improve transparent mode

caddyhttp/proxy/proxy.go

@@ -30,6 +30,8 @@ type Upstream interface {
 	Select() *UpstreamHost
 	// Checks if subpath is not an ignored path
 	AllowedPath(string) bool
+	// Is Upstream in transparent mode?
+	Transparent() bool
 }
 
 // UpstreamHostDownFunc can be used to customize how Down behaves.
@@ -94,6 +96,7 @@ func (p Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
 	start := time.Now()
 	for time.Now().Sub(start) < tryDuration {
 		host := upstream.Select()
+
 		if host == nil {
 			return http.StatusBadGateway, errUnreachable
 		}
@@ -125,6 +128,9 @@ func (p Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
 			if v, ok := host.UpstreamHeaders["Host"]; ok {
 				outreq.Host = replacer.Replace(v[len(v)-1])
 			}
+			if upstream.Transparent() {
+				host.UpstreamHeaders.Set("Host", host.Name)
+			}
 			// modify headers for request that will be sent to the upstream host
 			upHeaders := createHeadersByRules(host.UpstreamHeaders, r.Header, replacer)
 			for k, v := range upHeaders {

caddyhttp/proxy/proxy_test.go

@@ -687,6 +687,10 @@ func (u *fakeUpstream) AllowedPath(requestPath string) bool {
 	return true
 }
 
+func (u *fakeUpstream) Transparent() bool {
+	return true
+}
+
 // newWebSocketTestProxy returns a test proxy that will
 // redirect to the specified backendAddr. The function
 // also sets up the rules/environment for testing WebSocket
@@ -729,6 +733,10 @@ func (u *fakeWsUpstream) AllowedPath(requestPath string) bool {
 	return true
 }
 
+func (u *fakeWsUpstream) Transparent() bool {
+	return true
+}
+
 // recorderHijacker is a ResponseRecorder that can
 // be hijacked.
 type recorderHijacker struct {

caddyhttp/proxy/upstream.go

@@ -102,10 +102,6 @@ func NewStaticUpstreams(c caddyfile.Dispenser) ([]Upstream, error) {
 			upstream.Hosts[i] = uh
 		}
 
-		if upstream.transparent {
-			upstream.upstreamHeaders.Add("Host", upstream.Hosts[0].Name)
-		}
-
 		if upstream.HealthCheck.Path != "" {
 			upstream.HealthCheck.Client = http.Client{
 				Timeout: upstream.HealthCheck.Timeout,
@@ -372,6 +368,11 @@ func (u *staticUpstream) Select() *UpstreamHost {
 	return u.Policy.Select(pool)
 }
 
+// Transparent returns true if upstream in transparent mode
+func (u *staticUpstream) Transparent() bool {
+	return u.transparent
+}
+
 func (u *staticUpstream) AllowedPath(requestPath string) bool {
 	for _, ignoredSubPath := range u.IgnoredSubPaths {
 		if httpserver.Path(path.Clean(requestPath)).Matches(path.Join(u.From(), ignoredSubPath)) {

caddyhttp/proxy/upstream_test.go

@@ -209,12 +209,8 @@ func TestParseBlock(t *testing.T) {
 		for _, upstream := range upstreams {
 			headers := upstream.Select().UpstreamHeaders
 
-			if _, ok := headers["Host"]; !ok {
-				t.Errorf("Test %d: Could not find the Host header", i+1)
-			}
-
-			if v, _ := headers["Host"]; v[0] != upstream.Select().Name {
-				t.Errorf("Test %d: Host not match first hostname in upstream", i+1)
+			if !upstream.Transparent() {
+				t.Errorf("Test %d: Upstream should be in transparent mode", i+1)
 			}
 
 			if _, ok := headers["X-Real-Ip"]; !ok {