/
client.go
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/
client.go
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// Copyright (c) 2021 Moriyoshi Koizumi.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
package inverse_tcp_tunnel
import (
"context"
"fmt"
"io"
"net"
"net/url"
"os"
"strings"
"sync"
"time"
"github.com/rs/zerolog"
"golang.org/x/net/proxy"
)
type ClientConfig struct {
Target1 string
Target2 string
ProxyURL string
Logger zerolog.Logger
}
type upstreamConn struct {
mu sync.Mutex
dsAddr addrKey
conn net.Conn
closed bool
writerChan chan []byte
}
type clientPacket struct {
upstream *upstreamConn
payload []byte
}
type Client struct {
logger zerolog.Logger
reconnectionInterval time.Duration
downstreamConnMu sync.Mutex
downstreamConn net.Conn
downstreamDialer func(context.Context) (net.Conn, error)
upstreamDialer func(context.Context) (net.Conn, error)
upstreamConnsMu sync.Mutex
upstreamConns map[net.Conn]*upstreamConn
upstreamConnsByDSAddr map[addrKey]*upstreamConn
packetChan chan clientPacket
connRequestChan chan addrKey
connCloseNoticeChan chan addrKey
gracefulShutdownChan chan struct{}
}
func doDial(ctx context.Context, dialer proxy.ContextDialer, addrRepr string) (net.Conn, error) {
var af, addr string
if strings.HasPrefix(addrRepr, "unix:") {
af = "unix"
addr = addrRepr[5:]
} else if strings.HasPrefix(addrRepr, "tcp:") {
af = "tcp"
addr = addrRepr[4:]
} else {
af = "tcp"
addr = addrRepr
}
return dialer.DialContext(ctx, af, addr)
}
func (c *Client) handleUpstream(ctx context.Context, wg *sync.WaitGroup, addr addrKey) {
ctx, cancel := context.WithCancel(ctx)
lc := c.logger.With().Str("addr", addr.String()).Logger()
l := lc.With().Str("module", "upstream_handler").Logger()
defer l.Debug().Msg("terminating")
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
l.Info().Msg("connecting to the upstream")
var err error
upstream := &upstreamConn{dsAddr: addr, writerChan: make(chan []byte)}
upstream.conn, err = c.upstreamDialer(ctx)
if err != nil {
l.Error().Msg(fmt.Sprintf("failed to connect to the upstream: %s", err.Error()))
err = sendCommand(c.downstreamConn, translateToErrorCode(err), &addr)
if err != nil {
l.Error().Err(err)
}
return
}
l.Info().Msg("connected to the upstream")
lc = lc.With().Str("remote_addr", upstream.conn.RemoteAddr().String()).Str("local_addr", upstream.conn.LocalAddr().String()).Logger()
c.upstreamConnsMu.Lock()
c.upstreamConns[upstream.conn] = upstream
c.upstreamConnsByDSAddr[upstream.dsAddr] = upstream
c.upstreamConnsMu.Unlock()
defer func() {
c.upstreamConnsMu.Lock()
delete(c.upstreamConns, upstream.conn)
delete(c.upstreamConnsByDSAddr, upstream.dsAddr)
c.upstreamConnsMu.Unlock()
}()
var innerWg sync.WaitGroup
innerWg.Add(1)
// reader
go func(wg *sync.WaitGroup) {
l := lc.With().Str("module", "upstream_handler/reader").Logger()
defer l.Debug().Msg("terminating")
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
buf := make([]byte, 131072)
outer:
for {
n, err := upstream.conn.Read(buf)
if err != nil {
if !os.IsTimeout(err) && err != io.EOF {
l.Error().Msg(fmt.Sprintf("failed to read: %s", err.Error()))
}
break outer
}
payload := make([]byte, n)
copy(payload, buf[:n])
c.packetChan <- clientPacket{upstream, payload}
}
}(&innerWg)
innerWg.Add(1)
// writer
go func(wg *sync.WaitGroup) {
l := lc.With().Str("module", "upstream_handler/writer").Logger()
