func() {
-		var s uint32
-		for {
-			if s == 0 {
-				s++
-				continue
-			}
-
-			c.sequence <- s
-			s++
-		}
-	}()
-
 	return &c
 }
 

udp/congestion/newreno/newreno_test.go

@@ -1,4 +1,4 @@
-package congestion
+package newreno
 
 import (
 	"context"

udp/flow.go

@@ -2,6 +2,7 @@ package udp
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log"
 	"mpbl3p/proxy"
@@ -19,6 +20,7 @@ type PacketWriter interface {
 
 type PacketConn interface {
 	PacketWriter
+	SetReadDeadline(t time.Time) error
 	ReadFromUDP(b []byte) (int, *net.UDPAddr, error)
 }
 
@@ -42,7 +44,6 @@ type Flow struct {
 	raddr  *net.UDPAddr
 
 	isAlive    bool
-	startup    bool
 	congestion Congestion
 
 	v proxy.MacVerifier
@@ -105,52 +106,82 @@ func (f *InitiatedFlow) Reconnect(ctx context.Context) error {
 	}
 
 	f.writer = conn
-	f.startup = true
 
 	// prod the connection once a second until we get an ack, then consider it alive
-	go func() {
-		seq, err := f.congestion.Sequence(ctx)
+	var exchanges []proxy.Exchange
+
+	if e, ok := f.congestion.(proxy.Exchange); ok {
+		exchanges = append(exchanges, e)
+	}
+
+	var exchangeData [][]byte
+
+	for _, e := range exchanges {
+		i, err := e.Initial(ctx)
 		if err != nil {
-			return
-		}
-
-		for !f.isAlive {
-			if ctx.Err() != nil {
-				return
-			}
-
-			p := Packet{
-				ack:  0,
-				nack: 0,
-				seq:  seq,
-				data: proxy.SimplePacket(nil),
-			}
-
-			_ = f.sendPacket(p, f.g)
-			time.Sleep(1 * time.Second)
-		}
-	}()
-
-	go func() {
-		_, _ = f.produceInternal(ctx, f.v, false)
-	}()
-	go f.earlyUpdateLoop(ctx, f.g, f.keepalive)
-
-	if err := f.readQueuePacket(ctx, conn); err != nil {
 			return err
 		}
 
-	f.isAlive = true
-	f.startup = false
+		if err = f.sendPacket(proxy.SimplePacket(i), f.g); err != nil {
+			return err
+		}
+
+		for once := true; once || !e.Complete(); once = false {
+			if err := func() error {
+				ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+				defer cancel()
+
+				var recv []byte
+				if recv, err = f.readPacket(ctx, conn); err != nil {
+					return err
+				}
+
+				var resp, data []byte
+				if resp, data, err = e.Handle(ctx, recv); err != nil {
+					return err
+				}
+
+				if data != nil {
+					exchangeData = append(exchangeData, data)
+				}
+
+				if resp != nil {
+					if err = f.sendPacket(proxy.SimplePacket(resp), f.g); err != nil {
+						return err
+					}
+				}
+
+				return nil
+			}(); err != nil {
+				return err
+			}
+		}
+	}
 
 	go func() {
+		for _, d := range exchangeData {
+			if err := f.queueDatagram(ctx, d); err != nil {
+				return
+			}
+		}
+
 		lockedAccept := func() {
 			f.mu.RLock()
 			defer f.mu.RUnlock()
 
-			if err := f.readQueuePacket(ctx, conn); err != nil {
-				log.Println(err)
+			var p []byte
+			if p, err = f.readPacket(ctx, conn); err != nil {
+				if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
+					return
 				}
+				log.Println(err)
+				return
+			}
+
+			if err := f.queueDatagram(ctx, p); err != nil {
+				return
+			}
+
 		}
 
 		for f.isAlive {
@@ -160,6 +191,7 @@ func (f *InitiatedFlow) Reconnect(ctx context.Context) error {
 		log.Println("no longer alive")
 	}()
 
+	f.isAlive = true
 	return nil
 }
 
@@ -260,7 +292,7 @@ func (f *Flow) queueDatagram(ctx context.Context, p []byte) error {
 	}
 }
 
-func (f *Flow) sendPacket(p Packet, g proxy.MacGenerator) error {
+func (f *Flow) sendPacket(p proxy.Packet, g proxy.MacGenerator) error {
 	b := p.Marshal()
 	b = proxy.AppendMac(b, g)
 
@@ -294,13 +326,24 @@ func (f *Flow) earlyUpdateLoop(ctx context.Context, g proxy.MacGenerator, keepal
 	}
 }
 
-func (f *Flow) readQueuePacket(ctx context.Context, c PacketConn) error {
-	// TODO: Replace 6000 with MTU+header size
+func (f *Flow) readPacket(ctx context.Context, c PacketConn) ([]byte, error) {
 	buf := make([]byte, 6000)
-	n, _, err := c.ReadFromUDP(buf)
-	if err != nil {
-		return err
+
+	if d, ok := ctx.Deadline(); ok {
+		if err := c.SetReadDeadline(d); err != nil {
+			return nil, err
+		}
 	}
 
-	return f.queueDatagram(ctx, buf[:n])
+	n, _, err := c.ReadFromUDP(buf)
+	if err != nil {
+		if err, ok := err.(net.Error); ok && err.Timeout() {
+			if ctx.Err() != nil {
+				return nil, ctx.Err()
+			}
+		}
+		return nil, err
+	}
+
+	return buf[:n], nil
 }