micro/tunnel/default.go

1344 lines
30 KiB
Go

package tunnel
import (
"errors"
"math/rand"
"strings"
"sync"
"time"
"github.com/google/uuid"
"github.com/micro/go-micro/transport"
"github.com/micro/go-micro/util/log"
)
var (
// DiscoverTime sets the time at which we fire discover messages
DiscoverTime = 30 * time.Second
// KeepAliveTime defines time interval we send keepalive messages to outbound links
KeepAliveTime = 30 * time.Second
// ReconnectTime defines time interval we periodically attempt to reconnect dead links
ReconnectTime = 5 * time.Second
)
// tun represents a network tunnel
type tun struct {
options Options
sync.RWMutex
// the unique id for this tunnel
id string
// tunnel token for session encryption
token string
// to indicate if we're connected or not
connected bool
// the send channel for all messages
send chan *message
// close channel
closed chan bool
// a map of sessions based on Micro-Tunnel-Channel
sessions map[string]*session
// outbound links
links map[string]*link
// listener
listener transport.Listener
}
// create new tunnel on top of a link
func newTunnel(opts ...Option) *tun {
rand.Seed(time.Now().UnixNano())
options := DefaultOptions()
for _, o := range opts {
o(&options)
}
return &tun{
options: options,
id: options.Id,
token: options.Token,
send: make(chan *message, 128),
closed: make(chan bool),
sessions: make(map[string]*session),
links: make(map[string]*link),
}
}
// Init initializes tunnel options
func (t *tun) Init(opts ...Option) error {
t.Lock()
for _, o := range opts {
o(&t.options)
}
t.Unlock()
return nil
}
// getSession returns a session from the internal session map.
// It does this based on the Micro-Tunnel-Channel and Micro-Tunnel-Session
func (t *tun) getSession(channel, session string) (*session, bool) {
// get the session
t.RLock()
s, ok := t.sessions[channel+session]
t.RUnlock()
return s, ok
}
// delSession deletes a session if it exists
func (t *tun) delSession(channel, session string) {
t.Lock()
if s, ok := t.sessions[channel+session]; ok {
s.Close()
}
delete(t.sessions, channel+session)
t.Unlock()
}
// listChannels returns a list of listening channels
func (t *tun) listChannels() []string {
t.RLock()
//nolint:prealloc
var channels []string
for _, session := range t.sessions {
if session.session != "listener" {
continue
}
channels = append(channels, session.channel)
}
t.RUnlock()
return channels
}
// newSession creates a new session and saves it
func (t *tun) newSession(channel, sessionId string) (*session, bool) {
// new session
s := &session{
tunnel: t.id,
channel: channel,
session: sessionId,
token: t.token,
closed: make(chan bool),
recv: make(chan *message, 128),
send: t.send,
errChan: make(chan error, 1),
}
// save session
t.Lock()
_, ok := t.sessions[channel+sessionId]
if ok {
// session already exists
t.Unlock()
return nil, false
}
t.sessions[channel+sessionId] = s
t.Unlock()
// return session
return s, true
}
// TODO: use tunnel id as part of the session
func (t *tun) newSessionId() string {
return uuid.New().String()
}
// announce will send a message to the link to tell the other side of a channel mapping we have.
// This usually happens if someone calls Dial and sends a discover message but otherwise we
// periodically send these messages to asynchronously manage channel mappings.
