The route proxy tells a backend the request was HTTPS, and for which name

NewSingleHostReverseProxy sets only X-Forwarded-For, so a backend that writes its own addresses saw
the plain hop from the proxy: Gitea's Go import tag named an http clone URL and go get refused the
SDK's module path. The proxy now sets X-Forwarded-Proto, -Host and -For from the request it received,
and keeps the Host header as it was.

examples/route-proxy/forwarded_test.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"crypto/tls"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+)
+
+// A backend behind the proxy learns the client used TLS and which name it asked for, so the addresses
+// it writes into its own pages are the ones a client can use (2026-10-03: a forge's Go import tag
+// named an http clone URL, and Go refused the module path).
+func TestABackendIsToldTheRequestWasHTTPSAndForWhichName(t *testing.T) {
+	var proto, host, fwdHost, fwdFor string
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		proto, host, fwdHost, fwdFor = r.Header.Get("X-Forwarded-Proto"), r.Host, r.Header.Get("X-Forwarded-Host"), r.Header.Get("X-Forwarded-For")
+	}))
+	defer backend.Close()
+	where, _ := url.Parse(backend.URL)
+	req := httptest.NewRequest(http.MethodGet, "https://git.example.org/novox/mesh-sdk/go?go-get=1", nil)
+	req.TLS = &tls.ConnectionState{}
+	req.Host = "git.example.org"
+	req.RemoteAddr = "192.0.2.7:51000"
+	towards(where).ServeHTTP(httptest.NewRecorder(), req)
+	if proto != "https" || fwdHost != "git.example.org" || host != "git.example.org" || fwdFor != "192.0.2.7" {
+		t.Errorf("the backend was told proto=%q host=%q forwarded-host=%q for=%q", proto, host, fwdHost, fwdFor)
+	}
+}

examples/route-proxy/main.go

@@ -273,7 +273,7 @@ func (t *table) set(routes map[string][]rule, public map[string]bool) {
 				log.Printf("route %s points at %q, which is not a URL: %v", host, r.target, err)
 				continue
 			}
-			r.to = httputil.NewSingleHostReverseProxy(where)
+			r.to = towards(where)
 			if r.insecure {
 				r.to.Transport = &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: true}}
 			}
@@ -1060,3 +1060,17 @@ func asPort(v any) (int, bool) {
 	}
 	return 0, false
 }
+
+// towards proxies to one backend and tells it what the client asked: **X-Forwarded-Proto, -Host and
+// -For**, set from the request this proxy received. A backend that builds its own addresses — a forge
+// writing its clone URL into a page, a login redirect — otherwise sees the plain HTTP hop from this
+// proxy and writes `http://`, though every client reached it over TLS: Go refused the forge's module
+// path for exactly that on 2026-10-03, its import tag naming an http clone URL.
+// The standard library's NewSingleHostReverseProxy sets only X-Forwarded-For.
+func towards(where *url.URL) *httputil.ReverseProxy {
+	return &httputil.ReverseProxy{Rewrite: func(pr *httputil.ProxyRequest) {
+		pr.SetURL(where)
+		pr.Out.Host = pr.In.Host
+		pr.SetXForwarded()
+	}}
+}