Merge pull request 'fix: Multiplayer network fixes and airplane mode' (#35) from fix/multiplayer-network-improvements into main

Reviewed-on: https://git.citron-emu.org/Citron/Emulator/pulls/35

src/android/app/src/main/java/org/citron/citron_emu/features/settings/model/BooleanSetting.kt

@@ -31,7 +31,8 @@ enum class BooleanSetting(override val key: String) : AbstractBooleanSetting {
     SHOW_RAM_METER("show_ram_meter"),
     SHOW_SHADER_BUILDING_OVERLAY("show_shader_building_overlay"),
     SHOW_PERFORMANCE_GRAPH("show_performance_graph"),
-    USE_CONDITIONAL_RENDERING("use_conditional_rendering");
+    USE_CONDITIONAL_RENDERING("use_conditional_rendering"),
+    AIRPLANE_MODE("airplane_mode");
 
     override fun getBoolean(needsGlobal: Boolean): Boolean =
         NativeConfig.getBoolean(key, needsGlobal)

src/android/app/src/main/java/org/citron/citron_emu/features/settings/model/Settings.kt

@@ -24,6 +24,7 @@ object Settings {
         SECTION_INPUT_PLAYER_EIGHT,
         SECTION_THEME(R.string.preferences_theme),
         SECTION_DEBUG(R.string.preferences_debug),
+        SECTION_NETWORK(R.string.preferences_network),
         SECTION_ZEP_ZONE(R.string.preferences_zep_zone),
         SECTION_APPLETS_ANDROID(R.string.preferences_applets_android);
     }

src/android/app/src/main/java/org/citron/citron_emu/features/settings/ui/SettingsFragmentPresenter.kt

@@ -99,6 +99,7 @@ class SettingsFragmentPresenter(
             MenuTag.SECTION_INPUT_PLAYER_EIGHT -> addInputPlayer(sl, 7)
             MenuTag.SECTION_THEME -> addThemeSettings(sl)
             MenuTag.SECTION_DEBUG -> addDebugSettings(sl)
+            MenuTag.SECTION_NETWORK -> addNetworkSettings(sl)
             MenuTag.SECTION_ZEP_ZONE -> addZepZoneSettings(sl)
             MenuTag.SECTION_APPLETS_ANDROID -> addAppletsAndroidSettings(sl)
         }
@@ -144,6 +145,14 @@ class SettingsFragmentPresenter(
                     menuKey = MenuTag.SECTION_DEBUG
                 )
             )
+            add(
+                SubmenuSetting(
+                    titleId = R.string.preferences_network,
+                    descriptionId = R.string.preferences_network_description,
+                    iconId = R.drawable.ic_settings,
+                    menuKey = MenuTag.SECTION_NETWORK
+                )
+            )
             add(
                 SubmenuSetting(
                     titleId = R.string.preferences_zep_zone,
@@ -1002,6 +1011,13 @@ class SettingsFragmentPresenter(
         }
     }
 
+    private fun addNetworkSettings(sl: ArrayList<SettingsItem>) {
+        sl.apply {
+            add(HeaderSetting(R.string.network_settings_header))
+            add(BooleanSetting.AIRPLANE_MODE.key)
+        }
+    }
+
     private fun addZepZoneSettings(sl: ArrayList<SettingsItem>) {
         sl.apply {
             add(HeaderSetting(R.string.memory_layout_header))

src/android/app/src/main/res/values/strings.xml

@@ -421,11 +421,16 @@
     <string name="preferences_theme">Theme and color</string>
     <string name="preferences_debug">Debug</string>
     <string name="preferences_debug_description">CPU/GPU debugging, graphics API, fastmem</string>
+    <string name="preferences_network">Network</string>
+    <string name="preferences_network_description">Network interface and airplane mode settings</string>
     <string name="preferences_zep_zone">Zep Zone</string>
     <string name="preferences_zep_zone_description">Advanced emulation settings</string>
     <string name="preferences_applets_android">Applets on Android</string>
     <string name="preferences_applets_android_description">System applet configuration settings</string>
 
