diff --git a/Source/Core/Core/HW/EXI/BBA/BuiltIn.cpp b/Source/Core/Core/HW/EXI/BBA/BuiltIn.cpp
diff --git a/Source/Core/Core/HW/EXI/BBA/BuiltIn.h b/Source/Core/Core/HW/EXI/BBA/BuiltIn.h
@@ -0,0 +1,58 @@
+// Copyright 2022 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#ifdef _WIN32
+#include <WinSock2.h>
+#else
+#include <netinet/in.h>
+#endif
+
+#include <SFML/Network.hpp>
+#include "Common/CommonTypes.h"
+#include "Common/Network.h"
+
+constexpr u16 TCP_FLAG_SIN = 0x2;
+constexpr u16 TCP_FLAG_ACK = 0x10;
+constexpr u16 TCP_FLAG_PSH = 0x8;
+constexpr u16 TCP_FLAG_FIN = 0x1;
+constexpr u16 TCP_FLAG_RST = 0x4;
+
+constexpr u16 IP_PROTOCOL = 0x800;
+constexpr u16 ARP_PROTOCOL = 0x806;
+
+constexpr u8 MAX_TCP_BUFFER = 4;
+constexpr u16 MAX_UDP_LENGTH = 1500;
+constexpr u16 MAX_TCP_LENGTH = 440;
+
+struct TcpBuffer
+{
+  bool used;
+  u64 tick;
+  u32 seq_id;
+  std::vector<u8> data;
+};
+
+struct StackRef
+{
+  u32 ip;
+  u16 local;
+  u16 remote;
+  u16 type;
+  sf::IpAddress target;
+  u32 seq_num;
+  u32 ack_num;
+  u32 ack_base;
+  u16 window_size;
+  u64 delay;
+  std::array<TcpBuffer, MAX_TCP_BUFFER> tcp_buffers;
+  bool ready;
+  sockaddr_in from;
+  sockaddr_in to;
+  Common::MACAddress bba_mac{};
+  Common::MACAddress my_mac{};
+  sf::UdpSocket udp_socket;
+  sf::TcpSocket tcp_socket;
+  u64 poke_time;
+};
diff --git a/Source/Core/Core/HW/EXI/EXI_Device.cpp b/Source/Core/Core/HW/EXI/EXI_Device.cpp
@@ -143,6 +143,10 @@ std::unique_ptr<IEXIDevice> EXIDevice_Create(const EXIDeviceType device_type, co
     result = std::make_unique<CEXIETHERNET>(BBADeviceType::XLINK);
     break;
 
+  case EXIDeviceType::EthernetBuiltIn:
+    result = std::make_unique<CEXIETHERNET>(BBADeviceType::BuiltIn);
+    break;
+
   case EXIDeviceType::Gecko:
     result = std::make_unique<CEXIGecko>();
     break;

diff --git a/Source/Core/Core/HW/EXI/EXI_Device.h b/Source/Core/Core/HW/EXI/EXI_Device.h
@@ -37,6 +37,7 @@ enum class EXIDeviceType : int
   EthernetXLink,
   // Only used on Apple devices.
   EthernetTapServer,
+  EthernetBuiltIn,
   None = 0xFF
 };
 
@@ -79,7 +80,7 @@ std::unique_ptr<IEXIDevice> EXIDevice_Create(EXIDeviceType device_type, int chan
 
 template <>
 struct fmt::formatter<ExpansionInterface::EXIDeviceType>
-    : EnumFormatter<ExpansionInterface::EXIDeviceType::EthernetTapServer>
+    : EnumFormatter<ExpansionInterface::EXIDeviceType::EthernetBuiltIn>
 {
   static constexpr array_type names = {
       _trans("Dummy"),
@@ -95,6 +96,7 @@ struct fmt::formatter<ExpansionInterface::EXIDeviceType>
       _trans("Advance Game Port"),
       _trans("Broadband Adapter (XLink Kai)"),
       _trans("Broadband Adapter (tapserver)"),
+      _trans("Broadband Adapter (Built In)"),
   };
 
