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package p2p
import (
"bufio"
"bytes"
"fmt"
"io"
"io/ioutil"
"net"
"sync"
"time"
)
type Handlers map[string]func() Protocol
type proto struct {
in chan Msg
maxcode, offset MsgCode
messenger *messenger
}
func (rw *proto) WriteMsg(msg Msg) error {
if msg.Code >= rw.maxcode {
return NewPeerError(InvalidMsgCode, "not handled")
}
return rw.messenger.writeMsg(msg)
}
func (rw *proto) ReadMsg() (Msg, error) {
msg, ok := <-rw.in
if !ok {
return msg, io.EOF
}
return msg, nil
}
// eofSignal is used to 'lend' the network connection
// to a protocol. when the protocol's read loop has read the
// whole payload, the done channel is closed.
type eofSignal struct {
wrapped io.Reader
eof chan struct{}
}
func (r *eofSignal) Read(buf []byte) (int, error) {
n, err := r.wrapped.Read(buf)
if err != nil {
close(r.eof) // tell messenger that msg has been consumed
}
return n, err
}
// messenger represents a message-oriented peer connection.
// It keeps track of the set of protocols understood
// by the remote peer.
type messenger struct {
peer *Peer
handlers Handlers
// the mutex protects the connection
// so only one protocol can write at a time.
writeMu sync.Mutex
conn net.Conn
bufconn *bufio.ReadWriter
protocolLock sync.RWMutex
protocols map[string]*proto
offsets map[MsgCode]*proto
protoWG sync.WaitGroup
err chan error
pulse chan bool
}
func newMessenger(peer *Peer, conn net.Conn, errchan chan error, handlers Handlers) *messenger {
return &messenger{
conn: conn,
bufconn: bufio.NewReadWriter(bufio.NewReader(conn), bufio.NewWriter(conn)),
peer: peer,
handlers: handlers,
protocols: make(map[string]*proto),
err: errchan,
pulse: make(chan bool, 1),
}
}
func (m *messenger) Start() {
m.protocols[""] = m.startProto(0, "", &baseProtocol{})
go m.readLoop()
}
func (m *messenger) Stop() {
m.conn.Close()
m.protoWG.Wait()
}
const (
// maximum amount of time allowed for reading a message
msgReadTimeout = 5 * time.Second
// messages smaller than this many bytes will be read at
// once before passing them to a protocol.
wholePayloadSize = 64 * 1024
)
func (m *messenger) readLoop() {
defer m.closeProtocols()
for {
m.conn.SetReadDeadline(time.Now().Add(msgReadTimeout))
msg, err := readMsg(m.bufconn)
if err != nil {
m.err <- err
return
}
// send ping to heartbeat channel signalling time of last message
m.pulse <- true
proto, err := m.getProto(msg.Code)
if err != nil {
m.err <- err
return
}
msg.Code -= proto.offset
if msg.Size <= wholePayloadSize {
// optimization: msg is small enough, read all
// of it and move on to the next message
buf, err := ioutil.ReadAll(msg.Payload)
if err != nil {
m.err <- err
return
}
msg.Payload = bytes.NewReader(buf)
proto.in <- msg
} else {
pr := &eofSignal{msg.Payload, make(chan struct{})}
msg.Payload = pr
proto.in <- msg
<-pr.eof
}
}
}
func (m *messenger) closeProtocols() {
m.protocolLock.RLock()
for _, p := range m.protocols {
close(p.in)
}
m.protocolLock.RUnlock()
}
func (m *messenger) startProto(offset MsgCode, name string, impl Protocol) *proto {
proto := &proto{
in: make(chan Msg),
offset: offset,
maxcode: impl.Offset(),
messenger: m,
}
m.protoWG.Add(1)
go func() {
if err := impl.Start(m.peer, proto); err != nil && err != io.EOF {
logger.Errorf("protocol %q error: %v\n", name, err)
m.err <- err
}
m.protoWG.Done()
}()
return proto
}
// getProto finds the protocol responsible for handling
// the given message code.
func (m *messenger) getProto(code MsgCode) (*proto, error) {
m.protocolLock.RLock()
defer m.protocolLock.RUnlock()
for _, proto := range m.protocols {
if code >= proto.offset && code < proto.offset+proto.maxcode {
return proto, nil
}
}
return nil, NewPeerError(InvalidMsgCode, "%d", code)
}
// setProtocols starts all subprotocols shared with the
// remote peer. the protocols must be sorted alphabetically.
func (m *messenger) setRemoteProtocols(protocols []string) {
m.protocolLock.Lock()
defer m.protocolLock.Unlock()
offset := baseProtocolOffset
for _, name := range protocols {
protocolFunc, ok := m.handlers[name]
if !ok {
continue // not handled
}
inst := protocolFunc()
m.protocols[name] = m.startProto(offset, name, inst)
offset += inst.Offset()
}
}
// writeProtoMsg sends the given message on behalf of the given named protocol.
func (m *messenger) writeProtoMsg(protoName string, msg Msg) error {
m.protocolLock.RLock()
proto, ok := m.protocols[protoName]
m.protocolLock.RUnlock()
if !ok {
return fmt.Errorf("protocol %s not handled by peer", protoName)
}
if msg.Code >= proto.maxcode {
return NewPeerError(InvalidMsgCode, "code %x is out of range for protocol %q", msg.Code, protoName)
}
msg.Code += proto.offset
return m.writeMsg(msg)
}
// writeMsg writes a message to the connection.
func (m *messenger) writeMsg(msg Msg) error {
m.writeMu.Lock()
defer m.writeMu.Unlock()
if err := writeMsg(m.bufconn, msg); err != nil {
return err
}
return m.bufconn.Flush()
}
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