Add HTTP3 support (experimental)

Co-authored-by: Ludovic Fernandez <ldez@users.noreply.github.com>

pkg/server/server_entrypoint_tcp_http3.go

@@ -0,0 +1,87 @@
+package server
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/lucas-clemente/quic-go/http3"
+	"github.com/traefik/traefik/v2/pkg/config/static"
+	"github.com/traefik/traefik/v2/pkg/log"
+	"github.com/traefik/traefik/v2/pkg/tcp"
+)
+
+type http3server struct {
+	*http3.Server
+
+	http3conn net.PacketConn
+
+	lock   sync.RWMutex
+	getter func(info *tls.ClientHelloInfo) (*tls.Config, error)
+}
+
+func newHTTP3Server(ctx context.Context, configuration *static.EntryPoint, httpsServer *httpServer) (*http3server, error) {
+	if !configuration.EnableHTTP3 {
+		return nil, nil
+	}
+
+	conn, err := net.ListenPacket("udp", configuration.GetAddress())
+	if err != nil {
+		return nil, fmt.Errorf("error while starting http3 listener: %w", err)
+	}
+
+	h3 := &http3server{
+		http3conn: conn,
+		getter: func(info *tls.ClientHelloInfo) (*tls.Config, error) {
+			return nil, errors.New("no tls config")
+		},
+	}
+
+	h3.Server = &http3.Server{
+		Server: &http.Server{
+			Addr:         configuration.GetAddress(),
+			Handler:      httpsServer.Server.(*http.Server).Handler,
+			ErrorLog:     httpServerLogger,
+			ReadTimeout:  time.Duration(configuration.Transport.RespondingTimeouts.ReadTimeout),
+			WriteTimeout: time.Duration(configuration.Transport.RespondingTimeouts.WriteTimeout),
+			IdleTimeout:  time.Duration(configuration.Transport.RespondingTimeouts.IdleTimeout),
+			TLSConfig:    &tls.Config{GetConfigForClient: h3.getGetConfigForClient},
+		},
+	}
+
+	previousHandler := httpsServer.Server.(*http.Server).Handler
+
+	httpsServer.Server.(*http.Server).Handler = http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		err := h3.Server.SetQuicHeaders(rw.Header())
+		if err != nil {
+			log.FromContext(ctx).Errorf("failed to set HTTP3 headers: %v", err)
+		}
+
+		previousHandler.ServeHTTP(rw, req)
+	})
+
+	return h3, nil
+}
+
+func (e *http3server) Start() error {
+	return e.Serve(e.http3conn)
+}
+
+func (e *http3server) Switch(rt *tcp.Router) {
+	e.lock.Lock()
+	defer e.lock.Unlock()
+
+	e.getter = rt.GetTLSGetClientInfo()
+}
+
+func (e *http3server) getGetConfigForClient(info *tls.ClientHelloInfo) (*tls.Config, error) {
+	e.lock.RLock()
+	defer e.lock.RUnlock()
+
+	return e.getter(info)
+}