   constexpr formatter() : EnumFormatter(names) {}

diff --git a/Source/Core/Core/HW/EXI/EXI_DeviceEthernet.cpp b/Source/Core/Core/HW/EXI/EXI_DeviceEthernet.cpp
@@ -53,6 +53,11 @@ CEXIETHERNET::CEXIETHERNET(BBADeviceType type)
     INFO_LOG_FMT(SP1, "Created tapserver physical network interface.");
     break;
 #endif
+  case BBADeviceType::BuiltIn:
+    m_network_interface = std::make_unique<BuiltInBBAInterface>(
+        this, Config::Get(Config::MAIN_BBA_BUILTIN_DNS), Config::Get(Config::MAIN_BBA_BUILTIN_IP));
+    INFO_LOG_FMT(SP1, "Created Built in network interface.");
+    break;
   case BBADeviceType::XLINK:
     // TODO start BBA with network link down, bring it up after "connected" response from XLink
 
@@ -155,6 +160,17 @@ void CEXIETHERNET::ImmWrite(u32 data, u32 size)
     {
     case INTERRUPT:
       exi_status.interrupt &= data ^ 0xff;
+      // raise back if there is still data
+      if (page_ptr(BBA_RRP) != page_ptr(BBA_RWP))
+      {
+        if (mBbaMem[BBA_IMR] & INT_R)
+        {
+          mBbaMem[BBA_IR] |= INT_R;
+
+          exi_status.interrupt |= exi_status.TRANSFER;
+        }
+      }
+
       break;
     case INTERRUPT_MASK:
       exi_status.interrupt_mask = data;
@@ -228,9 +244,7 @@ void CEXIETHERNET::DMAWrite(u32 addr, u32 size)
 void CEXIETHERNET::DMARead(u32 addr, u32 size)
 {
   DEBUG_LOG_FMT(SP1, "DMA read: {:08x} {:x}", addr, size);
-
   Memory::CopyToEmu(addr, &mBbaMem[transfer.address], size);
-
   transfer.address += size;
 }
 
@@ -348,7 +362,6 @@ void CEXIETHERNET::MXCommandHandler(u32 data, u32 size)
       // MXSoftReset();
       m_network_interface->Activate();
     }
-
     if (((mBbaMem[BBA_NCRA] & NCRA_SR) ^ (data & NCRA_SR)) != 0)
     {
       DEBUG_LOG_FMT(SP1, "{} rx", (data & NCRA_SR) ? "start" : "stop");
@@ -415,7 +428,6 @@ void CEXIETHERNET::DirectFIFOWrite(const u8* data, u32 size)
 {
   // In direct mode, the hardware handles creating the state required by the
   // GMAC instead of finagling with packet descriptors and such
-
   u16* tx_fifo_count = (u16*)&mBbaMem[BBA_TXFIFOCNT];
 
   memcpy(tx_fifo.get() + *tx_fifo_count, data, size);
@@ -510,76 +522,80 @@ inline void CEXIETHERNET::inc_rwp()
 {
   u16* rwp = (u16*)&mBbaMem[BBA_RWP];
 
-  if (*rwp + 1 == page_ptr(BBA_RHBP))
+  if (*rwp == page_ptr(BBA_RHBP))
     *rwp = page_ptr(BBA_BP);
   else
     (*rwp)++;
 }
 
+inline void CEXIETHERNET::set_rwp(u16 value)
+{
+  u16* rwp = (u16*)&mBbaMem[BBA_RWP];
+  *rwp = value;
+}
+
 // This function is on the critical path for receiving data.
 // Be very careful about calling into the logger and other slow things
 bool CEXIETHERNET::RecvHandlePacket()
 {
   u8* write_ptr;
-  u8* end_ptr;
-  u8* read_ptr;
   Descriptor* descriptor;
   u32 status = 0;
   u16 rwp_initial = page_ptr(BBA_RWP);
-
+  u16 current_rwp = 0;
+  u32 off = 4;
   if (!RecvMACFilter())
     goto wait_for_next;
 
 #ifdef BBA_TRACK_PAGE_PTRS
   INFO_LOG_FMT(SP1, "RecvHandlePacket {:x}\n{}", mRecvBufferLength,
-               ArrayToString(mRecvBuffer, mRecvBufferLength, 0x100));
+               ArrayToString(mRecvBuffer.get(), mRecvBufferLength, 16));
 
   INFO_LOG_FMT(SP1, "{:x} {:x} {:x} {:x}", page_ptr(BBA_BP), page_ptr(BBA_RRP), page_ptr(BBA_RWP),
                page_ptr(BBA_RHBP));
 #endif
 
