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TCPConn.go
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TCPConn.go
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/*
* Copyright (c) 2015, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package psiphon
import (
"context"
"errors"
"fmt"
"net"
"sync/atomic"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/fragmentor"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/upstreamproxy"
)
// TCPConn is a customized TCP connection that supports the Closer interface
// and which may be created using options in DialConfig, including
// UpstreamProxyURL, DeviceBinder, IPv6Synthesizer, and ResolvedIPCallback.
// DeviceBinder is implemented using SO_BINDTODEVICE/IP_BOUND_IF, which
// requires syscall-level socket code.
type TCPConn struct {
net.Conn
isClosed int32
}
// NewTCPDialer creates a TCP Dialer.
//
// Note: do not set an UpstreamProxyURL in the config when using NewTCPDialer
// as a custom dialer for NewProxyAuthTransport (or http.Transport with a
// ProxyUrl), as that would result in double proxy chaining.
func NewTCPDialer(config *DialConfig) Dialer {
return func(ctx context.Context, network, addr string) (net.Conn, error) {
if network != "tcp" {
return nil, common.ContextError(fmt.Errorf("%s unsupported", network))
}
return DialTCP(ctx, addr, config)
}
}
// DialTCP creates a new, connected TCPConn.
func DialTCP(
ctx context.Context, addr string, config *DialConfig) (net.Conn, error) {
var conn net.Conn
var err error
if config.UpstreamProxyURL != "" {
conn, err = proxiedTcpDial(ctx, addr, config)
} else {
conn, err = tcpDial(ctx, addr, config)
}
if err != nil {
return nil, common.ContextError(err)
}
// Note: when an upstream proxy is used, we don't know what IP address
// was resolved, by the proxy, for that destination.
if config.ResolvedIPCallback != nil && config.UpstreamProxyURL == "" {
ipAddress := common.IPAddressFromAddr(conn.RemoteAddr())
if ipAddress != "" {
config.ResolvedIPCallback(ipAddress)
}
}
if config.FragmentorConfig.MayFragment() {
conn = fragmentor.NewConn(
config.FragmentorConfig,
func(message string) {
NoticeFragmentor(config.DiagnosticID, message)
},
conn)
}
return conn, nil
}
// proxiedTcpDial wraps a tcpDial call in an upstreamproxy dial.
func proxiedTcpDial(
ctx context.Context, addr string, config *DialConfig) (net.Conn, error) {
interruptConns := common.NewConns()
// Note: using interruptConns to interrupt a proxy dial assumes
// that the underlying proxy code will immediately exit with an
// error when all underlying conns unexpectedly close; e.g.,
// the proxy handshake won't keep retrying to dial new conns.
dialer := func(network, addr string) (net.Conn, error) {
conn, err := tcpDial(ctx, addr, config)
if conn != nil {
if !interruptConns.Add(conn) {
err = errors.New("already interrupted")
conn.Close()
conn = nil
}
}
if err != nil {
return nil, common.ContextError(err)
}
return conn, nil
}
upstreamDialer := upstreamproxy.NewProxyDialFunc(
&upstreamproxy.UpstreamProxyConfig{
ForwardDialFunc: dialer,
ProxyURIString: config.UpstreamProxyURL,
CustomHeaders: config.CustomHeaders,
})
type upstreamDialResult struct {
conn net.Conn
err error
}
resultChannel := make(chan upstreamDialResult)
go func() {
conn, err := upstreamDialer("tcp", addr)
if _, ok := err.(*upstreamproxy.Error); ok {
NoticeUpstreamProxyError(err)
}
resultChannel <- upstreamDialResult{
conn: conn,
err: err,
}
}()
var result upstreamDialResult
select {
case result = <-resultChannel:
case <-ctx.Done():
result.err = ctx.Err()
// Interrupt the goroutine
interruptConns.CloseAll()
<-resultChannel
}
if result.err != nil {
return nil, common.ContextError(result.err)
}
return result.conn, nil
}
// Close terminates a connected TCPConn or interrupts a dialing TCPConn.
func (conn *TCPConn) Close() (err error) {
if !atomic.CompareAndSwapInt32(&conn.isClosed, 0, 1) {
return nil
}
return conn.Conn.Close()
}
// IsClosed implements the Closer iterface. The return value
// indicates whether the TCPConn has been closed.
func (conn *TCPConn) IsClosed() bool {
return atomic.LoadInt32(&conn.isClosed) == 1
}
// CloseWrite calls net.TCPConn.CloseWrite when the underlying
// conn is a *net.TCPConn.
func (conn *TCPConn) CloseWrite() (err error) {
if conn.IsClosed() {
return common.ContextError(errors.New("already closed"))
}
tcpConn, ok := conn.Conn.(*net.TCPConn)
if !ok {
return common.ContextError(errors.New("conn is not a *net.TCPConn"))
}
return tcpConn.CloseWrite()
}