KeepAlive component for /server (no test)

server/gameplay.go

@@ -2,13 +2,13 @@ package server
 
 import (
 	_ "embed"
-	"github.com/Tnze/go-mc/chat"
-	"github.com/Tnze/go-mc/nbt"
 	"sync/atomic"
 
 	"github.com/google/uuid"
 
+	"github.com/Tnze/go-mc/chat"
 	"github.com/Tnze/go-mc/data/packetid"
+	"github.com/Tnze/go-mc/nbt"
 	"github.com/Tnze/go-mc/net"
 	pk "github.com/Tnze/go-mc/net/packet"
 )
@@ -34,10 +34,7 @@ var dimensionCodecSNBT string
 var dimensionSNBT string
 
 func (g *Game) AcceptPlayer(name string, id uuid.UUID, protocol int32, conn *net.Conn) {
-	remove := g.PlayerList.TryInsert(PlayerSample{
-		Name: name,
-		ID:   id,
-	})
+	remove := g.PlayerList.TryInsert(PlayerSample{Name: name, ID: id})
 	if remove == nil {
 		_ = conn.WritePacket(pk.Marshal(
 			packetid.ClientboundDisconnect,

server/keepalive.go

@@ -0,0 +1,166 @@
+package server
+
+import (
+	"container/heap"
+	"errors"
+	"github.com/Tnze/go-mc/data/packetid"
+	pk "github.com/Tnze/go-mc/net/packet"
+	"sync"
+	"time"
+)
+
+// keepAliveInterval represents the interval when the server sends keep alive
+const keepAliveInterval = time.Second * 15
+
+// keepAliveWaitInterval represents how long does the player expired
+const keepAliveWaitInterval = time.Second * 30
+
+type KeepAlive struct {
+	list     keepAliveHeap
+	listLock sync.Mutex
+
+	waitList  keepAliveHeap
+	waitItem  keepAliveItem
+	waitLock  sync.Mutex
+	waitTimer *time.Timer
+
+	onPlayerExpire func(p *Player)
+}
+
+func NewKeepAlive() (k KeepAlive) {
+	heap.Init(&k.list)
+	heap.Init(&k.waitList)
+	return
+}
+
+func (k *KeepAlive) AddPlayer(p *Player) {
+	k.listLock.Lock()
+	defer k.listLock.Unlock()
+
+	now := time.Now()
+	heap.Push(&k.list, keepAliveItem{
+		player:   p,
+		lastTick: now,
+	})
+}
+
+func (k *KeepAlive) RemovePlayer(p *Player) {
+	k.listLock.Lock()
+	defer k.listLock.Unlock()
+
+	for i, v := range k.list {
+		if v.player.UUID == p.UUID {
+			heap.Remove(&k.list, i)
+			return
+		}
+	}
+	panic("KeepAlive: Fail to remove player: " + p.UUID.String() + ": not found")
+}
+
+func (k *KeepAlive) Run() {
+	listTimer := time.NewTimer(keepAliveInterval)
+	k.waitTimer = time.NewTimer(keepAliveWaitInterval)
+	var listItem keepAliveItem
+	// The Notchian server uses a system-dependent time in milliseconds to generate the keep alive ID value.
+	// We don't do that here for security reason.
+	var keepAliveID int64
+
+	for {
+		select {
+		case now := <-listTimer.C:
+			if listItem.player == nil {
+				listItem = getEarliest(&k.list, &k.listLock, listTimer, keepAliveInterval)
+				break
+			}
+
+			// Send Clientbound KeepAlive packet.
+			listItem.player.WritePacket(Packet757(pk.Marshal(
+				packetid.ClientboundKeepAlive,
+				pk.Long(keepAliveID),
+			)))
+			keepAliveID++
+
+			// Clientbound KeepAlive packet is sent, add the player to waiting list.
+			k.waitLock.Lock()
+			heap.Push(&k.waitList, keepAliveItem{
+				player:   listItem.player,
+				lastTick: now,
+			})
+			k.waitLock.Unlock()
+
+			// Wait for next earliest player
