Client Synchronization: Transmit new packets to help mkw-server synchronize clients

payload/game/net/MiscPacketHandler.S

@@ -0,0 +1,8 @@
+#include <Common.S>
+
+PATCH_REPLACE_START(MiscPacketHandler_updateAsRacer, 0x4c)
+    // Original instruction sets RaceManager::m_canCountdownStart to true
+    // Nopped since mkw-server now handles this. Ideally, we'd rewrite in C++,
+    // but this function is complex and difficult to functionally match.
+    nop
+PATCH_REPLACE_END(MiscPacketHandler_updateAsRacer, 0x4c)

payload/game/net/MiscPacketHandler.cc

@@ -1,3 +1,43 @@
 #include "MiscPacketHandler.hh"
 
-namespace Net {} // namespace Net
+#include <sp/net/mkw_server/MKWServer.hh>
+
+namespace Net {
+
+void MiscPacketHandler::setAckReady() {
+    m_readyAcked = true;
+}
+
+void MiscPacketHandler::init() {
+    REPLACED(init)();
+
+    m_timeUntilReady = 240;
+    m_readyAcked = false;
+}
+
+void MiscPacketHandler::updateReadyTimer() {
+    if (m_timeUntilReady > 0) {
+        m_timeUntilReady--;
+    } else {
+        MKWServer::sendReadyPacket();
+        // Until we get an ack, try to send again in 5 frames.
+        m_timeUntilReady = 5;
+    }
+}
+
+void MiscPacketHandler::updateAsRacer() {
+    if (!m_readyAcked) {
+        updateReadyTimer();
+    }
+
+    REPLACED(updateAsRacer)();
+}
+
+} // namespace Net
+
+void MiscPacketHandler_setAckReady() {
+    // Need to check for nullptr in case if an ack is unexpectedly sent outside of race scene.
+    if (auto *miscPacketHandler = Net::MiscPacketHandler::Instance()) {
+        miscPacketHandler->setAckReady();
+    }
+}

payload/game/net/MiscPacketHandler.h

@@ -0,0 +1,4 @@
+#pragma once
+
+// Defined here to expose to C code.
+void MiscPacketHandler_setAckReady();

payload/game/net/MiscPacketHandler.hh

@@ -3,10 +3,7 @@
 #include <Common.hh>
 
 #include "game/net/records/Event.hh"
-#include "game/net/records/RH1.hh"
-#include "game/net/records/RH2.hh"
 #include "game/net/records/RaceData.hh"
-#include "game/net/records/Select.hh"
 
 extern "C" {
 #include <revolution/os.h>
@@ -16,16 +13,36 @@ namespace Net {
 
 // MiscPacketHandler runs exclusively in race scene. It handles everything netcode during a race.
 class MiscPacketHandler {
+public:
+    // Added. sets m_readyAcked
+    void setAckReady();
+
+    static MiscPacketHandler *Instance() {
+        return s_instance;
+    }
+
 private:
+    // 0x806532d8
+    // Called exactly once at the start of a race to initialize members.
+    // Hooked to initialize mkw-server members.
+    REPLACE void init();
+    void REPLACED(init)();
+
     // 0x80653728
     // The main loop. Runs when m_isPrepared is true. This runs in online races
     // but also rival ghost races to update friend status
     void update();
 
+    // Added.
+    // Updates m_timeUntilReady. Calls MKWServer::sendReadyPacket() when m_timeUntilReady is 0.
+    void updateReadyTimer();
+
     // 0x80654150
     // Runs only when racing. Synchronizes race start, imports, exports, and processes records
     // specifically as a racer.
-    void updateAsRacer();
+    // Hooked to handle mkw-server client synchronization.
+    REPLACE void updateAsRacer();
+    void REPLACED(updateAsRacer)();
 
     // 0x80654d08
     // Exports relevant records as a racer (as opposed to a spectator)
@@ -55,8 +72,14 @@ private:
     // Schecules a disconnect. Set if we're out of sync with other players.
     bool m_scheduleDisconnect;
 
-    // Padding
-    u8 _002[0x004 - 0x002];
+    // Added, was padding. Time (in frames) until we're ready to start the countdown.
+    // This is initialized to 240 frames (4 seconds) at the start of each race to account
+    // for the intro camera pan, and decremented each frame. When the timer is 0, send
+    // a ready packet to mkw-server.
+    u8 m_timeUntilReady;
+
+    // Added, was padding. Set when mkw-server has acked our ready packet.
+    bool m_readyAcked;
 
     // Bitfield set by RH1.raceSeed
     u32 m_aidsLoadedIntoRace;
@@ -94,3 +117,7 @@ private:
 static_assert(sizeof(MiscPacketHandler) == 0x1c8);
 
