Add packet capture for multiplayer traffic

src/frontend/qt_sdl/Config.cpp

@@ -309,6 +309,8 @@ LegacyEntry LegacyFile[] =
     {"GdbARM7BreakOnStartup", 1, "Gdb.ARM7.BreakOnStartup", true},
     {"GdbARM9BreakOnStartup", 1, "Gdb.ARM9.BreakOnStartup", true},
 #endif
+    {"PcapEnabled", 1, "Pcap.Enabled", false},
+    {"PcapPath", 2, "Pcap.Path", false},
 
     {"Camera0_InputType", 0, "DSi.Camera0.InputType", false},
     {"Camera0_ImagePath", 2, "DSi.Camera0.ImagePath", false},

src/frontend/qt_sdl/EmuInstance.cpp

@@ -39,6 +39,7 @@
 #include "Config.h"
 #include "Platform.h"
 #include "Net.h"
+#include "Net_PCap.h"
 #include "MPInterface.h"
 
 #include "NDS.h"
@@ -63,12 +64,14 @@
 
 const string kWifiSettingsPath = "wfcsettings.bin";
 extern Net net;
+extern std::optional<melonDS::LibPCap> pcap;
 
 
 EmuInstance::EmuInstance(int inst) : deleting(false),
     instanceID(inst),
     globalCfg(Config::GetGlobalTable()),
-    localCfg(Config::GetLocalTable(inst))
+    localCfg(Config::GetLocalTable(inst)),
+    packetCapture(nullptr), packetCaptureDumper(nullptr)
 {
     consoleType = globalCfg.GetInt("Emu.ConsoleType");
 
@@ -130,6 +133,7 @@
 
     audioDeInit();
     inputDeInit();
+    stopPacketCapture();
 }
 
 
@@ -1336,6 +1340,7 @@
     nds->Reset();
     setBatteryLevels();
     setDateTime();
+    startPacketCapture();
     return true;
 }
 
@@ -1805,6 +1810,7 @@
     cartType = 0;
     ndsSave = std::make_unique<SaveManager>(savname);
     loadCheats();
+    startPacketCapture();
 
     return true; // success
 }
@@ -1821,6 +1827,8 @@
     baseROMDir = "";
     baseROMName = "";
     baseAssetName = "";
+
+    stopPacketCapture();
 }
 
 bool EmuInstance::cartInserted()
@@ -2045,3 +2053,59 @@
             animatedSequenceRef.push_back(i);
     }
 }
+
+void EmuInstance::startPacketCapture()
+{
+    if (packetCapture != nullptr || packetCaptureDumper != nullptr)
+        stopPacketCapture();
+
+    if (!globalCfg.GetBool("Pcap.Enabled"))
+        return;
+
+    if (!pcap)
+        pcap = melonDS::LibPCap::New();
+
+    std::string pcapPath = getAssetPath(false, globalCfg.GetString("Pcap.Path"), instanceFileSuffix() + ".pcap");
+    Log(LogLevel::Debug, "Starting packet capture: %s\n", pcapPath.c_str());
+
+    packetCapture = pcap->open_dead(DLT_IEEE802_11, 1024);
+    packetCaptureDumper = pcap->dump_open(packetCapture, pcapPath.c_str());
+    if (packetCaptureDumper == nullptr)
+    {
+        Log(LogLevel::Error, "Failed to open pcap file: %s\n", pcap->geterr(packetCapture));
+        return stopPacketCapture();
+    }
+}
+
+void EmuInstance::stopPacketCapture()
+{
+    if (!pcap)
+        pcap = melonDS::LibPCap::New();
+
+    if (packetCaptureDumper != nullptr)
+    {
+        pcap->dump_flush(packetCaptureDumper);
+        pcap->dump_close(packetCaptureDumper);
+        packetCaptureDumper = nullptr;
+    }
+
+    if (packetCapture != nullptr)
+    {
+        pcap->close(packetCapture);
+        packetCapture = nullptr;
+    }
+}
+
+void EmuInstance::capturePacket(u8* data, int len)
+{
+    if (!pcap || packetCaptureDumper == nullptr || len < 12)
+        return;
+
+    // data contains a 12-byte hardware header, and a trailing 4-byte checksum.
+    // https://problemkaputt.de/gbatek.htm#dswifihardwareheaders
+    pcap_pkthdr hdr = {};
+    gettimeofday(&hdr.ts, NULL);
+    hdr.caplen = len - 12 - 4;
+    hdr.len = len - 12 - 4;
+    pcap->dump((unsigned char*)packetCaptureDumper, &hdr, data + 12);
+}

src/frontend/qt_sdl/EmuInstance.h

@@ -20,7 +20,9 @@
 #define EMUINSTANCE_H
 
 #include <SDL2/SDL.h>
+#include <pcap/pcap.h>
 
+#include "types.h"
 #include "NDS.h"
 #include "EmuThread.h"
 #include "Window.h"
@@ -136,6 +138,8 @@ class EmuInstance
     int getJoystickID() { return joystickID; }
     SDL_Joystick* getJoystick() { return joystick; }
 
