feat: Support Minecraft Java 1.21.11

Implement boss bar management for server transitions in versions 1.20.2 and above

- Introduced the ManagedViewer interface to handle boss bar registration and unregistration during server transitions.
- Added a bossBarManager to manage boss bars for connected players, ensuring proper handling of boss bar packets.
- Updated existing boss bar handling logic to respect the new management system, including packet writing and state management.
- Enhanced player session handling to accommodate the new boss bar management features.

This change improves the stability and user experience during server transitions by preventing disconnections related to boss bar updates.

Author: robinbraemer

pkg/edition/java/bossbar/bossbar.go

@@ -85,6 +85,20 @@ type Viewer interface {
 	proto.PacketWriter
 }
 
+// ManagedViewer is an optional interface for viewers that support boss bar management
+// during server transitions (1.20.2+). If a viewer implements this interface, the boss bar
+// will register/unregister with the viewer's manager and use WriteBossBarPacket for packets.
+type ManagedViewer interface {
+	Viewer
+	// RegisterBossBar registers a boss bar with this viewer's manager.
+	RegisterBossBar(bar BossBar)
+	// UnregisterBossBar unregisters a boss bar from this viewer's manager.
+	UnregisterBossBar(bar BossBar)
+	// WriteBossBarPacket writes a boss bar packet, respecting the dropping state.
+	// Returns true if the packet was written (or dropped intentionally).
+	WriteBossBarPacket(p *packet.BossBar) bool
+}
+
 // Color is the color of the percent bar.
 type Color = packet.Color
 

pkg/edition/java/bossbar/internal.go

@@ -44,7 +44,12 @@ func (b *bossBar) RemoveViewer(viewer Viewer) error {
 	p := b.createRemovePacket()
 	b.mu.Unlock()
 
-	return viewer.WritePacket(p)
+	// Unregister from the viewer's manager if supported
+	if m, ok := viewer.(ManagedViewer); ok {
+		m.UnregisterBossBar(b)
+	}
+
+	return writePacketToViewer(viewer, p)
 }
 
 func (b *bossBar) AddViewer(viewer Viewer) error {
@@ -65,12 +70,21 @@ func (b *bossBar) AddViewer(viewer Viewer) error {
 	p := b.createAddPacket()
 	b.mu.Unlock()
 
-	err := viewer.WritePacket(p)
+	// Register with the viewer's manager if supported
+	if m, ok := viewer.(ManagedViewer); ok {
+		m.RegisterBossBar(b)
+	}
+
+	err := writePacketToViewer(viewer, p)
 	if err != nil {
 		b.mu.Lock()
 		delete(b.viewers, viewer.ID())
 		b.mu.Unlock()
 		v.removed()
+		// Unregister on failure
+		if m, ok := viewer.(ManagedViewer); ok {
+			m.UnregisterBossBar(b)
+		}
 		return err
 	}
 
@@ -105,10 +119,24 @@ var _ BossBar = (*bossBar)(nil)
 
 func (b *bossBar) writeToViewers(p proto.Packet) {
 	for _, viewer := range b.viewers {
-		go func(v Viewer) { _ = v.WritePacket(p) }(viewer)
+		go func(v Viewer) { _ = writePacketToViewer(v, p) }(viewer)
 	}
 }
 
+// writePacketToViewer writes a packet to a viewer, using the managed writer if available.
+// For 1.20.2+ viewers with a manager, this respects the dropping state during server transitions.
+func writePacketToViewer(viewer Viewer, p proto.Packet) error {
+	if m, ok := viewer.(ManagedViewer); ok {
+		if bb, ok := p.(*bossbar.BossBar); ok {
+			if !m.WriteBossBarPacket(bb) {
+				return nil // dropped intentionally
+			}
+			return nil
+		}
+	}
+	return viewer.WritePacket(p)
+}
+
 func (b *bossBar) Name() component.Component {
 	b.mu.RLock()
 	defer b.mu.RUnlock()

pkg/edition/java/ping/pong.go

@@ -61,10 +61,15 @@ func (p *ServerPing) UnmarshalJSON(data []byte) error {
 		return fmt.Errorf("error decoding json: %w", err)
 	}
 
-	var err error
-	out.Alias.Description, err = componentutil.ParseTextComponent(out.Version.Protocol, string(out.Description))
-	if err != nil {
-		return fmt.Errorf("error decoding description: %w", err)
+	// Handle null or missing description (e.g., from backend server ping passthrough)
+	if len(out.Description) == 0 || string(out.Description) == "null" {
+		out.Alias.Description = &component.Text{} // empty component
+	} else {
+		var err error
+		out.Alias.Description, err = componentutil.ParseTextComponent(out.Version.Protocol, string(out.Description))
+		if err != nil {
+			return fmt.Errorf("error decoding description: %w", err)
+		}
 	}
 