-  write_ptr = ptr_from_page_ptr(BBA_RWP);
-  end_ptr = ptr_from_page_ptr(BBA_RHBP);
-  read_ptr = ptr_from_page_ptr(BBA_RRP);
+  write_ptr = &mBbaMem[page_ptr(BBA_RWP) << 8];
 
   descriptor = (Descriptor*)write_ptr;
-  write_ptr += 4;
-
-  for (u32 i = 0, off = 4; i < mRecvBufferLength; ++i, ++off)
+  current_rwp = page_ptr(BBA_RWP);
+  DEBUG_LOG_FMT(SP1, "Frame recv: {:x}", mRecvBufferLength);
+  for (u32 i = 0; i < mRecvBufferLength; i++)
   {
-    *write_ptr++ = mRecvBuffer[i];
-
-    if (off == 0xff)
+    write_ptr[off] = mRecvBuffer[i];
+    off++;
+    if (off == 0x100)
     {
       off = 0;
-      inc_rwp();
-    }
+      // avoid increasing the BBA register while copying
+      // sometime the OS can try to process when it's not completed
+      current_rwp = current_rwp == page_ptr(BBA_RHBP) ? page_ptr(BBA_BP) : ++current_rwp;
 
-    if (write_ptr == end_ptr)
-      write_ptr = ptr_from_page_ptr(BBA_BP);
+      write_ptr = &mBbaMem[current_rwp << 8];
 
-    if (write_ptr == read_ptr)
-    {
-      /*
-      halt copy
-      if (cur_packet_size >= PAGE_SIZE)
-        desc.status |= FO | BF
-      if (RBFIM)
-        raise RBFI
-      if (AUTORCVR)
-        discard bad packet
-      else
-        inc MPC instead of receiving packets
-      */
-      status |= DESC_FO | DESC_BF;
-      mBbaMem[BBA_IR] |= mBbaMem[BBA_IMR] & INT_RBF;
-      break;
+      if (page_ptr(BBA_RRP) == current_rwp)
+      {
+        /*
+        halt copy
+        if (cur_packet_size >= PAGE_SIZE)
+          desc.status |= FO | BF
+        if (RBFIM)
+          raise RBFI
+        if (AUTORCVR)
+          discard bad packet
+        else
+          inc MPC instead of receiving packets
+        */
+        status |= DESC_FO | DESC_BF;
+        mBbaMem[BBA_IR] |= mBbaMem[BBA_IMR] & INT_RBF;
+        break;
+      }
     }
   }
 
   // Align up to next page
   if ((mRecvBufferLength + 4) % 256)
-    inc_rwp();
+    current_rwp = current_rwp == page_ptr(BBA_RHBP) ? page_ptr(BBA_BP) : ++current_rwp;
 
 #ifdef BBA_TRACK_PAGE_PTRS
   INFO_LOG_FMT(SP1, "{:x} {:x} {:x} {:x}", page_ptr(BBA_BP), page_ptr(BBA_RRP), page_ptr(BBA_RWP),
@@ -602,7 +618,9 @@ bool CEXIETHERNET::RecvHandlePacket()
     }
   }
 
-  descriptor->set(*(u16*)&mBbaMem[BBA_RWP], 4 + mRecvBufferLength, status);
+  descriptor->set(current_rwp, 4 + mRecvBufferLength, status);
+
+  set_rwp(current_rwp);
 
   mBbaMem[BBA_LRPS] = status;
 

diff --git a/Source/Core/Core/HW/EXI/EXI_DeviceEthernet.h b/Source/Core/Core/HW/EXI/EXI_DeviceEthernet.h
@@ -13,7 +13,10 @@
 
 #include <SFML/Network.hpp>
 
+#include <mutex>
 #include "Common/Flag.h"
+#include "Common/Network.h"
+#include "Core/HW/EXI/BBA/BuiltIn.h"
 #include "Core/HW/EXI/EXI_Device.h"
 
 class PointerWrap;
@@ -204,6 +207,7 @@ enum class BBADeviceType
 #if defined(__APPLE__)
   TAPSERVER,
 #endif
+  BuiltIn,
 };
 
 class CEXIETHERNET : public IEXIDevice
@@ -289,7 +293,6 @@ class CEXIETHERNET : public IEXIDevice
     return ((u16)mBbaMem[index + 1] << 8) | mBbaMem[index];
   }
 
