Merge pull request #8861 from JosJuice/netplay-hash

Make netplay's "same game" check more robust

Source/Core/Core/CMakeLists.txt

@@ -37,6 +37,7 @@ add_library(core
   PatchEngine.h
   State.cpp
   State.h
+  SyncIdentifier.h
   SysConf.cpp
   SysConf.h
   TitleDatabase.cpp

Source/Core/Core/Core.vcxproj

@@ -673,6 +673,7 @@
     <ClInclude Include="PowerPC\PPCTables.h" />
     <ClInclude Include="PowerPC\Profiler.h" />
     <ClInclude Include="State.h" />
+    <ClInclude Include="SyncIdentifier.h" />
     <ClInclude Include="SysConf.h" />
     <ClInclude Include="Titles.h" />
     <ClInclude Include="TitleDatabase.h" />

Source/Core/Core/Core.vcxproj.filters

@@ -1757,7 +1757,8 @@
     </ClInclude>
     <ClInclude Include="HW\EXI\BBA\TAP_Win32.h">
       <Filter>HW %28Flipper/Hollywood%29\EXI - Expansion Interface\BBA</Filter>
-    </ClInclude>
+    </ClInclude>
+    <ClInclude Include="SyncIdentifier.h" />
   </ItemGroup>
   <ItemGroup>
     <Text Include="CMakeLists.txt" />

Source/Core/Core/NetPlayClient.cpp

@@ -53,9 +53,11 @@
 #include "Core/IOS/Uids.h"
 #include "Core/Movie.h"
 #include "Core/PowerPC/PowerPC.h"
+#include "Core/SyncIdentifier.h"
 #include "InputCommon/ControllerEmu/ControlGroup/Attachments.h"
 #include "InputCommon/GCAdapter.h"
 #include "InputCommon/InputConfig.h"
+#include "UICommon/GameFile.h"
 #include "VideoCommon/OnScreenDisplay.h"
 #include "VideoCommon/VideoConfig.h"
 
@@ -284,6 +286,22 @@ bool NetPlayClient::Connect()
   }
 }
 
+static void ReceiveSyncIdentifier(sf::Packet& spac, SyncIdentifier& sync_identifier)
+{
+  // We use a temporary variable here due to a potential long vs long long mismatch
+  sf::Uint64 dol_elf_size;
+  spac >> dol_elf_size;
+  sync_identifier.dol_elf_size = dol_elf_size;
+
+  spac >> sync_identifier.game_id;
+  spac >> sync_identifier.revision;
+  spac >> sync_identifier.disc_number;
+  spac >> sync_identifier.is_datel;
+
+  for (u8& x : sync_identifier.sync_hash)
+    spac >> x;
+}
+
 // called from ---NETPLAY--- thread
 unsigned int NetPlayClient::OnData(sf::Packet& packet)
 {
@@ -572,24 +590,25 @@ unsigned int NetPlayClient::OnData(sf::Packet& packet)
 
   case NP_MSG_CHANGE_GAME:
   {
+    std::string netplay_name;
     {
       std::lock_guard<std::recursive_mutex> lkg(m_crit.game);
-      packet >> m_selected_game;
+      ReceiveSyncIdentifier(packet, m_selected_game);
+      packet >> netplay_name;
     }
 
-    INFO_LOG(NETPLAY, "Game changed to %s", m_selected_game.c_str());
+    INFO_LOG(NETPLAY, "Game changed to %s", netplay_name.c_str());
 
     // update gui
-    m_dialog->OnMsgChangeGame(m_selected_game);
+    m_dialog->OnMsgChangeGame(m_selected_game, netplay_name);
 
     sf::Packet game_status_packet;
     game_status_packet << static_cast<MessageId>(NP_MSG_GAME_STATUS);
 
-    PlayerGameStatus status = m_dialog->FindGame(m_selected_game).empty() ?
+    SyncIdentifierComparison result;
-                                  PlayerGameStatus::NotFound :
+    m_dialog->FindGameFile(m_selected_game, &result);
-                                  PlayerGameStatus::Ok;
 
-    game_status_packet << static_cast<u32>(status);
+    game_status_packet << static_cast<u32>(result);
     Send(game_status_packet);
 
     sf::Packet ipl_status_packet;
@@ -609,7 +628,7 @@ unsigned int NetPlayClient::OnData(sf::Packet& packet)
       Player& player = m_players[pid];
       u32 status;
       packet >> status;
-      player.game_status = static_cast<PlayerGameStatus>(status);
+      player.game_status = static_cast<SyncIdentifierComparison>(status);
     }
 
     m_dialog->Update();
@@ -623,7 +642,7 @@ unsigned int NetPlayClient::OnData(sf::Packet& packet)
       packet >> m_current_game;
       packet >> m_net_settings.m_CPUthread;
 
-      INFO_LOG(NETPLAY, "Start of game %s", m_selected_game.c_str());
+      INFO_LOG(NETPLAY, "Start of game %s", m_selected_game.game_id.c_str());
 
       {
         std::underlying_type_t<PowerPC::CPUCore> core;
@@ -1172,10 +1191,10 @@ unsigned int NetPlayClient::OnData(sf::Packet& packet)
 
   case NP_MSG_COMPUTE_MD5:
   {
-    std::string file_identifier;
+    SyncIdentifier sync_identifier;
-    packet >> file_identifier;
+    ReceiveSyncIdentifier(packet, sync_identifier);
 
-    ComputeMD5(file_identifier);
+    ComputeMD5(sync_identifier);
   }
   break;
 
@@ -1382,11 +1401,15 @@ void NetPlayClient::GetPlayerList(std::string& list, std::vector<int>& pid_list)
 
     switch (player.game_status)
     {
-    case PlayerGameStatus::Ok:
+    case SyncIdentifierComparison::SameGame:
       ss << "ready";
       break;
 
-    case PlayerGameStatus::NotFound:
+    case SyncIdentifierComparison::DifferentVersion:
+      ss << "wrong game version";
+      break;
+
+    case SyncIdentifierComparison::DifferentGame:
       ss << "game missing";
       break;
 
@@ -2286,23 +2309,24 @@ bool NetPlayClient::DoAllPlayersHaveGame()
 {
   std::lock_guard<std::recursive_mutex> lkp(m_crit.players);
 
-  return std::all_of(std::begin(m_players), std::end(m_players),
+  return std::all_of(std::begin(m_players), std::end(m_players), [](auto entry) {
-                     [](auto entry) { return entry.second.game_status == PlayerGameStatus::Ok; });
+    return entry.second.game_status == SyncIdentifierComparison::SameGame;
+  });
 }
 
-void NetPlayClient::ComputeMD5(const std::string& file_identifier)
+void NetPlayClient::ComputeMD5(const SyncIdentifier& sync_identifier)
 {
   if (m_should_compute_MD5)
     return;
 
-  m_dialog->ShowMD5Dialog(file_identifier);
+  m_dialog->ShowMD5Dialog(sync_identifier.game_id);
   m_should_compute_MD5 = true;
 
   std::string file;
-  if (file_identifier == WII_SDCARD)
+  if (sync_identifier == GetSDCardIdentifier())
     file = File::GetUserPath(F_WIISDCARD_IDX);
-  else
+  else if (auto game = m_dialog->FindGameFile(sync_identifier))
-    file = m_dialog->FindGame(file_identifier);
+    file = game->GetFilePath();
 
   if (file.empty() || !File::Exists(file))
   {
@@ -2348,6 +2372,11 @@ void NetPlayClient::AdjustPadBufferSize(const unsigned int size)
   m_dialog->OnPadBufferChanged(size);
 }
 
+SyncIdentifier NetPlayClient::GetSDCardIdentifier()
+{
+  return SyncIdentifier{{}, "sd", {}, {}, {}, {}};
+}
+
 bool IsNetPlayRunning()
 {
   return netplay_client != nullptr;

