338 lines
6.6 KiB
Go
338 lines
6.6 KiB
Go
package tunnel
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import (
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"crypto/sha256"
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"errors"
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"fmt"
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"sync"
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"github.com/google/uuid"
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"github.com/micro/go-micro/network/link"
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"github.com/micro/go-micro/transport"
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)
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// tun represents a network tunnel
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type tun struct {
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// the link on top of which we build a tunnel
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link link.Link
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sync.RWMutex
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// to indicate if we're connected or not
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connected bool
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// the send channel for all messages
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send chan *message
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// close channel
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closed chan bool
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// a map of sockets based on Micro-Tunnel-Id
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sockets map[string]*socket
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}
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// create new tunnel on top of a link
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func newTunnel(link link.Link) *tun {
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return &tun{
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link: link,
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send: make(chan *message, 128),
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closed: make(chan bool),
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sockets: make(map[string]*socket),
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}
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}
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// getSocket returns a socket from the internal socket map.
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// It does this based on the Micro-Tunnel-Id and Micro-Tunnel-Session
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func (t *tun) getSocket(id, session string) (*socket, bool) {
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// get the socket
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t.RLock()
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s, ok := t.sockets[id+session]
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t.RUnlock()
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return s, ok
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}
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// newSocket creates a new socket and saves it
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func (t *tun) newSocket(id, session string) (*socket, bool) {
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// hash the id
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h := sha256.New()
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h.Write([]byte(id))
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id = fmt.Sprintf("%x", h.Sum(nil))
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// new socket
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s := &socket{
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id: id,
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session: session,
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closed: make(chan bool),
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recv: make(chan *message, 128),
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send: t.send,
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wait: make(chan bool),
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}
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// save socket
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t.Lock()
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_, ok := t.sockets[id+session]
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if ok {
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// socket already exists
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t.Unlock()
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return nil, false
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}
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t.sockets[id+session] = s
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t.Unlock()
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// return socket
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return s, true
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}
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// TODO: use tunnel id as part of the session
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func (t *tun) newSession() string {
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return uuid.New().String()
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}
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// process outgoing messages sent by all local sockets
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func (t *tun) process() {
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// manage the send buffer
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// all pseudo sockets throw everything down this
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for {
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select {
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case msg := <-t.send:
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nmsg := &transport.Message{
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Header: msg.data.Header,
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Body: msg.data.Body,
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}
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// set the tunnel id on the outgoing message
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nmsg.Header["Micro-Tunnel-Id"] = msg.id
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// set the session id
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nmsg.Header["Micro-Tunnel-Session"] = msg.session
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// send the message via the interface
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if err := t.link.Send(nmsg); err != nil {
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// no op
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// TODO: do something
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}
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case <-t.closed:
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return
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}
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}
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}
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// process incoming messages
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func (t *tun) listen() {
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for {
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// process anything via the net interface
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msg := new(transport.Message)
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err := t.link.Recv(msg)
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if err != nil {
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return
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}
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// first check Micro-Tunnel
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switch msg.Header["Micro-Tunnel"] {
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case "connect":
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// assuming new connection
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// TODO: do something with this
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continue
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case "close":
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// assuming connection closed
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// TODO: do something with this
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continue
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}
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// the tunnel id
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id := msg.Header["Micro-Tunnel-Id"]
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// the session id
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session := msg.Header["Micro-Tunnel-Session"]
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// if the session id is blank there's nothing we can do
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// TODO: check this is the case, is there any reason
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// why we'd have a blank session? Is the tunnel
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// used for some other purpose?
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if len(id) == 0 || len(session) == 0 {
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continue
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}
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// get the socket based on the tunnel id and session
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// this could be something we dialed in which case
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// we have a session for it otherwise its a listener
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s, exists := t.getSocket(id, session)
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if !exists {
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// try get it based on just the tunnel id
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// the assumption here is that a listener
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// has no session but its set a listener session
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s, exists = t.getSocket(id, "listener")
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if !exists {
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// drop it, we don't care about
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// messages we don't know about
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continue
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}
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}
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// is the socket closed?
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select {
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case <-s.closed:
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// closed
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delete(t.sockets, id)
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continue
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default:
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// process
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}
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// is the socket new?
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select {
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// if its new the socket is actually blocked waiting
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// for a connection. so we check if its waiting.
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case <-s.wait:
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// if its waiting e.g its new then we close it
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default:
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// set remote address of the socket
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s.remote = msg.Header["Remote"]
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close(s.wait)
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}
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// construct a new transport message
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tmsg := &transport.Message{
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Header: msg.Header,
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Body: msg.Body,
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}
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// construct the internal message
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imsg := &message{
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id: id,
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session: session,
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data: tmsg,
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}
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// append to recv backlog
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// we don't block if we can't pass it on
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select {
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case s.recv <- imsg:
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default:
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}
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}
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}
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func (t *tun) connect() error {
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return t.link.Send(&transport.Message{
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Header: map[string]string{
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"Micro-Tunnel": "connect",
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},
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})
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}
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func (t *tun) close() error {
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return t.link.Send(&transport.Message{
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Header: map[string]string{
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"Micro-Tunnel": "close",
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},
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})
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}
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// Close the tunnel
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func (t *tun) Close() error {
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t.Lock()
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defer t.Unlock()
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if !t.connected {
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return nil
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}
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select {
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case <-t.closed:
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return nil
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default:
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// close all the sockets
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for _, s := range t.sockets {
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s.Close()
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}
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// close the connection
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close(t.closed)
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t.connected = false
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// send a close message
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// we don't close the link
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// just the tunnel
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return t.close()
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}
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return nil
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}
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// Connect the tunnel
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func (t *tun) Connect() error {
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t.Lock()
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defer t.Unlock()
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// already connected
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if t.connected {
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return nil
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}
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// send the connect message
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if err := t.connect(); err != nil {
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return err
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}
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// set as connected
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t.connected = true
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// create new close channel
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t.closed = make(chan bool)
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// process messages to be sent
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go t.process()
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// process incoming messages
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go t.listen()
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return nil
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}
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// Dial an address
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func (t *tun) Dial(addr string) (Conn, error) {
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c, ok := t.newSocket(addr, t.newSession())
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if !ok {
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return nil, errors.New("error dialing " + addr)
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}
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// set remote
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c.remote = addr
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// set local
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c.local = t.link.Local()
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return c, nil
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}
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// Accept a connection on the address
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func (t *tun) Listen(addr string) (Listener, error) {
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// create a new socket by hashing the address
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c, ok := t.newSocket(addr, "listener")
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if !ok {
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return nil, errors.New("already listening on " + addr)
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}
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// set remote. it will be replaced by the first message received
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c.remote = t.link.Remote()
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// set local
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c.local = addr
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tl := &tunListener{
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addr: addr,
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// the accept channel
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accept: make(chan *socket, 128),
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// the channel to close
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closed: make(chan bool),
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// the connection
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conn: c,
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// the listener socket
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socket: c,
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}
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// this kicks off the internal message processor
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// for the listener so it can create pseudo sockets
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// per session if they do not exist or pass messages
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// to the existign sessions
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go tl.process()
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// return the listener
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return tl, nil
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}
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