mirror of
https://github.com/genuinetools/reg.git
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331 lines
7.2 KiB
Go
331 lines
7.2 KiB
Go
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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssh
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import (
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"encoding/binary"
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"fmt"
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"io"
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"log"
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"sync"
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"sync/atomic"
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)
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// debugMux, if set, causes messages in the connection protocol to be
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// logged.
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const debugMux = false
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// chanList is a thread safe channel list.
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type chanList struct {
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// protects concurrent access to chans
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sync.Mutex
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// chans are indexed by the local id of the channel, which the
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// other side should send in the PeersId field.
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chans []*channel
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// This is a debugging aid: it offsets all IDs by this
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// amount. This helps distinguish otherwise identical
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// server/client muxes
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offset uint32
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}
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// Assigns a channel ID to the given channel.
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func (c *chanList) add(ch *channel) uint32 {
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c.Lock()
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defer c.Unlock()
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for i := range c.chans {
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if c.chans[i] == nil {
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c.chans[i] = ch
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return uint32(i) + c.offset
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}
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}
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c.chans = append(c.chans, ch)
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return uint32(len(c.chans)-1) + c.offset
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}
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// getChan returns the channel for the given ID.
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func (c *chanList) getChan(id uint32) *channel {
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id -= c.offset
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c.Lock()
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defer c.Unlock()
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if id < uint32(len(c.chans)) {
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return c.chans[id]
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}
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return nil
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}
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func (c *chanList) remove(id uint32) {
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id -= c.offset
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c.Lock()
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if id < uint32(len(c.chans)) {
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c.chans[id] = nil
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}
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c.Unlock()
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}
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// dropAll forgets all channels it knows, returning them in a slice.
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func (c *chanList) dropAll() []*channel {
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c.Lock()
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defer c.Unlock()
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var r []*channel
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for _, ch := range c.chans {
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if ch == nil {
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continue
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}
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r = append(r, ch)
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}
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c.chans = nil
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return r
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}
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// mux represents the state for the SSH connection protocol, which
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// multiplexes many channels onto a single packet transport.
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type mux struct {
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conn packetConn
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chanList chanList
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incomingChannels chan NewChannel
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globalSentMu sync.Mutex
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globalResponses chan interface{}
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incomingRequests chan *Request
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errCond *sync.Cond
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err error
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}
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// When debugging, each new chanList instantiation has a different
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// offset.
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var globalOff uint32
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func (m *mux) Wait() error {
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m.errCond.L.Lock()
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defer m.errCond.L.Unlock()
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for m.err == nil {
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m.errCond.Wait()
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}
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return m.err
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}
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// newMux returns a mux that runs over the given connection.
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func newMux(p packetConn) *mux {
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m := &mux{
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conn: p,
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incomingChannels: make(chan NewChannel, chanSize),
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globalResponses: make(chan interface{}, 1),
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incomingRequests: make(chan *Request, chanSize),
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errCond: newCond(),
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}
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if debugMux {
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m.chanList.offset = atomic.AddUint32(&globalOff, 1)
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}
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go m.loop()
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return m
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}
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func (m *mux) sendMessage(msg interface{}) error {
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p := Marshal(msg)
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if debugMux {
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log.Printf("send global(%d): %#v", m.chanList.offset, msg)
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}
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return m.conn.writePacket(p)
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}
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func (m *mux) SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error) {
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if wantReply {
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m.globalSentMu.Lock()
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defer m.globalSentMu.Unlock()
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}
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if err := m.sendMessage(globalRequestMsg{
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Type: name,
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WantReply: wantReply,
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Data: payload,
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}); err != nil {
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return false, nil, err
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}
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if !wantReply {
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return false, nil, nil
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}
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msg, ok := <-m.globalResponses
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if !ok {
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return false, nil, io.EOF
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}
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switch msg := msg.(type) {
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case *globalRequestFailureMsg:
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return false, msg.Data, nil
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case *globalRequestSuccessMsg:
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return true, msg.Data, nil
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default:
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return false, nil, fmt.Errorf("ssh: unexpected response to request: %#v", msg)
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}
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}
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// ackRequest must be called after processing a global request that
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// has WantReply set.
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func (m *mux) ackRequest(ok bool, data []byte) error {
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if ok {
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return m.sendMessage(globalRequestSuccessMsg{Data: data})
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}
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return m.sendMessage(globalRequestFailureMsg{Data: data})
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}
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func (m *mux) Close() error {
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return m.conn.Close()
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}
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// loop runs the connection machine. It will process packets until an
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// error is encountered. To synchronize on loop exit, use mux.Wait.
