用GO写一个RPC框架 s03 (协议设计)

Posted 2021-09-03 dollarkillerx

前言

该RPC支持 TCP KCP UNIX 所以我们要对协议进行设计

https://github.com/dollarkill...

定义握手协议

握手逻辑:

1. 建立链接 通过非对称加密 传输 aes 密钥给服务端 (携带token)
2. 服务端 验证 token 并记录 aes 密钥 后面与客户端交互 都采用对称加密

起始符	keySize	tokenSize	errorSize	key	token	err
0x09	4	4	4	xxx	xxx	xxx	xxx

type Handshake struct {
    Key   []byte  // aes 加密 KEY
    Token []byte  // AUTH 校验使用
    Error []byte  // 错误填充
}

编码

func EncodeHandshake(key, token, err []byte) []byte {
    buf := make([]byte, 13+len(key)+len(token)+len(err))

    buf[0] = LightHandshakeSt
    binary.LittleEndian.PutUint32(buf[1:5], uint32(len(key)))
    binary.LittleEndian.PutUint32(buf[5:9], uint32(len(token)))
    binary.LittleEndian.PutUint32(buf[9:13], uint32(len(err)))

    st := 13
    endI := st + len(key)
    copy(buf[st:endI], key)

    st = endI
    endI = st + len(token)
    copy(buf[st:endI], token)

    st = endI
    endI = st + len(err)
    copy(buf[st:endI], err)

    return buf
}

解码

func (h *Handshake) Handshake(r io.Reader) error {
    headerByte := make([]byte, 13)

    // 读取标志位
    _, err := io.ReadFull(r, headerByte[:1])
    if err != nil {
        return err
    }

    if headerByte[0] != LightHandshakeSt {
        return errors.New("NO Light Handshake")
    }

    // 读取剩下的
    _, err = io.ReadFull(r, headerByte[1:])
    if err != nil {
        return err
    }

    // 解析头
    keySize := binary.LittleEndian.Uint32(headerByte[1:5])
    tokenSize := binary.LittleEndian.Uint32(headerByte[5:9])
    errorSize := binary.LittleEndian.Uint32(headerByte[9:13])

    bodyData := make([]byte, keySize+tokenSize+errorSize)
    _, err = io.ReadFull(r, bodyData)
    if err != nil {
        return err
    }

    var st uint32 = 0
    endIdx := keySize
    key := make([]byte, keySize)
    copy(key, bodyData[st:endIdx])
    h.Key = key

    st = endIdx
    endIdx = st + tokenSize
    token := make([]byte, tokenSize)
    copy(token, bodyData[st:endIdx])
    h.Token = token

    st = endIdx
    endIdx = st + errorSize
    errStr := make([]byte, errorSize)
    copy(errStr, bodyData[st:endIdx])
    h.Error = errStr

    return nil
}

定义传输协议

/**
    协议设计
    起始符 :  版本号 :  crc32校验 :   magicNumberSize:    serverNameSize :   serverMethodSize :  metaDataSize : payloadSize:  respType :   compressorType :    serializationType :    magicNumber :  serverName :   serverMethod :  metaData :  payload
        0x05  :  0x01  :     4     :        4         :         4         :         4          :       4       :      4     :      1    :          1       :           1          :        xxx     :       xxx   :        xxx     :    xxx    :    xxx
*/

type Message struct {
    Header        *Header
    MagicNumber   string
    ServiceName   string
    ServiceMethod string
    MetaData      []byte
    Payload       []byte
}

type Header struct {
    St                byte
    Version           byte
    Crc32             uint32
    MagicNumberSize   uint32
    ServerNameSize    uint32
    ServerMethodSize  uint32
    MetaDataSize      uint32
    PayloadSize       uint32
    RespType          byte
    CompressorType    byte
    SerializationType byte
}

编码

// EncodeMessage 基础编码
func EncodeMessage(magicStr string, server, method, metaData []byte, respType, compressorType, serializationType byte, payload []byte) (magic string, data []byte, err error) {
    var magicNumber = []byte(magicStr)
    if magicStr == "" {
        magicNumber = []byte(xid.New().String())
    }

    bufSize := HeadSize + len(server) + len(method) + len(metaData) + len(payload) + len(magicNumber)
    buf := make([]byte, bufSize)

