deconnect/internal/domains/deconnector/tunnel.go

package deconnector

import (
	"bufio"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
)

func (d *Deconnector) handleTunnel(clientConn net.Conn, host string, upstreamURL *url.URL) {
	d.app.Logger().WithField("host", host).Info("Handling CONNECT tunnel")

	upstreamConn, err := d.dialer.Dial()
	if err != nil {
		d.app.Logger().WithError(err).Error("upstream dial failed")
		fmt.Fprintf(clientConn, "HTTP/1.1 502 Bad Gateway\r\n\r\n")

		return
	}
	defer upstreamConn.Close()

	connectLine := fmt.Sprintf(
		"CONNECT %s HTTP/1.1\r\nHost: %s\r\n\r\n", host, host,
	)
	fmt.Fprint(upstreamConn, connectLine)

	resp, err := http.ReadResponse(bufio.NewReader(upstreamConn), nil)
	if err != nil || resp.StatusCode > 499 {
		d.app.Logger().WithError(err).Error("upstream CONNECT failed")
		fmt.Fprintf(clientConn, "HTTP/1.1 502 Bad Gateway\r\n\r\n")

		return
	}

	fmt.Fprintf(clientConn, "HTTP/1.1 200 Connection established\r\n\r\n")

	done := make(chan struct{}, 2)

	go func() { io.Copy(upstreamConn, clientConn); done <- struct{}{} }()
	go func() { io.Copy(clientConn, upstreamConn); done <- struct{}{} }()

	<-done
}