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Fix data race on WebSocketClient::_ctx (concurrent disconnect vs send/isConnected) #6

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Fix data race on WebSocketClient::_ctx (concurrent disconnect vs send/isConnected) #6

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48 changes: 32 additions & 16 deletions src/WebSocketClient.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -17,8 +17,12 @@ WebSocketClient::~WebSocketClient() {
}

bool WebSocketClient::isConnected() {
if (_ctx) {
return _ctx->isConnected();
// _ctx is published/cleared from connect()/disconnect() on a different thread
// than the senders/isConnected callers (media thread). Access it atomically so
// the shared_ptr read never races the reset()/assign (TSan-verified).
auto ctx = std::atomic_load(&_ctx);
if (ctx) {
return ctx->isConnected();
}
return false;
}
Expand Down Expand Up @@ -106,43 +110,51 @@ void WebSocketClient::enableCompression(bool enable) {

void WebSocketClient::setOpenCallback(OpenCallback callback) {
open_callback = std::move(callback);
if (_ctx) _ctx->setOpenCallback(open_callback);
auto ctx = std::atomic_load(&_ctx);
if (ctx) ctx->setOpenCallback(open_callback);
}

void WebSocketClient::setCloseCallback(CloseCallback callback) {
close_callback = std::move(callback);
if (_ctx) _ctx->setCloseCallback(close_callback);
auto ctx = std::atomic_load(&_ctx);
if (ctx) ctx->setCloseCallback(close_callback);
}

void WebSocketClient::setErrorCallback(ErrorCallback callback) {
error_callback = std::move(callback);
if (_ctx) _ctx->setErrorCallback(error_callback);
auto ctx = std::atomic_load(&_ctx);
if (ctx) ctx->setErrorCallback(error_callback);
}

void WebSocketClient::setMessageCallback(MessageCallback callback) {
message_callback = std::move(callback);
if (_ctx) _ctx->setMessageCallback(message_callback);
auto ctx = std::atomic_load(&_ctx);
if (ctx) ctx->setMessageCallback(message_callback);
}

void WebSocketClient::setBinaryCallback(BinaryCallback callback) {
binary_callback = std::move(callback);
if (_ctx) _ctx->setBinaryCallback(binary_callback);
auto ctx = std::atomic_load(&_ctx);
if (ctx) ctx->setBinaryCallback(binary_callback);
}

bool WebSocketClient::sendMessage(const std::string& message) {
return _ctx && _ctx->sendData(message.data(), message.size(), MessageType::TEXT);
auto ctx = std::atomic_load(&_ctx);
return ctx && ctx->sendData(message.data(), message.size(), MessageType::TEXT);
}

bool WebSocketClient::sendMessage(const char* msg, size_t len) {
return _ctx && _ctx->sendData(msg, len, MessageType::TEXT);
auto ctx = std::atomic_load(&_ctx);
return ctx && ctx->sendData(msg, len, MessageType::TEXT);
}

bool WebSocketClient::sendBinary(const void* data, size_t length) {
return _ctx && _ctx->sendData(data, length, MessageType::BINARY);
auto ctx = std::atomic_load(&_ctx);
return ctx && ctx->sendData(data, length, MessageType::BINARY);
}

void WebSocketClient::connect() {
if (_ctx) {
if (std::atomic_load(&_ctx)) {
return;
}

Expand All @@ -166,8 +178,8 @@ void WebSocketClient::connect() {
if (message_callback) ctx->setMessageCallback(message_callback);
if (binary_callback) ctx->setBinaryCallback(binary_callback);

_ctx = ctx;
_ctx->start();
std::atomic_store(&_ctx, ctx);
ctx->start();

} catch (...) {
// Failed to create or start context.
Expand All @@ -176,8 +188,12 @@ void WebSocketClient::connect() {
}

void WebSocketClient::disconnect() {
if (_ctx) {
_ctx->stop();
_ctx.reset();
// Atomically take and clear _ctx so a concurrent sendBinary/isConnected
// either sees the old context (and keeps it alive via its own shared_ptr
// copy) or sees null — never a torn read. stop() (which joins the event
// thread) runs OUTSIDE the swap, so it can't deadlock a callback thread.
auto ctx = std::atomic_exchange(&_ctx, std::shared_ptr<WebSocketContext>{});
if (ctx) {
ctx->stop();
}
}