func (t *tun) announce(channel, session string, link *link) {
// create the "announce" response message for a discover request
msg := &transport.Message{
Header: map[string]string{
"Micro-Tunnel": "announce",
"Micro-Tunnel-Id": t.id,
"Micro-Tunnel-Channel": channel,
"Micro-Tunnel-Session": session,
"Micro-Tunnel-Link": link.id,
},
}
// if no channel is present we've been asked to discover all channels
if len(channel) == 0 {
// get the list of channels
channels := t.listChannels()
// if there are no channels continue
if len(channels) == 0 {
return
}
// create a list of channels as comma separated list
channel = strings.Join(channels, ",")
// set channels as header
msg.Header["Micro-Tunnel-Channel"] = channel
} else {
// otherwise look for a single channel mapping
// looking for existing mapping as a listener
_, exists := t.getSession(channel, "listener")
if !exists {
return
}
}
log.Debugf("Tunnel sending announce for discovery of channel(s) %s", channel)
// send back the announcement
if err := link.Send(msg); err != nil {
log.Debugf("Tunnel failed to send announcement for channel(s) %s message: %v", channel, err)
}
}
// manage monitors outbound links and attempts to reconnect to the failed ones
func (t *tun) manage(reconnect time.Duration) {
r := time.NewTicker(reconnect)
defer r.Stop()
for {
select {
case <-t.closed:
return
case <-r.C:
t.manageLinks()
}
}
}
// manageLink sends channel discover requests periodically and
// keepalive messages to link
func (t *tun) manageLink(link *link) {
keepalive := time.NewTicker(KeepAliveTime)
defer keepalive.Stop()
discover := time.NewTicker(DiscoverTime)
defer discover.Stop()
wait := func(d time.Duration) {
// jitter
j := rand.Int63n(int64(d.Seconds() / 2.0))
time.Sleep(time.Duration(j) * time.Second)
}
for {
select {
case <-t.closed:
return
case <-link.closed:
return
case <-discover.C:
// wait half the discover time
wait(DiscoverTime)
// send a discovery message to the link
log.Debugf("Tunnel sending discover to link: %v", link.Remote())
if err := t.sendMsg("discover", link); err != nil {
log.Debugf("Tunnel failed to send discover to link %s: %v", link.Remote(), err)
}
case <-keepalive.C:
// wait half the keepalive time
wait(KeepAliveTime)
// send keepalive message
log.Debugf("Tunnel sending keepalive to link: %v", link.Remote())
if err := t.sendMsg("keepalive", link); err != nil {
log.Debugf("Tunnel error sending keepalive to link %v: %v", link.Remote(), err)
t.delLink(link.Remote())
return
}
}
}
}
// manageLinks is a function that can be called to immediately to link setup
// it purges dead links while generating new links for any nodes not connected
func (t *tun) manageLinks() {
delLinks := make(map[*link]string)
connected := make(map[string]bool)
t.RLock()
// get list of nodes from options
nodes := t.options.Nodes
// check the link status and purge dead links
for node, link := range t.links {
// check link status
switch link.State() {
case "closed", "error":
delLinks[link] = node
default:
connected[node] = true
}
}
t.RUnlock()
// build a list of links to connect to
var connect []string
for _, node := range nodes {
// check if we're connected
if _, ok := connected[node]; ok {
continue
}
// add nodes to connect o
connect = append(connect, node)
}
// delete the dead links
if len(delLinks) > 0 {
t.Lock()
for link, node := range delLinks {
log.Debugf("Tunnel deleting dead link for %s", node)
// check if the link exists
l, ok := t.links[node]
if ok {
// close and delete
l.Close()
delete(t.links, node)
}
// if the link does not match our own
if l != link {
// close our link just in case
link.Close()
}
}
t.Unlock()
}
var wg sync.WaitGroup
// establish new links
for _, node := range connect {
wg.Add(1)
go func(node string) {
defer wg.Done()
// create new link
// if we're using quic it should be a max 10 second handshake period
link, err := t.setupLink(node)
if err != nil {
log.Debugf("Tunnel failed to setup node link to %s: %v", node, err)
return
}
t.Lock()
// just check nothing else was setup in the interim
if _, ok := t.links[node]; ok {
link.Close()
t.Unlock()
return