Source/Core/Core/NetPlayClient.h

@@ -22,6 +22,7 @@
 #include "Common/SPSCQueue.h"
 #include "Common/TraversalClient.h"
 #include "Core/NetPlayProto.h"
+#include "Core/SyncIdentifier.h"
 #include "InputCommon/GCPadStatus.h"
 
 namespace UICommon
@@ -42,7 +43,8 @@ public:
   virtual void Update() = 0;
   virtual void AppendChat(const std::string& msg) = 0;
 
-  virtual void OnMsgChangeGame(const std::string& filename) = 0;
+  virtual void OnMsgChangeGame(const SyncIdentifier& sync_identifier,
+                               const std::string& netplay_name) = 0;
   virtual void OnMsgStartGame() = 0;
   virtual void OnMsgStopGame() = 0;
   virtual void OnMsgPowerButton() = 0;
@@ -59,9 +61,10 @@ public:
   virtual void OnGolferChanged(bool is_golfer, const std::string& golfer_name) = 0;
 
   virtual bool IsRecording() = 0;
-  virtual std::string FindGame(const std::string& game) = 0;
+  virtual std::shared_ptr<const UICommon::GameFile>
-  virtual std::shared_ptr<const UICommon::GameFile> FindGameFile(const std::string& game) = 0;
+  FindGameFile(const SyncIdentifier& sync_identifier,
-  virtual void ShowMD5Dialog(const std::string& file_identifier) = 0;
+               SyncIdentifierComparison* found = nullptr) = 0;
+  virtual void ShowMD5Dialog(const std::string& title) = 0;
   virtual void SetMD5Progress(int pid, int progress) = 0;
   virtual void SetMD5Result(int pid, const std::string& result) = 0;
   virtual void AbortMD5() = 0;
@@ -75,13 +78,6 @@ public:
   virtual void SetChunkedProgress(int pid, u64 progress) = 0;
 };
 
-enum class PlayerGameStatus
-{
-  Unknown,
-  Ok,
-  NotFound
-};
-
 class Player
 {
 public:
@@ -89,7 +85,7 @@ public:
   std::string name;
   std::string revision;
   u32 ping;
-  PlayerGameStatus game_status;
+  SyncIdentifierComparison game_status;
 
   bool IsHost() const { return pid == 1; }
 };
@@ -149,6 +145,8 @@ public:
 
   void AdjustPadBufferSize(unsigned int size);
 
+  static SyncIdentifier GetSDCardIdentifier();
+
 protected:
   struct AsyncQueueEntry
   {
@@ -182,7 +180,7 @@ protected:
   ENetPeer* m_server = nullptr;
   std::thread m_thread;
 
-  std::string m_selected_game;
+  SyncIdentifier m_selected_game;
   Common::Flag m_is_running{false};
   Common::Flag m_do_loop{true};
 
@@ -237,7 +235,7 @@ private:
   void Send(const sf::Packet& packet, u8 channel_id = DEFAULT_CHANNEL);
   void Disconnect();
   bool Connect();
-  void ComputeMD5(const std::string& file_identifier);
+  void ComputeMD5(const SyncIdentifier& sync_identifier);
   void DisplayPlayersPing();
   u32 GetPlayersMaxPing() const;
 

Source/Core/Core/NetPlayServer.cpp

@@ -51,6 +51,7 @@
 #include "Core/IOS/IOS.h"
 #include "Core/IOS/Uids.h"
 #include "Core/NetPlayClient.h"  //for NetPlayUI
+#include "Core/SyncIdentifier.h"
 #include "DiscIO/Enums.h"
 #include "InputCommon/ControllerEmu/ControlGroup/Attachments.h"
 #include "InputCommon/GCPadStatus.h"
@@ -182,7 +183,7 @@ void NetPlayServer::SetupIndex()
   session.region = Config::Get(Config::NETPLAY_INDEX_REGION);
   session.has_password = !Config::Get(Config::NETPLAY_INDEX_PASSWORD).empty();
   session.method = m_traversal_client ? "traversal" : "direct";
-  session.game_id = m_selected_game.empty() ? "UNKNOWN" : m_selected_game;
+  session.game_id = m_selected_game_name.empty() ? "UNKNOWN" : m_selected_game_name;
   session.player_count = static_cast<int>(m_players.size());
   session.in_game = m_is_running;
   session.port = GetPort();
@@ -238,7 +239,7 @@ void NetPlayServer::ThreadFunc()
       SendToClients(spac);
 
       m_index.SetPlayerCount(static_cast<int>(m_players.size()));
-      m_index.SetGame(m_selected_game);
+      m_index.SetGame(m_selected_game_name);
       m_index.SetInGame(m_is_running);
 
       m_update_pings = false;
@@ -348,6 +349,20 @@ void NetPlayServer::ThreadFunc()
   }
 }  // namespace NetPlay
 
+static void SendSyncIdentifier(sf::Packet& spac, const SyncIdentifier& sync_identifier)
+{
+  // We cast here due to a potential long vs long long mismatch
+  spac << static_cast<sf::Uint64>(sync_identifier.dol_elf_size);
+
+  spac << sync_identifier.game_id;
+  spac << sync_identifier.revision;
+  spac << sync_identifier.disc_number;
+  spac << sync_identifier.is_datel;
+
+  for (const u8& x : sync_identifier.sync_hash)
+    spac << x;
+}
+
 // called from ---NETPLAY--- thread
 unsigned int NetPlayServer::OnConnect(ENetPeer* socket, sf::Packet& rpac)
 {
@@ -413,11 +428,12 @@ unsigned int NetPlayServer::OnConnect(ENetPeer* socket, sf::Packet& rpac)
   Send(player.socket, spac);
 
   // send new client the selected game
-  if (!m_selected_game.empty())
+  if (!m_selected_game_name.empty())
   {
     spac.clear();
     spac << static_cast<MessageId>(NP_MSG_CHANGE_GAME);
-    spac << m_selected_game;
+    SendSyncIdentifier(spac, m_selected_game_identifier);
+    spac << m_selected_game_name;
     Send(player.socket, spac);
   }
 
@@ -913,7 +929,7 @@ unsigned int NetPlayServer::OnData(sf::Packet& packet, Client& player)
     u32 status;
     packet >> status;
 
-    m_players[player.pid].game_status = static_cast<PlayerGameStatus>(status);
+    m_players[player.pid].game_status = static_cast<SyncIdentifierComparison>(status);
 
     // send msg to other clients
     sf::Packet spac;
@@ -1153,16 +1169,19 @@ void NetPlayServer::SendChatMessage(const std::string& msg)
 }
 
 // called from ---GUI--- thread
-bool NetPlayServer::ChangeGame(const std::string& game)
+bool NetPlayServer::ChangeGame(const SyncIdentifier& sync_identifier,
+                               const std::string& netplay_name)
 {
   std::lock_guard<std::recursive_mutex> lkg(m_crit.game);
 
-  m_selected_game = game;
+  m_selected_game_identifier = sync_identifier;
+  m_selected_game_name = netplay_name;
 
   // send changed game to clients
   sf::Packet spac;
   spac << static_cast<MessageId>(NP_MSG_CHANGE_GAME);
-  spac << game;
+  SendSyncIdentifier(spac, m_selected_game_identifier);
+  spac << m_selected_game_name;
 
   SendAsyncToClients(std::move(spac));
 
@@ -1170,11 +1189,11 @@ bool NetPlayServer::ChangeGame(const std::string& game)
 }
 
 // called from ---GUI--- thread
-bool NetPlayServer::ComputeMD5(const std::string& file_identifier)
+bool NetPlayServer::ComputeMD5(const SyncIdentifier& sync_identifier)
 {
   sf::Packet spac;
   spac << static_cast<MessageId>(NP_MSG_COMPUTE_MD5);
-  spac << file_identifier;
+  SendSyncIdentifier(spac, sync_identifier);
 
   SendAsyncToClients(std::move(spac));
 
