// makeTCPDialer creates a custom dialer which creates TCPConn. An upstream
// proxy is used when specified.
func makeTCPDialer(config *DialConfig) func(network, addr string) (net.Conn, error) {
dialer := func(network, addr string) (net.Conn, error) {
if network != "tcp" {
return nil, errors.New("unsupported network type in TCPConn dialer")
}
conn, err := interruptibleTCPDial(addr, config)
if err != nil {
return nil, ContextError(err)
}
return conn, nil
}
if config.UpstreamProxyUrl != "" {
upstreamDialer := upstreamproxy.NewProxyDialFunc(
&upstreamproxy.UpstreamProxyConfig{
ForwardDialFunc: dialer,
ProxyURIString: config.UpstreamProxyUrl,
})
dialer = func(network, addr string) (conn net.Conn, err error) {
// The entire upstream dial is wrapped in an explicit timeout. This
// may include network connection read and writes when proxy auth negotation
// is performed.
type upstreamDialResult struct {
conn net.Conn
err error
}
if config.ConnectTimeout != 0 {
resultChannel := make(chan *upstreamDialResult, 2)
time.AfterFunc(config.ConnectTimeout, func() {
// TODO: we could "interrupt" the underlying TCPConn at this point, as
// it's being abandoned. But we don't have a reference to it. It's left
// to the outer DialConfig.PendingConns to track and clean up that TCPConn.
resultChannel <- &upstreamDialResult{nil, errors.New("upstreamproxy dial timeout")}
})
go func() {
conn, err := upstreamDialer(network, addr)
resultChannel <- &upstreamDialResult{conn, err}
}()
result := <-resultChannel
conn, err = result.conn, result.err
} else {
conn, err = upstreamDialer(network, addr)
}
if _, ok := err.(*upstreamproxy.Error); ok {
NoticeUpstreamProxyError(err)
}
return conn, err
}
}
return dialer
}
// proxiedTcpDial wraps a tcpDial call in an upstreamproxy dial.
func proxiedTcpDial(
addr string, config *DialConfig, dialResult chan error) (net.Conn, error) {
dialer := func(network, addr string) (net.Conn, error) {
return tcpDial(addr, config, dialResult)
}
upstreamDialer := upstreamproxy.NewProxyDialFunc(
&upstreamproxy.UpstreamProxyConfig{
ForwardDialFunc: dialer,
ProxyURIString: config.UpstreamProxyUrl,
})
netConn, err := upstreamDialer("tcp", addr)
if _, ok := err.(*upstreamproxy.Error); ok {
NoticeUpstreamProxyError(err)
}
return netConn, err
}