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// Copyright 2016 The CMux Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
package cmux
import (
"fmt"
"io"
"net"
"sync"
"time"
)
// Matcher matches a connection based on its content.
type Matcher func(io.Reader) bool
// MatchWriter is a match that can also write response (say to do handshake).
type MatchWriter func(io.Writer, io.Reader) bool
// ErrorHandler handles an error and returns whether
// the mux should continue serving the listener.
type ErrorHandler func(error) bool
var _ net.Error = ErrNotMatched{}
// ErrNotMatched is returned whenever a connection is not matched by any of
// the matchers registered in the multiplexer.
type ErrNotMatched struct {
c net.Conn
}
func (e ErrNotMatched) Error() string {
return fmt.Sprintf("mux: connection %v not matched by an matcher",
e.c.RemoteAddr())
}
// Temporary implements the net.Error interface.
func (e ErrNotMatched) Temporary() bool { return true }
// Timeout implements the net.Error interface.
func (e ErrNotMatched) Timeout() bool { return false }
type errListenerClosed string
func (e errListenerClosed) Error() string { return string(e) }
func (e errListenerClosed) Temporary() bool { return false }
func (e errListenerClosed) Timeout() bool { return false }
// ErrListenerClosed is returned from muxListener.Accept when the underlying
// listener is closed.
var ErrListenerClosed = errListenerClosed("mux: listener closed")
// for readability of readTimeout
var noTimeout time.Duration
// New instantiates a new connection multiplexer.
func New(l net.Listener) CMux {
return &cMux{
root: l,
bufLen: 1024,
errh: func(_ error) bool { return true },
donec: make(chan struct{}),
readTimeout: noTimeout,
}
}
// CMux is a multiplexer for network connections.
type CMux interface {
// Match returns a net.Listener that sees (i.e., accepts) only
// the connections matched by at least one of the matcher.
//
// The order used to call Match determines the priority of matchers.
Match(...Matcher) net.Listener
// MatchWithWriters returns a net.Listener that accepts only the
// connections that matched by at least of the matcher writers.
//
// Prefer Matchers over MatchWriters, since the latter can write on the
// connection before the actual handler.
//
// The order used to call Match determines the priority of matchers.
MatchWithWriters(...MatchWriter) net.Listener
// Serve starts multiplexing the listener. Serve blocks and perhaps
// should be invoked concurrently within a go routine.
Serve() error
// HandleError registers an error handler that handles listener errors.
HandleError(ErrorHandler)
// sets a timeout for the read of matchers
SetReadTimeout(time.Duration)
}
type matchersListener struct {
ss []MatchWriter
l muxListener
}
type cMux struct {
root net.Listener
bufLen int
errh ErrorHandler
donec chan struct{}
sls []matchersListener
readTimeout time.Duration
}
func matchersToMatchWriters(matchers []Matcher) []MatchWriter {
mws := make([]MatchWriter, 0, len(matchers))
for _, m := range matchers {
cm := m
mws = append(mws, func(w io.Writer, r io.Reader) bool {
return cm(r)
})
}
return mws
}
func (m *cMux) Match(matchers ...Matcher) net.Listener {
mws := matchersToMatchWriters(matchers)
return m.MatchWithWriters(mws...)
}
func (m *cMux) MatchWithWriters(matchers ...MatchWriter) net.Listener {
ml := muxListener{
Listener: m.root,
connc: make(chan net.Conn, m.bufLen),
}
m.sls = append(m.sls, matchersListener{ss: matchers, l: ml})
return ml
}
func (m *cMux) SetReadTimeout(t time.Duration) {
m.readTimeout = t
}
func (m *cMux) Serve() error {
var wg sync.WaitGroup
defer func() {
close(m.donec)
wg.Wait()
for _, sl := range m.sls {
close(sl.l.connc)
// Drain the connections enqueued for the listener.
for c := range sl.l.connc {
_ = c.Close()
}
}
}()
for {
c, err := m.root.Accept()
if err != nil {
if !m.handleErr(err) {
return err
}
continue
}
wg.Add(1)
go m.serve(c, m.donec, &wg)
}
}
func (m *cMux) serve(c net.Conn, donec <-chan struct{}, wg *sync.WaitGroup) {
defer wg.Done()
muc := newMuxConn(c)
if m.readTimeout > noTimeout {
_ = c.SetReadDeadline(time.Now().Add(m.readTimeout))
}
for _, sl := range m.sls {
for _, s := range sl.ss {
matched := s(muc.Conn, muc.startSniffing())
if matched {
muc.doneSniffing()
if m.readTimeout > noTimeout {
_ = c.SetReadDeadline(time.Time{})
}
select {
case sl.l.connc <- muc:
case <-donec:
_ = c.Close()
}
return
}
}
}
_ = c.Close()
err := ErrNotMatched{c: c}
if !m.handleErr(err) {
_ = m.root.Close()
}
}
func (m *cMux) HandleError(h ErrorHandler) {
m.errh = h
}
func (m *cMux) handleErr(err error) bool {
if !m.errh(err) {
return false
}
if ne, ok := err.(net.Error); ok {
return ne.Temporary()
}
return false
}
type muxListener struct {
net.Listener
connc chan net.Conn
}
func (l muxListener) Accept() (net.Conn, error) {
c, ok := <-l.connc
if !ok {
return nil, ErrListenerClosed
}
return c, nil
}
// MuxConn wraps a net.Conn and provides transparent sniffing of connection data.
type MuxConn struct {
net.Conn
buf bufferedReader
}
func newMuxConn(c net.Conn) *MuxConn {
return &MuxConn{
Conn: c,
buf: bufferedReader{source: c},
}
}
// From the io.Reader documentation:
//
// When Read encounters an error or end-of-file condition after
// successfully reading n > 0 bytes, it returns the number of
// bytes read. It may return the (non-nil) error from the same call
// or return the error (and n == 0) from a subsequent call.
// An instance of this general case is that a Reader returning
// a non-zero number of bytes at the end of the input stream may
// return either err == EOF or err == nil. The next Read should
// return 0, EOF.
func (m *MuxConn) Read(p []byte) (int, error) {
return m.buf.Read(p)
}
func (m *MuxConn) startSniffing() io.Reader {
m.buf.reset(true)
return &m.buf
}
func (m *MuxConn) doneSniffing() {
m.buf.reset(false)
}