 	*p = ServerPing(out.Alias)

pkg/edition/java/proto/packet/chat/session_command.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"go.minekube.com/gate/pkg/edition/java/proto/util"
+	"go.minekube.com/gate/pkg/edition/java/proto/version"
 	"go.minekube.com/gate/pkg/gate/proto"
 	"go.minekube.com/gate/pkg/util/errs"
 )
@@ -46,8 +47,13 @@ func (s *SessionPlayerCommand) Encode(c *proto.PacketContext, wr io.Writer) erro
 }
 
 func (s *SessionPlayerCommand) Decode(c *proto.PacketContext, rd io.Reader) error {
+	// Command length cap increased from 256 to 65536 in 1.20.5+
+	cap := 256
+	if c.Protocol.GreaterEqual(version.Minecraft_1_20_5) {
+		cap = util.DefaultMaxStringSize // 65536
+	}
 	var err error
-	s.Command, err = util.ReadStringMax(rd, 256)
+	s.Command, err = util.ReadStringMax(rd, cap)
 	if err != nil {
 		return err
 	}

pkg/edition/java/proto/packet/chat/unsigned_command.go

@@ -1,9 +1,10 @@
 package chat
 
 import (
+	"io"
+
 	"go.minekube.com/gate/pkg/edition/java/proto/util"
 	"go.minekube.com/gate/pkg/gate/proto"
-	"io"
 )
 
 type UnsignedPlayerCommand struct {
@@ -21,7 +22,8 @@ func (u *UnsignedPlayerCommand) Encode(c *proto.PacketContext, wr io.Writer) err
 }
 
 func (u *UnsignedPlayerCommand) Decode(c *proto.PacketContext, rd io.Reader) (err error) {
-	u.Command, err = util.ReadStringMax(rd, MaxServerBoundMessageLength)
+	// UnsignedPlayerCommand always uses 65536 cap since it's only available in 1.20.5+
+	u.Command, err = util.ReadStringMax(rd, util.DefaultMaxStringSize)
 	return err
 }
 

pkg/edition/java/proto/version/version.go

@@ -9,48 +9,49 @@ import (
 )
 