}
// save the link
t.links[node] = link
t.Unlock()
}(node)
}
// wait for all threads to finish
wg.Wait()
}
// process outgoing messages sent by all local sessions
func (t *tun) process() {
// manage the send buffer
// all pseudo sessions throw everything down this
for {
select {
case msg := <-t.send:
// build a list of links to send to
var sendTo []*link
var err error
t.RLock()
// build the list of links ot send to
for _, link := range t.links {
// get the values we need
link.RLock()
id := link.id
connected := link.connected
loopback := link.loopback
_, exists := link.channels[msg.channel]
link.RUnlock()
// if the link is not connected skip it
if !connected {
log.Debugf("Link for node %s not connected", id)
err = ErrLinkDisconnected
continue
}
// if the link was a loopback accepted connection
// and the message is being sent outbound via
// a dialled connection don't use this link
if loopback && msg.outbound {
err = ErrLinkLoopback
continue
}
// if the message was being returned by the loopback listener
// send it back up the loopback link only
if msg.loopback && !loopback {
err = ErrLinkRemote
continue
}
// check the multicast mappings
if msg.mode == Multicast {
// channel mapping not found in link
if !exists {
continue
}
} else {
// if we're picking the link check the id
// this is where we explicitly set the link
// in a message received via the listen method
if len(msg.link) > 0 && id != msg.link {
err = ErrLinkNotFound
continue
}
}
// add to link list
sendTo = append(sendTo, link)
}
t.RUnlock()
// no links to send to
if len(sendTo) == 0 {
log.Debugf("No links to send message type: %s channel: %s", msg.typ, msg.channel)
t.respond(msg, err)
continue
}
// send the message
go t.sendTo(sendTo, msg)
case <-t.closed:
return
}
}
}
// send response back for a message to the caller
func (t *tun) respond(msg *message, err error) {
select {
case msg.errChan <- err:
default:
}
}
// sendTo sends a message to the chosen links
func (t *tun) sendTo(links []*link, msg *message) error {
// the function that sends the actual message
send := func(link *link, msg *transport.Message) error {
if err := link.Send(msg); err != nil {
log.Debugf("Tunnel error sending %+v to %s: %v", msg.Header, link.Remote(), err)
t.delLink(link.Remote())
return err
}
return nil
}
newMsg := &transport.Message{
Header: make(map[string]string),
}
// set the data
if msg.data != nil {
for k, v := range msg.data.Header {
newMsg.Header[k] = v
}
newMsg.Body = msg.data.Body
}
// set message head
newMsg.Header["Micro-Tunnel"] = msg.typ
// set the tunnel id on the outgoing message
newMsg.Header["Micro-Tunnel-Id"] = msg.tunnel
// set the tunnel channel on the outgoing message
newMsg.Header["Micro-Tunnel-Channel"] = msg.channel
// set the session id
newMsg.Header["Micro-Tunnel-Session"] = msg.session
// error channel for call
errChan := make(chan error, len(links))
// execute in parallel
sendTo := func(l *link, m *transport.Message, errChan chan error) {
errChan <- send(l, m)
}
// send the message
for _, link := range links {
// send the message via the current link
log.Tracef("Tunnel sending %+v to %s", newMsg.Header, link.Remote())
// blast it in a go routine since its multicast/broadcast
if msg.mode > Unicast {
// make a copy
m := &transport.Message{
Header: make(map[string]string),
Body: make([]byte, len(newMsg.Body)),
}
copy(m.Body, newMsg.Body)
for k, v := range newMsg.Header {
m.Header[k] = v
}
go sendTo(link, m, errChan)
continue
}
// otherwise send as unicast
if err := send(link, newMsg); err != nil {
// put in the error chan if it failed
errChan <- err
continue
}
// sent successfully so just return
t.respond(msg, nil)
return nil
}
// either all unicast attempts failed or we're
// checking the multicast/broadcast attempts
var err error
// check all the errors
for i := 0; i < len(links); i++ {
err = <-errChan
// success
if err == nil {
break
}
}
// return error. it's non blocking
t.respond(msg, err)
return err
}
func (t *tun) delLink(remote string) {
t.Lock()
// get the link
for id, link := range t.links {
if link.id != remote {
continue
}