defer l.Debug().Msg("terminating")
defer upstream.conn.Close()
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
outer:
for {
select {
case <-ctx.Done():
break outer
case payload, ok := <-upstream.writerChan:
if !ok {
break outer
}
n, err := upstream.conn.Write(payload)
if err != nil {
if !os.IsTimeout(err) && err != io.EOF {
l.Error().Msg(fmt.Sprintf("failed to write: %s", err.Error()))
}
break outer
}
if n != len(payload) {
l.Error().Msg(fmt.Sprintf("failed to write %d bytes (%d bytes actual)", len(payload), n))
}
}
}
}(&innerWg)
l.Info().Msg("sending reply for a connection request")
err = sendCommand(c.downstreamConn, cmdSuccess, &addr)
if err != nil {
l.Error().Err(err)
}
innerWg.Wait()
l.Info().Msg("sending close notice")
err = sendCommand(c.downstreamConn, cmdConnClose, &addr)
if err != nil {
l.Error().Err(err)
}
}
func (c *Client) handleDownstreamConn(ctx context.Context, wg *sync.WaitGroup) {
lc := c.logger.With().Str("remote_addr", c.downstreamConn.RemoteAddr().String()).Logger()
l := lc.With().Str("module", "downstrem_handler").Logger()
ctx, cancel := context.WithCancel(ctx)
defer l.Debug().Msg("terminating")
defer func() {
l.Info().Msg(fmt.Sprintf("downstream connection (%s) closed", c.downstreamConn.RemoteAddr().String()))
c.downstreamConnMu.Lock()
defer c.downstreamConnMu.Unlock()
c.downstreamConn.Close()
c.downstreamConn = nil
}()
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
var innerWg sync.WaitGroup
innerWg.Add(1)
// reader
go func(wg *sync.WaitGroup) {
l := lc.With().Str("module", "dowwnstream_handler/reader").Logger()
defer l.Debug().Msg("terminating")
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
outer:
for {
var cmd int
var addr addrKey
var payload []byte
err := recvRequestOrPacket(c.downstreamConn, &cmd, &addr, &payload)
if err != nil {
if !os.IsTimeout(err) {
l.Error().Err(err)
}
break outer
}
if payload == nil {
switch cmd {
case cmdConnect:
l.Info().Func(func(e *zerolog.Event) { e.Msg(fmt.Sprintf("received connection request: %s", addr.String())) })
c.connRequestChan <- addr
case cmdCloseNotify:
l.Info().Func(func(e *zerolog.Event) {
e.Msg(fmt.Sprintf("received connection close notification: %s", addr.String()))
})
c.connCloseNoticeChan <- addr
}
} else {
l.Debug().Func(func(e *zerolog.Event) { e.Msg(fmt.Sprintf("received packet of %d bytes", len(payload))) })
c.upstreamConnsMu.Lock()
upstream, ok := c.upstreamConnsByDSAddr[addr]
c.upstreamConnsMu.Unlock()
if !ok {
l.Error().Msg("upstream has gone")
continue
}
upstream.mu.Lock()
closed := upstream.closed
writerChan := upstream.writerChan
upstream.mu.Unlock()
if !closed {
writerChan <- payload
}
}
}
}(&innerWg)
innerWg.Add(1)
// writer
go func(wg *sync.WaitGroup) {
l := lc.With().Str("module", "dowwnstream_handler/writer").Logger()
defer l.Debug().Msg("terminating")
defer cancel()
defer c.downstreamConn.Close()
defer wg.Done()
l.Debug().Msg("launched")
outer:
for {
select {
case <-ctx.Done():
break outer
case p, ok := <-c.packetChan:
if !ok {
break outer
}
l.Debug().Func(func(e *zerolog.Event) { e.Msg(fmt.Sprintf("sending packet of %d bytes", len(p.payload))) })
sendPacket(c.downstreamConn, cmdPacket, p.upstream.dsAddr.ToTCPAddr(), p.payload)
}
}
}(&innerWg)
innerWg.Wait()
}
func (c *Client) Run(ctx context.Context) error {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