 } // namespace Net
+
+// Exposed to C b/c UDP packets are handled in a C function (DWCi_GT2UnrecognizedMessageCallback).
+// TODO: Rewrite in C++.
+extern "C" void MiscPacketHandler_setAckReady();

payload/game/system/RaceManager.cc

@@ -60,3 +60,9 @@ void RaceManager::Player::calc() {
 }
 
 } // namespace System
+
+void RaceManager_startCountdown() {
+    if (auto *raceManager = System::RaceManager::Instance()) {
+        raceManager->startCountdown();
+    }
+}

payload/game/system/RaceManager.h

@@ -0,0 +1,4 @@
+#pragma once
+
+// Defined here to expose to C code.
+void RaceManager_startCountdown();

payload/game/system/RaceManager.hh

@@ -46,6 +46,10 @@ public:
         return m_countdownTimer;
     }
 
+    void startCountdown() {
+        m_canCountdownStart = true;
+    }
+
     static RaceManager *Instance() {
         return s_instance;
     }
@@ -78,3 +82,8 @@ private:
 static_assert(sizeof(RaceManager) == 0x4c);
 
 } // namespace System
+
+// Exposed to C b/c UDP packets are handled in a C function (DWCi_GT2UnrecognizedMessageCallback).
+// And we need to be able to start the countdown from UDP packet handling.
+// TODO: Rewrite in C++.
+extern "C" void RaceManager_startCountdown();

payload/revolution/dwc/DWCTransport.c

@@ -1,7 +1,29 @@
 #include "DWCTransport.h"
 
+#include <game/net/MiscPacketHandler.h>
+#include <game/system/RaceManager.h>
+
 #include <sp/net/mkw_server/MKWServer.h>
 
+#include <string.h>
+
+#define START_MESSAGE "ST"
+#define PING_MESSAGE "PI"
+#define READY_ACK_MESSAGE "RA"
+
+bool isReadyAckPacket(const u8 *message, s32 len) {
+    return len == 2 &&
+            strncmp((const char *)message, READY_ACK_MESSAGE, strlen(READY_ACK_MESSAGE)) == 0;
+}
+
+bool isStartPacket(const u8 *message, s32 len) {
+    return len == 2 && strncmp((const char *)message, START_MESSAGE, strlen(START_MESSAGE)) == 0;
+}
+
+bool isPingPacket(const u8 *message, s32 len) {
+    return len == 2 && strncmp((const char *)message, PING_MESSAGE, strlen(PING_MESSAGE)) == 0;
+}
+
 BOOL DWCi_GT2UnrecognizedMessageCallback(GT2Socket socket, u32 ip, u16 port, const u8 *message,
         s32 len) {
     if (message == NULL || len == 0) {
@@ -14,6 +36,23 @@ BOOL DWCi_GT2UnrecognizedMessageCallback(GT2Socket socket, u32 ip, u16 port, con
         return GT2True;
     }
 
+    if (isReadyAckPacket(message, len)) {
+        SP_LOG("Received ready ACK packet from mkw-server!");
+        MiscPacketHandler_setAckReady();
+        return GT2True;
+    }
+
+    if (isStartPacket(message, len)) {
+        SP_LOG("Received Start packet from mkw-server!");
+        RaceManager_startCountdown();
+        return GT2True;
+    }
+
+    if (isPingPacket(message, len)) {
+        sendPong();
+        return GT2True;
+    }
+
     MKWServerPacketType messageType = message[0];
     switch (messageType) {
     case MKW_SERVER_RACE_PACKET:

payload/sp/net/mkw_server/MKWServer.cc

@@ -53,14 +53,28 @@ bool hasMKWServerAddress() {
     return s_mkwServerAddr.addr.addr != 0 && s_mkwServerAddr.port != 0;
 }
 
+void sendReadyPacket() {
+    if (!hasMKWServerAddress()) {
+        SP_LOG("sendReady() can't send: Don't have mkw-server address!");
+        return;
+    }
+
+    u8 msg[2] = {0x52, 0x45}; // RE
+
+    bool result = SOSendTo(s_dwcMatch->qrec->hbsock, &msg, sizeof(msg), 0, &s_mkwServerAddr);
+    if (!result) {
+        SP_LOG("Failed to send Race packet to mkw-server! SOSendTo failed!");
+    }
+}
+
 bool trySendRacePacketToMKWServer(const void *data, u32 size) {
     if (!hasMKWServerAddress()) {
         return false;
     }
 
     bool result = SOSendTo(s_dwcMatch->qrec->hbsock, data, size, 0, &s_mkwServerAddr);
     if (!result) {
-        SP_LOG("Failed to send to MKW Server!");
+        SP_LOG("Failed to send Race packet to mkw-server!");
     }
     return result;
 }
@@ -94,6 +108,20 @@ bool handleSearchIdPacket(const u8 *packet, u32 size) {
     return true;
 }
 
