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connection.go
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connection.go
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// Copyright 2017 VMware, Inc. 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 telnet
import (
"bytes"
"errors"
"io"
"io/ioutil"
"net"
"sync"
log "github.com/Sirupsen/logrus"
)
type optCallBackFunc func(byte, byte)
type connOpts struct {
// conn is the underlying connection
conn net.Conn
fsm *fsm
serverOpts map[byte]bool
clientOpts map[byte]bool
optCallback optCallBackFunc
Handlers
}
// Conn is the struct representing the telnet connection
type Conn struct {
connOpts
// the connection write channel. Everything required to be written to the connection goes to this channel
writeCh chan []byte
// dataRW is the data buffer. It is written to by the FSM and read from by the data handler
dataRW io.ReadWriter
cmdBuffer bytes.Buffer
handlerWriter io.WriteCloser
// used in the dataHandlerWrapper to notify that the telnet connection is closed
dataHandlerCloseCh chan chan struct{}
// used in the dataHandlerWrapper to notify that data has been writeen to the dataRW buffer
dataWrittenCh chan bool
// connWriteDoneCh closes the write loop when the telnet connection is closed
connWriteDoneCh chan chan struct{}
closedMutex sync.Mutex
closed bool
}
// Safely read/write concurrently to the data Buffer
// databuffer is written to by the FSM and it is read from by the dataHandler
type dataReadWriter struct {
buf bytes.Buffer
sync.Mutex
}
func (drw *dataReadWriter) Read(p []byte) (int, error) {
drw.Lock()
defer drw.Unlock()
return drw.buf.Read(p)
}
func (drw *dataReadWriter) Write(p []byte) (int, error) {
drw.Lock()
defer drw.Unlock()
return drw.buf.Write(p)
}
// This is the Writer that is passed to the handlers to write to the telnet connection
type connectionWriter struct {
ch chan []byte
}
func (cw *connectionWriter) Write(b []byte) (int, error) {
if cw.ch != nil {
cw.ch <- b
}
return len(b), nil
}
func (cw *connectionWriter) Close() error {
close(cw.ch)
cw.ch = nil
return nil
}
func newConn(opts *connOpts) *Conn {
tc := &Conn{
connOpts: *opts,
writeCh: make(chan []byte),
dataHandlerCloseCh: make(chan chan struct{}),
dataWrittenCh: make(chan bool),
connWriteDoneCh: make(chan chan struct{}),
closed: false,
}
if tc.optCallback == nil {
tc.optCallback = tc.handleOptionCommand
}
tc.handlerWriter = &connectionWriter{
ch: tc.writeCh,
}
tc.dataRW = &dataReadWriter{}
tc.fsm.tc = tc
return tc
}
//UnderlyingConnection returns the underlying TCP connection
func (c *Conn) UnderlyingConnection() net.Conn {
return c.conn
}
func (c *Conn) writeLoop() {
log.Debugf("entered write loop")
for {
select {
case writeBytes := <-c.writeCh:
c.conn.Write(writeBytes)
case ch := <-c.connWriteDoneCh:
ch <- struct{}{}
return
}
}
}
func (c *Conn) startNegotiation() {
for k := range c.serverOpts {
log.Infof("sending WILL %d", k)
c.sendCmd(Will, k)
}
for k := range c.clientOpts {
log.Infof("sending DO %d", k)
c.sendCmd(Do, k)
}
}
// close closes the telnet connection
func (c *Conn) close() {
c.closedMutex.Lock()
defer c.closedMutex.Unlock()
c.closed = true
log.Infof("Closing the connection")
c.conn.Close()
c.closeConnLoopWrite()
c.closeDatahandler()
c.handlerWriter.Close()
log.Infof("telnet connection closed")
// calling the CloseHandler passed by vspc
c.CloseHandler(c)
}
func (c *Conn) closeConnLoopWrite() {
connLoopWriteCh := make(chan struct{})
c.connWriteDoneCh <- connLoopWriteCh
<-connLoopWriteCh
log.Debugf("connection loop write-side closed")
}
func (c *Conn) closeDatahandler() {
dataCh := make(chan struct{})
c.dataHandlerCloseCh <- dataCh
<-dataCh
}
func (c *Conn) sendCmd(cmd byte, opt byte) {
c.writeCh <- []byte{Iac, cmd, opt}
log.Debugf("Sending command: %v %v", cmd, opt)
}
func (c *Conn) handleOptionCommand(cmd byte, opt byte) {
if cmd == Will || cmd == Wont {
if _, ok := c.clientOpts[opt]; !ok {
c.sendCmd(Dont, opt)
return
}
c.sendCmd(Do, opt)
}
if cmd == Do || cmd == Dont {
if _, ok := c.serverOpts[opt]; !ok {
c.sendCmd(Wont, opt)
return
}
log.Debugf("Sending WILL command")
c.sendCmd(Will, opt)
}
}
func (c *Conn) dataHandlerWrapper(w io.Writer, r io.Reader) {
defer func() {
log.Debugf("data handler closed")
}()
for {
select {
case ch := <-c.dataHandlerCloseCh:
ch <- struct{}{}
return
case <-c.dataWrittenCh:
// #nosec: Errors unhandled.
if b, _ := ioutil.ReadAll(r); len(b) > 0 {
c.DataHandler(w, b, c)
}
}
}
}
func (c *Conn) cmdHandlerWrapper(w io.Writer, r io.Reader) {
// #nosec: Errors unhandled.
if cmd, _ := ioutil.ReadAll(r); len(cmd) > 0 {
c.CmdHandler(w, cmd, c)
}
}
// IsClosed returns true if the connection is already closed
func (c *Conn) IsClosed() bool {
c.closedMutex.Lock()
defer c.closedMutex.Unlock()
return c.closed
}
// WriteData writes telnet data to the underlying connection doubling every IAC
func (c *Conn) WriteData(b []byte) (int, error) {
var escaped []byte
for _, v := range b {
if v == Iac {
escaped = append(escaped, 255)
}
escaped = append(escaped, v)
}
if c.IsClosed() {
return -1, errors.New("telnet connection is already closed")
}
c.writeCh <- escaped
return len(b), nil
}