xs/xsnet/tun.go

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// hkextun.go - Tunnel setup using an established xsnet.Conn
// Copyright (c) 2017-2020 Russell Magee
// Licensed under the terms of the MIT license (see LICENSE.mit in this
// distribution)
//
// golang implementation by Russ Magee (rmagee_at_gmail.com)
package xsnet
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"net"
"strings"
"sync"
"time"
"blitter.com/go/xs/logger"
)
type (
// Tunnels
// --
// 1. client is given (lport, remhost, rport) by local user
// 2. client sends [CSOTunReq:rport] to server
// client=> [CSOTunReq:rport] =>remhost
//
// remhost starts worker to receive/send data using rport
// remhost replies to client with rport to acknowledge tun is ready
// client<= [CSOTunAck:rport] <=remhost
// ... or if rhost rport refuses connection, sends
// [CSOTunRefused:rport]
//
// client starts worker to receive/send data using lport
// ... client disconnects: sends remhost [CSOTunClose:rport]
// ... or server disconnects: sends client [CSOTunClose:lport]
// server at any time sends [CSOTunRefused:rport] if daemon died
// --
// TunEndpoint [securePort:peer:dataPort]
TunEndpoint struct {
Rport uint16 // Names are from client's perspective
Lport uint16 // ... ie., RPort is on server, LPort is on client
Peer string //net.Addr
Died bool // set by client upon receipt of a CSOTunDisconn
KeepAlive uint32 // must be reset by client to keep server dial() alive
Ctl chan rune //See TunCtl_* consts
Data chan []byte
}
)
func (hc *Conn) CollapseAllTunnels(client bool) {
for k, t := range *hc.tuns {
var tunDst bytes.Buffer
binary.Write(&tunDst, binary.BigEndian, t.Lport)
binary.Write(&tunDst, binary.BigEndian, t.Rport)
if client {
hc.WritePacket(tunDst.Bytes(), CSOTunHangup)
} else {
hc.WritePacket(tunDst.Bytes(), CSOTunDisconn)
}
delete(*hc.tuns, k)
}
}
func (hc *Conn) InitTunEndpoint(lp uint16, p string /* net.Addr */, rp uint16) {
hc.Lock()
defer hc.Unlock()
if (*hc.tuns) == nil {
(*hc.tuns) = make(map[uint16]*TunEndpoint)
}
if (*hc.tuns)[rp] == nil {
var addrs []net.Addr
if p == "" {
addrs, _ = net.InterfaceAddrs()
p = addrs[0].String()
}
(*hc.tuns)[rp] = &TunEndpoint{ /*Status: CSOTunSetup,*/ Peer: p,
Lport: lp, Rport: rp, Data: make(chan []byte, 1),
Ctl: make(chan rune, 1)}
logger.LogDebug(fmt.Sprintf("InitTunEndpoint [%d:%s:%d]", lp, p, rp))
} else {
logger.LogDebug(fmt.Sprintf("InitTunEndpoint [reusing] %v", (*hc.tuns)[rp]))
if (*hc.tuns)[rp].Data == nil {
// When re-using a tunnel it will have its
// data channel removed on closure. Re-create it
(*hc.tuns)[rp].Data = make(chan []byte, 1)
}
(*hc.tuns)[rp].KeepAlive = 0
(*hc.tuns)[rp].Died = false
}
return
}
func (hc *Conn) StartClientTunnel(lport, rport uint16) {
hc.InitTunEndpoint(lport, "", rport)
go func() {
var wg sync.WaitGroup
for cmd := range (*hc.tuns)[rport].Ctl {
if cmd == 'a' {
l, e := net.Listen("tcp4", fmt.Sprintf(":%d", lport))
if e != nil {
logger.LogDebug(fmt.Sprintf("[ClientTun] Could not get lport %d! (%s)", lport, e))
} else {
logger.LogDebug(fmt.Sprintf("[ClientTun] Listening for client tunnel port %d", lport))
for {
c, e := l.Accept() // blocks until new conn
// If tunnel is being re-used, re-init it
if (*hc.tuns)[rport] == nil {
hc.InitTunEndpoint(lport, "", rport)
}
// ask server to dial() its side, rport
var tunDst bytes.Buffer
binary.Write(&tunDst, binary.BigEndian, lport)
binary.Write(&tunDst, binary.BigEndian, rport)
hc.WritePacket(tunDst.Bytes(), CSOTunSetup)
if e != nil {
logger.LogDebug(fmt.Sprintf("[ClientTun] Accept() got error(%v), hanging up.", e))
} else {
logger.LogDebug(fmt.Sprintf("[ClientTun] Accepted tunnel client %v", (*hc.tuns)[rport]))
// outside client -> tunnel lport
wg.Add(1)
go func() {
defer func() {
if c.Close() != nil {
logger.LogDebug("[ClientTun] worker A: conn c already closed")
} else {
logger.LogDebug("[ClientTun] worker A: closed conn c")
}
wg.Done()
}()
logger.LogDebug("[ClientTun] worker A: starting")
var tunDst bytes.Buffer
binary.Write(&tunDst, binary.BigEndian, lport)
binary.Write(&tunDst, binary.BigEndian, rport)
for {
rBuf := make([]byte, 1024)
//Read data from c, encrypt/write via hc to client(lport)
c.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
n, e := c.Read(rBuf)
if e != nil {
if e == io.EOF {
logger.LogDebug(fmt.Sprintf("[ClientTun] worker A: lport Disconnected: shutting down tunnel %v", (*hc.tuns)[rport]))
// if Died was already set, server-side already is gone.
