refactor: remove unused NewKeypressKeepAliveMessage function from HID RPC

- Updated `handleHidRPCKeyboardInput` to return errors directly instead of keys down state.
- Refactored `rpcKeyboardReport` and `rpcKeypressReport` to return errors instead of states.
- Introduced a queue for managing key down state updates in the `Session` struct to prevent input handling stalls.
- Adjusted the `UpdateKeysDown` method to handle state changes more efficiently.
- Removed unnecessary logging and commented-out code for clarity.

hidrpc.go

@@ -25,11 +25,7 @@ func handleHidRPCMessage(message hidrpc.Message, session *Session) {
 		}
 		session.hidRPCAvailable = true
 	case hidrpc.TypeKeypressReport, hidrpc.TypeKeyboardReport:
-		keysDownState, err := handleHidRPCKeyboardInput(message)
+		rpcErr = handleHidRPCKeyboardInput(message)
-		if keysDownState != nil {
-			session.reportHidRPCKeysDownState(*keysDownState)
-		}
-		rpcErr = err
 	case hidrpc.TypeKeypressKeepAliveReport:
 		gadget.DelayAutoRelease()
 	case hidrpc.TypePointerReport:
@@ -95,27 +91,25 @@ func onHidMessage(msg hidQueueMessage, session *Session) {
 	}
 }
 
-func handleHidRPCKeyboardInput(message hidrpc.Message) (*usbgadget.KeysDownState, error) {
+func handleHidRPCKeyboardInput(message hidrpc.Message) error {
 	switch message.Type() {
 	case hidrpc.TypeKeypressReport:
 		keypressReport, err := message.KeypressReport()
 		if err != nil {
 			logger.Warn().Err(err).Msg("failed to get keypress report")
-			return nil, err
+			return err
 		}
-		keysDownState, rpcError := rpcKeypressReport(keypressReport.Key, keypressReport.Press)
+		return rpcKeypressReport(keypressReport.Key, keypressReport.Press)
-		return &keysDownState, rpcError
 	case hidrpc.TypeKeyboardReport:
 		keyboardReport, err := message.KeyboardReport()
 		if err != nil {
 			logger.Warn().Err(err).Msg("failed to get keyboard report")
-			return nil, err
+			return err
 		}
-		keysDownState, rpcError := rpcKeyboardReport(keyboardReport.Modifier, keyboardReport.Keys)
+		return rpcKeyboardReport(keyboardReport.Modifier, keyboardReport.Keys)
-		return &keysDownState, rpcError
 	}
 
-	return nil, fmt.Errorf("unknown HID RPC message type: %d", message.Type())
+	return fmt.Errorf("unknown HID RPC message type: %d", message.Type())
 }
 
 func reportHidRPC(params any, session *Session) {

internal/hidrpc/hidrpc.go

@@ -99,11 +99,3 @@ func NewKeydownStateMessage(state usbgadget.KeysDownState) *Message {
 		d: data,
 	}
 }
-
-// NewKeypressKeepAliveMessage creates a new keypress keep alive message.
-func NewKeypressKeepAliveMessage() *Message {
-	return &Message{
-		t: TypeKeypressKeepAliveReport,
-		d: []byte{},
-	}
-}

internal/usbgadget/hid_keyboard.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"sync"
 	"time"
 
 	"github.com/rs/xid"
@@ -27,7 +28,7 @@ var keyboardConfig = gadgetConfigItem{
 
 // macOS default: 15 * 15 = 225ms https://discussions.apple.com/thread/1316947?sortBy=rank
 // Linux default: 250ms https://man.archlinux.org/man/kbdrate.8.en
-// Windows default: 1ms `HKEY_CURRENT_USER\Control Panel\Accessibility\Keyboard Response\AutoRepeatDelay`
+// Windows default: 1s `HKEY_CURRENT_USER\Control Panel\Accessibility\Keyboard Response\AutoRepeatDelay`
 const autoReleaseKeyboardInterval = time.Millisecond * 100
 
 // Source: https://www.kernel.org/doc/Documentation/usb/gadget_hid.txt
@@ -153,95 +154,79 @@ func (u *UsbGadget) GetKeysDownState() KeysDownState {
 	return u.keysDownState
 }
 