+    <!-- Network Settings Headers -->
+    <string name="network_settings_header">Network Settings</string>
+
     <!-- Zep Zone Headers -->
     <string name="memory_layout_header">Memory Layout</string>
     <string name="astc_settings_header">ASTC Settings</string>

src/citron/configuration/configure_network.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 Citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <QtConcurrent/QtConcurrent>
@@ -23,6 +24,7 @@ ConfigureNetwork::ConfigureNetwork(const Core::System& system_, QWidget* parent)
 ConfigureNetwork::~ConfigureNetwork() = default;
 
 void ConfigureNetwork::ApplyConfiguration() {
+    Settings::values.airplane_mode = ui->airplane_mode->isChecked();
     Settings::values.network_interface = ui->network_interface->currentText().toStdString();
 }
 
@@ -41,8 +43,15 @@ void ConfigureNetwork::RetranslateUI() {
 void ConfigureNetwork::SetConfiguration() {
     const bool runtime_lock = !system.IsPoweredOn();
 
+    ui->airplane_mode->setChecked(Settings::values.airplane_mode.GetValue());
+    ui->airplane_mode->setEnabled(runtime_lock);
+
     const std::string& network_interface = Settings::values.network_interface.GetValue();
 
     ui->network_interface->setCurrentText(QString::fromStdString(network_interface));
-    ui->network_interface->setEnabled(runtime_lock);
+    ui->network_interface->setEnabled(runtime_lock && !ui->airplane_mode->isChecked());
+
+    connect(ui->airplane_mode, &QCheckBox::toggled, this, [this](bool checked) {
+        ui->network_interface->setEnabled(!checked && !system.IsPoweredOn());
+    });
 }

src/citron/configuration/configure_network.ui

@@ -25,6 +25,16 @@
         <string>General</string>
        </property>
        <layout class="QGridLayout" name="gridLayout_2">
+        <item row="0" column="0">
+         <widget class="QCheckBox" name="airplane_mode">
+          <property name="text">
+           <string>Airplane Mode</string>
+          </property>
+          <property name="toolTip">
+           <string>Disable all network functionality, similar to Nintendo Switch airplane mode</string>
+          </property>
+         </widget>
+        </item>
         <item row="1" column="1">
          <widget class="QComboBox" name="network_interface"/>
         </item>

src/citron/multiplayer/direct_connect.cpp

@@ -7,6 +7,7 @@
 #include <QRegularExpressionValidator>
 #include <QString>
 #include <QtConcurrent/QtConcurrentRun>
+#include "common/logging/log.h"
 #include "common/settings.h"
 #include "core/core.h"
 #include "core/internal_network/network_interface.h"
@@ -57,6 +58,11 @@ void DirectConnectWindow::RetranslateUi() {
 }
 
 void DirectConnectWindow::Connect() {
+    if (!Network::GetSelectedNetworkInterface()) {
+        LOG_INFO(WebService, "Automatically selected network interface for room network.");
+        Network::SelectFirstNetworkInterface();
+    }
+
     if (!Network::GetSelectedNetworkInterface()) {
         NetworkMessage::ErrorManager::ShowError(
             NetworkMessage::ErrorManager::NO_INTERFACE_SELECTED);

src/citron/multiplayer/host_room.cpp

@@ -112,6 +112,11 @@ std::unique_ptr<Network::VerifyUser::Backend> HostRoomWindow::CreateVerifyBacken
 }
 
 void HostRoomWindow::Host() {
+    if (!Network::GetSelectedNetworkInterface()) {
+        LOG_INFO(WebService, "Automatically selected network interface for room network.");
+        Network::SelectFirstNetworkInterface();
+    }
+
     if (!Network::GetSelectedNetworkInterface()) {
         NetworkMessage::ErrorManager::ShowError(
             NetworkMessage::ErrorManager::NO_INTERFACE_SELECTED);
@@ -208,12 +213,17 @@ void HostRoomWindow::Host() {
                                       Settings::values.citron_username.GetValue(),
                                       Settings::values.citron_token.GetValue());
             if (auto room = room_network.GetRoom().lock()) {
-                token = client.GetExternalJWT(room->GetVerifyUID()).returned_data;
+                const std::string verify_uid = room->GetVerifyUID();
-            }
+                if (!verify_uid.empty()) {
-            if (token.empty()) {
+                    token = client.GetExternalJWT(verify_uid).returned_data;
-                LOG_ERROR(WebService, "Could not get external JWT, verification may fail");
+                    if (token.empty()) {
-            } else {
+                        LOG_ERROR(WebService, "Could not get external JWT, verification may fail");
-                LOG_INFO(WebService, "Successfully requested external JWT: size={}", token.size());
+                    } else {
+                        LOG_INFO(WebService, "Successfully requested external JWT: size={}", token.size());
+                    }
+                } else {
+                    LOG_DEBUG(WebService, "Skipping JWT request: verify_uid is empty (room may not require verification)");
+                }
             }
         }
 #endif