 var (
-	Unknown          = v(-1, "Unknown")
-	Legacy           = v(-2, "Legacy")
-	Minecraft_1_7_2  = v(4, "1.7.2", "1.7.3", "1.7.4", "1.7.5")
-	Minecraft_1_7_6  = v(5, "1.7.6", "1.7.7", "1.7.8", "1.7.9", "1.7.10")
-	Minecraft_1_8    = v(47, "1.8", "1.8.1", "1.8.2", "1.8.3", "1.8.4", "1.8.5", "1.8.6", "1.8.7", "1.8.8", "1.8.9")
-	Minecraft_1_9    = v(107, "1.9")
-	Minecraft_1_9_1  = v(108, "1.9.1")
-	Minecraft_1_9_4  = v(110, "1.9.3", "1.9.4")
-	Minecraft_1_10   = v(210, "1.10", "1.10.1", "1.10.2")
-	Minecraft_1_11   = v(315, "1.11")
-	Minecraft_1_11_1 = v(316, "1.11.1", "1.11.2")
-	Minecraft_1_12   = v(335, "1.12")
-	Minecraft_1_12_1 = v(338, "1.12.1")
-	Minecraft_1_12_2 = v(340, "1.12.2")
-	Minecraft_1_13   = v(393, "1.13")
-	Minecraft_1_13_2 = v(404, "1.13.2")
-	Minecraft_1_14   = v(477, "1.14")
-	Minecraft_1_15   = v(573, "1.15")
-	Minecraft_1_16   = v(735, "1.16")
-	Minecraft_1_16_1 = v(736, "1.16.1")
-	Minecraft_1_16_2 = v(751, "1.16.2")
-	Minecraft_1_16_3 = v(753, "1.16.3")
-	Minecraft_1_16_4 = v(754, "1.16.4", "1.16.5")
-	Minecraft_1_17   = v(755, "1.17")
-	Minecraft_1_17_1 = v(756, "1.17.1")
-	Minecraft_1_18   = v(757, "1.18", "1.18.1")
-	Minecraft_1_18_2 = v(758, "1.18.2")
-	Minecraft_1_19   = v(759, "1.19")
-	Minecraft_1_19_1 = v(760, "1.19.1", "1.19.2")
-	Minecraft_1_19_3 = v(761, "1.19.3")
-	Minecraft_1_19_4 = v(762, "1.19.4")
-	Minecraft_1_20   = v(763, "1.20", "1.20.1")
-	Minecraft_1_20_2 = v(764, "1.20.2")
-	Minecraft_1_20_3 = v(765, "1.20.3", "1.20.4")
-	Minecraft_1_20_5 = v(766, "1.20.5", "1.20.6")
-	Minecraft_1_21   = v(767, "1.21", "1.21.1")
-	Minecraft_1_21_2 = v(768, "1.21.2", "1.21.3")
-	Minecraft_1_21_4 = v(769, "1.21.4")
-	Minecraft_1_21_5 = v(770, "1.21.5")
-	Minecraft_1_21_6 = v(771, "1.21.6")
-	Minecraft_1_21_7 = v(772, "1.21.7", "1.21.8")
-	Minecraft_1_21_9 = v(773, "1.21.9", "1.21.10")
+	Unknown           = v(-1, "Unknown")
+	Legacy            = v(-2, "Legacy")
+	Minecraft_1_7_2   = v(4, "1.7.2", "1.7.3", "1.7.4", "1.7.5")
+	Minecraft_1_7_6   = v(5, "1.7.6", "1.7.7", "1.7.8", "1.7.9", "1.7.10")
+	Minecraft_1_8     = v(47, "1.8", "1.8.1", "1.8.2", "1.8.3", "1.8.4", "1.8.5", "1.8.6", "1.8.7", "1.8.8", "1.8.9")
+	Minecraft_1_9     = v(107, "1.9")
+	Minecraft_1_9_1   = v(108, "1.9.1")
+	Minecraft_1_9_4   = v(110, "1.9.3", "1.9.4")
+	Minecraft_1_10    = v(210, "1.10", "1.10.1", "1.10.2")
+	Minecraft_1_11    = v(315, "1.11")
+	Minecraft_1_11_1  = v(316, "1.11.1", "1.11.2")
+	Minecraft_1_12    = v(335, "1.12")
+	Minecraft_1_12_1  = v(338, "1.12.1")
+	Minecraft_1_12_2  = v(340, "1.12.2")
+	Minecraft_1_13    = v(393, "1.13")
+	Minecraft_1_13_2  = v(404, "1.13.2")
+	Minecraft_1_14    = v(477, "1.14")
+	Minecraft_1_15    = v(573, "1.15")
+	Minecraft_1_16    = v(735, "1.16")
+	Minecraft_1_16_1  = v(736, "1.16.1")
+	Minecraft_1_16_2  = v(751, "1.16.2")
+	Minecraft_1_16_3  = v(753, "1.16.3")
+	Minecraft_1_16_4  = v(754, "1.16.4", "1.16.5")
+	Minecraft_1_17    = v(755, "1.17")
+	Minecraft_1_17_1  = v(756, "1.17.1")
+	Minecraft_1_18    = v(757, "1.18", "1.18.1")
+	Minecraft_1_18_2  = v(758, "1.18.2")
+	Minecraft_1_19    = v(759, "1.19")
+	Minecraft_1_19_1  = v(760, "1.19.1", "1.19.2")
+	Minecraft_1_19_3  = v(761, "1.19.3")
+	Minecraft_1_19_4  = v(762, "1.19.4")
+	Minecraft_1_20    = v(763, "1.20", "1.20.1")
+	Minecraft_1_20_2  = v(764, "1.20.2")
+	Minecraft_1_20_3  = v(765, "1.20.3", "1.20.4")
+	Minecraft_1_20_5  = v(766, "1.20.5", "1.20.6")
+	Minecraft_1_21    = v(767, "1.21", "1.21.1")
+	Minecraft_1_21_2  = v(768, "1.21.2", "1.21.3")
+	Minecraft_1_21_4  = v(769, "1.21.4")
+	Minecraft_1_21_5  = v(770, "1.21.5")
+	Minecraft_1_21_6  = v(771, "1.21.6")
+	Minecraft_1_21_7  = v(772, "1.21.7", "1.21.8")
+	Minecraft_1_21_9  = v(773, "1.21.9", "1.21.10")
+	Minecraft_1_21_11 = v(774, "1.21.11")
 
 	// Versions ordered from lowest to highest
 	Versions = []*proto.Version{
@@ -70,7 +71,7 @@ var (
 		Minecraft_1_18, Minecraft_1_18_2,
 		Minecraft_1_19, Minecraft_1_19_1, Minecraft_1_19_3, Minecraft_1_19_4,
 		Minecraft_1_20, Minecraft_1_20_2, Minecraft_1_20_3, Minecraft_1_20_5,
-		Minecraft_1_21, Minecraft_1_21_2, Minecraft_1_21_4, Minecraft_1_21_5, Minecraft_1_21_6, Minecraft_1_21_7, Minecraft_1_21_9,
+		Minecraft_1_21, Minecraft_1_21_2, Minecraft_1_21_4, Minecraft_1_21_5, Minecraft_1_21_6, Minecraft_1_21_7, Minecraft_1_21_9, Minecraft_1_21_11,
 	}
 )
 