-func (u *UsbGadget) updateKeyDownState(state KeysDownState) {
-	u.log.Trace().Interface("old", u.keysDownState).Interface("new", state).Msg("acquiring keyboardStateLock for updateKeyDownState")
-
-	// this is intentional to unlock keyboard state lock before onKeysDownChange callback
-	{
-		u.keyboardStateLock.Lock()
-		defer u.keyboardStateLock.Unlock()
-
-		if u.keysDownState.Modifier == state.Modifier &&
-			bytes.Equal(u.keysDownState.Keys, state.Keys) {
-			return // No change in key down state
-		}
-
-		u.log.Trace().Interface("old", u.keysDownState).Interface("new", state).Msg("keysDownState updated")
-		u.keysDownState = state
-	}
-
-	if u.onKeysDownChange != nil {
-		u.log.Trace().Interface("state", state).Msg("calling onKeysDownChange")
-		(*u.onKeysDownChange)(state)
-		u.log.Trace().Interface("state", state).Msg("onKeysDownChange called")
-	}
-}
-
 func (u *UsbGadget) SetOnKeysDownChange(f func(state KeysDownState)) {
 	u.onKeysDownChange = &f
 }
 
 func (u *UsbGadget) scheduleAutoRelease(key byte) {
-	u.log.Trace().Msg("scheduling autoRelease")
 	u.kbdAutoReleaseLock.Lock()
 	defer unlockWithLog(&u.kbdAutoReleaseLock, u.log, "autoRelease scheduled")
 
-	if u.kbdAutoReleaseTimer != nil {
+	if u.kbdAutoReleaseTimers[key] != nil {
-		u.kbdAutoReleaseTimer.Stop()
+		u.kbdAutoReleaseTimers[key].Stop()
 	}
 
-	u.kbdAutoReleaseTimer = time.AfterFunc(autoReleaseKeyboardInterval, func() {
+	u.kbdAutoReleaseTimers[key] = time.AfterFunc(autoReleaseKeyboardInterval, func() {
-		u.performAutoRelease()
+		u.performAutoRelease(key)
 	})
 }
 
-func (u *UsbGadget) cancelAutoRelease() {
+func (u *UsbGadget) cancelAutoRelease(key byte) {
-	u.log.Trace().Msg("cancelling autoRelease")
 	u.kbdAutoReleaseLock.Lock()
 	defer unlockWithLog(&u.kbdAutoReleaseLock, u.log, "autoRelease cancelled")
 
-	if u.kbdAutoReleaseTimer != nil {
+	if timer := u.kbdAutoReleaseTimers[key]; timer != nil {
-		u.kbdAutoReleaseTimer.Stop()
+		timer.Stop()
+		u.kbdAutoReleaseTimers[key] = nil
+		delete(u.kbdAutoReleaseTimers, key)
 	}
 }
 
 func (u *UsbGadget) DelayAutoRelease() {
-	u.log.Trace().Msg("delaying autoRelease")
 	u.kbdAutoReleaseLock.Lock()
 	defer unlockWithLog(&u.kbdAutoReleaseLock, u.log, "autoRelease delayed")
 
-	if u.kbdAutoReleaseTimer == nil {
+	if u.kbdAutoReleaseTimers == nil {
 		return
 	}
 
-	u.kbdAutoReleaseTimer.Reset(autoReleaseKeyboardInterval)
+	for _, timer := range u.kbdAutoReleaseTimers {
-
+		if timer != nil {
-	u.log.Trace().Msg("auto-release timer reset")
+			timer.Reset(autoReleaseKeyboardInterval)
+		}
+	}
 }
 
-func (u *UsbGadget) performAutoRelease() {
+func (u *UsbGadget) performAutoRelease(key byte) {
-	u.log.Trace().Msg("performing autoRelease")
 	u.kbdAutoReleaseLock.Lock()
-	defer unlockWithLog(&u.kbdAutoReleaseLock, u.log, "autoRelease unlocked")
 
