Function proxyHTTPScheme

http.go:185–302

Service an incoming HTTP connection on conn by sending a request out to the world through dst. If the URL in the request does not contain a scheme, use the specified scheme for the proxied request.

(dst http.RoundTripper, conn net.Conn, outgoingScheme string)

// Service an incoming HTTP connection on conn by sending a request out to the world through dst.
// If the URL in the request does not contain a scheme, use the specified scheme for the proxied request.
func proxyHTTPScheme(dst http.RoundTripper, conn net.Conn, outgoingScheme string) {
	defer handlePanic()
	defer conn.Close()

	verbosef("intercepted a connection to %v", conn.LocalAddr())

	// wrap the connection with a byte counter
	counts := countBytesConn{Conn: conn}
	conn = &counts

	// read the HTTP request (TODO: support HTTP/2 using golang.org/x/net/http2)
	req, err := http.ReadRequest(bufio.NewReader(conn))
	if err != nil {
		errorf("error reading http request over tls server conn: %v, aborting", err)
		return
	}
	defer req.Body.Close()

	verbosef("decoded an HTTP request for %v sent to %v", req.URL, conn.LocalAddr())

	// the request may contain a relative URL but we need an absolute URL for call to RoundTrip
	if req.URL.Host == "" {
		req.URL.Host = req.Host
		if req.URL.Host == "" {
			req.URL.Host = conn.LocalAddr().String()
		}
	}
	if req.URL.Scheme == "" {
		req.URL.Scheme = outgoingScheme
	}

	// add the IP to which we intercepted packets as a context variable
	req = req.WithContext(context.WithValue(req.Context(), dialToContextKey, conn.LocalAddr().String()))

	// capture the request body into memory for inspection later
	var reqbody bytes.Buffer
	req.Body = TeeReadCloser(req.Body, &reqbody)

	// it seems that harlog assumes that request.GetBody will be non-nil whenever request.Body is non-nil
	req.GetBody = func() (io.ReadCloser, error) { return req.Body, nil }

	// do roundtrip to the actual server in the world -- we use RoundTrip here because
	// we do not want to follow redirects or accumulate our own cookies
	resp, err := dst.RoundTrip(req)
	if err != nil {
		// error here means the server hostname could not be resolved, or a TCP connection could not be made,
		// or TLS could not be negotiated, or something like that
		errbody := []byte(err.Error())
		resp = &http.Response{
			Proto:         "HTTP/1.1",
			ProtoMajor:    1,
			ProtoMinor:    1,
			Status:        http.StatusText(http.StatusBadGateway),
			StatusCode:    http.StatusBadGateway,
			Header:        make(http.Header),
			ContentLength: int64(len(errbody)),
			Body:          io.NopCloser(bytes.NewReader(errbody)),
		}