BBA/BuiltIn: Add an ARP table

Source/Core/Core/HW/EXI/BBA/BuiltIn.cpp

@@ -174,6 +174,8 @@ void CEXIETHERNET::BuiltInBBAInterface::Deactivate()
     ref.ip = 0;
   }
 
+  m_arp_table.clear();
+
   // Wait for read thread to exit.
   if (m_read_thread.joinable())
     m_read_thread.join();
@@ -206,7 +208,8 @@ void CEXIETHERNET::BuiltInBBAInterface::HandleARP(const Common::ARPPacket& packe
   }
   else
   {
-    response.arp_header = Common::ARPHeader(arpdata.target_ip, m_fake_mac, m_current_ip, bba_mac);
+    response.arp_header = Common::ARPHeader(arpdata.target_ip, ResolveAddress(arpdata.target_ip),
+                                            m_current_ip, bba_mac);
   }
 
   WriteToQueue(response.Build());
@@ -488,6 +491,21 @@ void CEXIETHERNET::BuiltInBBAInterface::HandleUDPFrame(const Common::UDPPacket&
   ref->udp_socket.send(data.data(), data.size(), target, ntohs(udp_header.destination_port));
 }
 
+const Common::MACAddress& CEXIETHERNET::BuiltInBBAInterface::ResolveAddress(u32 inet_ip)
+{
+  auto it = m_arp_table.lower_bound(inet_ip);
+  if (it != m_arp_table.end() && it->first == inet_ip)
+  {
+    return it->second;
+  }
+  else
+  {
+    return m_arp_table
+        .emplace_hint(it, inet_ip, Common::GenerateMacAddress(Common::MACConsumer::BBA))
+        ->second;
+  }
+}
+
 bool CEXIETHERNET::BuiltInBBAInterface::SendFrame(const u8* frame, u32 size)
 {
   std::lock_guard<std::mutex> lock(m_mtx);

Source/Core/Core/HW/EXI/EXI_DeviceEthernet.h

@@ -4,6 +4,8 @@
 #pragma once
 
 #include <atomic>
+#include <map>
+#include <mutex>
 #include <thread>
 #include <vector>
 
@@ -13,7 +15,6 @@
 
 #include <SFML/Network.hpp>
 
-#include <mutex>
 #include "Common/Flag.h"
 #include "Common/Network.h"
 #include "Core/HW/EXI/BBA/BuiltIn.h"
@@ -445,6 +446,7 @@ private:
     std::string m_local_ip;
     u32 m_current_ip = 0;
     u32 m_router_ip = 0;
+    std::map<u32, Common::MACAddress> m_arp_table;
 #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
@@ -464,6 +466,7 @@ private:
     void HandleTCPFrame(const Common::TCPPacket& packet);
     void InitUDPPort(u16 port);
     void HandleUDPFrame(const Common::UDPPacket& packet);
+    const Common::MACAddress& ResolveAddress(u32 inet_ip);
   };
 
   std::unique_ptr<NetworkInterface> m_network_interface;