-	key := u.kbdAutoReleaseLastKey
+	if u.kbdAutoReleaseTimers[key] == nil {
-
+		u.log.Warn().Uint8("key", key).Msg("autoRelease timer not found")
-	select {
+		u.kbdAutoReleaseLock.Unlock()
-	case <-u.keyboardStateCtx.Done():
 		return
-	default:
 	}
 
-	// we just reset the keyboard state to 0 no matter what
+	u.kbdAutoReleaseTimers[key].Stop()
-	u.log.Trace().Uint8("key", key).Msg("auto-releasing keyboard key")
+	u.kbdAutoReleaseTimers[key] = nil
-	_, err := u.keypressReport(key, false, false)
+	delete(u.kbdAutoReleaseTimers, key)
-	if err != nil {
+	u.kbdAutoReleaseLock.Unlock()
-		u.log.Warn().Uint8("key", key).Msg("failed to auto-release keyboard key")
+
+	// Skip if already released
+	state := u.GetKeysDownState()
+	alreadyReleased := true
+
+	for i := range state.Keys {
+		if state.Keys[i] == key {
+			alreadyReleased = false
+			break
+		}
 	}
 
-	u.kbdAutoReleaseTimer = nil
+	if alreadyReleased {
+		return
+	}
 
-	u.log.Trace().Uint8("key", key).Msg("auto release performed")
+	u.keypressReport(key, false)
 }
 
 func (u *UsbGadget) listenKeyboardEvents() {
@@ -313,7 +298,11 @@ func (u *UsbGadget) OpenKeyboardHidFile() error {
 	return u.openKeyboardHidFile()
 }
 
+var keyboardWriteHidFileLock sync.Mutex
+
 func (u *UsbGadget) keyboardWriteHidFile(modifier byte, keys []byte) error {
+	keyboardWriteHidFileLock.Lock()
+	defer keyboardWriteHidFileLock.Unlock()
 	if err := u.openKeyboardHidFile(); err != nil {
 		return err
 	}
@@ -337,17 +326,29 @@ func (u *UsbGadget) UpdateKeysDown(modifier byte, keys []byte) KeysDownState {
 		}
 	}
 
-	downState := KeysDownState{
+	state := KeysDownState{
 		Modifier: modifier,
 		Keys:     []byte(keys[:]),
 	}
-	u.updateKeyDownState(downState)
+
-	return downState
+	u.keyboardStateLock.Lock()
+
+	if u.keysDownState.Modifier == state.Modifier &&
+		bytes.Equal(u.keysDownState.Keys, state.Keys) {
+		u.keyboardStateLock.Unlock()
+		return state // No change in key down state
+	}
+
+	u.keysDownState = state
+	u.keyboardStateLock.Unlock()
+
+	if u.onKeysDownChange != nil {
+		(*u.onKeysDownChange)(state) // this enques to the outgoing hidrpc queue via usb.go → currentSession.enqueueKeysDownState(...)
+	}
+	return state
 }
 
-func (u *UsbGadget) KeyboardReport(modifier byte, keys []byte) (KeysDownState, error) {
+func (u *UsbGadget) KeyboardReport(modifier byte, keys []byte) error {
-	u.keyboardLock.Lock()
-	defer u.keyboardLock.Unlock()
 	defer u.resetUserInputTime()
 
 	if len(keys) > hidKeyBufferSize {
@@ -362,7 +363,8 @@ func (u *UsbGadget) KeyboardReport(modifier byte, keys []byte) (KeysDownState, e
 		u.log.Warn().Uint8("modifier", modifier).Uints8("keys", keys).Msg("Could not write keyboard report to hidg0")
 	}
 
-	return u.UpdateKeysDown(modifier, keys), err
+	u.UpdateKeysDown(modifier, keys)
+	return err
 }
 
 const (
@@ -402,10 +404,10 @@ var KeyCodeToMaskMap = map[byte]byte{
 	RightSuper:   ModifierMaskRightSuper,
 }
 
-func (u *UsbGadget) keypressReportNonThreadSafe(key byte, press bool, autoRelease bool) (KeysDownState, error) {
+func (u *UsbGadget) keypressReport(key byte, press bool) (KeysDownState, error) {
 	defer u.resetUserInputTime()
 