// close and delete
log.Debugf("Tunnel deleting link node: %s remote: %s", id, link.Remote())
link.Close()
delete(t.links, id)
}
t.Unlock()
}
// process incoming messages
func (t *tun) listen(link *link) {
// remove the link on exit
defer func() {
t.delLink(link.Remote())
}()
// let us know if its a loopback
var loopback bool
var connected bool
// set the connected value
link.RLock()
connected = link.connected
link.RUnlock()
for {
// process anything via the net interface
msg := new(transport.Message)
if err := link.Recv(msg); err != nil {
log.Debugf("Tunnel link %s receive error: %v", link.Remote(), err)
return
}
// TODO: figure out network authentication
// for now we use tunnel token to encrypt/decrypt
// session communication, but we will probably need
// some sort of network authentication (token) to avoid
// having rogue actors spamming the network
// message type
mtype := msg.Header["Micro-Tunnel"]
// the tunnel id
id := msg.Header["Micro-Tunnel-Id"]
// the tunnel channel
channel := msg.Header["Micro-Tunnel-Channel"]
// the session id
sessionId := msg.Header["Micro-Tunnel-Session"]
// if its not connected throw away the link
// the first message we process needs to be connect
if !connected && mtype != "connect" {
log.Debugf("Tunnel link %s not connected", link.id)
return
}
// this state machine block handles the only message types
// that we know or care about; connect, close, open, accept,
// discover, announce, session, keepalive
switch mtype {
case "connect":
log.Debugf("Tunnel link %s received connect message", link.Remote())
link.Lock()
// check if we're connecting to ourselves?
if id == t.id {
link.loopback = true
loopback = true
}
// set to remote node
link.id = link.Remote()
// set as connected
link.connected = true
connected = true
link.Unlock()
// save the link once connected
t.Lock()
t.links[link.Remote()] = link
t.Unlock()
// send back an announcement of our channels discovery
go t.announce("", "", link)
// ask for the things on the other wise
go t.sendMsg("discover", link)
// nothing more to do
continue
case "close":
// if there is no channel then we close the link
// as its a signal from the other side to close the connection
if len(channel) == 0 {
log.Debugf("Tunnel link %s received close message", link.Remote())
return
}
log.Debugf("Tunnel link %s received close message for %s", link.Remote(), channel)
// the entire listener was closed by the remote side so we need to
// remove the channel mapping for it. should we also close sessions?
if sessionId == "listener" {
link.delChannel(channel)
// TODO: find all the non listener unicast sessions
// and close them. think aboud edge cases first
continue
}
// assuming there's a channel and session
// try get the dialing socket
s, exists := t.getSession(channel, sessionId)
if exists && !loopback {
// only delete the session if its unicast
// otherwise ignore close on the multicast
if s.mode == Unicast {
// only delete this if its unicast
// but not if its a loopback conn
t.delSession(channel, sessionId)
continue
}
}
// otherwise its a session mapping of sorts
case "keepalive":
log.Debugf("Tunnel link %s received keepalive", link.Remote())
// save the keepalive
link.keepalive()
continue
// a new connection dialled outbound
case "open":
log.Debugf("Tunnel link %s received open %s %s", link.id, channel, sessionId)
// we just let it pass through to be processed
// an accept returned by the listener
case "accept":
s, exists := t.getSession(channel, sessionId)
// just set accepted on anything not unicast
if exists && s.mode > Unicast {
s.accepted = true
continue
}
// if its already accepted move on
if exists && s.accepted {
continue
}
// otherwise we're going to process to accept
// a continued session
case "session":
// process message
log.Tracef("Tunnel received %+v from %s", msg.Header, link.Remote())
// an announcement of a channel listener
case "announce":
log.Tracef("Tunnel received %+v from %s", msg.Header, link.Remote())
// process the announcement
channels := strings.Split(channel, ",")
// update mapping in the link
link.setChannel(channels...)
