core/sockets: Add missing socket services and functions from switchbrew

- Add Unknown39 and Unknown40 functions to BSD service for [20.0.0+]
- Implement bsd:nu service with ISfUserService and ISfAssignedNetworkInterfaceService
- Add dns:priv and ethc:c/ethc:i service stubs
- Update CMakeLists.txt to include new socket service files
- All new functions include basic stub implementations following existing patterns

This completes the socket services implementation based on switchbrew.org documentation.

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

src/core/hle/service/sockets/ethc.cpp

@@ -0,0 +1,122 @@
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/hle/service/sockets/ethc.h"
+#include "core/hle/service/ipc_helpers.h"
+#include "core/hle/service/sockets/sockets.h"
+
+namespace Service::Sockets {
+
+ETHC_C::ETHC_C(Core::System& system_) : ServiceFramework{system_, "ethc:c"} {
+    // clang-format off
+    static const FunctionInfo functions[] = {
+        {0, &ETHC_C::Unknown0, "Unknown0"},
+        {1, &ETHC_C::Unknown1, "Unknown1"},
+        {2, &ETHC_C::Unknown2, "Unknown2"},
+        {3, &ETHC_C::Unknown3, "Unknown3"},
+        {4, &ETHC_C::Unknown4, "Unknown4"},
+    };
+    // clang-format on
+
+    RegisterHandlers(functions);
+}
+
+ETHC_C::~ETHC_C() = default;
+
+void ETHC_C::Unknown0(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:c Unknown0");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_C::Unknown1(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:c Unknown1");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_C::Unknown2(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:c Unknown2");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_C::Unknown3(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:c Unknown3");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_C::Unknown4(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:c Unknown4");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+ETHC_I::ETHC_I(Core::System& system_) : ServiceFramework{system_, "ethc:i"} {
+    // clang-format off
+    static const FunctionInfo functions[] = {
+        {0, &ETHC_I::Unknown0, "Unknown0"},
+        {1, &ETHC_I::Unknown1, "Unknown1"},
+        {2, &ETHC_I::Unknown2, "Unknown2"},
+        {3, &ETHC_I::Unknown3, "Unknown3"},
+        {4, &ETHC_I::Unknown4, "Unknown4"},
+    };
+    // clang-format on
+
+    RegisterHandlers(functions);
+}
+
+ETHC_I::~ETHC_I() = default;
+
+void ETHC_I::Unknown0(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:i Unknown0");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_I::Unknown1(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:i Unknown1");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_I::Unknown2(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:i Unknown2");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_I::Unknown3(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:i Unknown3");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+void ETHC_I::Unknown4(HLERequestContext& ctx) {
+    LOG_WARNING(Service, "(STUBBED) called ethc:i Unknown4");
+    IPC::ResponseBuilder rb{ctx, 4};
+    rb.Push(ResultSuccess);
+    rb.Push<s32>(-1);
+    rb.PushEnum(Errno::SUCCESS);
+}
+
+} // namespace Service::Sockets