@@ -1260,7 +1279,7 @@ bool NetPlayServer::StartGame()
   const sf::Uint64 initial_rtc = GetInitialNetPlayRTC();
 
   const std::string region = SConfig::GetDirectoryForRegion(
-      SConfig::ToGameCubeRegion(m_dialog->FindGameFile(m_selected_game)->GetRegion()));
+      SConfig::ToGameCubeRegion(m_dialog->FindGameFile(m_selected_game_identifier)->GetRegion()));
 
   // sync GC SRAM with clients
   if (!g_SRAM_netplay_initialized)
@@ -1395,7 +1414,7 @@ bool NetPlayServer::SyncSaveData()
     }
   }
 
-  const auto game = m_dialog->FindGameFile(m_selected_game);
+  const auto game = m_dialog->FindGameFile(m_selected_game_identifier);
   if (game == nullptr)
   {
     PanicAlertT("Selected game doesn't exist in game list!");
@@ -1618,7 +1637,7 @@ bool NetPlayServer::SyncCodes()
   m_codes_synced = false;
 
   // Get Game Path
-  const auto game = m_dialog->FindGameFile(m_selected_game);
+  const auto game = m_dialog->FindGameFile(m_selected_game_identifier);
   if (game == nullptr)
   {
     PanicAlertT("Selected game doesn't exist in game list!");

Source/Core/Core/NetPlayServer.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <SFML/Network/Packet.hpp>
+
 #include <map>
 #include <memory>
 #include <mutex>
@@ -14,19 +15,20 @@
 #include <unordered_map>
 #include <unordered_set>
 #include <utility>
+
 #include "Common/Event.h"
 #include "Common/QoSSession.h"
 #include "Common/SPSCQueue.h"
 #include "Common/Timer.h"
 #include "Common/TraversalClient.h"
 #include "Core/NetPlayProto.h"
+#include "Core/SyncIdentifier.h"
 #include "InputCommon/GCPadStatus.h"
 #include "UICommon/NetPlayIndex.h"
 
 namespace NetPlay
 {
 class NetPlayUI;
-enum class PlayerGameStatus;
 
 class NetPlayServer : public TraversalClientClient
 {
@@ -43,8 +45,8 @@ public:
                 const NetTraversalConfig& traversal_config);
   ~NetPlayServer();
 
-  bool ChangeGame(const std::string& game);
+  bool ChangeGame(const SyncIdentifier& sync_identifier, const std::string& netplay_name);
-  bool ComputeMD5(const std::string& file_identifier);
+  bool ComputeMD5(const SyncIdentifier& sync_identifier);
   bool AbortMD5();
   void SendChatMessage(const std::string& msg);
 
@@ -80,7 +82,7 @@ private:
     PlayerId pid;
     std::string name;
     std::string revision;
-    PlayerGameStatus game_status;
+    SyncIdentifierComparison game_status;
     bool has_ipl_dump;
 
     ENetPeer* socket;
@@ -180,7 +182,8 @@ private:
   Common::SPSCQueue<AsyncQueueEntry, false> m_async_queue;
   Common::SPSCQueue<ChunkedDataQueueEntry, false> m_chunked_data_queue;
 
-  std::string m_selected_game;
+  SyncIdentifier m_selected_game_identifier;
+  std::string m_selected_game_name;
   std::thread m_thread;
   Common::Event m_chunked_data_event;
   Common::Event m_chunked_data_complete_event;

Source/Core/Core/SyncIdentifier.h

@@ -0,0 +1,46 @@
+// Copyright 2020 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <string>
+#include <tuple>
+
+#include "Common/CommonTypes.h"
+
+namespace NetPlay
+{
+struct SyncIdentifier
+{
+  u64 dol_elf_size;
+  std::string game_id;
+  u16 revision;
+  u8 disc_number;
+  bool is_datel;
+
+  // This hash is intended to be (but is not guaranteed to be):
+  // 1. Identical for discs with no differences that affect netplay/TAS sync
+  // 2. Different for discs with differences that affect netplay/TAS sync
+  // 3. Much faster than hashing the entire disc
+  // The way the hash is calculated may change with updates to Dolphin.
+  std::array<u8, 20> sync_hash;
+
+  bool operator==(const SyncIdentifier& s) const
+  {
+    return std::tie(dol_elf_size, game_id, revision, disc_number, is_datel, sync_hash) ==
+           std::tie(s.dol_elf_size, s.game_id, s.revision, s.disc_number, s.is_datel, s.sync_hash);
+  }
+  bool operator!=(const SyncIdentifier& s) const { return !operator==(s); }
+};
+
+enum class SyncIdentifierComparison
+{
+  SameGame,
+  DifferentVersion,
+  DifferentGame,
+  Unknown,
+};
+
+}  // namespace NetPlay

Source/Core/DiscIO/DiscExtractor.cpp

@@ -245,19 +245,26 @@ bool ExportBI2Data(const Volume& volume, const Partition& partition,
   return ExportData(volume, partition, 0x440, 0x2000, export_filename);
 }
 
+std::optional<u64> GetApploaderSize(const Volume& volume, const Partition& partition)
+{
+  constexpr u64 header_size = 0x20;
+  const std::optional<u32> apploader_size = volume.ReadSwapped<u32>(0x2440 + 0x14, partition);
+  const std::optional<u32> trailer_size = volume.ReadSwapped<u32>(0x2440 + 0x18, partition);
+  if (!apploader_size || !trailer_size)
+    return std::nullopt;
+
+  return header_size + *apploader_size + *trailer_size;
+}
+
 bool ExportApploader(const Volume& volume, const Partition& partition,
                      const std::string& export_filename)
 {
   if (!IsDisc(volume.GetVolumeType()))
     return false;
 
-  std::optional<u32> apploader_size = volume.ReadSwapped<u32>(0x2440 + 0x14, partition);
+  const std::optional<u64> apploader_size = GetApploaderSize(volume, partition);
-  const std::optional<u32> trailer_size = volume.ReadSwapped<u32>(0x2440 + 0x18, partition);
+  if (!apploader_size)
-  constexpr u32 header_size = 0x20;
-  if (!apploader_size || !trailer_size)
     return false;
-  *apploader_size += *trailer_size + header_size;
-  DEBUG_LOG(DISCIO, "Apploader size -> %x", *apploader_size);
 
   return ExportData(volume, partition, 0x2440, *apploader_size, export_filename);
 }

Source/Core/DiscIO/DiscExtractor.h

@@ -61,6 +61,7 @@ bool ExportHeader(const Volume& volume, const Partition& partition,
                   const std::string& export_filename);
 bool ExportBI2Data(const Volume& volume, const Partition& partition,
                    const std::string& export_filename);
+std::optional<u64> GetApploaderSize(const Volume& volume, const Partition& partition);
 bool ExportApploader(const Volume& volume, const Partition& partition,
                      const std::string& export_filename);
 std::optional<u64> GetBootDOLOffset(const Volume& volume, const Partition& partition);

Source/Core/DiscIO/Volume.cpp

@@ -9,12 +9,16 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
+#include <mbedtls/sha1.h>
+
 #include "Common/CommonTypes.h"
 #include "Common/StringUtil.h"
 
+#include "Core/IOS/ES/Formats.h"
 #include "DiscIO/Blob.h"
 #include "DiscIO/Enums.h"
 #include "DiscIO/VolumeDisc.h"
@@ -28,6 +32,43 @@ const IOS::ES::TicketReader Volume::INVALID_TICKET{};
 const IOS::ES::TMDReader Volume::INVALID_TMD{};
 const std::vector<u8> Volume::INVALID_CERT_CHAIN{};
 