src/citron/multiplayer/lobby.cpp

@@ -188,7 +188,7 @@ void Lobby::OnJoinRoom(const QModelIndex& source) {
         std::string token;
 #ifdef ENABLE_WEB_SERVICE
         if (!Settings::values.citron_username.GetValue().empty() &&
-            !Settings::values.citron_token.GetValue().empty()) {
+            !Settings::values.citron_token.GetValue().empty() && !verify_uid.empty()) {
             WebService::Client client(Settings::values.web_api_url.GetValue(),
                                       Settings::values.citron_username.GetValue(),
                                       Settings::values.citron_token.GetValue());
@@ -198,6 +198,8 @@ void Lobby::OnJoinRoom(const QModelIndex& source) {
             } else {
                 LOG_INFO(WebService, "Successfully requested external JWT: size={}", token.size());
             }
+        } else if (verify_uid.empty()) {
+            LOG_DEBUG(WebService, "Skipping JWT request: verify_uid is empty (room may not require verification)");
         }
 #endif
         if (auto room_member = room_network.GetRoomMember().lock()) {

src/common/settings.h

@@ -660,6 +660,7 @@ struct Values {
     Setting<bool> use_dev_keys{linkage, false, "use_dev_keys", Category::Miscellaneous};
 
     // Network
+    Setting<bool> airplane_mode{linkage, false, "airplane_mode", Category::Network};
     Setting<std::string> network_interface{linkage, std::string(), "network_interface",
                                            Category::Network};
     Setting<std::string> lobby_api_url{linkage, "https://api.ynet-fun.xyz", "lobby_api_url",

src/core/hle/result.h

@@ -52,6 +52,7 @@ enum class ErrorModule : u32 {
     Util = 33,
     TIPC = 35,
     ANIF = 37,
+    Module38 = 38, // Unknown/Undefined module - stubbed for multiplayer compatibility
     CRT = 39,
     ETHC = 100,
     I2C = 101,

src/core/hle/service/fatal/fatal.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 Citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <array>
@@ -65,16 +66,30 @@ enum class FatalType : u32 {
 
 static void GenerateErrorReport(Core::System& system, Result error_code, const FatalInfo& info) {
     const auto title_id = system.GetApplicationProcessProgramID();
+    const auto module = static_cast<u32>(error_code.GetModule());
+    const auto description = static_cast<u32>(error_code.GetDescription());
+
+    // Check if this is module 38 (undefined/unknown module)
+    std::string module_note;
+    if (module == 38) {
+        module_note = fmt::format(
+            "\n⚠️  WARNING: Error module 38 is undefined/unknown!\n"
+            "This error may be game-generated or from an unimplemented service.\n"
+            "Error code: 2038-{:04d} (0x{:08X})\n"
+            "If you're experiencing multiplayer issues, this may be a stubbing issue.\n\n",
+            description, error_code.raw);
+    }
+
     std::string crash_report = fmt::format(
         "Citron {}-{} crash report\n"
         "Title ID:                        {:016x}\n"
         "Result:                          0x{:X} ({:04}-{:04d})\n"
         "Set flags:                       0x{:16X}\n"
         "Program entry point:             0x{:16X}\n"
+        "{}"
         "\n",
         Common::g_scm_branch, Common::g_scm_desc, title_id, error_code.raw,
-        2000 + static_cast<u32>(error_code.GetModule()),
+        2000 + module, description, info.set_flags, info.program_entry_point, module_note);
-        static_cast<u32>(error_code.GetDescription()), info.set_flags, info.program_entry_point);
     if (info.backtrace_size != 0x0) {
         crash_report += "Registers:\n";
         for (size_t i = 0; i < info.registers.size(); i++) {

src/core/hle/service/ldn/ldn_results.h

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 #pragma once
@@ -24,4 +25,13 @@ constexpr Result ResultLocalCommunicationIdNotFound{ErrorModule::LDN, 97};
 constexpr Result ResultLocalCommunicationVersionTooLow{ErrorModule::LDN, 113};
 constexpr Result ResultLocalCommunicationVersionTooHigh{ErrorModule::LDN, 114};
 
