func exchangeHello(c net.Conn, h protocol.HelloMessage) (protocol.HelloMessage, error) {
if err := c.SetDeadline(time.Now().Add(2 * time.Second)); err != nil {
return protocol.HelloMessage{}, err
}
defer c.SetDeadline(time.Time{})
header := make([]byte, 8)
msg := h.MustMarshalXDR()
binary.BigEndian.PutUint32(header[:4], protocol.HelloMessageMagic)
binary.BigEndian.PutUint32(header[4:], uint32(len(msg)))
if _, err := c.Write(header); err != nil {
return protocol.HelloMessage{}, err
}
if _, err := c.Write(msg); err != nil {
return protocol.HelloMessage{}, err
}
if _, err := io.ReadFull(c, header); err != nil {
return protocol.HelloMessage{}, err
}
if binary.BigEndian.Uint32(header[:4]) != protocol.HelloMessageMagic {
return protocol.HelloMessage{}, fmt.Errorf("incorrect magic")
}
msgSize := binary.BigEndian.Uint32(header[4:])
if msgSize > 1024 {
return protocol.HelloMessage{}, fmt.Errorf("hello message too big")
}
buf := make([]byte, msgSize)
var hello protocol.HelloMessage
if _, err := io.ReadFull(c, buf); err != nil {
return protocol.HelloMessage{}, err
}
if err := hello.UnmarshalXDR(buf); err != nil {
return protocol.HelloMessage{}, err
}
return hello, nil
}