+template <typename T>
+static void AddToSyncHash(mbedtls_sha1_context* context, const T& data)
+{
+  static_assert(std::is_trivially_copyable_v<T>);
+  mbedtls_sha1_update_ret(context, reinterpret_cast<const u8*>(&data), sizeof(data));
+}
+
+void Volume::ReadAndAddToSyncHash(mbedtls_sha1_context* context, u64 offset, u64 length,
+                                  const Partition& partition) const
+{
+  std::vector<u8> buffer(length);
+  if (Read(offset, length, buffer.data(), partition))
+    mbedtls_sha1_update_ret(context, buffer.data(), buffer.size());
+}
+
+void Volume::AddTMDToSyncHash(mbedtls_sha1_context* context, const Partition& partition) const
+{
+  // We want to hash some important parts of the TMD, but nothing that changes when fakesigning.
+  // (Fakesigned WADs are very popular, and we don't want people with properly signed WADs to
+  // unnecessarily be at a disadvantage due to most netplay partners having fakesigned WADs.)
+
+  const IOS::ES::TMDReader& tmd = GetTMD(partition);
+  if (!tmd.IsValid())
+    return;
+
+  AddToSyncHash(context, tmd.GetIOSId());
+  AddToSyncHash(context, tmd.GetTitleId());
+  AddToSyncHash(context, tmd.GetTitleFlags());
+  AddToSyncHash(context, tmd.GetGroupId());
+  AddToSyncHash(context, tmd.GetRegion());
+  AddToSyncHash(context, tmd.GetTitleVersion());
+  AddToSyncHash(context, tmd.GetBootIndex());
+
+  for (const IOS::ES::Content& content : tmd.GetContents())
+    AddToSyncHash(context, content);
+}
+
 std::map<Language, std::string> Volume::ReadWiiNames(const std::vector<char16_t>& data)
 {
   std::map<Language, std::string> names;

Source/Core/DiscIO/Volume.h

@@ -12,6 +12,8 @@
 #include <string>
 #include <vector>
 
+#include <mbedtls/sha1.h>
+
 #include "Common/CommonTypes.h"
 #include "Common/StringUtil.h"
 #include "Common/Swap.h"
@@ -143,6 +145,13 @@ public:
   virtual u64 GetRawSize() const = 0;
   virtual const BlobReader& GetBlobReader() const = 0;
 
+  // This hash is intended to be (but is not guaranteed to be):
+  // 1. Identical for discs with no differences that affect netplay/TAS sync
+  // 2. Different for discs with differences that affect netplay/TAS sync
+  // 3. Much faster than hashing the entire disc
+  // The way the hash is calculated may change with updates to Dolphin.
+  virtual std::array<u8, 20> GetSyncHash() const = 0;
+
 protected:
   template <u32 N>
   std::string DecodeString(const char (&data)[N]) const
@@ -156,6 +165,10 @@ protected:
       return CP1252ToUTF8(string);
   }
 
+  void ReadAndAddToSyncHash(mbedtls_sha1_context* context, u64 offset, u64 length,
+                            const Partition& partition) const;
+  void AddTMDToSyncHash(mbedtls_sha1_context* context, const Partition& partition) const;
+
   virtual u32 GetOffsetShift() const { return 0; }
   static std::map<Language, std::string> ReadWiiNames(const std::vector<char16_t>& data);
 

Source/Core/DiscIO/VolumeDisc.cpp

@@ -4,11 +4,17 @@
 
 #include "DiscIO/VolumeDisc.h"
 
+#include <memory>
 #include <optional>
 #include <string>
+#include <vector>
+
+#include <mbedtls/sha1.h>
 
 #include "Common/CommonTypes.h"
+#include "DiscIO/DiscExtractor.h"
 #include "DiscIO/Enums.h"
+#include "DiscIO/Filesystem.h"
 
 namespace DiscIO
 {
@@ -90,4 +96,35 @@ bool VolumeDisc::IsNKit() const
   return ReadSwapped<u32>(0x200, PARTITION_NONE) == NKIT_MAGIC;
 }
 
+void VolumeDisc::AddGamePartitionToSyncHash(mbedtls_sha1_context* context) const
+{
+  const Partition partition = GetGamePartition();
+
+  // All headers at the beginning of the partition, plus the apploader
+  ReadAndAddToSyncHash(context, 0, 0x2440 + GetApploaderSize(*this, partition).value_or(0),
+                       partition);
+
+  // Boot DOL (may be missing if this is a Datel disc)
+  const std::optional<u64> dol_offset = GetBootDOLOffset(*this, partition);
+  if (dol_offset)
+  {
+    ReadAndAddToSyncHash(context, *dol_offset,
+                         GetBootDOLSize(*this, partition, *dol_offset).value_or(0), partition);
+  }
+
+  // File system
+  const std::optional<u64> fst_offset = GetFSTOffset(*this, partition);
+  if (fst_offset)
+    ReadAndAddToSyncHash(context, *fst_offset, GetFSTSize(*this, partition).value_or(0), partition);
+
+  // opening.bnr (name and banner)
+  const FileSystem* file_system = GetFileSystem(partition);
+  if (file_system)
+  {
+    std::unique_ptr<FileInfo> file_info = file_system->FindFileInfo("opening.bnr");
+    if (file_info && !file_info->IsDirectory())
+      ReadAndAddToSyncHash(context, file_info->GetOffset(), file_info->GetSize(), partition);
+  }
+}
+
 }  // namespace DiscIO

Source/Core/DiscIO/VolumeDisc.h

@@ -7,6 +7,8 @@
 #include <optional>
 #include <string>
 
+#include <mbedtls/sha1.h>
+
 #include "Common/CommonTypes.h"
 #include "DiscIO/Volume.h"
 
@@ -26,6 +28,7 @@ public:
 
 protected:
   Region RegionCodeToRegion(std::optional<u32> region_code) const;
+  void AddGamePartitionToSyncHash(mbedtls_sha1_context* context) const;
 };
 
 }  // namespace DiscIO

Source/Core/DiscIO/VolumeGC.cpp

@@ -11,6 +11,8 @@
 #include <utility>
 #include <vector>
 
+#include <mbedtls/sha1.h>
+
 #include "Common/Assert.h"
 #include "Common/ColorUtil.h"
 #include "Common/CommonTypes.h"
@@ -137,6 +139,19 @@ bool VolumeGC::IsDatelDisc() const
   return !GetBootDOLOffset(*this, PARTITION_NONE).has_value();
 }
 
+std::array<u8, 20> VolumeGC::GetSyncHash() const
+{
+  mbedtls_sha1_context context;
+  mbedtls_sha1_init(&context);
+  mbedtls_sha1_starts_ret(&context);
+
+  AddGamePartitionToSyncHash(&context);
+
+  std::array<u8, 20> hash;
+  mbedtls_sha1_finish_ret(&context, hash.data());
+  return hash;
+}
+
 VolumeGC::ConvertedGCBanner VolumeGC::LoadBannerFile() const
 {
   GCBanner banner_file;

Source/Core/DiscIO/VolumeGC.h

@@ -51,6 +51,8 @@ public:
   u64 GetRawSize() const override;
   const BlobReader& GetBlobReader() const override;
 
+  std::array<u8, 20> GetSyncHash() const override;
+
 private:
   static const u32 GC_BANNER_WIDTH = 96;
   static const u32 GC_BANNER_HEIGHT = 32;

Source/Core/DiscIO/VolumeVerifier.cpp

@@ -479,8 +479,8 @@ std::vector<Partition> VolumeVerifier::CheckPartitions()
       AddProblem(Severity::Low,
                  Common::GetStringT(
                      "The data partition is not at its normal position. This will affect the "
-                     "emulated loading times. When using NetPlay or sending input recordings to "
+                     "emulated loading times. You will be unable to share input recordings and use "
-                     "other people, you will experience desyncs if anyone is using a good dump."));
+                     "NetPlay with anyone who is using a good dump."));
     }
   }
 
@@ -783,10 +783,10 @@ void VolumeVerifier::CheckDiscSize(const std::vector<Partition>& partitions)
         {
           AddProblem(
               Severity::Low,
-              Common::GetStringT("This disc image has an unusual size. This will likely make the "
+              Common::GetStringT(
-                                 "emulated loading times longer. When using NetPlay or sending "
+                  "This disc image has an unusual size. This will likely make the emulated "
-                                 "input recordings to other people, you will likely experience "
+                  "loading times longer. You will likely be unable to share input recordings "
-                                 "desyncs if anyone is using a good dump."));
+                  "and use NetPlay with anyone who is using a good dump."));
         }
         else
         {

