engine: server: pregenerate CRC table and testpacket data

engine/server/server.h

@@ -378,6 +378,13 @@ typedef struct
 	entity_state_t	*static_entities;		// [MAX_STATIC_ENTITIES];
 
 	challenge_t	challenges[MAX_CHALLENGES];	// to prevent invalid IPs from connecting
+
+	sizebuf_t testpacket;         // pregenerataed testpacket, only needs CRC32 patching
+	byte      *testpacket_buf;    // check for NULL if testpacket is available
+	byte      *testpacket_crcpos; // pointer to write pregenerated crc (unaligned!!!)
+	uint32_t  *testpacket_crcs;   // checksums lookup table
+	int       testpacket_filepos; // file position (need to calculate lookup table pos)
+	int       testpacket_filelen; // file and lookup table length
 } server_static_t;
 
 //=============================================================================

engine/server/sv_client.c

@@ -832,14 +832,10 @@ SV_TestBandWidth
 */
 void SV_TestBandWidth( netadr_t from )
 {
-	int	version = Q_atoi( Cmd_Argv( 1 ));
-	int	packetsize = Q_atoi( Cmd_Argv( 2 ));
-	byte	send_buf[FRAGMENT_MAX_SIZE];
-	dword	crcValue = 0;
-	byte	*filepos;
-	int	crcpos;
-	file_t	*test;
-	sizebuf_t	send;
+	const int version = Q_atoi( Cmd_Argv( 1 ));
+	const int packetsize = Q_atoi( Cmd_Argv( 2 ));
+	uint32_t crc;
+	int ofs;
 
 	// don't waste time of protocol mismatched
 	if( version != PROTOCOL_VERSION )
@@ -848,32 +844,29 @@ void SV_TestBandWidth( netadr_t from )
 		return;
 	}
 
-	test = FS_Open( "gfx.wad", "rb", false );
-
-	if( FS_FileLength( test ) < sizeof( send_buf ))
+	// quickly reject invalid packets
+	if( !svs.testpacket_buf ||
+		( packetsize <= FRAGMENT_MIN_SIZE ) ||
+		( packetsize > FRAGMENT_MAX_SIZE ))
 	{
 		// skip the test and just get challenge
 		SV_GetChallenge( from );
 		return;
 	}
 
-	// write the packet header
-	MSG_Init( &send, "BandWidthPacket", send_buf, sizeof( send_buf ));
-	MSG_WriteLong( &send, -1 );	// -1 sequence means out of band
-	MSG_WriteString( &send, "testpacket" );
-	crcpos = MSG_GetNumBytesWritten( &send );
-	MSG_WriteLong( &send, 0 ); // reserve space for crc
-	filepos = send.pData + MSG_GetNumBytesWritten( &send );
-	packetsize = packetsize - MSG_GetNumBytesWritten( &send ); // adjust the packet size
-	FS_Read( test, filepos, packetsize );
-	FS_Close( test );
+	// don't go out of bounds
+	ofs = packetsize - svs.testpacket_filepos - 1;
+	if(( ofs < 0 ) || ( ofs > svs.testpacket_filelen ))
+	{
+		SV_GetChallenge( from );
+		return;
+	}
 
-	CRC32_ProcessBuffer( &crcValue, filepos, packetsize );	// calc CRC
-	MSG_SeekToBit( &send, packetsize << 3, SEEK_CUR );
-	*(uint *)&send.pData[crcpos] = crcValue;
+	crc = svs.testpacket_crcs[ofs];
+	memcpy( svs.testpacket_crcpos, &crc, sizeof( crc ));
 
 	// send the datagram
-	NET_SendPacket( NS_SERVER, MSG_GetNumBytesWritten( &send ), MSG_GetData( &send ), from );
+	NET_SendPacket( NS_SERVER, packetsize, MSG_GetData( &svs.testpacket ), from );
 }
 
 /*

engine/server/sv_init.c

@@ -882,6 +882,77 @@ static qboolean CRC32_MapFile( dword *crcvalue, const char *filename, qboolean m
 	return 1;
 }
 
+/*
+================
+SV_GenerateTestPacket
+================
+*/
+static void SV_GenerateTestPacket( void )
+{
+	const int maxsize = FRAGMENT_MAX_SIZE;
+	uint32_t crc;
+	file_t *file;
+	byte *filepos;
+	int i, filesize;
+
+	// testpacket already generated once, exit
+	// testpacket and lookup table takes ~300k of memory
+	// disable for low memory mode
+	if( svs.testpacket_buf || XASH_LOW_MEMORY >= 0 )
+		return;
+
+	// don't need in singleplayer with full client
+	if( svs.maxclients <= 1 && !Host_IsDedicated( ))
+		return;
+
+	file = FS_Open( "gfx.wad", "rb", false );
+	if( FS_FileLength( file ) < maxsize )
+	{
+		FS_Close( file );
+		return;
+	}
+
+	svs.testpacket_buf = Mem_Malloc( host.mempool, sizeof( *svs.testpacket_buf ) * maxsize );
+
+	// write packet base data
+	MSG_Init( &svs.testpacket, "BandWidthTest", svs.testpacket_buf, maxsize );
+	MSG_WriteLong( &svs.testpacket, -1 );
+	MSG_WriteString( &svs.testpacket, "testpacket" );
+	svs.testpacket_crcpos = svs.testpacket.pData + MSG_GetNumBytesWritten( &svs.testpacket );
+	MSG_WriteDword( &svs.testpacket, 0 ); // to be changed by crc
+
+	// time to read our file
+	svs.testpacket_filepos = MSG_GetNumBytesWritten( &svs.testpacket );
+	svs.testpacket_filelen = maxsize - svs.testpacket_filepos;
+
+	filepos = svs.testpacket.pData + svs.testpacket_filepos;
+	FS_Read( file, filepos, svs.testpacket_filelen );
+	FS_Close( file );
+
+	// now generate checksums lookup table
+	svs.testpacket_crcs = Mem_Malloc( host.mempool, sizeof( *svs.testpacket_crcs ) * svs.testpacket_filelen );
+	crc = 0; // intentional omit of CRC32_Init because of the client
+
+	// TODO: shrink to minimum!
+	for( i = 0; i < svs.testpacket_filelen; i++ )
+	{
+		uint32_t crc2;
+
+		CRC32_ProcessByte( &crc, filepos[i] );
+		svs.testpacket_crcs[i] = crc;
+#if 0
+		// test
+		crc2 = 0;
+		CRC32_ProcessBuffer( &crc2, filepos, i + 1 );
+		if( svs.testpacket_crcs[i] != crc2 )
+		{
+			Con_Printf( "%d: 0x%x != 0x%x\n", i, svs.testpacket_crcs[i], crc2 );
+			svs.testpacket_crcs[i] = crc = crc2;
+		}
+#endif
+	}
+}
+
 /*
 ================
 SV_SpawnServer
@@ -1026,6 +1097,9 @@ qboolean SV_SpawnServer( const char *mapname, const char *startspot, qboolean ba
 	// clear physics interaction links
 	SV_ClearWorld();
 
+	// pregenerate test packet
+	SV_GenerateTestPacket();
+
 	return true;
 }