// this was an announcement not intended for anything
// if the dialing side sent "discover" then a session
// id would be present. We skip in case of multicast.
switch sessionId {
case "listener", "multicast", "":
continue
}
// get the session that asked for the discovery
s, exists := t.getSession(channel, sessionId)
if exists {
// don't bother it's already discovered
if s.discovered {
continue
}
msg := &message{
typ: "announce",
tunnel: id,
channel: channel,
session: sessionId,
link: link.id,
}
// send the announce back to the caller
select {
case <-s.closed:
case s.recv <- msg:
}
}
continue
case "discover":
// send back an announcement
go t.announce(channel, sessionId, link)
continue
default:
// blackhole it
continue
}
// strip tunnel message header
for k := range msg.Header {
if strings.HasPrefix(k, "Micro-Tunnel") {
delete(msg.Header, k)
}
}
// if the session id is blank there's nothing we can do
// TODO: check this is the case, is there any reason
// why we'd have a blank session? Is the tunnel
// used for some other purpose?
if len(channel) == 0 || len(sessionId) == 0 {
continue
}
var s *session
var exists bool
// If its a loopback connection then we've enabled link direction
// listening side is used for listening, the dialling side for dialling
switch {
case loopback, mtype == "open":
s, exists = t.getSession(channel, "listener")
// only return accept to the session
case mtype == "accept":
log.Debugf("Tunnel received accept message for channel: %s session: %s", channel, sessionId)
s, exists = t.getSession(channel, sessionId)
if exists && s.accepted {
continue
}
default:
// get the session based on the tunnel id and session
// this could be something we dialed in which case
// we have a session for it otherwise its a listener
s, exists = t.getSession(channel, sessionId)
if !exists {
// try get it based on just the tunnel id
// the assumption here is that a listener
// has no session but its set a listener session
s, exists = t.getSession(channel, "listener")
}
}
// bail if no session or listener has been found
if !exists {
log.Tracef("Tunnel skipping no channel: %s session: %s exists", channel, sessionId)
// drop it, we don't care about
// messages we don't know about
continue
}
// is the session closed?
select {
case <-s.closed:
// closed
delete(t.sessions, channel)
continue
default:
// otherwise process
}
log.Tracef("Tunnel using channel: %s session: %s type: %s", s.channel, s.session, mtype)
// construct a new transport message
tmsg := &transport.Message{
Header: msg.Header,
Body: msg.Body,
}
// construct the internal message
imsg := &message{
tunnel: id,
typ: mtype,
channel: channel,
session: sessionId,
mode: s.mode,
data: tmsg,
link: link.id,
loopback: loopback,
errChan: make(chan error, 1),
}
// append to recv backlog
// we don't block if we can't pass it on
select {
case s.recv <- imsg:
default:
}
}
}
func (t *tun) sendMsg(method string, link *link) error {
return link.Send(&transport.Message{
Header: map[string]string{
"Micro-Tunnel": method,
"Micro-Tunnel-Id": t.id,
},
})
}
// setupLink connects to node and returns link if successful
// It returns error if the link failed to be established
func (t *tun) setupLink(node string) (*link, error) {
log.Debugf("Tunnel setting up link: %s", node)
c, err := t.options.Transport.Dial(node)
if err != nil {
log.Debugf("Tunnel failed to connect to %s: %v", node, err)
return nil, err
}
log.Debugf("Tunnel connected to %s", node)
// create a new link
link := newLink(c)
// set link id to remote side
link.Lock()
link.id = c.Remote()
link.Unlock()
// send the first connect message
if err := t.sendMsg("connect", link); err != nil {
link.Close()
return nil, err
}
// we made the outbound connection
// and sent the connect message
link.connected = true
// process incoming messages
go t.listen(link)
// manage keepalives and discovery messages
go t.manageLink(link)
return link, nil
}
func (t *tun) setupLinks() {
var wg sync.WaitGroup
for _, node := range t.options.Nodes {
wg.Add(1)
go func(node string) {
defer wg.Done()
// we're not trying to fix existing links
if _, ok := t.links[node]; ok {
return
}
// create new link
link, err := t.setupLink(node)
if err != nil {
log.Debugf("Tunnel failed to setup node link to %s: %v", node, err)
return
}
// save the link
t.links[node] = link
}(node)
}
// wait for all threads to finish
wg.Wait()
}
// connect the tunnel to all the nodes and listen for incoming tunnel connections
func (t *tun) connect() error {
l, err := t.options.Transport.Listen(t.options.Address)
if err != nil {
return err
}
// save the listener
t.listener = l
go func() {
// accept inbound connections
err := l.Accept(func(sock transport.Socket) {
log.Debugf("Tunnel accepted connection from %s", sock.Remote())
// create a new link
link := newLink(sock)
// manage the link
go t.manageLink(link)
// listen for inbound messages.
