cs2-sendproxy/src/detour.cpp

#include "detour.h"

#include "common.h"
#include "gameconfig.h"
#include "overrides.h"
#include "playerslot.h"

extern CGameConfig* g_gameConfig;
extern bool g_armed;

using SendSnapshotFn = void (*)(void*, void*);
using PackEntitiesFn = void (*)(void*, void*, int, void*, void*, void*, void*);
using PackEntityFn = void (*)(void*, void*, int, void*, void*, void*, void*, void*, void*, void*);
static SendSnapshotFn g_sendSnapshot = nullptr;
static PackEntitiesFn g_packEntities = nullptr;
static PackEntityFn g_packEntity = nullptr;
static funchook_t* g_snapshotHook = nullptr;
static funchook_t* g_packHook = nullptr;
static funchook_t* g_packEntityHook = nullptr;
static uint64_t g_snapshotCalls = 0;
static uint64_t g_packCalls = 0;
static uint64_t g_packEntityCalls = 0;
static uint64_t g_packEntityGenericSpoofs = 0;
static uint64_t g_fullUpdateWrites = 0;
static int g_fullUpdateBudget = 0;
static thread_local CPlayerSlot g_currentRecipient(-1);
static thread_local CPlayerSlot g_lastSnapshotRecipient(-1);

static CPlayerSlot SlotFromClient(void* client)
{
	int offset = g_gameConfig ? g_gameConfig->GetOffset("CServerSideClient_Slot") : -1;
	if (offset < 0)
		return CPlayerSlot(-1);
	return *reinterpret_cast<CPlayerSlot*>(reinterpret_cast<uint8_t*>(client) + offset);
}

struct ScopedRecipient
{
	explicit ScopedRecipient(CPlayerSlot slot) : previous(g_currentRecipient)
	{
		g_currentRecipient = slot;
	}

	~ScopedRecipient()
	{
		g_currentRecipient = previous;
	}

	CPlayerSlot previous;
};

static void Detour_SendSnapshot(void* client, void* snapshot)
{
	++g_snapshotCalls;
	CPlayerSlot slot(client ? SlotFromClient(client) : CPlayerSlot(-1));
	g_lastSnapshotRecipient = slot;
	ScopedRecipient recipient(slot);
	if (client && g_fullUpdateBudget > 0)
	{
		int offset = g_gameConfig ? g_gameConfig->GetOffset("CServerSideClient_DeltaTick") : -1;
		if (offset >= 0)
		{
			*reinterpret_cast<int*>(reinterpret_cast<uint8_t*>(client) + offset) = -1;
			--g_fullUpdateBudget;
			++g_fullUpdateWrites;
		}
	}

	g_sendSnapshot(client, snapshot);
}

static void Detour_PackEntities(void* self, void* arg1, int arg2, void* arg3, void* arg4, void* arg5, void* arg6)
{
	++g_packCalls;
	CPlayerSlot recipient((arg2 >= 0 && arg2 < 64) ? arg2 : -1);
	ScopedRecipient scopedRecipient(recipient);
	g_packEntities(self, arg1, arg2, arg3, arg4, arg5, arg6);
}

static void Detour_PackEntity(void* self, void* arg1, int entityIndex, void* entityData, void* arg4, void* arg5, void* arg6, void* arg7, void* arg8, void* arg9)
{
	++g_packEntityCalls;

	if (!g_armed || !entityData || !g_overrides.HasPackedOverrides())
	{
		g_packEntity(self, arg1, entityIndex, entityData, arg4, arg5, arg6, arg7, arg8, arg9);
		return;
	}

	CPlayerSlot recipient = g_currentRecipient;
	if (recipient.Get() < 0 && g_lastSnapshotRecipient.Get() >= 0)
		recipient = g_lastSnapshotRecipient;
	auto applied = g_overrides.ApplyForPackedEntity(recipient, entityIndex, entityData);
	g_packEntityGenericSpoofs += applied.size();
	g_packEntity(self, arg1, entityIndex, entityData, arg4, arg5, arg6, arg7, arg8, arg9);
	g_overrides.Restore(applied);
}

static bool InitPackEntityDetour(CGameConfig* config)
{
	void* packEntityTarget = config->ResolveSignature("CNetworkGameServer_PackEntity");
	if (!packEntityTarget)
	{
		SPWarning("CNetworkGameServer_PackEntity signature missing; override hook disabled\n");
		return true;
	}

	g_packEntity = reinterpret_cast<PackEntityFn>(packEntityTarget);
	g_packEntityHook = funchook_create();
	if (!g_packEntityHook)
		return false;

	if (funchook_prepare(g_packEntityHook, reinterpret_cast<void**>(&g_packEntity), reinterpret_cast<void*>(Detour_PackEntity)) != 0)
		return false;
	if (funchook_install(g_packEntityHook, 0) != 0)
		return false;

	SPMessage("detoured CNetworkGameServer_PackEntity at %p\n", packEntityTarget);
	return true;
}

bool InitSnapshotDetour(CGameConfig* config)
{
	void* target = config->ResolveSignature("CServerSideClient_SendSnapshot");
	if (!target)
	{
		SPWarning("CServerSideClient_SendSnapshot signature missing; snapshot hook disabled\n");
		return true;
	}

	g_sendSnapshot = reinterpret_cast<SendSnapshotFn>(target);
	g_snapshotHook = funchook_create();
	if (!g_snapshotHook)
		return false;

	if (funchook_prepare(g_snapshotHook, reinterpret_cast<void**>(&g_sendSnapshot), reinterpret_cast<void*>(Detour_SendSnapshot)) != 0)
		return false;
	if (funchook_install(g_snapshotHook, 0) != 0)
		return false;

	SPMessage("detoured CServerSideClient_SendSnapshot at %p\n", target);

	void* packTarget = config->ResolveSignature("CNetworkGameServer_PackEntities_Normal");
	if (!packTarget)
	{
		SPWarning("CNetworkGameServer_PackEntities_Normal signature missing; pack counter hook disabled\n");
		return true;
	}

	g_packEntities = reinterpret_cast<PackEntitiesFn>(packTarget);
	g_packHook = funchook_create();
	if (!g_packHook)
		return false;

	if (funchook_prepare(g_packHook, reinterpret_cast<void**>(&g_packEntities), reinterpret_cast<void*>(Detour_PackEntities)) != 0)
		return false;
	if (funchook_install(g_packHook, 0) != 0)
		return false;

	SPMessage("detoured CNetworkGameServer_PackEntities_Normal at %p\n", packTarget);
	if (!InitPackEntityDetour(config))
		return false;
	return true;
}

void ShutdownSnapshotDetour()
{
	if (g_packEntityHook)
	{
		funchook_uninstall(g_packEntityHook, 0);
		funchook_destroy(g_packEntityHook);
		g_packEntityHook = nullptr;
	}
	if (g_packHook)
	{
		funchook_uninstall(g_packHook, 0);
		funchook_destroy(g_packHook);
		g_packHook = nullptr;
	}
	if (g_snapshotHook)
	{
		funchook_uninstall(g_snapshotHook, 0);
		funchook_destroy(g_snapshotHook);
		g_snapshotHook = nullptr;
	}
	g_sendSnapshot = nullptr;
	g_packEntities = nullptr;
	g_packEntity = nullptr;
}