Source/Core/DiscIO/VolumeWad.cpp

@@ -40,6 +40,7 @@ VolumeWAD::VolumeWAD(std::unique_ptr<BlobReader> reader) : m_reader(std::move(re
   m_ticket_size = m_reader->ReadSwapped<u32>(0x10).value_or(0);
   m_tmd_size = m_reader->ReadSwapped<u32>(0x14).value_or(0);
   m_data_size = m_reader->ReadSwapped<u32>(0x18).value_or(0);
+  m_opening_bnr_size = m_reader->ReadSwapped<u32>(0x1C).value_or(0);
 
   m_cert_chain_offset = Common::AlignUp(m_hdr_size, 0x40);
   m_ticket_offset = m_cert_chain_offset + Common::AlignUp(m_cert_chain_size, 0x40);
@@ -342,4 +343,22 @@ const BlobReader& VolumeWAD::GetBlobReader() const
   return *m_reader;
 }
 
+std::array<u8, 20> VolumeWAD::GetSyncHash() const
+{
+  // We can skip hashing the contents since the TMD contains hashes of the contents.
+  // We specifically don't hash the ticket, since its console ID can differ without any problems.
+
+  mbedtls_sha1_context context;
+  mbedtls_sha1_init(&context);
+  mbedtls_sha1_starts_ret(&context);
+
+  AddTMDToSyncHash(&context, PARTITION_NONE);
+
+  ReadAndAddToSyncHash(&context, m_opening_bnr_offset, m_opening_bnr_size, PARTITION_NONE);
+
+  std::array<u8, 20> hash;
+  mbedtls_sha1_finish_ret(&context, hash.data());
+  return hash;
+}
+
 }  // namespace DiscIO

Source/Core/DiscIO/VolumeWad.h

@@ -70,6 +70,8 @@ public:
   u64 GetRawSize() const override;
   const BlobReader& GetBlobReader() const override;
 
+  std::array<u8, 20> GetSyncHash() const override;
+
 private:
   std::unique_ptr<BlobReader> m_reader;
   IOS::ES::TicketReader m_ticket;
@@ -85,6 +87,7 @@ private:
   u32 m_ticket_size = 0;
   u32 m_tmd_size = 0;
   u32 m_data_size = 0;
+  u32 m_opening_bnr_size = 0;
 };
 
 }  // namespace DiscIO

Source/Core/DiscIO/VolumeWii.cpp

@@ -362,6 +362,33 @@ const BlobReader& VolumeWii::GetBlobReader() const
   return *m_reader;
 }
 
+std::array<u8, 20> VolumeWii::GetSyncHash() const
+{
+  mbedtls_sha1_context context;
+  mbedtls_sha1_init(&context);
+  mbedtls_sha1_starts_ret(&context);
+
+  // Disc header
+  ReadAndAddToSyncHash(&context, 0, 0x80, PARTITION_NONE);
+
+  // Region code
+  ReadAndAddToSyncHash(&context, 0x4E000, 4, PARTITION_NONE);
+
+  // The data offset of the game partition - an important factor for disc drive timings
+  const u64 data_offset = PartitionOffsetToRawOffset(0, GetGamePartition());
+  mbedtls_sha1_update_ret(&context, reinterpret_cast<const u8*>(&data_offset), sizeof(data_offset));
+
+  // TMD
+  AddTMDToSyncHash(&context, GetGamePartition());
+
+  // Game partition contents
+  AddGamePartitionToSyncHash(&context);
+
+  std::array<u8, 20> hash;
+  mbedtls_sha1_finish_ret(&context, hash.data());
+  return hash;
+}
+
 bool VolumeWii::CheckH3TableIntegrity(const Partition& partition) const
 {
   auto it = m_partitions.find(partition);

Source/Core/DiscIO/VolumeWii.h

@@ -92,6 +92,7 @@ public:
   bool IsSizeAccurate() const override;
   u64 GetRawSize() const override;
   const BlobReader& GetBlobReader() const override;
+  std::array<u8, 20> GetSyncHash() const override;
 
   // The in parameter can either contain all the data to begin with,
   // or read_function can write data into the in parameter when called.

Source/Core/DolphinQt/GameList/GameList.cpp

@@ -398,9 +398,7 @@ void GameList::ShowContextMenu(const QPoint&)
 
     QAction* netplay_host = new QAction(tr("Host with NetPlay"), menu);
 
-    connect(netplay_host, &QAction::triggered, [this, game] {
+    connect(netplay_host, &QAction::triggered, [this, game] { emit NetPlayHost(*game); });
-      emit NetPlayHost(QString::fromStdString(game->GetUniqueIdentifier()));
-    });
 
     connect(&Settings::Instance(), &Settings::EmulationStateChanged, menu, [=](Core::State state) {
       netplay_host->setEnabled(state == Core::State::Uninitialized);
@@ -740,6 +738,11 @@ GameList::FindSecondDisc(const UICommon::GameFile& game) const
   return m_model->FindSecondDisc(game);
 }
 
+std::string GameList::GetNetPlayName(const UICommon::GameFile& game) const
+{
+  return m_model->GetNetPlayName(game);
+}
+
 void GameList::SetViewColumn(int col, bool view)
 {
   m_list->setColumnHidden(col, !view);

Source/Core/DolphinQt/GameList/GameList.h

@@ -32,6 +32,7 @@ public:
   bool HasMultipleSelected() const;
   std::shared_ptr<const UICommon::GameFile> FindGame(const std::string& path) const;
   std::shared_ptr<const UICommon::GameFile> FindSecondDisc(const UICommon::GameFile& game) const;
+  std::string GetNetPlayName(const UICommon::GameFile& game) const;
 
   void SetListView() { SetPreferredView(true); }
   void SetGridView() { SetPreferredView(false); }
@@ -47,7 +48,7 @@ public:
 
 signals:
   void GameSelected();
-  void NetPlayHost(const QString& game_id);
+  void NetPlayHost(const UICommon::GameFile& game);
   void SelectionChanged(std::shared_ptr<const UICommon::GameFile> game_file);
   void OpenGeneralSettings();
 

Source/Core/DolphinQt/GameList/GameListModel.cpp

@@ -313,14 +313,9 @@ std::shared_ptr<const UICommon::GameFile> GameListModel::GetGameFile(int index)
   return m_games[index];
 }
 
-QString GameListModel::GetPath(int index) const
+std::string GameListModel::GetNetPlayName(const UICommon::GameFile& game) const
 {
-  return QString::fromStdString(m_games[index]->GetFilePath());
+  return game.GetNetPlayName(m_title_database);
-}
-
-QString GameListModel::GetUniqueIdentifier(int index) const
-{
-  return QString::fromStdString(m_games[index]->GetUniqueIdentifier());
 }
 
 void GameListModel::AddGame(const std::shared_ptr<const UICommon::GameFile>& game)

Source/Core/DolphinQt/GameList/GameListModel.h

@@ -37,10 +37,7 @@ public:
   int columnCount(const QModelIndex& parent) const override;
 
   std::shared_ptr<const UICommon::GameFile> GetGameFile(int index) const;
-  // Path of the game at the specified index.
+  std::string GetNetPlayName(const UICommon::GameFile& game) const;
-  QString GetPath(int index) const;
-  // Unique identifier of the game at the specified index.
-  QString GetUniqueIdentifier(int index) const;
   bool ShouldDisplayGameListItem(int index) const;
   void SetSearchTerm(const QString& term);
 

Source/Core/DolphinQt/MainWindow.cpp

@@ -1374,7 +1374,7 @@ bool MainWindow::NetPlayJoin()
   return true;
 }
 
-bool MainWindow::NetPlayHost(const QString& game_id)
+bool MainWindow::NetPlayHost(const UICommon::GameFile& game)
 {
   if (Core::IsRunning())
   {
@@ -1419,7 +1419,8 @@ bool MainWindow::NetPlayHost(const QString& game_id)
     return false;
   }
 