+void sendPong() {
+    if (!hasMKWServerAddress()) {
+        SP_LOG("sendPong() can't send: Don't have mkw-server address!");
+        return;
+    }
+
+    u8 msg[2] = {0x50, 0x4F}; // PO
+
+    bool result = SOSendTo(s_dwcMatch->qrec->hbsock, &msg, sizeof(msg), 0, &s_mkwServerAddr);
+    if (!result) {
+        SP_LOG("Failed to send Pong packet to mkw-server! SOSendTo failed!");
+    }
+}
+
 bool sendMessageToQR2(const u8 *data, u32 size) {
     SOSockAddrIn qr2Addr;
     qr2Addr.len = sizeof(SOSockAddrIn);

payload/sp/net/mkw_server/MKWServer.h

@@ -6,4 +6,6 @@
 
 EXTERN_C bool verifySearchIdMagic(const u8 *packet, u32 size);
 
-EXTERN_C bool handleSearchIdPacket(const u8 *packet, u32 size);
+EXTERN_C bool handleSearchIdPacket(const u8 *packet, u32 size);
+
+EXTERN_C void sendPong();

payload/sp/net/mkw_server/MKWServer.hh

@@ -19,11 +19,15 @@ u64 getSearchId();
 
 bool hasMKWServerAddress();
 
+void sendReadyPacket();
+
 EXTERN_C bool trySendRacePacketToMKWServer(const void *data, u32 size);
 
 EXTERN_C bool verifySearchIdMagic(const u8 *packet, u32 size);
 
 EXTERN_C bool handleSearchIdPacket(const u8 *packet, u32 size);
 
+EXTERN_C void sendPong();
+
 bool sendMessageToQR2(const u8 *data, u32 size);
 } // namespace MKWServer

port.py

@@ -478,6 +478,7 @@ def port(self, address):
         Chunk(0x809c1988, 0x809c198c, 0x809bd378),
         Chunk(0x809c19a0, 0x809c19bc, 0x809bd180),
         Chunk(0x809c1e38, 0x809c1e3c, 0x809bd508),
+        Chunk(0x809c1f50, 0x809c1f54, 0x809bd790),
         Chunk(0x809c20e0, 0x809c20e4, 0x809bd920),
         Chunk(0x809c2108, 0x809c210c, 0x809bd958),
         Chunk(0x809c2118, 0x809c211c, 0x809bd940),
@@ -536,6 +537,7 @@ def port(self, address):
         Chunk(0x809c18f8, 0x809c18fc, 0x809c0958),
         Chunk(0x809c1988, 0x809c198c, 0x809c09e8),
         Chunk(0x809c19a0, 0x809c19bc, 0x809c0a00),
+        Chunk(0x809c1f50, 0x809c1f54, 0x809c0fb0),
         Chunk(0x809c20e0, 0x809c20e4, 0x809c1140),
         Chunk(0x809c2108, 0x809c210c, 0x809c1168),
         Chunk(0x809c2118, 0x809c211c, 0x809c1178),
@@ -635,6 +637,7 @@ def port(self, address):
         Chunk(0x809c1988, 0x809c198c, 0x809affc8),
         Chunk(0x809c19a0, 0x809c19bc, 0x809affe0),
         Chunk(0x809c1e38, 0x809c1e3c, 0x809b0478),
+        Chunk(0x809c1f50, 0x809c1f54, 0x809b0590),
         Chunk(0x809c20e0, 0x809c20e4, 0x809b0720),
         Chunk(0x809c2108, 0x809c210c, 0x809b0748),
         Chunk(0x809c2118, 0x809c211c, 0x809b0758),

symbols.txt

@@ -528,7 +528,9 @@
 0x8063e924 _ZN2UI24LayoutUIControlScaleFade5vf_28Ev
 0x80643168 onInit
 0x80649590 DCPageCalc
+0x806532d8 _ZN3Net17MiscPacketHandler4initEv
 0x80654038 _ZNK3Net17MiscPacketHandler16isEveryoneInRaceEv
+0x80654150 MiscPacketHandler_updateAsRacer
 0x80654150 _ZN3Net17MiscPacketHandler13updateAsRacerEv
 0x806554a0 _ZN3Net17MiscPacketHandler21processRecvRH1RecordsEv
 0x806554a0 MiscPacketHandler_handleLaggings
@@ -588,6 +590,7 @@
 0x809bd740 _ZN6System9RootScene10s_instanceE
 0x809c18f8 _ZN4Kart17KartObjectManager10s_instanceE
 0x809c1e38 _ZN2UI14SectionManager10s_instanceE
+0x809c1f50 _ZN3Net17MiscPacketHandler10s_instanceE
 0x809c20d8 _ZN3Net10NetManager10s_instanceE
 0x809c20e0 _ZN3Net11RoomHandler10s_instanceE
 0x809c2100 _ZN3Net13SelectHandler10s_instanceE