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func (m *mux) loop() {
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var err error
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for err == nil {
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err = m.onePacket()
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}
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for _, ch := range m.chanList.dropAll() {
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ch.close()
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}
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close(m.incomingChannels)
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close(m.incomingRequests)
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close(m.globalResponses)
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m.conn.Close()
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m.errCond.L.Lock()
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m.err = err
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m.errCond.Broadcast()
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m.errCond.L.Unlock()
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if debugMux {
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log.Println("loop exit", err)
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}
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}
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// onePacket reads and processes one packet.
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func (m *mux) onePacket() error {
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packet, err := m.conn.readPacket()
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if err != nil {
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return err
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}
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if debugMux {
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if packet[0] == msgChannelData || packet[0] == msgChannelExtendedData {
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log.Printf("decoding(%d): data packet - %d bytes", m.chanList.offset, len(packet))
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} else {
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p, _ := decode(packet)
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log.Printf("decoding(%d): %d %#v - %d bytes", m.chanList.offset, packet[0], p, len(packet))
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}
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}
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switch packet[0] {
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case msgChannelOpen:
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return m.handleChannelOpen(packet)
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case msgGlobalRequest, msgRequestSuccess, msgRequestFailure:
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return m.handleGlobalPacket(packet)
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}
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// assume a channel packet.
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if len(packet) < 5 {
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return parseError(packet[0])
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}
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id := binary.BigEndian.Uint32(packet[1:])
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ch := m.chanList.getChan(id)
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if ch == nil {
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return fmt.Errorf("ssh: invalid channel %d", id)
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}
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return ch.handlePacket(packet)
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}
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func (m *mux) handleGlobalPacket(packet []byte) error {
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msg, err := decode(packet)
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if err != nil {
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return err
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}
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switch msg := msg.(type) {
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case *globalRequestMsg:
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m.incomingRequests <- &Request{
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Type: msg.Type,
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WantReply: msg.WantReply,
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Payload: msg.Data,
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mux: m,
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}
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case *globalRequestSuccessMsg, *globalRequestFailureMsg:
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m.globalResponses <- msg
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default:
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panic(fmt.Sprintf("not a global message %#v", msg))
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}
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return nil
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}
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// handleChannelOpen schedules a channel to be Accept()ed.
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func (m *mux) handleChannelOpen(packet []byte) error {
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var msg channelOpenMsg
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if err := Unmarshal(packet, &msg); err != nil {
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return err
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}
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if msg.MaxPacketSize < minPacketLength || msg.MaxPacketSize > 1<<31 {
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failMsg := channelOpenFailureMsg{
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PeersID: msg.PeersID,
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Reason: ConnectionFailed,
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Message: "invalid request",
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Language: "en_US.UTF-8",
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}
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return m.sendMessage(failMsg)
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}
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c := m.newChannel(msg.ChanType, channelInbound, msg.TypeSpecificData)
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c.remoteId = msg.PeersID
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c.maxRemotePayload = msg.MaxPacketSize
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c.remoteWin.add(msg.PeersWindow)
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m.incomingChannels <- c
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return nil
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}
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func (m *mux) OpenChannel(chanType string, extra []byte) (Channel, <-chan *Request, error) {
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ch, err := m.openChannel(chanType, extra)
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if err != nil {
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return nil, nil, err
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}
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return ch, ch.incomingRequests, nil
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}
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func (m *mux) openChannel(chanType string, extra []byte) (*channel, error) {
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ch := m.newChannel(chanType, channelOutbound, extra)
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ch.maxIncomingPayload = channelMaxPacket
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open := channelOpenMsg{
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ChanType: chanType,
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PeersWindow: ch.myWindow,
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MaxPacketSize: ch.maxIncomingPayload,
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TypeSpecificData: extra,
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PeersID: ch.localId,
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}
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if err := m.sendMessage(open); err != nil {
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return nil, err
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}
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switch msg := (<-ch.msg).(type) {
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case *channelOpenConfirmMsg:
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return ch, nil
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case *channelOpenFailureMsg:
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return nil, &OpenChannelError{msg.Reason, msg.Message}
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default:
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return nil, fmt.Errorf("ssh: unexpected packet in response to channel open: %T", msg)
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}
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}
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