-  Settings::Instance().GetNetPlayServer()->ChangeGame(game_id.toStdString());
+  Settings::Instance().GetNetPlayServer()->ChangeGame(game.GetSyncIdentifier(),
+                                                      m_game_list->GetNetPlayName(game));
 
   // Join our local server
   return NetPlayJoin();

Source/Core/DolphinQt/MainWindow.h

@@ -158,7 +158,7 @@ private:
 
   void NetPlayInit();
   bool NetPlayJoin();
-  bool NetPlayHost(const QString& game_id);
+  bool NetPlayHost(const UICommon::GameFile& game);
   void NetPlayQuit();
 
   void OnBootGameCubeIPL(DiscIO::Region region);

Source/Core/DolphinQt/NetPlay/GameListDialog.cpp

@@ -4,12 +4,15 @@
 
 #include "DolphinQt/NetPlay/GameListDialog.h"
 
+#include <memory>
+
 #include <QDialogButtonBox>
 #include <QListWidget>
 #include <QVBoxLayout>
 
 #include "DolphinQt/GameList/GameListModel.h"
 #include "DolphinQt/Settings.h"
+#include "UICommon/GameFile.h"
 
 GameListDialog::GameListDialog(QWidget* parent) : QDialog(parent)
 {
@@ -35,12 +38,8 @@ void GameListDialog::CreateWidgets()
 
 void GameListDialog::ConnectWidgets()
 {
-  connect(m_game_list, &QListWidget::itemSelectionChanged, [this] {
+  connect(m_game_list, &QListWidget::itemSelectionChanged,
-    int row = m_game_list->currentRow();
+          [this] { m_button_box->setEnabled(m_game_list->currentRow() != -1); });
-
-    m_button_box->setEnabled(row != -1);
-    m_game_id = m_game_list->currentItem()->text();
-  });
 
   connect(m_game_list, &QListWidget::itemDoubleClicked, this, &GameListDialog::accept);
   connect(m_button_box, &QDialogButtonBox::accepted, this, &GameListDialog::accept);
@@ -54,16 +53,21 @@ void GameListDialog::PopulateGameList()
 
   for (int i = 0; i < game_list_model->rowCount(QModelIndex()); i++)
   {
-    auto* item = new QListWidgetItem(game_list_model->GetUniqueIdentifier(i));
+    std::shared_ptr<const UICommon::GameFile> game = game_list_model->GetGameFile(i);
+
+    auto* item =
+        new QListWidgetItem(QString::fromStdString(game_list_model->GetNetPlayName(*game)));
+    item->setData(Qt::UserRole, QVariant::fromValue(std::move(game)));
     m_game_list->addItem(item);
   }
 
   m_game_list->sortItems();
 }
 
-const QString& GameListDialog::GetSelectedUniqueID() const
+const UICommon::GameFile& GameListDialog::GetSelectedGame() const
 {
-  return m_game_id;
+  auto items = m_game_list->selectedItems();
+  return *items[0]->data(Qt::UserRole).value<std::shared_ptr<const UICommon::GameFile>>();
 }
 
 int GameListDialog::exec()

Source/Core/DolphinQt/NetPlay/GameListDialog.h

@@ -11,6 +11,11 @@ class QVBoxLayout;
 class QListWidget;
 class QDialogButtonBox;
 
+namespace UICommon
+{
+class GameFile;
+}
+
 class GameListDialog : public QDialog
 {
   Q_OBJECT
@@ -18,7 +23,7 @@ public:
   explicit GameListDialog(QWidget* parent);
 
   int exec() override;
-  const QString& GetSelectedUniqueID() const;
+  const UICommon::GameFile& GetSelectedGame() const;
 
 private:
   void CreateWidgets();
@@ -28,5 +33,4 @@ private:
   QVBoxLayout* m_main_layout;
   QListWidget* m_game_list;
   QDialogButtonBox* m_button_box;
-  QString m_game_id;
 };

Source/Core/DolphinQt/NetPlay/NetPlayDialog.cpp

@@ -21,6 +21,7 @@
 #include <QTableWidget>
 #include <QTextBrowser>
 
+#include <algorithm>
 #include <sstream>
 
 #include "Common/CommonPaths.h"
@@ -37,6 +38,7 @@
 #include "Core/ConfigManager.h"
 #include "Core/Core.h"
 #include "Core/NetPlayServer.h"
+#include "Core/SyncIdentifier.h"
 
 #include "DolphinQt/GameList/GameListModel.h"
 #include "DolphinQt/NetPlay/ChunkedProgressDialog.h"
@@ -153,17 +155,19 @@ void NetPlayDialog::CreateMainLayout()
 
   m_md5_menu = m_menu_bar->addMenu(tr("Checksum"));
   m_md5_menu->addAction(tr("Current game"), this, [this] {
-    Settings::Instance().GetNetPlayServer()->ComputeMD5(m_current_game);
+    Settings::Instance().GetNetPlayServer()->ComputeMD5(m_current_game_identifier);
   });
   m_md5_menu->addAction(tr("Other game..."), this, [this] {
     GameListDialog gld(this);
 
     if (gld.exec() != QDialog::Accepted)
       return;
-    Settings::Instance().GetNetPlayServer()->ComputeMD5(gld.GetSelectedUniqueID().toStdString());
+    Settings::Instance().GetNetPlayServer()->ComputeMD5(gld.GetSelectedGame().GetSyncIdentifier());
+  });
+  m_md5_menu->addAction(tr("SD Card"), this, [] {
+    Settings::Instance().GetNetPlayServer()->ComputeMD5(
+        NetPlay::NetPlayClient::GetSDCardIdentifier());
   });
-  m_md5_menu->addAction(tr("SD Card"), this,
-                        [] { Settings::Instance().GetNetPlayServer()->ComputeMD5(WII_SDCARD); });
 
   m_other_menu = m_menu_bar->addMenu(tr("Other"));
   m_record_input_action = m_other_menu->addAction(tr("Record Inputs"));
@@ -321,9 +325,14 @@ void NetPlayDialog::ConnectWidgets()
     GameListDialog gld(this);
     if (gld.exec() == QDialog::Accepted)
     {
-      auto unique_id = gld.GetSelectedUniqueID();
+      Settings& settings = Settings::Instance();
-      Settings::Instance().GetNetPlayServer()->ChangeGame(unique_id.toStdString());
+
-      Settings::GetQSettings().setValue(QStringLiteral("netplay/hostgame"), unique_id);
+      const UICommon::GameFile& game = gld.GetSelectedGame();
+      const std::string netplay_name = settings.GetGameListModel()->GetNetPlayName(game);
+
+      settings.GetNetPlayServer()->ChangeGame(game.GetSyncIdentifier(), netplay_name);
+      Settings::GetQSettings().setValue(QStringLiteral("netplay/hostgame"),
+                                        QString::fromStdString(netplay_name));
     }
   });
 
@@ -416,7 +425,7 @@ void NetPlayDialog::OnStart()
     return;
   }
 
-  const auto game = FindGameFile(m_current_game);
+  const auto game = FindGameFile(m_current_game_identifier);
   if (!game)
   {
     PanicAlertT("Selected game doesn't exist in game list!");
@@ -583,11 +592,12 @@ void NetPlayDialog::UpdateDiscordPresence()
 {
 #ifdef USE_DISCORD_PRESENCE
   // both m_current_game and m_player_count need to be set for the status to be displayed correctly
-  if (m_player_count == 0 || m_current_game.empty())
+  if (m_player_count == 0 || m_current_game_name.empty())
     return;
 
   const auto use_default = [this]() {
-    Discord::UpdateDiscordPresence(m_player_count, Discord::SecretType::Empty, "", m_current_game);
+    Discord::UpdateDiscordPresence(m_player_count, Discord::SecretType::Empty, "",
+                                   m_current_game_name);
   };
 
   if (Core::IsRunning())
@@ -602,7 +612,8 @@ void NetPlayDialog::UpdateDiscordPresence()
         return use_default();
 