if hc.TunIsAlive(rport) {
hc.WritePacket(tunDst.Bytes(), CSOTunHangup)
}
hc.ShutdownTun(rport) // FIXME: race-C
break
} else if strings.Contains(e.Error(), "i/o timeout") {
if !hc.TunIsAlive(rport) {
logger.LogDebug(fmt.Sprintf("[ClientTun] worker A: timeout: Server side died, hanging up %v", (*hc.tuns)[rport]))
hc.ShutdownTun(rport)
break
}
} else {
logger.LogDebug(fmt.Sprintf("[ClientTun] worker A: Read error from lport of tun %v\n%s", (*hc.tuns)[rport], e))
if hc.TunIsAlive(rport) {
hc.WritePacket(tunDst.Bytes(), CSOTunHangup)
}
hc.ShutdownTun(rport)
break
}
}
if n > 0 {
rBuf = append(tunDst.Bytes(), rBuf[:n]...)
_, de := hc.WritePacket(rBuf[:n+4], CSOTunData)
if de != nil {
logger.LogDebug(fmt.Sprintf("[ClientTun] worker A: Error writing to tunnel %v, %s]\n", (*hc.tuns)[rport], de))
break
}
}
}
logger.LogDebug("[ClientTun] worker A: exiting")
}()
// tunnel lport -> outside client (c)
wg.Add(1)
go func() {
defer func() {
if c.Close() != nil {
logger.LogDebug("[ClientTun] worker B: conn c already closed")
} else {
logger.LogDebug("[ClientTun] worker B: closed conn c")
}
wg.Done()
}()
logger.LogDebug("[ClientTun] worker B: starting")
for {
bytes, ok := <-(*hc.tuns)[rport].Data // FIXME: race-C w/ShutdownTun calls
if ok {
c.SetWriteDeadline(time.Now().Add(200 * time.Millisecond))
_, e := c.Write(bytes)
if e != nil {
logger.LogDebug(fmt.Sprintf("[ClientTun] worker B: lport conn closed"))
break
}
} else {
logger.LogDebug(fmt.Sprintf("[ClientTun] worker B: Channel was closed?"))
break
}
}
logger.LogDebug("[ClientTun] worker B: exiting")
}()
} // end Accept() worker block
wg.Wait()
// When both workers have exited due to a disconnect or other
// condition, it's safe to remove the tunnel descriptor.
logger.LogDebug("[ClientTun] workers exited")
hc.ShutdownTun(rport)
} // end for-accept
} // end Listen() block
}
} // end t.Ctl for
}()
}
func (hc *Conn) AgeTunnel(endp uint16) uint32 {
hc.Lock()
defer hc.Unlock()
(*hc.tuns)[endp].KeepAlive += 1
return (*hc.tuns)[endp].KeepAlive
}
func (hc *Conn) ResetTunnelAge(endp uint16) {
hc.Lock()
defer hc.Unlock()
(*hc.tuns)[endp].KeepAlive = 0
}
func (hc *Conn) TunIsNil(endp uint16) bool {
hc.Lock()
defer hc.Unlock()
return (*hc.tuns)[endp] == nil
}
func (hc *Conn) TunIsAlive(endp uint16) bool {
hc.Lock()
defer hc.Unlock()
return !(*hc.tuns)[endp].Died
}
func (hc *Conn) MarkTunDead(endp uint16) {
hc.Lock()
defer hc.Unlock()
(*hc.tuns)[endp].Died = true
}
func (hc *Conn) ShutdownTun(endp uint16) {
hc.Lock()
defer hc.Unlock()
if (*hc.tuns)[endp] != nil {
(*hc.tuns)[endp].Died = true
if (*hc.tuns)[endp].Data != nil {
close((*hc.tuns)[endp].Data)
(*hc.tuns)[endp].Data = nil
}
}
delete((*hc.tuns), endp)
}
func (hc *Conn) StartServerTunnel(lport, rport uint16) {
hc.InitTunEndpoint(lport, "", rport)
var err error
go func() {
var wg sync.WaitGroup
//
// worker to age server tunnel and kill it if keepalives
// stop from client
//
wg.Add(1)
go func() {
defer wg.Done()
for {
time.Sleep(100 * time.Millisecond)
if hc.TunIsNil(rport) {
logger.LogDebug("[ServerTun] worker A: Client endpoint removed.")