-	l := u.log.With().Uint8("key", key).Bool("press", press).Bool("autoRelease", autoRelease).Logger()
+	l := u.log.With().Uint8("key", key).Bool("press", press).Logger()
 	if l.GetLevel() <= zerolog.DebugLevel {
 		requestID := xid.New()
 		l = l.With().Str("requestID", requestID.String()).Logger()
@@ -470,64 +472,21 @@ func (u *UsbGadget) keypressReportNonThreadSafe(key byte, press bool, autoReleas
 		}
 	}
 
-	if l.GetLevel() <= zerolog.DebugLevel {
-		l = l.With().Uint8("modifier", modifier).Uints8("keys", keys).Logger()
-	}
-
-	l.Trace().Msg("writing keypress report to hidg0")
-
 	err := u.keyboardWriteHidFile(modifier, keys)
-	if err != nil {
-		l.Warn().Msg("Could not write keypress report to hidg0")
-	}
-
-	l.Trace().Msg("keypress report written to hidg0")
-
-	if press {
-		{
-			l.Trace().Msg("acquiring kbdAutoReleaseLock to update last key")
-			u.kbdAutoReleaseLock.Lock()
-			u.kbdAutoReleaseLastKey = key
-			unlockWithLog(&u.kbdAutoReleaseLock, u.log, "last key updated")
-		}
-
-		if autoRelease {
-			u.scheduleAutoRelease(key)
-		}
-	} else {
-		if autoRelease {
-			u.cancelAutoRelease()
-		}
-	}
-
 	return u.UpdateKeysDown(modifier, keys), err
 }
 
-type keypressReportResult struct {
+func (u *UsbGadget) KeypressReport(key byte, press bool) error {
-	KeysDownState KeysDownState
+	state, err := u.keypressReport(key, press)
-	Error         error
+	isRolledOver := state.Keys[0] == hidErrorRollOver
-}
 
-func (u *UsbGadget) keypressReport(key byte, press bool, autoRelease bool) (KeysDownState, error) {
+	if isRolledOver {
-	u.keyboardLock.Lock()
+		u.cancelAutoRelease(key)
-	defer u.keyboardLock.Unlock()
+	} else if press {
-
+		u.scheduleAutoRelease(key)
-	r := make(chan keypressReportResult)
+	} else {
-	go func() {
+		u.cancelAutoRelease(key)
-		state, err := u.keypressReportNonThreadSafe(key, press, autoRelease)
-		r <- keypressReportResult{KeysDownState: state, Error: err}
-	}()
-
-	select {
-	case <-time.After(1 * time.Second):
-		u.log.Warn().Msg("keypressReport timed out, possibly stuck")
-		return u.keysDownState, fmt.Errorf("keypressReport timed out, possibly stuck")
-	case ret := <-r:
-		u.log.Debug().Msg("keypressReport handled")
-		return ret.KeysDownState, ret.Error
 	}
-}
 
-func (u *UsbGadget) KeypressReport(key byte, press bool) (KeysDownState, error) {
+	return err
-	return u.keypressReport(key, press, true)
 }

internal/usbgadget/usbgadget.go

@@ -69,8 +69,7 @@ type UsbGadget struct {
 	keysDownState KeysDownState // keyboard dynamic state (modifier keys and pressed keys)
 
 	kbdAutoReleaseLock   sync.Mutex
-	kbdAutoReleaseTimer   *time.Timer
+	kbdAutoReleaseTimers map[byte]*time.Timer
-	kbdAutoReleaseLastKey byte
 
 	keyboardStateLock   sync.Mutex
 	keyboardStateCtx    context.Context
@@ -136,6 +135,7 @@ func newUsbGadget(name string, configMap map[string]gadgetConfigItem, enabledDev
 		keyboardStateCancel:  keyboardCancel,
 		keyboardState:        0,
 		keysDownState:        KeysDownState{Modifier: 0, Keys: []byte{0, 0, 0, 0, 0, 0}}, // must be initialized to hidKeyBufferSize (6) zero bytes
+		kbdAutoReleaseTimers: make(map[byte]*time.Timer),
 		enabledDevices:       *enabledDevices,
 		lastUserInput:        time.Now(),
 		log:                  logger,
@@ -163,10 +163,10 @@ func (u *UsbGadget) Close() error {
 