+			listItem = getEarliest(&k.list, &k.listLock, listTimer, keepAliveInterval)
+
+		case <-k.waitTimer.C:
+			if k.waitItem.player == nil {
+				k.waitItem = getEarliest(&k.waitList, &k.waitLock, k.waitTimer, keepAliveWaitInterval)
+				break
+			}
+			k.onPlayerExpire(k.waitItem.player)
+			k.waitItem = getEarliest(&k.waitList, &k.waitLock, k.waitTimer, keepAliveWaitInterval)
+		}
+	}
+}
+
+func (k *KeepAlive) TickPlayer(player *Player, packet Packet757) error {
+	var KeepAliveID pk.Long
+	if err := pk.Packet(packet).Scan(&KeepAliveID); err != nil {
+		return err
+	}
+	k.waitLock.Lock()
+	defer k.waitLock.Unlock()
+
+	if k.waitItem.player.UUID == player.UUID {
+		if k.waitTimer.Stop() {
+			k.waitItem = getEarliest(&k.waitList, &k.waitLock, k.waitTimer, keepAliveWaitInterval)
+		} else {
+			<-k.waitTimer.C
+			return errors.New("keepalive: player " + player.UUID.String() + " is already expired")
+		}
+	} else {
+		for i, v := range k.waitList {
+			if v.player.UUID == player.UUID {
+				heap.Remove(&k.waitList, i)
+				goto Success
+			}
+		}
+		return errors.New("keepalive: player " + player.UUID.String() + " not found")
+	}
+Success:
+	heap.Push(&k.list, keepAliveItem{
+		player:   player,
+		lastTick: time.Now(),
+	})
+	return nil
+}
+
+func getEarliest(list *keepAliveHeap, listLock *sync.Mutex, timer *time.Timer, interval time.Duration) (item keepAliveItem) {
+	listLock.Lock()
+	defer listLock.Unlock()
+
+	if list.Len() == 0 {
+		timer.Reset(interval)
+	} else {
+		item = heap.Pop(list).(keepAliveItem)
+		timer.Reset(time.Until(item.lastTick.Add(interval)))
+	}
+	return
+}
+
+type keepAliveItem struct {
+	player   *Player
+	lastTick time.Time
+}
+
+type keepAliveHeap []keepAliveItem
+
+func (k *keepAliveHeap) Len() int           { return len(*k) }
+func (k *keepAliveHeap) Less(i, j int) bool { return (*k)[i].lastTick.Before((*k)[j].lastTick) }
+func (k *keepAliveHeap) Swap(i, j int)      { (*k)[i], (*k)[j] = (*k)[j], (*k)[i] }
+func (k *keepAliveHeap) Push(x interface{}) { *k = append(*k, x.(keepAliveItem)) }
+func (k *keepAliveHeap) Pop() (x interface{}) {
+	i := len(*k) - 1
+	x = (*k)[i]
+	*k = (*k)[:i]
+	return
+}

server/player.go

@@ -3,10 +3,15 @@ package server
 import (
 	"github.com/Tnze/go-mc/net"
 	pk "github.com/Tnze/go-mc/net/packet"
+	"github.com/google/uuid"
+	"sync"
 )
 
 type Player struct {
 	*net.Conn
+	writeLock sync.Mutex
+
+	uuid.UUID
 	EntityID int32
 	Gamemode byte
 	handlers map[int32][]packetHandlerFunc
@@ -18,6 +23,8 @@ type Packet757 pk.Packet
 
 // WritePacket to player client. The type of parameter will update per version.
 func (p *Player) WritePacket(packet Packet757) error {
+	p.writeLock.Lock()
+	defer p.writeLock.Unlock()
 	return p.Conn.WritePacket(pk.Packet(packet))
 }
 
@@ -26,7 +33,7 @@ type PacketHandler struct {
 	F  packetHandlerFunc
 }
 
-type packetHandlerFunc func(player *Player, packet Packet757) error
+type packetHandlerFunc func(packet Packet757) error
 
 func (p *Player) Add(ph PacketHandler) {
 	if p.handlers == nil {