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portforward.go
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portforward.go
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/*
Copyright 2015 The Kubernetes Authors.
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 portforward
import (
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"strconv"
"strings"
"sync"
"k8s.io/client-go/pkg/api"
"k8s.io/client-go/pkg/kubelet/server/portforward"
"k8s.io/client-go/pkg/util/httpstream"
"k8s.io/client-go/pkg/util/runtime"
)
// PortForwarder knows how to listen for local connections and forward them to
// a remote pod via an upgraded HTTP request.
type PortForwarder struct {
ports []ForwardedPort
stopChan <-chan struct{}
dialer httpstream.Dialer
streamConn httpstream.Connection
listeners []io.Closer
Ready chan struct{}
requestIDLock sync.Mutex
requestID int
out io.Writer
errOut io.Writer
}
// ForwardedPort contains a Local:Remote port pairing.
type ForwardedPort struct {
Local uint16
Remote uint16
}
/*
valid port specifications:
5000
- forwards from localhost:5000 to pod:5000
8888:5000
- forwards from localhost:8888 to pod:5000
0:5000
:5000
- selects a random available local port,
forwards from localhost:<random port> to pod:5000
*/
func parsePorts(ports []string) ([]ForwardedPort, error) {
var forwards []ForwardedPort
for _, portString := range ports {
parts := strings.Split(portString, ":")
var localString, remoteString string
if len(parts) == 1 {
localString = parts[0]
remoteString = parts[0]
} else if len(parts) == 2 {
localString = parts[0]
if localString == "" {
// support :5000
localString = "0"
}
remoteString = parts[1]
} else {
return nil, fmt.Errorf("Invalid port format '%s'", portString)
}
localPort, err := strconv.ParseUint(localString, 10, 16)
if err != nil {
return nil, fmt.Errorf("Error parsing local port '%s': %s", localString, err)
}
remotePort, err := strconv.ParseUint(remoteString, 10, 16)
if err != nil {
return nil, fmt.Errorf("Error parsing remote port '%s': %s", remoteString, err)
}
if remotePort == 0 {
return nil, fmt.Errorf("Remote port must be > 0")
}
forwards = append(forwards, ForwardedPort{uint16(localPort), uint16(remotePort)})
}
return forwards, nil
}
// New creates a new PortForwarder.
func New(dialer httpstream.Dialer, ports []string, stopChan <-chan struct{}, readyChan chan struct{}, out, errOut io.Writer) (*PortForwarder, error) {
if len(ports) == 0 {
return nil, errors.New("You must specify at least 1 port")
}
parsedPorts, err := parsePorts(ports)
if err != nil {
return nil, err
}
return &PortForwarder{
dialer: dialer,
ports: parsedPorts,
stopChan: stopChan,
Ready: readyChan,
out: out,
errOut: errOut,
}, nil
}
// ForwardPorts formats and executes a port forwarding request. The connection will remain
// open until stopChan is closed.
func (pf *PortForwarder) ForwardPorts() error {
defer pf.Close()
var err error
pf.streamConn, _, err = pf.dialer.Dial(portforward.PortForwardProtocolV1Name)
if err != nil {
return fmt.Errorf("error upgrading connection: %s", err)
}
defer pf.streamConn.Close()
return pf.forward()
}
// forward dials the remote host specific in req, upgrades the request, starts
// listeners for each port specified in ports, and forwards local connections
// to the remote host via streams.
func (pf *PortForwarder) forward() error {
var err error
listenSuccess := false
for _, port := range pf.ports {
err = pf.listenOnPort(&port)
switch {
case err == nil:
listenSuccess = true
default:
if pf.errOut != nil {
fmt.Fprintf(pf.errOut, "Unable to listen on port %d: %v\n", port.Local, err)
}
}
}
if !listenSuccess {
return fmt.Errorf("Unable to listen on any of the requested ports: %v", pf.ports)
}
if pf.Ready != nil {
close(pf.Ready)
}
// wait for interrupt or conn closure
select {
case <-pf.stopChan:
case <-pf.streamConn.CloseChan():
runtime.HandleError(errors.New("lost connection to pod"))
}
return nil
}
// listenOnPort delegates tcp4 and tcp6 listener creation and waits for connections on both of these addresses.