    buf[0] = LightSt
    buf[1] = byte(V1)
    binary.LittleEndian.PutUint32(buf[6:10], uint32(len(magicNumber)))
    binary.LittleEndian.PutUint32(buf[10:14], uint32(len(server)))
    binary.LittleEndian.PutUint32(buf[14:18], uint32(len(method)))
    binary.LittleEndian.PutUint32(buf[18:22], uint32(len(metaData)))
    binary.LittleEndian.PutUint32(buf[22:26], uint32(len(payload)))
    buf[26] = respType
    buf[27] = compressorType
    buf[28] = serializationType

    st := HeadSize
    endI := st + len(magicNumber)
    copy(buf[st:endI], magicNumber)

    st = endI
    endI = st + len(server)
    copy(buf[st:endI], server)

    st = endI
    endI = st + len(method)
    copy(buf[st:endI], method)

    st = endI
    endI = st + len(metaData)
    copy(buf[st:endI], metaData)

    st = endI
    endI = st + len(payload)
    copy(buf[st:endI], payload)

    if Crc32 {
        u := crc32.ChecksumIEEE(buf[6:])
        binary.LittleEndian.PutUint32(buf[2:6], u)
    }

    return string(magicNumber), buf, nil
}

解码

func (m *Protocol) IODecode(r io.Reader) (*Message, error) {
    headerByte := make([]byte, HeadSize)
    // 读取标志位
    _, err := io.ReadFull(r, headerByte[:1])
    if err != nil {
        return nil, err
    }

    if headerByte[0] != LightSt {
        log.Println(headerByte)
        return nil, errors.New("NO Light")
    }

    // 读取剩下的
    _, err = io.ReadFull(r, headerByte[1:])
    if err != nil {
        return nil, err
    }

    // 解析 header
    header, err := DecodeHeader(headerByte)
    if err != nil {
        return nil, err
    }

    bodyLen := header.MagicNumberSize + header.ServerNameSize + header.ServerMethodSize + header.MetaDataSize + header.PayloadSize
    bodyData := make([]byte, bodyLen)
    _, err = io.ReadFull(r, bodyData)
    if err != nil {
        return nil, err
    }

    msg, err := DecodeMessageV2(bodyData, header, 0)
    if err != nil {
        return nil, err
    }

    return msg, nil
}

func DecodeHeader(data []byte) (*Header, error) {
    var header Header
    header.St = data[0]
    header.Version = data[1]
    header.Crc32 = binary.LittleEndian.Uint32(data[2:6])
    if Crc32 {
        u := crc32.ChecksumIEEE(data[6:])
        if header.Crc32 != u {
            return nil, errors.New("CRC Calibration")
        }
    }
    header.MagicNumberSize = binary.LittleEndian.Uint32(data[6:10])
    header.ServerNameSize = binary.LittleEndian.Uint32(data[10:14])
    header.ServerMethodSize = binary.LittleEndian.Uint32(data[14:18])
    header.MetaDataSize = binary.LittleEndian.Uint32(data[18:22])
    header.PayloadSize = binary.LittleEndian.Uint32(data[22:26])
    header.RespType = data[26]
    header.CompressorType = data[27]
    header.SerializationType = data[28]

    return &header, nil
}

// DecodeMessage 完整Decode
func DecodeMessage(data []byte) (*Message, error) {
    header, err := DecodeHeader(data)
    if err != nil {
        return nil, err
    }
    return DecodeMessageV2(data, header, HeadSize)
}

func DecodeMessageV2(data []byte, header *Header, headSize uint32) (*Message, error) {
    var result Message
    result.Header = header
    var st uint32 = headSize
    endI := st + header.MagicNumberSize
    les := endI - st
    magicNumber := make([]byte, les)
    copy(magicNumber, data[st:endI])
    result.MagicNumber = string(magicNumber)

    st = endI
    endI = st + header.ServerNameSize
    les = endI - st
    serverName := make([]byte, les)
    copy(serverName, data[st:endI])
    result.ServiceName = string(serverName)

    st = endI
    endI = st + header.ServerMethodSize
    les = endI - st
    serverMethodSize := make([]byte, les)
    copy(serverMethodSize, data[st:endI])
    result.ServiceMethod = string(serverMethodSize)

    st = endI
    endI = st + header.MetaDataSize
    les = endI - st
    metaDataSize := make([]byte, les)
    copy(metaDataSize, data[st:endI])
    result.MetaData = metaDataSize

    st = endI
    endI = st + header.PayloadSize
    les = endI - st
    payloadSize := make([]byte, les)
    copy(payloadSize, data[st:endI])
    result.Payload = payloadSize

    return &result, nil
}