 	// Stop auto-release timer
 	u.kbdAutoReleaseLock.Lock()
-	if u.kbdAutoReleaseTimer != nil {
+	for _, timer := range u.kbdAutoReleaseTimers {
-		u.kbdAutoReleaseTimer.Stop()
+		timer.Stop()
-		u.kbdAutoReleaseTimer = nil
 	}
+	u.kbdAutoReleaseTimers = make(map[byte]*time.Timer)
 	u.kbdAutoReleaseLock.Unlock()
 
 	// Close HID files

jsonrpc.go

@@ -1059,9 +1059,7 @@ var rpcHandlers = map[string]RPCHandler{
 	"getNetworkSettings":     {Func: rpcGetNetworkSettings},
 	"setNetworkSettings":     {Func: rpcSetNetworkSettings, Params: []string{"settings"}},
 	"renewDHCPLease":         {Func: rpcRenewDHCPLease},
-	"keyboardReport":         {Func: rpcKeyboardReport, Params: []string{"modifier", "keys"}},
 	"getKeyboardLedState":    {Func: rpcGetKeyboardLedState},
-	"keypressReport":         {Func: rpcKeypressReport, Params: []string{"key", "press"}},
 	"getKeyDownState":        {Func: rpcGetKeysDownState},
 	"absMouseReport":         {Func: rpcAbsMouseReport, Params: []string{"x", "y", "buttons"}},
 	"relMouseReport":         {Func: rpcRelMouseReport, Params: []string{"dx", "dy", "buttons"}},

ui/src/components/WebRTCVideo.tsx

@@ -237,6 +237,7 @@ export default function WebRTCVideo() {
   const keyDownHandler = useCallback(
     (e: KeyboardEvent) => {
       e.preventDefault();
+      if (e.repeat) return;
       const code = getAdjustedKeyCode(e);
       const hidKey = keys[code];
 

ui/src/hooks/useHidRpc.ts

@@ -36,11 +36,16 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
   }, [rpcHidChannel, rpcHidProtocolVersion]);
 
   const rpcHidUnreliableReady = useMemo(() => {
-    return rpcHidUnreliableChannel?.readyState === "open" && rpcHidProtocolVersion !== null;
+    return (
+      rpcHidUnreliableChannel?.readyState === "open" && rpcHidProtocolVersion !== null
+    );
   }, [rpcHidUnreliableChannel, rpcHidProtocolVersion]);
 
   const rpcHidUnreliableNonOrderedReady = useMemo(() => {
-    return rpcHidUnreliableNonOrderedChannel?.readyState === "open" && rpcHidProtocolVersion !== null;
+    return (
+      rpcHidUnreliableNonOrderedChannel?.readyState === "open" &&
+      rpcHidProtocolVersion !== null
+    );
   }, [rpcHidUnreliableNonOrderedChannel, rpcHidProtocolVersion]);
 
   const rpcHidStatus = useMemo(() => {
@@ -50,7 +55,15 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
     return `ready (v${rpcHidProtocolVersion}${rpcHidUnreliableReady ? "+u" : ""})`;
   }, [rpcHidChannel, rpcHidUnreliableReady, rpcHidProtocolVersion]);
 
-  const sendMessage = useCallback((message: RpcMessage, { ignoreHandshakeState, useUnreliableChannel, requireOrdered = true }: sendMessageParams = {}) => {
+  const sendMessage = useCallback(
+    (
+      message: RpcMessage,
+      {
+        ignoreHandshakeState,
+        useUnreliableChannel,
+        requireOrdered = true,
+      }: sendMessageParams = {},
+    ) => {
       if (rpcHidChannel?.readyState !== "open") return;
       if (!rpcHidReady && !ignoreHandshakeState) return;
 