-  inline u8* ptr_from_page_ptr(int const index) const { return &mBbaMem[page_ptr(index) << 8]; }
   bool IsMXCommand(u32 const data);
   bool IsWriteCommand(u32 const data);
   const char* GetRegisterName() const;
@@ -299,9 +302,11 @@ class CEXIETHERNET : public IEXIDevice
   void SendFromDirectFIFO();
   void SendFromPacketBuffer();
   void SendComplete();
+  void SendCompleteBack();
   u8 HashIndex(const u8* dest_eth_addr);
   bool RecvMACFilter();
   void inc_rwp();
+  void set_rwp(u16 value);
   bool RecvHandlePacket();
 
   std::unique_ptr<u8[]> mBbaMem;
@@ -413,6 +418,54 @@ class CEXIETHERNET : public IEXIDevice
 #endif
   };
 
+  class BuiltInBBAInterface : public NetworkInterface
+  {
+  public:
+    BuiltInBBAInterface(CEXIETHERNET* eth_ref, std::string dns_ip, std::string local_ip)
+        : NetworkInterface(eth_ref), m_dns_ip(std::move(dns_ip)), m_local_ip(std::move(local_ip))
+    {
+    }
+    bool Activate() override;
+    void Deactivate() override;
+    bool IsActivated() override;
+    bool SendFrame(const u8* frame, u32 size) override;
+    bool RecvInit() override;
+    void RecvStart() override;
+    void RecvStop() override;
+
+  private:
+    std::string m_mac_id;
+    std::string m_dns_ip;
+    bool m_active = false;
+    u16 m_ip_frame_id = 0;
+    u8 m_queue_read = 0;
+    u8 m_queue_write = 0;
+    std::array<std::vector<u8>, 16> m_queue_data;
+    std::mutex m_mtx;
+    std::string m_local_ip;
+    u32 m_current_ip = 0;
+    u32 m_router_ip = 0;
+#if defined(WIN32) || defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) ||          \
+    defined(__OpenBSD__) || defined(__NetBSD__) || defined(__HAIKU__)
+    std::array<StackRef, 10> network_ref{};  // max 10 at same time, i think most gc game had a
+                                             // limit of 8 in the gc framework
+    std::thread m_read_thread;
+    Common::Flag m_read_enabled;
+    Common::Flag m_read_thread_shutdown;
+    Common::MACAddress m_fake_mac{};
+    static void ReadThreadHandler(BuiltInBBAInterface* self);
+#endif
+    void WriteToQueue(const std::vector<u8>& data);
+    StackRef* GetAvailableSlot(u16 port);
+    StackRef* GetTCPSlot(u16 src_port, u16 dst_port, u32 ip);
+
+    void HandleARP(const Common::ARPPacket& packet);
+    void HandleDHCP(const Common::UDPPacket& packet);
+    void HandleTCPFrame(const Common::TCPPacket& packet);
+    void InitUDPPort(u16 port);
+    void HandleUDPFrame(const Common::UDPPacket& packet);
+  };
+
   std::unique_ptr<NetworkInterface> m_network_interface;
 
   std::unique_ptr<u8[]> mRecvBuffer;

diff --git a/Source/Core/DolphinLib.props b/Source/Core/DolphinLib.props
@@ -254,6 +254,7 @@
     <ClInclude Include="Core\HW\DVD\DVDMath.h" />
     <ClInclude Include="Core\HW\DVD\DVDThread.h" />
     <ClInclude Include="Core\HW\DVD\FileMonitor.h" />
+    <ClInclude Include="Core\HW\EXI\BBA\BuiltIn.h" />
     <ClInclude Include="Core\HW\EXI\BBA\TAP_Win32.h" />
     <ClInclude Include="Core\HW\EXI\EXI_Channel.h" />
     <ClInclude Include="Core\HW\EXI\EXI_Device.h" />
@@ -869,6 +870,7 @@
     <ClCompile Include="Core\HW\DVD\DVDMath.cpp" />
     <ClCompile Include="Core\HW\DVD\DVDThread.cpp" />
     <ClCompile Include="Core\HW\DVD\FileMonitor.cpp" />
+    <ClCompile Include="Core\HW\EXI\BBA\BuiltIn.cpp" />
     <ClCompile Include="Core\HW\EXI\BBA\TAP_Win32.cpp" />
     <ClCompile Include="Core\HW\EXI\BBA\XLINK_KAI_BBA.cpp" />
     <ClCompile Include="Core\HW\EXI\EXI_Channel.cpp" />

diff --git a/Source/Core/DolphinQt/Settings/BroadbandAdapterSettingsDialog.cpp b/Source/Core/DolphinQt/Settings/BroadbandAdapterSettingsDialog.cpp
@@ -48,6 +48,15 @@ void BroadbandAdapterSettingsDialog::InitControls()
     window_title = tr("Broadband Adapter MAC Address");
     break;
 