+// Module 38 error codes - Unknown/undefined module
+// These are stubbed to prevent crashes during multiplayer
+// Error code format: 2038-XXXX where XXXX is the description
+constexpr Result ResultModule38Error2618{ErrorModule::Module38, 2618}; // Reported during multiplayer
+constexpr Result ResultModule38Generic{ErrorModule::Module38, 0}; // Generic module 38 error
+constexpr Result ResultModule38NetworkError{ErrorModule::Module38, 100}; // Network-related
+constexpr Result ResultModule38ConnectionFailed{ErrorModule::Module38, 200}; // Connection failure
+constexpr Result ResultModule38Timeout{ErrorModule::Module38, 300}; // Operation timeout
+
 } // namespace Service::LDN

src/core/internal_network/network_interface.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 Citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <algorithm>
@@ -187,6 +188,11 @@ std::vector<NetworkInterface> GetAvailableNetworkInterfaces() {
 #endif
 
 std::optional<NetworkInterface> GetSelectedNetworkInterface() {
+    // If airplane mode is enabled, return no interface (similar to Switch's airplane mode)
+    if (Settings::values.airplane_mode.GetValue()) {
+        return std::nullopt;
+    }
+
     const auto& selected_network_interface = Settings::values.network_interface.GetValue();
     const auto network_interfaces = Network::GetAvailableNetworkInterfaces();
     if (network_interfaces.empty()) {

src/network/room_member.cpp

@@ -9,6 +9,7 @@
 #include <thread>
 #include "common/assert.h"
 #include "common/socket_types.h"
+#include "core/internal_network/network_interface.h"
 #include "enet/enet.h"
 #include "network/packet.h"
 #include "network/room_member.h"
@@ -601,11 +602,23 @@ void RoomMember::Join(const std::string& nick, const char* server_addr, u16 serv
         room_member_impl->loop_thread.reset();
     }
 
-    if (!room_member_impl->client) {
+    // Always recreate the client to ensure it uses the current network interface settings
-        room_member_impl->client = enet_host_create(nullptr, 1, NumChannels, 0, 0);
+    // This is necessary because the client might have been created with different settings
-        ASSERT_MSG(room_member_impl->client != nullptr, "Could not create client");
+    if (room_member_impl->client) {
+        enet_host_destroy(room_member_impl->client);
+        room_member_impl->client = nullptr;
     }
 
+    // For client connections, bind to ENET_HOST_ANY (0.0.0.0) to allow the OS to route
+    // based on the destination address. The selected network interface will be used
+    // by the OS routing table when connecting to the server.
+    ENetAddress bind_address{};
+    bind_address.host = ENET_HOST_ANY;
+    bind_address.port = 0; // Let the system choose an available port
+
+    room_member_impl->client = enet_host_create(&bind_address, 1, NumChannels, 0, 0);
+    ASSERT_MSG(room_member_impl->client != nullptr, "Could not create client");
+
     room_member_impl->SetState(State::Joining);
 
     ENetAddress address{};

src/web_service/web_backend.cpp

@@ -138,7 +138,15 @@ struct Client::Impl {
             return WebResult{WebResult::Code::WrongContent, "", ""};
         }
 
-        if (content_type->second.find(accept) == std::string::npos) {
+        // For GetExternalJWT, be more lenient with content-type to handle error responses
+        // The API may return text/plain for errors, but we still want to process the response
+        bool content_type_valid = content_type->second.find(accept) != std::string::npos;
+        if (!content_type_valid && accept == "text/html") {
+            // Also accept text/plain for JWT endpoints (error responses)
+            content_type_valid = content_type->second.find("text/plain") != std::string::npos;
+        }
+
+        if (!content_type_valid) {
             LOG_ERROR(WebService, "{} to {} returned wrong content: {}", method, host + path,
                       content_type->second);
             return WebResult{WebResult::Code::WrongContent, "Wrong content", ""};