fix: Multiplayer network fixes and airplane mode

- Auto-select network interface for direct connect/host room
- Always recreate ENet client on join for fresh bindings
- Add airplane mode toggle (Desktop & Android)
- Fix JWT verification with empty verify_uid
- Improve content-type handling for JWT endpoints

Signed-off-by: Zephyron <zephyron@citron-emu.org>

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()),
-        static_cast<u32>(error_code.GetDescription()), info.set_flags, info.program_entry_point);
+        2000 + module, description, info.set_flags, info.program_entry_point, module_note);
     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()) {