break
}
age := hc.AgeTunnel(rport)
if age > 25 {
hc.MarkTunDead(rport)
logger.LogDebug("[ServerTun] worker A: Client died, hanging up.")
break
}
}
}()
for cmd := range (*hc.tuns)[rport].Ctl {
var c net.Conn
logger.LogDebug(fmt.Sprintf("[ServerTun] got Ctl '%c'.", cmd))
if cmd == 'd' {
// if re-using tunnel, re-init it
if hc.TunIsNil(rport) {
hc.InitTunEndpoint(lport, "", rport)
}
logger.LogDebug("[ServerTun] dialling...")
c, err = net.Dial("tcp4", fmt.Sprintf(":%d", rport))
if err != nil {
logger.LogDebug(fmt.Sprintf("[ServerTun] Dial() error for tun %v: %s", (*hc.tuns)[rport], err))
var resp bytes.Buffer
binary.Write(&resp, binary.BigEndian /*lport*/, uint16(0))
binary.Write(&resp, binary.BigEndian, rport)
hc.WritePacket(resp.Bytes(), CSOTunRefused)
} else {
logger.LogDebug(fmt.Sprintf("[ServerTun] Tunnel Opened - %v", (*hc.tuns)[rport]))
var resp bytes.Buffer
binary.Write(&resp, binary.BigEndian, lport)
binary.Write(&resp, binary.BigEndian, rport)
logger.LogDebug(fmt.Sprintf("[ServerTun] Writing CSOTunSetupAck %v", (*hc.tuns)[rport]))
hc.WritePacket(resp.Bytes(), CSOTunSetupAck)
//
// worker to read data from the rport (to encrypt & send to client)
//
wg.Add(1)
go func() {
defer func() {
logger.LogDebug("[ServerTun] worker A: deferred hangup")
if c.Close() != nil {
logger.LogDebug("[ServerTun] workerA: conn c already closed")
}
wg.Done()
}()
logger.LogDebug("[ServerTun] worker A: starting")
var tunDst bytes.Buffer
binary.Write(&tunDst, binary.BigEndian, (*hc.tuns)[rport].Lport)
binary.Write(&tunDst, binary.BigEndian, (*hc.tuns)[rport].Rport)
for {
rBuf := make([]byte, 1024)
// Read data from c, encrypt/write via hc to client(lport)
c.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
n, e := c.Read(rBuf)
if e != nil {
if e == io.EOF {
logger.LogDebug(fmt.Sprintf("[ServerTun] worker A: rport Disconnected: shutting down tunnel %v", (*hc.tuns)[rport]))
if hc.TunIsAlive(rport) {
hc.WritePacket(tunDst.Bytes(), CSOTunDisconn)
}
hc.ShutdownTun(rport) // FIXME: race-A
break
} else if strings.Contains(e.Error(), "i/o timeout") {
if !hc.TunIsAlive(rport) {
logger.LogDebug(fmt.Sprintf("[ServerTun] worker A: timeout: Server side died, hanging up %v", (*hc.tuns)[rport]))
hc.ShutdownTun(rport) // FIXME: race-B
break
}
} else {
logger.LogDebug(fmt.Sprintf("[ServerTun] worker A: Read error from rport of tun %v: %s", (*hc.tuns)[rport], e))
if hc.TunIsAlive(rport) {
hc.WritePacket(tunDst.Bytes(), CSOTunDisconn)
}
hc.ShutdownTun(rport) // FIXME: race-C
break
}
}
if n > 0 {
rBuf = append(tunDst.Bytes(), rBuf[:n]...)
hc.WritePacket(rBuf[:n+4], CSOTunData)
}
}
logger.LogDebug("[ServerTun] worker A: exiting")
}()
// worker to read data from client (already decrypted) & fwd to rport
wg.Add(1)
go func() {
defer func() {
logger.LogDebug("[ServerTun] worker B: deferred hangup")
if c.Close() != nil {
logger.LogDebug("[ServerTun] worker B: conn c already closed")
}
wg.Done()
}()
logger.LogDebug("[ServerTun] worker B: starting")
for {
rData, ok := <-(*hc.tuns)[rport].Data // FIXME: race-A, race-B, race-C (w/ShutdownTun() calls)
if ok {
c.SetWriteDeadline(time.Now().Add(200 * time.Millisecond))
_, e := c.Write(rData)
if e != nil {
logger.LogDebug(fmt.Sprintf("[ServerTun] worker B: ERROR writing to rport conn"))
break
}
} else {
logger.LogDebug(fmt.Sprintf("[ServerTun] worker B: Channel was closed?"))
break
}
}
logger.LogDebug("[ServerTun] worker B: exiting")
}()
wg.Wait()
} // end if Dialled successfully
delete((*hc.tuns), rport)
}
} // t.Ctl read loop
logger.LogDebug("[ServerTun] Tunnel exiting t.Ctl read loop - channel closed??")
}()
}