+  case Type::BuiltIn:
+    address_label = new QLabel(tr("Enter the DNS server to use:"));
+    address_placeholder = QStringLiteral("8.8.8.8");
+    current_address = QString::fromStdString(Config::Get(Config::MAIN_BBA_BUILTIN_DNS));
+    description = new QLabel(tr("Use 8.8.8.8 for normal DNS, else enter your custom one"));
+
+    window_title = tr("Broadband Adapter DNS setting");
+    break;
+
   case Type::XLinkKai:
     address_label = new QLabel(tr("Enter IP address of device running the XLink Kai Client:"));
     address_placeholder = QString::fromStdString("127.0.0.1");
@@ -103,6 +112,9 @@ void BroadbandAdapterSettingsDialog::SaveAddress()
     Config::SetBaseOrCurrent(Config::MAIN_BBA_MAC, bba_new_address);
     break;
 
+  case Type::BuiltIn:
+    Config::SetBaseOrCurrent(Config::MAIN_BBA_BUILTIN_DNS, bba_new_address);
+    break;
   case Type::XLinkKai:
     Config::SetBaseOrCurrent(Config::MAIN_BBA_XLINK_IP, bba_new_address);
     break;

diff --git a/Source/Core/DolphinQt/Settings/BroadbandAdapterSettingsDialog.h b/Source/Core/DolphinQt/Settings/BroadbandAdapterSettingsDialog.h
@@ -15,6 +15,7 @@ class BroadbandAdapterSettingsDialog final : public QDialog
   {
     Ethernet,
     XLinkKai,
+    BuiltIn
   };
 
   explicit BroadbandAdapterSettingsDialog(QWidget* target, Type bba_type);

diff --git a/Source/Core/DolphinQt/Settings/GameCubePane.cpp b/Source/Core/DolphinQt/Settings/GameCubePane.cpp
@@ -120,6 +120,7 @@ void GameCubePane::CreateWidgets()
 #ifdef __APPLE__
            EXIDeviceType::EthernetTapServer,
 #endif
+           EXIDeviceType::EthernetBuiltIn,
        })
   {
     m_slot_combos[ExpansionInterface::Slot::SP1]->addItem(tr(fmt::format("{:n}", device).c_str()),
@@ -259,7 +260,8 @@ void GameCubePane::UpdateButton(ExpansionInterface::Slot slot)
     break;
   case ExpansionInterface::Slot::SP1:
     has_config = (device == ExpansionInterface::EXIDeviceType::Ethernet ||
-                  device == ExpansionInterface::EXIDeviceType::EthernetXLink);
+                  device == ExpansionInterface::EXIDeviceType::EthernetXLink ||
+                  device == ExpansionInterface::EXIDeviceType::EthernetBuiltIn);
     break;
   }
 
@@ -293,6 +295,11 @@ void GameCubePane::OnConfigPressed(ExpansionInterface::Slot slot)
     BroadbandAdapterSettingsDialog(this, BroadbandAdapterSettingsDialog::Type::XLinkKai).exec();
     return;
   }
+  case ExpansionInterface::EXIDeviceType::EthernetBuiltIn:
+  {
+    BroadbandAdapterSettingsDialog(this, BroadbandAdapterSettingsDialog::Type::BuiltIn).exec();
+    return;
+  }
   default:
     PanicAlertFmt("Unknown settings pressed for {}", device);
     return;
-Original file line number
+Diff line change
@@ Expand Up / @@ -15,6 +15,7 @@ class BroadbandAdapterSettingsDialog final : public QDialog @@
       {
         Ethernet,
         XLinkKai,
+        BuiltIn
       };
       explicit BroadbandAdapterSettingsDialog(QWidget* target, Type bba_type);
@@ Expand Down @@