// only save the link once connected.
// we do this inside liste
t.listen(link)
})
t.RLock()
defer t.RUnlock()
// still connected but the tunnel died
if err != nil && t.connected {
log.Logf("Tunnel listener died: %v", err)
}
}()
return nil
}
// Connect the tunnel
func (t *tun) Connect() error {
t.Lock()
defer t.Unlock()
// already connected
if t.connected {
// do it immediately
t.setupLinks()
// setup links
return nil
}
// connect the tunnel: start the listener
if err := t.connect(); err != nil {
return err
}
// set as connected
t.connected = true
// create new close channel
t.closed = make(chan bool)
// process outbound messages to be sent
// process sends to all links
go t.process()
// call setup before managing them
t.setupLinks()
// manage the links
go t.manage(ReconnectTime)
return nil
}
func (t *tun) close() error {
// close all the sessions
for id, s := range t.sessions {
s.Close()
delete(t.sessions, id)
}
// close all the links
for node, link := range t.links {
link.Send(&transport.Message{
Header: map[string]string{
"Micro-Tunnel": "close",
"Micro-Tunnel-Id": t.id,
},
})
link.Close()
delete(t.links, node)
}
// close the listener
// this appears to be blocking
return t.listener.Close()
}
// pickLink will pick the best link based on connectivity, delay, rate and length
func (t *tun) pickLink(links []*link) *link {
var metric float64
var chosen *link
// find the best link
for i, link := range links {
// don't use disconnected or errored links
if link.State() != "connected" {
continue
}
// skip the loopback
if link.Loopback() {
continue
}
// get the link state info
d := float64(link.Delay())
l := float64(link.Length())
r := link.Rate()
// metric = delay x length x rate
m := d * l * r
// first link so just and go
if i == 0 {
metric = m
chosen = link
continue
}
// we found a better metric
if m < metric {
metric = m
chosen = link
}
}
// if there's no link we're just going to mess around
if chosen == nil {
i := rand.Intn(len(links))
return links[i]
}
// we chose the link with;
// the lowest delay e.g least messages queued
// the lowest rate e.g the least messages flowing
// the lowest length e.g the smallest roundtrip time
return chosen
}
func (t *tun) Address() string {
t.RLock()
defer t.RUnlock()
if !t.connected {
return t.options.Address
}
return t.listener.Addr()
}
// Close the tunnel
func (t *tun) Close() error {
t.Lock()
defer t.Unlock()
if !t.connected {
return nil
}
log.Debug("Tunnel closing")
select {
case <-t.closed:
return nil
default:
close(t.closed)
t.connected = false
}
// send a close message
// we don't close the link
// just the tunnel
return t.close()
}
// Dial an address
func (t *tun) Dial(channel string, opts ...DialOption) (Session, error) {
// get the options
options := DialOptions{
Timeout: DefaultDialTimeout,
Wait: true,
}
for _, o := range opts {
o(&options)
}
log.Debugf("Tunnel dialing %s", channel)
// create a new session
c, ok := t.newSession(channel, t.newSessionId())
if !ok {
return nil, errors.New("error dialing " + channel)
}
// set remote
c.remote = channel
// set local
c.local = "local"
// outbound session
c.outbound = true
// set the mode of connection unicast/multicast/broadcast
c.mode = options.Mode
// set the dial timeout
c.dialTimeout = options.Timeout
// set read timeout set to never
c.readTimeout = time.Duration(-1)
// set the link
c.link = options.Link
var links []*link
// did we measure the rtt
var measured bool
t.RLock()
// non multicast so we need to find the link
for _, link := range t.links {
// use the link specified it its available
if len(c.link) > 0 && link.id != c.link {
continue
}
// get the channel
lastMapped := link.getChannel(channel)
// we have at least one channel mapping