@@ -72,19 +85,22 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
       }
 
       rpcHidChannel?.send(data as unknown as ArrayBuffer);
-  }, [
+    },
+    [
       rpcHidChannel,
       rpcHidUnreliableChannel,
       rpcHidUnreliableNonOrderedChannel,
       rpcHidReady,
       rpcHidUnreliableReady,
       rpcHidUnreliableNonOrderedReady,
-  ]);
+    ],
+  );
 
   const reportKeyboardEvent = useCallback(
     (keys: number[], modifier: number) => {
       sendMessage(new KeyboardReportMessage(keys, modifier));
-    }, [sendMessage],
+    },
+    [sendMessage],
   );
 
   const reportKeypressEvent = useCallback(
@@ -96,7 +112,9 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
 
   const reportAbsMouseEvent = useCallback(
     (x: number, y: number, buttons: number) => {
-      sendMessage(new PointerReportMessage(x, y, buttons), { useUnreliableChannel: true });
+      sendMessage(new PointerReportMessage(x, y, buttons), {
+        useUnreliableChannel: true,
+      });
     },
     [sendMessage],
   );
@@ -109,7 +127,7 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
   );
 
   const reportKeypressKeepAlive = useCallback(() => {
-    sendMessage(KEEPALIVE_MESSAGE, { useUnreliableChannel: true, requireOrdered: false });
+    sendMessage(KEEPALIVE_MESSAGE);
   }, [sendMessage]);
 
   const sendHandshake = useCallback(() => {
@@ -119,7 +137,8 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
     sendMessage(new HandshakeMessage(HID_RPC_VERSION), { ignoreHandshakeState: true });
   }, [rpcHidChannel, rpcHidProtocolVersion, sendMessage]);
 
-  const handleHandshake = useCallback((message: HandshakeMessage) => {
+  const handleHandshake = useCallback(
+    (message: HandshakeMessage) => {
       if (!message.version) {
         console.error("Received handshake message without version", message);
         return;
@@ -134,7 +153,9 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
       }
 
       setRpcHidProtocolVersion(message.version);
-  }, [setRpcHidProtocolVersion]);
+    },
+    [setRpcHidProtocolVersion],
+  );
 
   useEffect(() => {
     if (!rpcHidChannel) return;
@@ -168,12 +189,12 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
     };
 
     const openHandler = () => {
-      console.warn("HID RPC channel opened");
+      console.info("HID RPC channel opened");
       sendHandshake();
     };
 
     const closeHandler = () => {
-      console.warn("HID RPC channel closed");
+      console.info("HID RPC channel closed");
       setRpcHidProtocolVersion(null);
     };
 
@@ -186,15 +207,13 @@ export function useHidRpc(onHidRpcMessage?: (payload: RpcMessage) => void) {
       rpcHidChannel.removeEventListener("close", closeHandler);
       rpcHidChannel.removeEventListener("open", openHandler);
     };
-  },
+  }, [
-    [
     rpcHidChannel,
     onHidRpcMessage,
     setRpcHidProtocolVersion,
     sendHandshake,
     handleHandshake,
-    ],
+  ]);
-  );
 
   return {
     reportKeyboardEvent,

ui/src/hooks/useKeyboard.ts

@@ -1,6 +1,12 @@
 import { useCallback, useRef } from "react";
 
-import { hidErrorRollOver, hidKeyBufferSize, KeysDownState, useHidStore, useRTCStore } from "@/hooks/stores";
+import {
+  hidErrorRollOver,
+  hidKeyBufferSize,
+  KeysDownState,
+  useHidStore,
+  useRTCStore,
+} from "@/hooks/stores";
 import { JsonRpcResponse, useJsonRpc } from "@/hooks/useJsonRpc";
 import { useHidRpc } from "@/hooks/useHidRpc";
 import { KeyboardLedStateMessage, KeysDownStateMessage } from "@/hooks/hidRpc";
@@ -31,7 +37,7 @@ export default function useKeyboard() {
     reportKeypressEvent: sendKeypressEventHidRpc,
     reportKeypressKeepAlive: sendKeypressKeepAliveHidRpc,
     rpcHidReady,
-  } = useHidRpc((message) => {
+  } = useHidRpc(message => {
     switch (message.constructor) {
       case KeysDownStateMessage:
         setKeysDownState((message as KeysDownStateMessage).keysDownState);
@@ -52,7 +58,9 @@ export default function useKeyboard() {
     async (state: KeysDownState) => {
       if (rpcDataChannel?.readyState !== "open" && !rpcHidReady) return;
 
