Introduce a fast proxy mode to improve HTTP/1.1 performances with backends

Co-authored-by: Romain <rtribotte@users.noreply.github.com>
Co-authored-by: Julien Salleyron <julien.salleyron@gmail.com>

pkg/proxy/fast/upgrade.go

@@ -0,0 +1,104 @@
+package fast
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"strings"
+
+	"github.com/traefik/traefik/v3/pkg/proxy/httputil"
+	"github.com/valyala/fasthttp"
+	"golang.org/x/net/http/httpguts"
+)
+
+// switchProtocolCopier exists so goroutines proxying data back and
+// forth have nice names in stacks.
+type switchProtocolCopier struct {
+	user, backend io.ReadWriter
+}
+
+func (c switchProtocolCopier) copyFromBackend(errc chan<- error) {
+	_, err := io.Copy(c.user, c.backend)
+	errc <- err
+}
+
+func (c switchProtocolCopier) copyToBackend(errc chan<- error) {
+	_, err := io.Copy(c.backend, c.user)
+	errc <- err
+}
+
+func handleUpgradeResponse(rw http.ResponseWriter, req *http.Request, reqUpType string, res *fasthttp.Response, backConn net.Conn) {
+	defer backConn.Close()
+
+	resUpType := upgradeTypeFastHTTP(&res.Header)
+
+	if !strings.EqualFold(reqUpType, resUpType) {
+		httputil.ErrorHandler(rw, req, fmt.Errorf("backend tried to switch protocol %q when %q was requested", resUpType, reqUpType))
+		return
+	}
+
+	hj, ok := rw.(http.Hijacker)
+	if !ok {
+		httputil.ErrorHandler(rw, req, fmt.Errorf("can't switch protocols using non-Hijacker ResponseWriter type %T", rw))
+		return
+	}
+	backConnCloseCh := make(chan bool)
+	go func() {
+		// Ensure that the cancellation of a request closes the backend.
+		// See issue https://golang.org/issue/35559.
+		select {
+		case <-req.Context().Done():
+		case <-backConnCloseCh:
+		}
+		_ = backConn.Close()
+	}()
+
+	defer close(backConnCloseCh)
+
+	conn, brw, err := hj.Hijack()
+	if err != nil {
+		httputil.ErrorHandler(rw, req, fmt.Errorf("hijack failed on protocol switch: %w", err))
+		return
+	}
+	defer conn.Close()
+
+	for k, values := range rw.Header() {
+		for _, v := range values {
+			res.Header.Add(k, v)
+		}
+	}
+
+	if err := res.Header.Write(brw.Writer); err != nil {
+		httputil.ErrorHandler(rw, req, fmt.Errorf("response write: %w", err))
+		return
+	}
+
+	if err := brw.Flush(); err != nil {
+		httputil.ErrorHandler(rw, req, fmt.Errorf("response flush: %w", err))
+		return
+	}
+
+	errc := make(chan error, 1)
+	spc := switchProtocolCopier{user: conn, backend: backConn}
+	go spc.copyToBackend(errc)
+	go spc.copyFromBackend(errc)
+	<-errc
+}
+
+func upgradeType(h http.Header) string {
+	if !httpguts.HeaderValuesContainsToken(h["Connection"], "Upgrade") {
+		return ""
+	}
+
+	return h.Get("Upgrade")
+}
+
+func upgradeTypeFastHTTP(h fasthttpHeader) string {
+	if !bytes.Contains(h.Peek("Connection"), []byte("Upgrade")) {
+		return ""
+	}
+
+	return string(h.Peek("Upgrade"))
+}