       Discord::UpdateDiscordPresence(m_player_count, Discord::SecretType::RoomID,
-                                     std::string(host_id.begin(), host_id.end()), m_current_game);
+                                     std::string(host_id.begin(), host_id.end()),
+                                     m_current_game_name);
     }
     else
     {
@@ -612,7 +623,7 @@ void NetPlayDialog::UpdateDiscordPresence()
 
       Discord::UpdateDiscordPresence(
           m_player_count, Discord::SecretType::IPAddress,
-          Discord::CreateSecretFromIPAddress(*m_external_ip_address, port), m_current_game);
+          Discord::CreateSecretFromIPAddress(*m_external_ip_address, port), m_current_game_name);
     }
   }
   else
@@ -660,9 +671,10 @@ void NetPlayDialog::UpdateGUI()
     return '|' + str + '|';
   };
 
-  static const std::map<NetPlay::PlayerGameStatus, QString> player_status{
+  static const std::map<NetPlay::SyncIdentifierComparison, QString> player_status{
-      {NetPlay::PlayerGameStatus::Ok, tr("OK")},
+      {NetPlay::SyncIdentifierComparison::SameGame, tr("OK")},
-      {NetPlay::PlayerGameStatus::NotFound, tr("Not Found")},
+      {NetPlay::SyncIdentifierComparison::DifferentVersion, tr("Wrong Version")},
+      {NetPlay::SyncIdentifierComparison::DifferentGame, tr("Not Found")},
   };
 
   for (int i = 0; i < m_player_count; i++)
@@ -805,15 +817,17 @@ void NetPlayDialog::AppendChat(const std::string& msg)
   QApplication::alert(this);
 }
 
-void NetPlayDialog::OnMsgChangeGame(const std::string& title)
+void NetPlayDialog::OnMsgChangeGame(const NetPlay::SyncIdentifier& sync_identifier,
+                                    const std::string& netplay_name)
 {
-  QString qtitle = QString::fromStdString(title);
+  QString qname = QString::fromStdString(netplay_name);
-  QueueOnObject(this, [this, qtitle, title] {
+  QueueOnObject(this, [this, qname, netplay_name, &sync_identifier] {
-    m_game_button->setText(qtitle);
+    m_game_button->setText(qname);
-    m_current_game = title;
+    m_current_game_identifier = sync_identifier;
+    m_current_game_name = netplay_name;
     UpdateDiscordPresence();
   });
-  DisplayMessage(tr("Game changed to \"%1\"").arg(qtitle), "magenta");
+  DisplayMessage(tr("Game changed to \"%1\"").arg(qname), "magenta");
 }
 
 void NetPlayDialog::GameStatusChanged(bool running)
@@ -859,7 +873,12 @@ void NetPlayDialog::OnMsgStartGame()
     auto client = Settings::Instance().GetNetPlayClient();
 
     if (client)
-      client->StartGame(FindGame(m_current_game));
+    {
+      if (auto game = FindGameFile(m_current_game_identifier))
+        client->StartGame(game->GetFilePath());
+      else
+        PanicAlertT("Selected game doesn't exist in game list!");
+    }
     UpdateDiscordPresence();
   });
 }
@@ -1017,29 +1036,24 @@ bool NetPlayDialog::IsRecording()
   return false;
 }
 
-std::string NetPlayDialog::FindGame(const std::string& game)
+std::shared_ptr<const UICommon::GameFile>
+NetPlayDialog::FindGameFile(const NetPlay::SyncIdentifier& sync_identifier,
+                            NetPlay::SyncIdentifierComparison* found)
 {
-  std::optional<std::string> path = RunOnObject(this, [this, &game] {
+  NetPlay::SyncIdentifierComparison temp;
-    for (int i = 0; i < m_game_list_model->rowCount(QModelIndex()); i++)
+  if (!found)
-    {
+    found = &temp;
-      if (m_game_list_model->GetUniqueIdentifier(i).toStdString() == game)
+
-        return m_game_list_model->GetPath(i).toStdString();
+  *found = NetPlay::SyncIdentifierComparison::DifferentGame;
-    }
-    return std::string("");
-  });
-  if (path)
-    return *path;
-  return std::string("");
-}
 
-std::shared_ptr<const UICommon::GameFile> NetPlayDialog::FindGameFile(const std::string& game)
-{
   std::optional<std::shared_ptr<const UICommon::GameFile>> game_file =
-      RunOnObject(this, [this, &game] {
+      RunOnObject(this, [this, &sync_identifier, found] {
         for (int i = 0; i < m_game_list_model->rowCount(QModelIndex()); i++)
         {
-          if (m_game_list_model->GetUniqueIdentifier(i).toStdString() == game)
+          auto game_file = m_game_list_model->GetGameFile(i);
-            return m_game_list_model->GetGameFile(i);
+          *found = std::min(*found, game_file->CompareSyncIdentifier(sync_identifier));
+          if (*found == NetPlay::SyncIdentifierComparison::SameGame)
+            return game_file;
         }
         return static_cast<std::shared_ptr<const UICommon::GameFile>>(nullptr);
       });
@@ -1126,15 +1140,15 @@ void NetPlayDialog::SaveSettings()
   Config::SetBase(Config::NETPLAY_NETWORK_MODE, network_mode);
 }
 
-void NetPlayDialog::ShowMD5Dialog(const std::string& file_identifier)
+void NetPlayDialog::ShowMD5Dialog(const std::string& title)
 {
-  QueueOnObject(this, [this, file_identifier] {
+  QueueOnObject(this, [this, title] {
     m_md5_menu->setEnabled(false);
 
     if (m_md5_dialog->isVisible())
       m_md5_dialog->close();
 
-    m_md5_dialog->show(QString::fromStdString(file_identifier));
+    m_md5_dialog->show(QString::fromStdString(title));
   });
 }
 

Source/Core/DolphinQt/NetPlay/NetPlayDialog.h

@@ -45,7 +45,8 @@ public:
   void Update() override;
   void AppendChat(const std::string& msg) override;
 
-  void OnMsgChangeGame(const std::string& filename) override;
+  void OnMsgChangeGame(const NetPlay::SyncIdentifier& sync_identifier,
+                       const std::string& netplay_name) override;
   void OnMsgStartGame() override;
   void OnMsgStopGame() override;
   void OnMsgPowerButton() override;
@@ -65,13 +66,14 @@ public:
   void OnIndexRefreshFailed(const std::string error) override;
 
   bool IsRecording() override;
-  std::string FindGame(const std::string& game) override;
+  std::shared_ptr<const UICommon::GameFile>
-  std::shared_ptr<const UICommon::GameFile> FindGameFile(const std::string& game) override;
+  FindGameFile(const NetPlay::SyncIdentifier& sync_identifier,
+               NetPlay::SyncIdentifierComparison* found = nullptr) override;
 
   void LoadSettings();
   void SaveSettings();
 
-  void ShowMD5Dialog(const std::string& file_identifier) override;
+  void ShowMD5Dialog(const std::string& title) override;
   void SetMD5Progress(int pid, int progress) override;
   void SetMD5Result(int pid, const std::string& result) override;
   void AbortMD5() override;
@@ -145,7 +147,8 @@ private:
   MD5Dialog* m_md5_dialog;
   ChunkedProgressDialog* m_chunked_progress_dialog;
   PadMappingDialog* m_pad_mapping;
-  std::string m_current_game;
+  NetPlay::SyncIdentifier m_current_game_identifier;
+  std::string m_current_game_name;
   Common::Lazy<std::string> m_external_ip_address;
   std::string m_nickname;
   GameListModel* m_game_list_model = nullptr;

Source/Core/DolphinQt/NetPlay/NetPlaySetupDialog.cpp

@@ -4,6 +4,8 @@
 
 #include "DolphinQt/NetPlay/NetPlaySetupDialog.h"
 