-      console.debug(`Send keyboardReport keys: ${state.keys}, modifier: ${state.modifier}`);
+      console.debug(
+        `Send keyboardReport keys: ${state.keys}, modifier: ${state.modifier}`,
+      );
 
       if (rpcHidReady) {
         console.debug("Sending keyboard report via HidRPC");
@@ -60,20 +68,18 @@ export default function useKeyboard() {
         return;
       }
 
-      send("keyboardReport", { keys: state.keys, modifier: state.modifier }, (resp: JsonRpcResponse) => {
+      send(
+        "keyboardReport",
+        { keys: state.keys, modifier: state.modifier },
+        (resp: JsonRpcResponse) => {
           if ("error" in resp) {
             console.error(`Failed to send keyboard report ${state}`, resp.error);
           }
-      });
         },
-    [
-      rpcDataChannel?.readyState,
-      rpcHidReady,
-      send,
-      sendKeyboardEventHidRpc,
-    ],
       );
-
+    },
+    [rpcDataChannel?.readyState, rpcHidReady, send, sendKeyboardEventHidRpc],
+  );
 
   // executeMacro is used to execute a macro consisting of multiple steps.
   // Each step can have multiple keys, multiple modifiers and a delay.
@@ -81,10 +87,14 @@ export default function useKeyboard() {
   // After the delay, the keys and modifiers are released and the next step is executed.
   // If a step has no keys or modifiers, it is treated as a delay-only step.
   // A small pause is added between steps to ensure that the device can process the events.
-  const executeMacro = async (steps: { keys: string[] | null; modifiers: string[] | null; delay: number }[]) => {
+  const executeMacro = async (
+    steps: { keys: string[] | null; modifiers: string[] | null; delay: number }[],
+  ) => {
     for (const [index, step] of steps.entries()) {
       const keyValues = (step.keys || []).map(key => keys[key]).filter(Boolean);
-      const modifierMask: number = (step.modifiers || []).map(mod => modifiers[mod]).reduce((acc, val) => acc + val, 0);
+      const modifierMask: number = (step.modifiers || [])
+        .map(mod => modifiers[mod])
+        .reduce((acc, val) => acc + val, 0);
 
       // If the step has keys and/or modifiers, press them and hold for the delay
       if (keyValues.length > 0 || modifierMask > 0) {
@@ -119,6 +129,8 @@ export default function useKeyboard() {
       clearInterval(keepAliveTimerRef.current);
     }
 
+    sendKeypressKeepAliveHidRpc();
+
     // Create new interval timer
     keepAliveTimerRef.current = setInterval(() => {
       sendKeypressKeepAliveHidRpc();
@@ -174,7 +186,11 @@ export default function useKeyboard() {
         sendKeypress(key, press);
       } else {
         // if the keyPress api is not available, we need to handle the key locally
-        const downState = simulateDeviceSideKeyHandlingForLegacyDevices(keysDownState, key, press);
+        const downState = simulateDeviceSideKeyHandlingForLegacyDevices(
+          keysDownState,
+          key,
+          press,
+        );
         sendKeyboardEvent(downState); // then we send the full state
 
         // if we just sent ErrorRollOver, reset to empty state
@@ -194,7 +210,11 @@ export default function useKeyboard() {
   );
 