pkg/edition/java/proxy/bossbar_manager.go

@@ -0,0 +1,130 @@
+package proxy
+
+import (
+	"sync"
+
+	"go.minekube.com/gate/pkg/edition/java/bossbar"
+	bossbarpacket "go.minekube.com/gate/pkg/edition/java/proto/packet/bossbar"
+	"go.minekube.com/gate/pkg/edition/java/proto/version"
+	"go.minekube.com/gate/pkg/util/uuid"
+)
+
+// bossBarManager handles dropping and resending boss bar packets on versions 1.20.2 and newer
+// because the client deletes all boss bars during the config phase, and sending update packets
+// would cause the client to be disconnected.
+type bossBarManager struct {
+	player *connectedPlayer
+
+	mu          sync.Mutex
+	bossBars    map[uuid.UUID]bossbar.BossBar // keyed by boss bar ID
+	dropPackets bool
+}
+
+func newBossBarManager(player *connectedPlayer) *bossBarManager {
+	return &bossBarManager{
+		player:   player,
+		bossBars: make(map[uuid.UUID]bossbar.BossBar),
+	}
+}
+
+// shouldManage returns true if this player's protocol version requires boss bar management.
+func (m *bossBarManager) shouldManage() bool {
+	return m.player.Protocol().GreaterEqual(version.Minecraft_1_20_2)
+}
+
+// RegisterBossBar registers a proxy-level boss bar with this player.
+// This should be called when a boss bar is shown to the player.
+func (m *bossBarManager) RegisterBossBar(bar bossbar.BossBar) {
+	if !m.shouldManage() {
+		return
+	}
+	m.mu.Lock()
+	m.bossBars[bar.ID()] = bar
+	m.mu.Unlock()
+}
+
+// UnregisterBossBar unregisters a proxy-level boss bar from this player.
+// This should be called when a boss bar is hidden from the player.
+func (m *bossBarManager) UnregisterBossBar(bar bossbar.BossBar) {
+	if !m.shouldManage() {
+		return
+	}
+	m.mu.Lock()
+	delete(m.bossBars, bar.ID())
+	m.mu.Unlock()
+}
+
+// WritePacket writes a boss bar packet to the player, respecting the drop state.
+// Returns true if the packet was written (or dropped intentionally), false on error.
+func (m *bossBarManager) WritePacket(p *bossbarpacket.BossBar) bool {
+	m.mu.Lock()
+	drop := m.dropPackets
+	m.mu.Unlock()
+
+	if drop {
+		// Intentionally drop the packet during server transition
+		return true
+	}
+
+	return m.player.WritePacket(p) == nil
+}
+
+// StartDropping prevents boss bar update packets from being sent to the player.
+// This should be called when the player enters config state for server switching.
+func (m *bossBarManager) StartDropping() {
+	if !m.shouldManage() {
+		return
+	}
+	m.mu.Lock()
+	m.dropPackets = true
+	m.mu.Unlock()
+}
+
+// SendBossBars re-creates all proxy-level boss bars for the player and stops dropping packets.
+// This should be called after the player has joined a new server.
+func (m *bossBarManager) SendBossBars() {
+	if !m.shouldManage() {
+		return
+	}
+
+	m.mu.Lock()
+	bars := make([]bossbar.BossBar, 0, len(m.bossBars))
+	for _, bar := range m.bossBars {
+		bars = append(bars, bar)
+	}
+	m.dropPackets = false
+	m.mu.Unlock()
+
+	// Re-add the player as a viewer to each boss bar, which will send the ADD packet
+	for _, bar := range bars {
+		// The boss bar package handles creating the add packet
+		_ = bar.AddViewer(m.player)
+	}
+}
+
+// IsDropping returns true if boss bar packets are currently being dropped.
+func (m *bossBarManager) IsDropping() bool {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.dropPackets
+}
+
+// Implement bossbar.ManagedViewer interface on connectedPlayer
+
+// RegisterBossBar implements bossbar.ManagedViewer.
+func (p *connectedPlayer) RegisterBossBar(bar bossbar.BossBar) {
+	p.bossBarManager.RegisterBossBar(bar)
+}
+
+// UnregisterBossBar implements bossbar.ManagedViewer.
+func (p *connectedPlayer) UnregisterBossBar(bar bossbar.BossBar) {
+	p.bossBarManager.UnregisterBossBar(bar)
+}
+
+// WriteBossBarPacket implements bossbar.ManagedViewer.
+func (p *connectedPlayer) WriteBossBarPacket(packet *bossbarpacket.BossBar) bool {
+	return p.bossBarManager.WritePacket(packet)
+}
+
+// Compile-time assertion that connectedPlayer implements bossbar.ManagedViewer
+var _ bossbar.ManagedViewer = (*connectedPlayer)(nil)