l := c.logger
var wg sync.WaitGroup
t := time.NewTicker(c.reconnectionInterval)
defer t.Stop()
wg.Add(1)
// event handler
go func(wg *sync.WaitGroup) {
l := l.With().Str("module", "event_handler").Logger()
defer l.Debug().Msg("terminating")
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
outer:
for {
select {
case <-ctx.Done():
break outer
case r, ok := <-c.connRequestChan:
if !ok {
break outer
}
wg.Add(1)
go c.handleUpstream(ctx, wg, r)
case r, ok := <-c.connCloseNoticeChan:
if !ok {
break outer
}
c.upstreamConnsMu.Lock()
upstream, ok := c.upstreamConnsByDSAddr[r]
c.upstreamConnsMu.Unlock()
// upstream is not gone yet
if ok {
upstream.mu.Lock()
if !upstream.closed {
upstream.closed = true
close(upstream.writerChan)
}
upstream.mu.Unlock()
}
}
}
}(&wg)
wg.Add(1)
// downstream watchdog
go func(wg *sync.WaitGroup) {
l := l.With().Str("module", "downstream_watchdog").Logger()
defer l.Debug().Msg("terminating")
defer cancel()
defer wg.Done()
l.Debug().Msg("launched")
for {
select {
case <-t.C:
go func() {
c.downstreamConnMu.Lock()
defer c.downstreamConnMu.Unlock()
if c.downstreamConn == nil {
l.Info().Msg("downstream is unconnected. trying to connect...")
downstreamConn, err := c.downstreamDialer(ctx)
if err != nil {
l.Error().Msg(fmt.Sprintf("failed to connect to downstream: %s", err.Error()))
return
}
l.Info().Msg(
fmt.Sprintf(
"downstream connection establised: %s => %s",
downstreamConn.LocalAddr().String(),
downstreamConn.RemoteAddr().String(),
),
)
c.downstreamConn = downstreamConn
wg.Add(1)
go c.handleDownstreamConn(ctx, wg)
}
}()
}
}
}(&wg)
wg.Wait()
return nil
}
func chooseDialer(defaultDialer, proxyDialer proxy.ContextDialer, target string) func(context.Context) (net.Conn, error) {
if strings.HasPrefix(target, "proxy:") {
target := target[6:]
return func(ctx context.Context) (net.Conn, error) {
if proxyDialer == nil {
return nil, fmt.Errorf("no proxy connection is configured for %s", target)
}
return doDial(ctx, proxyDialer, target)
}
} else {
return func(ctx context.Context) (net.Conn, error) {
return doDial(ctx, defaultDialer, target)
}
}
}
func NewClient(ctx context.Context, config ClientConfig) (*Client, error) {
var downstreamConn net.Conn
var err error
defer func() {
if err != nil {
if downstreamConn != nil {
downstreamConn.Close()
}
}
}()
defaultDialer := &net.Dialer{}
var proxyDialer proxy.ContextDialer
if config.ProxyURL != "" {
proxyURL, err := url.Parse(config.ProxyURL)
if err != nil {
return nil, fmt.Errorf("failed to parse proxy url: %s: %w", config.ProxyURL, err)
}
_proxyDialer, err := proxy.FromURL(proxyURL, defaultDialer)
if err != nil {
return nil, fmt.Errorf("failed to create a proxy dialer: %w", err)
}
var ok bool
proxyDialer, ok = _proxyDialer.(proxy.ContextDialer)
if !ok {
return nil, fmt.Errorf("proxy dialer does not implement ContextDialer")
}
}
return &Client{
reconnectionInterval: time.Second,
downstreamDialer: chooseDialer(defaultDialer, proxyDialer, config.Target1),
upstreamDialer: chooseDialer(defaultDialer, proxyDialer, config.Target2),
upstreamConns: make(map[net.Conn]*upstreamConn),
upstreamConnsByDSAddr: make(map[addrKey]*upstreamConn),
packetChan: make(chan clientPacket, 1),
connRequestChan: make(chan addrKey, 1),
connCloseNoticeChan: make(chan addrKey, 1),
logger: config.Logger,
gracefulShutdownChan: make(chan struct{}),
}, nil
}