+    void capturePacket(melonDS::u8* data, int len);
+
 private:
     static int lastSep(const std::string& path);
     std::string getAssetPath(bool gba, const std::string& configpath, const std::string& ext, const std::string& file);
@@ -219,6 +223,11 @@ class EmuInstance
     bool hotkeyPressed(int id)  { return hotkeyPress   & (1<<id); }
     bool hotkeyReleased(int id) { return hotkeyRelease & (1<<id); }
 
+    void startPacketCapture();
+    void stopPacketCapture();
+    pcap_t* packetCapture;
+    pcap_dumper_t* packetCaptureDumper;
+
     bool deleting;
 
     int instanceID;

src/frontend/qt_sdl/EmuSettingsDialog.cpp

@@ -18,6 +18,7 @@
 
 #include <QFileDialog>
 #include <QMessageBox>
+#include <QTemporaryFile>
 
 #include "types.h"
 #include "Platform.h"
@@ -107,9 +108,12 @@ EmuSettingsDialog::EmuSettingsDialog(QWidget* parent) : QDialog(parent), ui(new
     ui->cbGdbBOSA7->setDisabled(true);
     ui->cbGdbBOSA9->setDisabled(true);
 #endif
+    ui->cbPcapEnabled->setChecked(cfg.GetBool("Pcap.Enabled"));
+    ui->txtPcapPath->setText(cfg.GetQString("Pcap.Path"));
 
     on_chkEnableJIT_toggled();
     on_cbGdbEnabled_toggled();
+    on_cbPcapEnabled_toggled();
     on_chkExternalBIOS_toggled();
 
     const int imgsizes[] = {256, 512, 1024, 2048, 4096, 0};
@@ -292,6 +296,8 @@ void EmuSettingsDialog::done(int r)
             instcfg.SetBool("Gdb.ARM7.BreakOnStartup", ui->cbGdbBOSA7->isChecked());
             instcfg.SetBool("Gdb.ARM9.BreakOnStartup", ui->cbGdbBOSA9->isChecked());
 #endif
+            cfg.SetBool("Pcap.Enabled", ui->cbPcapEnabled->isChecked());
+            cfg.SetQString("Pcap.Path", ui->txtPcapPath->text());
 
             cfg.SetInt("Emu.ConsoleType", ui->cbxConsoleType->currentIndex());
             cfg.SetBool("Emu.DirectBoot", ui->chkDirectBoot->isChecked());
@@ -565,6 +571,30 @@ void EmuSettingsDialog::on_cbGdbEnabled_toggled()
     ui->cbGdbBOSA9->setDisabled(disabled);
 }
 
+void EmuSettingsDialog::on_cbPcapEnabled_toggled()
+{
+    bool disabled = !ui->cbPcapEnabled->isChecked();
+    ui->txtPcapPath->setDisabled(disabled);
+    ui->btnPcapBrowse->setDisabled(disabled);
+}
+
+void EmuSettingsDialog::on_btnPcapBrowse_clicked()
+{
+    QString dir = QFileDialog::getExistingDirectory(this,
+                                                     "Select packet captures path...",
+                                                     lastBIOSFolder);
+
+    if (dir.isEmpty()) return;
+
+    if (!QTemporaryFile(dir).open())
+    {
+        QMessageBox::critical(this, "melonDS", "Unable to write to packet captures directory.\nPlease check file/folder write permissions.");
+        return;
+    }
+
+    ui->txtPcapPath->setText(dir);
+}
+
 void EmuSettingsDialog::on_chkExternalBIOS_toggled()
 {
     bool disabled = !ui->chkExternalBIOS->isChecked();

src/frontend/qt_sdl/EmuSettingsDialog.h

@@ -80,6 +80,8 @@ private slots:
     void on_chkExternalBIOS_toggled();
 
     void on_cbGdbEnabled_toggled();
+    void on_cbPcapEnabled_toggled();
+    void on_btnPcapBrowse_clicked();
 
 private:
     void verifyFirmware();