fix(websocket): try connecting to all hosts (#6631)

CHANGELOG.md

@@ -25,6 +25,7 @@
 - Bugfix: Fixed settings occasionally not opening when clicking on "Manage Accounts" in the account switcher. (#6543)
 - Bugfix: Fixed font change not resulting in forced layout update. (#6536)
 - Bugfix: Fixed scrollbar rect computation potentially resulting in overflows. (#6547)
+- Bugfix: Fixed websocket connections failing if the DNS resolving gave bad hosts. (#6631)
 - Bugfix: Forward query params to websocket URLs. (#6141)
 - Bugfix: Fixed Lua errors from handlers of HTTP requests not being logged. (#6452)
 - Bugfix: Fixed restore button not showing on Windows. (#6565)

src/common/websockets/detail/WebSocketConnectionImpl.cpp

@@ -7,6 +7,8 @@
 #include <boost/beast/core/bind_handler.hpp>
 #include <boost/beast/websocket/ssl.hpp>
 
+using namespace std::literals::string_view_literals;
+
 namespace chatterino::ws::detail {
 
 namespace asio = boost::asio;
@@ -93,30 +95,61 @@ void WebSocketConnectionHelper<Derived, Inner>::onResolve(
         return;
     }
 
-    qCDebug(chatterinoWebsocket) << *this << "Resolved host";
+    this->resolvedEndpoints = results;
+
+    this->tryConnect(this->resolvedEndpoints.begin());
+}
+
+template <typename Derived, typename Inner>
+void WebSocketConnectionHelper<Derived, Inner>::tryConnect(
+    boost::asio::ip::tcp::resolver::results_type::const_iterator
+        endpointIterator)
+{
+    if (endpointIterator == this->resolvedEndpoints.end())
+    {
+        this->fail("Ran out of resolved endpoints"sv, u"connect");
+        return;
+    }
+
+    const auto &endpoint = endpointIterator->endpoint();
+
+    qCDebug(chatterinoWebsocket)
+        << *this << "connect to" << endpoint.address().to_string();
 
     beast::get_lowest_layer(this->stream)
         .expires_after(std::chrono::seconds{30});
+
     beast::get_lowest_layer(this->stream)
-        .async_connect(results, beast::bind_front_handler(
-                                    &WebSocketConnectionHelper::onTcpHandshake,
-                                    this->shared_from_this()));
+        .async_connect(endpoint,
+                       beast::bind_front_handler(
+                           &WebSocketConnectionHelper::onTcpHandshake,
+                           this->shared_from_this(), endpointIterator));
 }
 
 template <typename Derived, typename Inner>
 void WebSocketConnectionHelper<Derived, Inner>::onTcpHandshake(
-    boost::system::error_code ec,
-    const asio::ip::tcp::resolver::endpoint_type &ep)
+    boost::asio::ip::tcp::resolver::results_type::const_iterator
+        endpointIterator,
+    boost::system::error_code ec)
 {
+    const auto &ep = endpointIterator->endpoint();
+
     if (ec)
     {
-        this->fail(ec, u"TCP handshake");
+        qCDebug(chatterinoWebsocket)
+            << *this << "error in tcp handshake" << ep.address().to_string()
+            << ec.message();
+        this->tryConnect(++endpointIterator);
         return;
     }
 
-    qCDebug(chatterinoWebsocket) << *this << "TCP handshake done";
+    qCDebug(chatterinoWebsocket)
+        << *this << "TCP handshake done" << ep.address().to_string();
     this->options.url.setPort(ep.port());
 
+    // We are done with the endpoints, we can clear the range.
+    this->resolvedEndpoints = {};
+
     this->derived()->afterTcpHandshake();
 }
 
@@ -319,9 +352,16 @@ void WebSocketConnectionHelper<Derived, Inner>::closeImpl()
 template <typename Derived, typename Inner>
 void WebSocketConnectionHelper<Derived, Inner>::fail(
     boost::system::error_code ec, QStringView op)
+{
+    this->fail(ec.message(), op);
+}
+
+template <typename Derived, typename Inner>
+void WebSocketConnectionHelper<Derived, Inner>::fail(std::string_view ec,
+                                                     QStringView op)
 {
     qCWarning(chatterinoWebsocket)
-        << *this << "Failed:" << op << QUtf8StringView(ec.message());
+        << *this << "Failed:" << op << QUtf8StringView(ec);
     if (this->stream.is_open())
     {
         this->closeImpl();

src/common/websockets/detail/WebSocketConnectionImpl.hpp

@@ -41,6 +41,7 @@ protected:
     Derived *derived();
 
     void fail(boost::system::error_code ec, QStringView op);
+    void fail(std::string_view ec, QStringView op);
     void doWsHandshake();
 
     void closeImpl();
@@ -57,15 +58,31 @@ private:
 
     void onResolve(boost::system::error_code ec,
                    const boost::asio::ip::tcp::resolver::results_type &results);
+
+    /// Initialize a TCP connection to the given endpoint iterator in `resolvedEndpoints`.
+    ///
+    /// If we failed to connect, try the next iterator.
+    ///
+    /// If the iterator is invalid, we have run out of endpoints to try, and deem this
+    /// connection a failure.
+    void tryConnect(boost::asio::ip::tcp::resolver::results_type::const_iterator
+                        endpointIterator);
     void onTcpHandshake(
-        boost::system::error_code ec,
-        const boost::asio::ip::tcp::resolver::endpoint_type &ep);
+        boost::asio::ip::tcp::resolver::results_type::const_iterator
+            endpointIterator,
+        boost::system::error_code ec);
     void onWsHandshake(boost::system::error_code ec);
 
     void onReadDone(boost::system::error_code ec, size_t bytesRead);
     void onWriteDone(boost::system::error_code ec, size_t bytesWritten);
 
     friend Derived;
+
+    /// A range of endpoints from the `onResolve` function.
+    ///
+    /// When we successfully resolve the host, we try to connect by
+    /// iterating over these results.
+    boost::asio::ip::tcp::resolver::results_type resolvedEndpoints;
 };
 
 /// A WebSocket connection over TLS (wss://).