Merge pull request 'service: network: Fix lobby SDK crashes and performance drops in multiplayer' (#107) from fix/mitigate-sdk-crash into main

Reviewed-on: https://git.citron-emu.org/Citron/Emulator/pulls/107

src/core/hle/service/ldn/lan_discovery.cpp

@@ -77,16 +77,17 @@ void LANDiscovery::SetState(State new_state) {
 }
 
 Result LANDiscovery::GetNetworkInfo(NetworkInfo& out_network) const {
+    std::scoped_lock lock{packet_mutex};
     if (state == State::AccessPointCreated || state == State::StationConnected) {
         std::memcpy(&out_network, &network_info, sizeof(network_info));
         return ResultSuccess;
     }
-
     return ResultBadState;
 }
 
 Result LANDiscovery::GetNetworkInfo(NetworkInfo& out_network,
                                     std::span<NodeLatestUpdate> out_updates) {
+    std::scoped_lock lock{packet_mutex};
     if (out_updates.size() > NodeCountMax) {
         return ResultInvalidBufferCount;
     }
@@ -376,7 +377,9 @@ void LANDiscovery::UpdateNodes() {
         }
         station.OverrideInfo();
     }
-    network_info.ldn.node_count = count + 1;
+
+    // Node Count Guard: Ensure we always report at least 1 node
+    network_info.ldn.node_count = std::max<u8>(1, count + 1);
 
     for (auto local_ip : connected_clients) {
         SendPacket(Network::LDNPacketType::SyncNetwork, network_info, local_ip);
@@ -387,6 +390,7 @@ void LANDiscovery::UpdateNodes() {
 
 void LANDiscovery::OnSyncNetwork(const NetworkInfo& info) {
     network_info = info;
+
     if (state == State::StationOpened) {
         SetState(State::StationConnected);
     }
@@ -567,10 +571,20 @@ void LANDiscovery::ReceivePacket(const Network::LDNPacket& packet) {
     }
     case Network::LDNPacketType::SyncNetwork: {
         if (state == State::StationOpened || state == State::StationConnected) {
-            LOG_INFO(Frontend, "SyncNetwork packet received!");
+            if (packet.data.size() < sizeof(NetworkInfo)) {
+                break;
+            }
+
             NetworkInfo info{};
             std::memcpy(&info, packet.data.data(), sizeof(NetworkInfo));
 
+            if (state == State::StationConnected) {
+                if (std::memcmp(&info.network_id.session_id, &network_info.network_id.session_id, sizeof(SessionId)) != 0) {
+                    break;
+                }
+            }
+
+            LOG_INFO(Frontend, "SyncNetwork packet received!");
             OnSyncNetwork(info);
         } else {
             LOG_INFO(Frontend, "SyncNetwork packet received but in wrong State!");

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

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
@@ -112,7 +113,7 @@ protected:
     static constexpr Ssid fake_ssid{"CitronFakeSsidForLdn"};
 
     bool inited{};
-    std::mutex packet_mutex;
+    mutable std::mutex packet_mutex;
     std::array<LanStation, StationCountMax> stations;
     std::array<NodeLatestUpdate, NodeCountMax> node_changes{};
     std::array<u8, NodeCountMax> node_last_states{};

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

@@ -553,25 +553,10 @@ std::pair<s32, Errno> BSD::SocketImpl(Domain domain, Type type, Protocol protoco
     descriptor.protocol = Translate(protocol);
     descriptor.is_connection_based = IsConnectionBased(type);
 
-    // Try to reuse a socket from the pool if using proxy
     if (using_proxy) {
-        SocketPoolKey key{descriptor.domain, descriptor.type, descriptor.protocol};
+        descriptor.socket = std::make_shared<Network::ProxySocket>(room_network);
-        std::lock_guard lock(socket_pool_mutex);
+        descriptor.socket->Initialize(descriptor.domain, descriptor.type, descriptor.protocol);
-
+        LOG_DEBUG(Service, "Created new ProxySocket for fd={}", fd);
-        auto it = socket_pool.find(key);
-        if (it != socket_pool.end() && !it->second.empty()) {
-            descriptor.socket = it->second.back();
-            it->second.pop_back();
-
-            // call Initialize here so socket_proxy.cpp functions work
-            descriptor.socket->Initialize(descriptor.domain, descriptor.type, descriptor.protocol);
-
-            LOG_DEBUG(Service, "Reused socket from pool for fd={}", fd);
-        } else {
-            descriptor.socket = std::make_shared<Network::ProxySocket>(room_network);
-            descriptor.socket->Initialize(descriptor.domain, descriptor.type, descriptor.protocol);
-            LOG_DEBUG(Service, "Created new ProxySocket for fd={}", fd);
-        }
     } else {
         descriptor.socket = std::make_shared<Network::Socket>();
         descriptor.socket->Initialize(descriptor.domain, descriptor.type, descriptor.protocol);
@@ -1008,39 +993,17 @@ Errno BSD::CloseImpl(s32 fd) {
         return Errno::BADF;
     }
 
-    // Capture the socket pointer and info before we lock and reset the table entry
     std::shared_ptr<Network::SocketBase> socket_to_close;
-    SocketPoolKey key;
-    bool is_proxy = false;
 
     {
         std::lock_guard lock(fd_table_mutex);
-        auto& descriptor = file_descriptors[fd];
+        socket_to_close = file_descriptors[fd]->socket;
-        socket_to_close = descriptor->socket;
-        key = {descriptor->domain, descriptor->type, descriptor->protocol};
-        is_proxy = std::dynamic_pointer_cast<Network::ProxySocket>(socket_to_close) != nullptr;
-
-        // Remove it from the table immediately so OnProxyPacketReceived stops seeing it
         file_descriptors[fd].reset();
     }
 
     const Errno bsd_errno = Translate(socket_to_close->Close());
-    if (bsd_errno != Errno::SUCCESS) {
-        return bsd_errno;
-    }
-
     LOG_INFO(Service, "Close socket fd={}", fd);
 
-    auto room_member = room_network.GetRoomMember().lock();
-    if (is_proxy && room_member && room_member->IsConnected()) {
-        std::lock_guard lock(socket_pool_mutex);
-        constexpr size_t MAX_POOL_SIZE = 8;
-        if (socket_pool[key].size() < MAX_POOL_SIZE) {
-            socket_pool[key].push_back(socket_to_close);
-            LOG_DEBUG(Service, "Returned socket fd={} to pool", fd);
-        }
-    }
-
     return bsd_errno;
 }
 

src/core/internal_network/socket_proxy.cpp

@@ -34,14 +34,13 @@ void ProxySocket::HandleProxyPacket(const ProxyPacket& packet) {
 
     const auto my_ip = room_member->GetFakeIpAddress();
 
-    // If the sender (local_endpoint) is OUR IP, ignore it.
+    // 1. Ignore our own echo
-    // We don't want to process our own sent packets.
     if (packet.local_endpoint.ip == my_ip) {
         return;
     }
 
-    // Only accept packets meant for us or actual broadcasts.
+    // 2. Ignore packets meant for other people
-    if (packet.remote_endpoint.ip != my_ip && !packet.broadcast) {
+    if (!packet.broadcast && packet.remote_endpoint.ip != my_ip) {
         return;
     }
 
@@ -173,7 +172,7 @@ std::pair<s32, Errno> ProxySocket::RecvFrom(int flags, std::span<u8> message, So
             return {-1, Errno::AGAIN};
         }
 
-        std::this_thread::yield();
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
 
         const auto time_diff = std::chrono::steady_clock::now() - timestamp;
         const auto time_diff_ms =