// If both listener creation fail, an error is raised.
func (pf *PortForwarder) listenOnPort(port *ForwardedPort) error {
errTcp4 := pf.listenOnPortAndAddress(port, "tcp4", "127.0.0.1")
errTcp6 := pf.listenOnPortAndAddress(port, "tcp6", "[::1]")
if errTcp4 != nil && errTcp6 != nil {
return fmt.Errorf("All listeners failed to create with the following errors: %s, %s", errTcp4, errTcp6)
}
return nil
}
// listenOnPortAndAddress delegates listener creation and waits for new connections
// in the background f
func (pf *PortForwarder) listenOnPortAndAddress(port *ForwardedPort, protocol string, address string) error {
listener, err := pf.getListener(protocol, address, port)
if err != nil {
return err
}
pf.listeners = append(pf.listeners, listener)
go pf.waitForConnection(listener, *port)
return nil
}
// getListener creates a listener on the interface targeted by the given hostname on the given port with
// the given protocol. protocol is in net.Listen style which basically admits values like tcp, tcp4, tcp6
func (pf *PortForwarder) getListener(protocol string, hostname string, port *ForwardedPort) (net.Listener, error) {
listener, err := net.Listen(protocol, fmt.Sprintf("%s:%d", hostname, port.Local))
if err != nil {
runtime.HandleError(fmt.Errorf("Unable to create listener: Error %s", err))
return nil, err
}
listenerAddress := listener.Addr().String()
host, localPort, _ := net.SplitHostPort(listenerAddress)
localPortUInt, err := strconv.ParseUint(localPort, 10, 16)
if err != nil {
return nil, fmt.Errorf("Error parsing local port: %s from %s (%s)", err, listenerAddress, host)
}
port.Local = uint16(localPortUInt)
if pf.out != nil {
fmt.Fprintf(pf.out, "Forwarding from %s:%d -> %d\n", hostname, localPortUInt, port.Remote)
}
return listener, nil
}
// waitForConnection waits for new connections to listener and handles them in
// the background.
func (pf *PortForwarder) waitForConnection(listener net.Listener, port ForwardedPort) {
for {
conn, err := listener.Accept()
if err != nil {
// TODO consider using something like https://github.com/hydrogen18/stoppableListener?
if !strings.Contains(strings.ToLower(err.Error()), "use of closed network connection") {
runtime.HandleError(fmt.Errorf("Error accepting connection on port %d: %v", port.Local, err))
}
return
}
go pf.handleConnection(conn, port)
}
}
func (pf *PortForwarder) nextRequestID() int {
pf.requestIDLock.Lock()
defer pf.requestIDLock.Unlock()
id := pf.requestID
pf.requestID++
return id
}
// handleConnection copies data between the local connection and the stream to
// the remote server.
func (pf *PortForwarder) handleConnection(conn net.Conn, port ForwardedPort) {
defer conn.Close()
if pf.out != nil {
fmt.Fprintf(pf.out, "Handling connection for %d\n", port.Local)
}
requestID := pf.nextRequestID()
// create error stream
headers := http.Header{}
headers.Set(api.StreamType, api.StreamTypeError)
headers.Set(api.PortHeader, fmt.Sprintf("%d", port.Remote))
headers.Set(api.PortForwardRequestIDHeader, strconv.Itoa(requestID))
errorStream, err := pf.streamConn.CreateStream(headers)
if err != nil {
runtime.HandleError(fmt.Errorf("error creating error stream for port %d -> %d: %v", port.Local, port.Remote, err))
return
}
// we're not writing to this stream
errorStream.Close()
errorChan := make(chan error)
go func() {
message, err := ioutil.ReadAll(errorStream)
switch {
case err != nil:
errorChan <- fmt.Errorf("error reading from error stream for port %d -> %d: %v", port.Local, port.Remote, err)
case len(message) > 0:
errorChan <- fmt.Errorf("an error occurred forwarding %d -> %d: %v", port.Local, port.Remote, string(message))
}
close(errorChan)
}()
// create data stream
headers.Set(api.StreamType, api.StreamTypeData)
dataStream, err := pf.streamConn.CreateStream(headers)
if err != nil {
runtime.HandleError(fmt.Errorf("error creating forwarding stream for port %d -> %d: %v", port.Local, port.Remote, err))
return
}
localError := make(chan struct{})
remoteDone := make(chan struct{})
go func() {
// Copy from the remote side to the local port.
if _, err := io.Copy(conn, dataStream); err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
runtime.HandleError(fmt.Errorf("error copying from remote stream to local connection: %v", err))
}
// inform the select below that the remote copy is done
close(remoteDone)
}()
go func() {
// inform server we're not sending any more data after copy unblocks
defer dataStream.Close()
// Copy from the local port to the remote side.
if _, err := io.Copy(dataStream, conn); err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
runtime.HandleError(fmt.Errorf("error copying from local connection to remote stream: %v", err))
// break out of the select below without waiting for the other copy to finish
close(localError)
}
}()
// wait for either a local->remote error or for copying from remote->local to finish
select {
case <-remoteDone:
case <-localError:
}
// always expect something on errorChan (it may be nil)
err = <-errorChan
if err != nil {
runtime.HandleError(err)
}
}
func (pf *PortForwarder) Close() {
// stop all listeners
for _, l := range pf.listeners {
if err := l.Close(); err != nil {
runtime.HandleError(fmt.Errorf("error closing listener: %v", err))
}
}
}