+#include <memory>
+
 #include <QCheckBox>
 #include <QComboBox>
 #include <QDialogButtonBox>
@@ -24,6 +26,7 @@
 #include "DolphinQt/QtUtils/UTF8CodePointCountValidator.h"
 #include "DolphinQt/Settings.h"
 
+#include "UICommon/GameFile.h"
 #include "UICommon/NetPlayIndex.h"
 
 NetPlaySetupDialog::NetPlaySetupDialog(QWidget* parent)
@@ -347,7 +350,7 @@ void NetPlaySetupDialog::accept()
       return;
     }
 
-    emit Host(items[0]->text());
+    emit Host(*items[0]->data(Qt::UserRole).value<std::shared_ptr<const UICommon::GameFile>>());
   }
 }
 
@@ -358,11 +361,11 @@ void NetPlaySetupDialog::PopulateGameList()
   m_host_games->clear();
   for (int i = 0; i < m_game_list_model->rowCount(QModelIndex()); i++)
   {
-    auto title = m_game_list_model->GetUniqueIdentifier(i);
+    std::shared_ptr<const UICommon::GameFile> game = m_game_list_model->GetGameFile(i);
-    auto path = m_game_list_model->GetPath(i);
 
-    auto* item = new QListWidgetItem(title);
+    auto* item =
-    item->setData(Qt::UserRole, path);
+        new QListWidgetItem(QString::fromStdString(m_game_list_model->GetNetPlayName(*game)));
+    item->setData(Qt::UserRole, QVariant::fromValue(std::move(game)));
     m_host_games->addItem(item);
   }
 

Source/Core/DolphinQt/NetPlay/NetPlaySetupDialog.h

@@ -18,6 +18,11 @@ class QPushButton;
 class QSpinBox;
 class QTabWidget;
 
+namespace UICommon
+{
+class GameFile;
+}
+
 class NetPlaySetupDialog : public QDialog
 {
   Q_OBJECT
@@ -29,7 +34,7 @@ public:
 
 signals:
   bool Join();
-  bool Host(const QString& game_identifier);
+  bool Host(const UICommon::GameFile& game);
 
 private:
   void CreateMainLayout();

Source/Core/UICommon/GameFile.cpp

@@ -5,6 +5,7 @@
 #include "UICommon/GameFile.h"
 
 #include <algorithm>
+#include <array>
 #include <cinttypes>
 #include <cstdio>
 #include <cstring>
@@ -13,11 +14,13 @@
 #include <memory>
 #include <sstream>
 #include <string>
+#include <string_view>
 #include <tuple>
 #include <utility>
 #include <vector>
 
 #include <fmt/format.h>
+#include <mbedtls/sha1.h>
 #include <pugixml.hpp>
 
 #include "Common/ChunkFile.h"
@@ -532,7 +535,7 @@ std::vector<DiscIO::Language> GameFile::GetLanguages() const
   return languages;
 }
 
-std::string GameFile::GetUniqueIdentifier() const
+std::string GameFile::GetNetPlayName(const Core::TitleDatabase& title_database) const
 {
   std::vector<std::string> info;
   if (!GetGameID().empty())
@@ -540,12 +543,7 @@ std::string GameFile::GetUniqueIdentifier() const
   if (GetRevision() != 0)
     info.push_back("Revision " + std::to_string(GetRevision()));
 
-  std::string name = GetLongName(DiscIO::Language::English);
+  const std::string name = GetName(title_database);
-  if (name.empty())
-  {
-    // Use the file name as a fallback. Not necessarily consistent, but it's the best we have
-    name = m_file_name;
-  }
 
   int disc_number = GetDiscNumber() + 1;
 
@@ -566,6 +564,66 @@ std::string GameFile::GetUniqueIdentifier() const
   return name + " (" + ss.str() + ")";
 }
 
+std::array<u8, 20> GameFile::GetSyncHash() const
+{
+  std::array<u8, 20> hash{};
+
+  if (m_platform == DiscIO::Platform::ELFOrDOL)
+  {
+    std::string buffer;
+    if (File::ReadFileToString(m_file_path, buffer))
+      mbedtls_sha1_ret(reinterpret_cast<unsigned char*>(buffer.data()), buffer.size(), hash.data());
+  }
+  else
+  {
+    if (std::unique_ptr<DiscIO::Volume> volume = DiscIO::CreateVolume(m_file_path))
+      hash = volume->GetSyncHash();
+  }
+
+  return hash;
+}
+
+NetPlay::SyncIdentifier GameFile::GetSyncIdentifier() const
+{
+  const u64 dol_elf_size = m_platform == DiscIO::Platform::ELFOrDOL ? m_file_size : 0;
+  return NetPlay::SyncIdentifier{dol_elf_size,  m_game_id,       m_revision,
+                                 m_disc_number, m_is_datel_disc, GetSyncHash()};
+}
+
+NetPlay::SyncIdentifierComparison
+GameFile::CompareSyncIdentifier(const NetPlay::SyncIdentifier& sync_identifier) const
+{
+  const bool is_elf_or_dol = m_platform == DiscIO::Platform::ELFOrDOL;
+  if ((is_elf_or_dol ? m_file_size : 0) != sync_identifier.dol_elf_size)
+    return NetPlay::SyncIdentifierComparison::DifferentGame;
+
+  const auto trim = [](const std::string& str, size_t n) {
+    return std::string_view(str.data(), std::min(n, str.size()));
+  };
+
+  if (trim(m_game_id, 3) != trim(sync_identifier.game_id, 3))
+    return NetPlay::SyncIdentifierComparison::DifferentGame;
+
+  if (m_disc_number != sync_identifier.disc_number || m_is_datel_disc != sync_identifier.is_datel)
+    return NetPlay::SyncIdentifierComparison::DifferentGame;
+
+  const NetPlay::SyncIdentifierComparison mismatch_result =
+      is_elf_or_dol || m_is_datel_disc ? NetPlay::SyncIdentifierComparison::DifferentGame :
+                                         NetPlay::SyncIdentifierComparison::DifferentVersion;
+
+  if (m_game_id != sync_identifier.game_id)
+  {
+    const bool game_id_is_title_id = m_game_id.size() > 6 || sync_identifier.game_id.size() > 6;
+    return game_id_is_title_id ? NetPlay::SyncIdentifierComparison::DifferentGame : mismatch_result;
+  }
+
+  if (m_revision != sync_identifier.revision)
+    return mismatch_result;
+
+  return GetSyncHash() == sync_identifier.sync_hash ? NetPlay::SyncIdentifierComparison::SameGame :
+                                                      mismatch_result;
+}
+
 std::string GameFile::GetWiiFSPath() const
 {
   ASSERT(DiscIO::IsWii(m_platform));

Source/Core/UICommon/GameFile.h

@@ -4,11 +4,13 @@
 
 #pragma once
 
+#include <array>
 #include <map>
 #include <string>
 #include <vector>
 
 #include "Common/CommonTypes.h"
+#include "Core/SyncIdentifier.h"
 #include "DiscIO/Blob.h"
 #include "DiscIO/Enums.h"
 
@@ -80,7 +82,16 @@ public:
   u16 GetRevision() const { return m_revision; }
   // 0 is the first disc, 1 is the second disc
   u8 GetDiscNumber() const { return m_disc_number; }
-  std::string GetUniqueIdentifier() const;
+  std::string GetNetPlayName(const Core::TitleDatabase& title_database) const;
+
+  // This function is slow
+  std::array<u8, 20> GetSyncHash() const;
+  // This function is slow
+  NetPlay::SyncIdentifier GetSyncIdentifier() const;
+  // This function is slow if all of game_id, revision, disc_number, is_datel are identical
+  NetPlay::SyncIdentifierComparison
+  CompareSyncIdentifier(const NetPlay::SyncIdentifier& sync_identifier) const;
+
   std::string GetWiiFSPath() const;
   DiscIO::Region GetRegion() const { return m_region; }
   DiscIO::Country GetCountry() const { return m_country; }