package p2p import ( "bytes" "errors" "fmt" "io" "io/ioutil" "net" "sync" "sync/atomic" "time" "github.com/ethereum/go-ethereum/rlp" ) // Msg defines the structure of a p2p message. // // Note that a Msg can only be sent once since the Payload reader is // consumed during sending. It is not possible to create a Msg and // send it any number of times. If you want to reuse an encoded // structure, encode the payload into a byte array and create a // separate Msg with a bytes.Reader as Payload for each send. type Msg struct { Code uint64 Size uint32 // size of the paylod Payload io.Reader } // Decode parses the RLP content of a message into // the given value, which must be a pointer. // // For the decoding rules, please see package rlp. func (msg Msg) Decode(val interface{}) error { if err := rlp.Decode(msg.Payload, val); err != nil { return newPeerError(errInvalidMsg, "(code %#x) (size %d) %v", msg.Code, msg.Size, err) } return nil } func (msg Msg) String() string { return fmt.Sprintf("msg #%v (%v bytes)", msg.Code, msg.Size) } // Discard reads any remaining payload data into a black hole. func (msg Msg) Discard() error { _, err := io.Copy(ioutil.Discard, msg.Payload) return err } type MsgReader interface { ReadMsg() (Msg, error) } type MsgWriter interface { // WriteMsg sends a message. It will block until the message's // Payload has been consumed by the other end. // // Note that messages can be sent only once because their // payload reader is drained. WriteMsg(Msg) error } // MsgReadWriter provides reading and writing of encoded messages. // Implementations should ensure that ReadMsg and WriteMsg can be // called simultaneously from multiple goroutines. type MsgReadWriter interface { MsgReader MsgWriter } // Send writes an RLP-encoded message with the given code. // data should encode as an RLP list. func Send(w MsgWriter, msgcode uint64, data interface{}) error { size, r, err := rlp.EncodeToReader(data) if err != nil { return err } return w.WriteMsg(Msg{Code: msgcode, Size: uint32(size), Payload: r}) } // SendItems writes an RLP with the given code and data elements. // For a call such as: // // SendItems(w, code, e1, e2, e3) // // the message payload will be an RLP list containing the items: // // [e1, e2, e3] // func SendItems(w MsgWriter, msgcode uint64, elems ...interface{}) error { return Send(w, msgcode, elems) } // netWrapper wraps a MsgReadWriter with locks around // ReadMsg/WriteMsg and applies read/write deadlines. type netWrapper struct { rmu, wmu sync.Mutex rtimeout, wtimeout time.Duration conn net.Conn wrapped MsgReadWriter } func (rw *netWrapper) ReadMsg() (Msg, error) { rw.rmu.Lock() defer rw.rmu.Unlock() rw.conn.SetReadDeadline(time.Now().Add(rw.rtimeout)) return rw.wrapped.ReadMsg() } func (rw *netWrapper) WriteMsg(msg Msg) error { rw.wmu.Lock() defer rw.wmu.Unlock() rw.conn.SetWriteDeadline(time.Now().Add(rw.wtimeout)) return rw.wrapped.WriteMsg(msg) } // eofSignal wraps a reader with eof signaling. the eof channel is // closed when the wrapped reader returns an error or when count bytes // have been read. type eofSignal struct { wrapped io.Reader count uint32 // number of bytes left eof chan<- struct{} } // note: when using eofSignal to detect whether a message payload // has been read, Read might not be called for zero sized messages. func (r *eofSignal) Read(buf []byte) (int, error) { if r.count == 0 { if r.eof != nil { r.eof <- struct{}{} r.eof = nil } return 0, io.EOF } max := len(buf) if int(r.count) < len(buf) { max = int(r.count) } n, err := r.wrapped.Read(buf[:max]) r.count -= uint32(n) if (err != nil || r.count == 0) && r.eof != nil { r.eof <- struct{}{} // tell Peer that msg has been consumed r.eof = nil } return n, err } // MsgPipe creates a message pipe. Reads on one end are matched // with writes on the other. The pipe is full-duplex, both ends // implement MsgReadWriter. func MsgPipe() (*MsgPipeRW, *MsgPipeRW) { var ( c1, c2 = make(chan Msg), make(chan Msg) closing = make(chan struct{}) closed = new(int32) rw1 = &MsgPipeRW{c1, c2, closing, closed} rw2 = &MsgPipeRW{c2, c1, closing, closed} ) return rw1, rw2 } // ErrPipeClosed is returned from pipe operations after the // pipe has been closed. var ErrPipeClosed = errors.New("p2p: read or write on closed message pipe") // MsgPipeRW is an endpoint of a MsgReadWriter pipe. type MsgPipeRW struct { w chan<- Msg r <-chan Msg closing chan struct{} closed *int32 } // WriteMsg sends a messsage on the pipe. // It blocks until the receiver has consumed the message payload. func (p *MsgPipeRW) WriteMsg(msg Msg) error { if atomic.LoadInt32(p.closed) == 0 { consumed := make(chan struct{}, 1) msg.Payload = &eofSignal{msg.Payload, msg.Size, consumed} select { case p.w <- msg: if msg.Size > 0 { // wait for payload read or discard <-consumed } return nil case <-p.closing: } } return ErrPipeClosed } // ReadMsg returns a message sent on the other end of the pipe. func (p *MsgPipeRW) ReadMsg() (Msg, error) { if atomic.LoadInt32(p.closed) == 0 { select { case msg := <-p.r: return msg, nil case <-p.closing: } } return Msg{}, ErrPipeClosed } // Close unblocks any pending ReadMsg and WriteMsg calls on both ends // of the pipe. They will return ErrPipeClosed. Note that Close does // not interrupt any reads from a message payload. func (p *MsgPipeRW) Close() error { if atomic.AddInt32(p.closed, 1) != 1 { // someone else is already closing atomic.StoreInt32(p.closed, 1) // avoid overflow return nil } close(p.closing) return nil } // ExpectMsg reads a message from r and verifies that its // code and encoded RLP content match the provided values. // If content is nil, the payload is discarded and not verified. func ExpectMsg(r MsgReader, code uint64, content interface{}) error { msg, err := r.ReadMsg() if err != nil { return err } if msg.Code != code { return fmt.Errorf("message code mismatch: got %d, expected %d", msg.Code, code) } if content == nil { return msg.Discard() } else { contentEnc, err := rlp.EncodeToBytes(content) if err != nil { panic("content encode error: " + err.Error()) } if int(msg.Size) != len(contentEnc) { return fmt.Errorf("message size mismatch: got %d, want %d", msg.Size, len(contentEnc)) } actualContent, err := ioutil.ReadAll(msg.Payload) if err != nil { return err } if !bytes.Equal(actualContent, contentEnc) { return fmt.Errorf("message payload mismatch:\ngot: %x\nwant: %x", actualContent, contentEnc) } } return nil }