DSR Server Communication

Authors: metal-crow

• SFSocketManager::Send
• SVFW::SFStreamManagerTCP::SendToServer
• SVFW::SFRPCManagerImpl::BuildClientTypeXRequestPacket
  • This is what encases the packet in layer 2 structure and encrypts it
  • Some async level between this and SendToServer
• RPCSystem::LoginPacket/CommonPacket
• QueueGeneralRequestTask takes the created packet, and puts it in the send queue
  • The class responsible for this level (from here to RPCSystem is an async queue) is FromNet::RequestManager
• Build_X_GeneralRequestTask takes in the raw data for type X, makes it a flatbuffer, and sends to QueueGeneralRequestTask
  • These built the flatbuffer from back to front, putting the type in nearly last

• Recv
• SVFW::SFStreamManagerTCP:RecvServerPacket
  • This encrypted data is copied out via MoveDataFromStreamConnection_To_Array
• SVFW::SFRPCManagerImpl::RecvServerTypeXandPassToDecode gets the packet data and depending on the layer 2 packet type selects a decode
• SVFW::SFRPCManagerImpl::DecodeServerTypeXPacket loads the SVFW::SFEncryptorSodium class and calls it method to decrypt the packet
• SFSharedKeyEncryptor::Decryptor
• FromNet::RPCSystem::ResponseFunctionArgs_Load_Flatbuffer finishes with the flatbuffer at FromNet::RPCSystem::ResponseFunctionArgs→GeneralRequestContext→ResponseArgs→GeneralRequestResult→sub→message_bytes_start
  • Load_Flatbuffer_Into_GeneralRequestContext
  • Get_Layer1Data_from_Flatbuffer
  • Load_Flatbuffer_Into_GeneralRequestContext_Parent
• SVFW::SFRPCManagerImpl::ParseServerTypeXFlatbuffer
  • The string for the packet being received is in array @141b0f580 (for parent type 6)
  • This filters based on FlatbufferWrapper to the next function
• SVFW::SFRPCManagerImpl::ParseServerFlatbuf_X
  • This unwraps the outer FlatbufferWrapper layer, checks the length and packet number, and passes on the flatbuffer

For responses to Requests

• FromNet::RPCSystem::ResponseFunctionArgs_Load_Flatbuffer
• Load_Flatbuffer_Into_GeneralRequestContext
• Load_Flatbuffer_Into_GeneralRequestContext_Parent
  • This creates a FromNet::GeneralRequestTask_Data class from the flatbuffer (via copy)
• FromNet::RPCSystem::ResponseArg::Copy_into_Self
  • Saves the FromNet::GeneralRequestTask_Data into the RPCSystem class, specifically FromNet::RPCSystem::GeneralRequestContext::ResponseArgs→GeneralRequestResult

For Push Requests

• PushRequest_Recv
• ProcessPushRequestType_()

This is a good overview Flatbuffers are used for the data storage itself. Examples of this at a byte-level are at this speadsheet.

Of note, the raw flatbuffer itself is not sent to the server. It is wrapped in another struct before being sent. This is of the form:

FlatbufferWrapper {
	uint8_t: Packet type. 
		Sending = 4, 5, 6, 7. Type 4 is normal client packet, type 7 does not have any main data and is used as the client heartbeat. Other 2 are login, logout
		Receiving = 5 6 ? ?. Type 5 is normal client packet response. 6 is PushRequest type, and doesn’t have a packet number, and is a uint16_t
	uint32_t: packet number. Incremented per packet, response has the matching number.
	flatbuffer itself
}

Protobuf Inspector (online as https://protobuf-decoder.netlify.app/) is a good tool to RE the packets.

The first header in the data/flatbuffer always contains a byte representing the message type. A mapping for these to their string names is embedded in the binary.

For Requests (client initiates communication with server), it's FromNet::RequestManager::RequestFunctionNameList at address 141a73420.

For Push Requests (Server initiates communication with client), it's FromNet::RequestManager::PushRequestFunctionNameList at address 141a735a0.

7. RequestCreateBloodMessage

• Actually for orange soapstone, not bloodstains.

17. RequestGetBreakInTargetList

• Get the players you can invade in your area.
• The player includes a number of their settings, like SL, weapon level, NatType, AreaId, etc.
• The server then responds with a list of users you can connect to that fit the given settings.

27. RequestGetSignList

• Gets type 25 as response from server

33. RequestUpdatePlayerStatus

• Includes a large number of player flags, such as stats, equipment, and other character info.
• Not all flags need be included.
• This also includes anti-cheat triggered flags and game version flags.