if !lastMapped.IsZero() {
links = append(links, link)
c.discovered = true
}
}
t.RUnlock()
// link option was specified to pick the link
if len(options.Link) > 0 {
// link not found and one was specified so error out
if len(links) == 0 {
// delete session and return error
t.delSession(c.channel, c.session)
log.Debugf("Tunnel deleting session %s %s: %v", c.session, c.channel, ErrLinkNotFound)
return nil, ErrLinkNotFound
}
// assume discovered because we picked
c.discovered = true
// link asked for and found and now
// we've been asked not to wait so return
if !options.Wait {
c.accepted = true
return c, nil
}
}
// discovered so set the link if not multicast
if c.discovered && c.mode == Unicast {
// pick a link if not specified
if len(c.link) == 0 {
// pickLink will pick the best link
link := t.pickLink(links)
// set the link
c.link = link.id
}
}
// if its not already discovered we need to attempt to do so
if !c.discovered {
// piggy back roundtrip
nowRTT := time.Now()
// attempt to discover the link
err := c.Discover()
if err != nil {
t.delSession(c.channel, c.session)
log.Debugf("Tunnel deleting session %s %s: %v", c.session, c.channel, err)
return nil, err
}
// set roundtrip
d := time.Since(nowRTT)
// set the link time
t.RLock()
link, ok := t.links[c.link]
t.RUnlock()
if ok {
// set the rountrip time
link.setRTT(d)
// set measured to true
measured = true
}
}
// return early if its not unicast
// we will not wait for "open" for multicast
// and we will not wait it told not to
if c.mode != Unicast || !options.Wait {
return c, nil
}
// Note: we go no further for multicast or broadcast.
// This is a unicast session so we call "open" and wait
// for an "accept"
// reset now in case we use it
now := time.Now()
// try to open the session
if err := c.Open(); err != nil {
// delete the session
t.delSession(c.channel, c.session)
log.Debugf("Tunnel deleting session %s %s: %v", c.session, c.channel, err)
return nil, err
}
// set time take to open
d := time.Since(now)
// if we haven't measured the roundtrip do it now
if !measured {
// set the link time
t.RLock()
link, ok := t.links[c.link]
t.RUnlock()
if ok {
// set the rountrip time
link.setRTT(d)
}
}
return c, nil
}
// Accept a connection on the address
func (t *tun) Listen(channel string, opts ...ListenOption) (Listener, error) {
log.Debugf("Tunnel listening on %s", channel)
options := ListenOptions{
// Read timeout defaults to never
Timeout: time.Duration(-1),
}
for _, o := range opts {
o(&options)
}
// create a new session by hashing the address
c, ok := t.newSession(channel, "listener")
if !ok {
return nil, errors.New("already listening on " + channel)
}
// delete function removes the session when closed
delFunc := func() {
t.delSession(channel, "listener")
}
// set remote. it will be replaced by the first message received
c.remote = "remote"
// set local
c.local = channel
// set mode
c.mode = options.Mode
// set the timeout
c.readTimeout = options.Timeout
tl := &tunListener{
channel: channel,
// tunnel token
token: t.token,
// the accept channel
accept: make(chan *session, 128),
// the channel to close
closed: make(chan bool),
// tunnel closed channel
tunClosed: t.closed,
// the listener session
session: c,
// delete session
delFunc: delFunc,
}
// this kicks off the internal message processor
// for the listener so it can create pseudo sessions
// per session if they do not exist or pass messages
// to the existign sessions
go tl.process()
// return the listener
return tl, nil
}
func (t *tun) Links() []Link {
t.RLock()
links := make([]Link, 0, len(t.links))
for _, link := range t.links {
links = append(links, link)
}
t.RUnlock()
return links
}
func (t *tun) String() string {
return "mucp"
}