From d0b5db9437ea450c2bbaa209f8933f3155b2cc30 Mon Sep 17 00:00:00 2001
From: Kleissner <peter@kleissner.investments>
Date: Thu, 4 Nov 2021 21:20:47 +0100
Subject: [PATCH] UDT: Removing light ACK. This reduces complexity.

---
 udt/packet/packet.go               |  6 +---
 udt/packet/packet_lightack.go      | 47 ------------------------------
 udt/packet/packet_lightack_test.go | 13 ---------
 udt/udtsocket.go                   |  2 +-
 udt/udtsocket_send.go              | 14 ---------
 5 files changed, 2 insertions(+), 80 deletions(-)
 delete mode 100644 udt/packet/packet_lightack.go
 delete mode 100644 udt/packet/packet_lightack_test.go

diff --git a/udt/packet/packet.go b/udt/packet/packet.go
index bbff770..4cbc139 100644
--- a/udt/packet/packet.go
+++ b/udt/packet/packet.go
@@ -175,11 +175,7 @@ func DecodePacket(data []byte) (p Packet, err error) {
 		case ptKeepalive:
 			p = &KeepAlivePacket{}
 		case ptAck:
-			if len(data) == 20 {
-				p = &LightAckPacket{}
-			} else {
-				p = &AckPacket{}
-			}
+			p = &AckPacket{}
 		case ptNak:
 			p = &NakPacket{}
 		case ptCongestion:
diff --git a/udt/packet/packet_lightack.go b/udt/packet/packet_lightack.go
deleted file mode 100644
index a2e94d0..0000000
--- a/udt/packet/packet_lightack.go
+++ /dev/null
@@ -1,47 +0,0 @@
-package packet
-
-// Structure of packets and functions for writing/reading them
-
-import (
-	"errors"
-)
-
-// LightAckPacket is a UDT variant of the ACK packet for acknowledging received data with minimal information
-type LightAckPacket struct {
-	ctrlHeader
-	PktSeqHi PacketID // The packet sequence number to which all the previous packets have been received (excluding)
-}
-
-// WriteTo writes this packet to the provided buffer, returning the length of the packet
-func (p *LightAckPacket) WriteTo(buf []byte) (uint, error) {
-	l := len(buf)
-	if l < 20 {
-		return 0, errors.New("lightack packet too small")
-	}
-
-	if _, err := p.writeHdrTo(buf, ptAck, 0); err != nil {
-		return 0, err
-	}
-
-	endianness.PutUint32(buf[16:20], p.PktSeqHi.Seq)
-
-	return 20, nil
-}
-
-func (p *LightAckPacket) readFrom(data []byte) (err error) {
-	l := len(data)
-	if l < 20 {
-		return errors.New("lightack packet too small")
-	}
-	if _, err = p.readHdrFrom(data); err != nil {
-		return err
-	}
-	p.PktSeqHi = PacketID{endianness.Uint32(data[16:20])}
-
-	return nil
-}
-
-// PacketType returns the packetType associated with this packet
-func (p *LightAckPacket) PacketType() PacketType {
-	return ptAck
-}
diff --git a/udt/packet/packet_lightack_test.go b/udt/packet/packet_lightack_test.go
deleted file mode 100644
index e14a55b..0000000
--- a/udt/packet/packet_lightack_test.go
+++ /dev/null
@@ -1,13 +0,0 @@
-package packet
-
-import (
-	"testing"
-)
-
-func TestLightAckPacket(t *testing.T) {
-	pkt1 := &LightAckPacket{
-		PktSeqHi: PacketID{Seq: 91},
-	}
-	pkt1.SetHeader(59, 100)
-	testPacket(pkt1, t)
-}
diff --git a/udt/udtsocket.go b/udt/udtsocket.go
index a7d2e6b..fb7c77a 100644
--- a/udt/udtsocket.go
+++ b/udt/udtsocket.go
@@ -690,7 +690,7 @@ func (s *udtSocket) readPacket(m *multiplexer, p packet.Packet) {
 		s.readHandshake(m, sp)
 	case *packet.ShutdownPacket: // sent by either peer
 		s.shutdownEvent <- shutdownMessage{sockState: sockStateClosed, permitLinger: s.isServer} // if client tells us done, it is done.
-	case *packet.AckPacket, *packet.LightAckPacket, *packet.NakPacket: // receiver -> sender
+	case *packet.AckPacket, *packet.NakPacket: // receiver -> sender
 		s.sendEvent <- recvPktEvent{pkt: p, now: now}
 	case *packet.UserDefControlPacket:
 		s.cong.onCustomMsg(*sp)
diff --git a/udt/udtsocket_send.go b/udt/udtsocket_send.go
index efa36d6..bf17fbf 100644
--- a/udt/udtsocket_send.go
+++ b/udt/udtsocket_send.go
@@ -131,8 +131,6 @@ func (s *udtSocketSend) goSendEvent() {
 			switch sp := evt.pkt.(type) {
 			case *packet.AckPacket:
 				s.ingestAck(sp, evt.now)
-			case *packet.LightAckPacket:
-				s.ingestLightAck(sp, evt.now)
 			case *packet.NakPacket:
 				s.ingestNak(sp, evt.now)
 			case *packet.CongestionPacket:
@@ -365,18 +363,6 @@ func (s *udtSocketSend) sendDataPacket(dp sendPacketEntry, isResend bool) {
 	}
 }
 
-// ingestLightAck is called to process a "light" ACK packet
-func (s *udtSocketSend) ingestLightAck(p *packet.LightAckPacket, now time.Time) {
-	// Update the largest acknowledged sequence number.
-
-	pktSeqHi := p.PktSeqHi
-	diff := pktSeqHi.BlindDiff(s.recvAckSeq)
-	if diff > 0 {
-		s.flowWindowSize += uint(diff)
-		s.recvAckSeq = pktSeqHi
-	}
-}
-
 func (s *udtSocketSend) assertValidSentPktID(pktType string, pktSeq packet.PacketID) bool {
 	if s.sendPktSeq.BlindDiff(pktSeq) < 0 {
 		s.shutdownEvent <- shutdownMessage{sockState: sockStateCorrupted, permitLinger: false,