   // IMPORTANT: See the keyPressReportApiAvailable comment above for the reason this exists
-  function simulateDeviceSideKeyHandlingForLegacyDevices(state: KeysDownState, key: number, press: boolean): KeysDownState {
+  function simulateDeviceSideKeyHandlingForLegacyDevices(
+    state: KeysDownState,
+    key: number,
+    press: boolean,
+  ): KeysDownState {
     // IMPORTANT: This code parallels the logic in the kernel's hid-gadget driver
     // for handling key presses and releases. It ensures that the USB gadget
     // behaves similarly to a real USB HID keyboard. This logic is paralleled
@@ -223,7 +243,7 @@ export default function useKeyboard() {
         // and if we find a zero byte, we can place the key there (if press is true)
         if (keys[i] === key || keys[i] === 0) {
           if (press) {
-            keys[i] = key // overwrites the zero byte or the same key if already pressed
+            keys[i] = key; // overwrites the zero byte or the same key if already pressed
           } else {
             // we are releasing the key, remove it from the buffer
             if (keys[i] !== 0) {
@@ -239,13 +259,15 @@ export default function useKeyboard() {
       // If we reach here it means we didn't find an empty slot or the key in the buffer
       if (overrun) {
         if (press) {
-          console.warn(`keyboard buffer overflow current keys ${keys}, key: ${key} not added`);
+          console.warn(
+            `keyboard buffer overflow current keys ${keys}, key: ${key} not added`,
+          );
           // Fill all key slots with ErrorRollOver (0x01) to indicate overflow
           keys.length = hidKeyBufferSize;
           keys.fill(hidErrorRollOver);
         } else {
           // If we are releasing a key, and we didn't find it in a slot, who cares?
-          console.debug(`key ${key} not found in buffer, nothing to release`)
+          console.debug(`key ${key} not found in buffer, nothing to release`);
         }
       }
     }

usb.go

@@ -33,7 +33,7 @@ func initUsbGadget() {
 
 	gadget.SetOnKeysDownChange(func(state usbgadget.KeysDownState) {
 		if currentSession != nil {
-			currentSession.reportHidRPCKeysDownState(state)
+			currentSession.enqueueKeysDownState(state)
 		}
 	})
 
@@ -43,11 +43,11 @@ func initUsbGadget() {
 	}
 }
 
-func rpcKeyboardReport(modifier byte, keys []byte) (usbgadget.KeysDownState, error) {
+func rpcKeyboardReport(modifier byte, keys []byte) error {
 	return gadget.KeyboardReport(modifier, keys)
 }
 
-func rpcKeypressReport(key byte, press bool) (usbgadget.KeysDownState, error) {
+func rpcKeypressReport(key byte, press bool) error {
 	return gadget.KeypressReport(key, press)
 }
 

webrtc.go

@@ -13,6 +13,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/jetkvm/kvm/internal/hidrpc"
 	"github.com/jetkvm/kvm/internal/logging"
+	"github.com/jetkvm/kvm/internal/usbgadget"
 	"github.com/pion/webrtc/v4"
 	"github.com/rs/zerolog"
 )
@@ -30,6 +31,8 @@ type Session struct {
 	hidRPCAvailable bool
 	hidQueueLock    sync.Mutex
 	hidQueue        []chan hidQueueMessage
+
+	keysDownStateQueue chan usbgadget.KeysDownState
 }
 
 type hidQueueMessage struct {
@@ -96,6 +99,32 @@ func (s *Session) handleQueues(index int) {
 	}
 }
 
+const keysDownStateQueueSize = 256
+
+func (s *Session) initKeysDownStateQueue() {
+	// serialise outbound key state reports so unreliable links can't stall input handling
+	s.keysDownStateQueue = make(chan usbgadget.KeysDownState, keysDownStateQueueSize)
+	go s.handleKeysDownStateQueue()
+}
+
+func (s *Session) handleKeysDownStateQueue() {
+	for state := range s.keysDownStateQueue {
+		s.reportHidRPCKeysDownState(state)
+	}
+}
+
+func (s *Session) enqueueKeysDownState(state usbgadget.KeysDownState) {
+	if s == nil || s.keysDownStateQueue == nil {
+		return
+	}
+
+	select {
+	case s.keysDownStateQueue <- state:
+	default:
+		hidRPCLogger.Warn().Msg("dropping keys down state update; queue full")
+	}
+}
+
 func getOnHidMessageHandler(session *Session, scopedLogger *zerolog.Logger, channel string) func(msg webrtc.DataChannelMessage) {
 	return func(msg webrtc.DataChannelMessage) {
 		l := scopedLogger.With().
@@ -181,6 +210,7 @@ func newSession(config SessionConfig) (*Session, error) {
 	session := &Session{peerConnection: peerConnection}
 	session.rpcQueue = make(chan webrtc.DataChannelMessage, 256)
 	session.initQueues()
+	session.initKeysDownStateQueue()
 
 	go func() {
 		for msg := range session.rpcQueue {