examples/route-proxy/main.go

@@ -416,8 +416,17 @@ func handler(held *table) http.Handler {
 			// **Named, not a bare 404.** A route that was withdrawn and a name that never existed
 			// are different things, and a proxy that says only "not found" makes an operator go
 			// and read the mesh to tell them apart. What it is serving is the answer to both.
+			//
+			// And since a host may now be routed only on some paths, those are a third thing:
+			// saying "no route for this name" while listing that very name as served is a
+			// contradiction an operator would have to disbelieve the proxy to get past.
 			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 			w.WriteHeader(http.StatusNotFound)
+			if held.routed(r.Host) {
+				fmt.Fprintf(w, "%s is served here, but no route covers %q.\n",
+					bareHost(r.Host), r.URL.Path)
+				return
+			}
 			fmt.Fprintf(w, "no route for %q in this mesh.\nserving: %s\n",
 				r.Host, strings.Join(held.names(), ", "))
 			return
@@ -524,7 +533,7 @@ func routesFrom(path string) (map[string][]rule, error) {
 		host := strings.ToLower(name)
 
 		made := rule{path: asPath(c.Values["path"])}
-		if p, ok := asPort(c.Values["priority"]); ok {
+		if p, ok := asWhole(c.Values["priority"]); ok {
 			made.priority = p
 		}
 		made.policy.deny, _ = c.Values["deny"].(bool)
@@ -574,6 +583,26 @@ func routesFrom(path string) (map[string][]rule, error) {
 	return out, nil
 }
 
+// asWhole is any whole number the mesh wrote, whatever its magnitude.
+//
+// **Not asPort.** Priority was read with the port reader first, which caps at 65535 — so a rule
+// declared at a priority above that silently became priority 0 and stopped shadowing the route it
+// exists to shadow. The one real rule this has to reproduce is declared at 100000, so the bug was
+// exactly load-bearing. A priority is an ordering, not a port: it has no range.
+func asWhole(v any) (int, bool) {
+	switch n := v.(type) {
+	case float64:
+		// JSON makes a float of every number, so a non-integral one was not meant as a priority.
+		if n != float64(int(n)) {
+			return 0, false
+		}
+		return int(n), true
+	case int:
+		return n, true
+	}
+	return 0, false
+}
+
 // asPath is the path prefix a rule is scoped to, or "" for every path.
 func asPath(v any) string {
 	p, _ := v.(string)

examples/route-proxy/policy_test.go

@@ -231,3 +231,43 @@ func TestPriorityOutranksPathLength(t *testing.T) {
 		t.Fatalf("a higher priority did not win: %+v", rules[0])
 	}
 }
+
+// A priority above a port number survives, because a priority is an ordering and not a port.
+//
+// **Found by review, and it was load-bearing.** Priority was first read with the port reader, which
+// caps at 65535 — so a rule declared above that silently became priority 0 and stopped shadowing the
+// route it exists to shadow. The one real rule this has to reproduce is declared at 100000, so the
+// capability would have shipped looking complete and doing nothing.
+func TestAPriorityAboveAPortNumberSurvives(t *testing.T) {
+	at, port := served(t, "the workload")
+	proxy := proxyFor(t, `{"given":[
+	  {"from":"forge","node":"anchor","at":"`+at+`","values":{"name":"forge.example","port":`+strconv.Itoa(port)+`}},
+	  {"from":"forge","node":"anchor","values":{"name":"forge.example","path":"/api/internal","priority":100000,"deny":true}}
+	]}`)
+
+	if got := ask(t, proxy, "forge.example", "/api/internal/hook", [2]string{}).StatusCode; got != http.StatusForbidden {
+		t.Fatalf("a rule declared at priority 100000 answered %d instead of refusing", got)
+	}
+}
+
+// A host routed only on some paths says so, rather than claiming the name is not served here.
+//
+// Saying "no route for this name" while listing that very name as served is a contradiction an
+// operator has to disbelieve the proxy to get past — and path scoping makes it reachable, because a
+// host can now have rules that none of this request's paths match.
+func TestAHostRoutedOnlyOnSomePathsSaysSo(t *testing.T) {
+	proxy := proxyFor(t, `{"given":[
+	  {"from":"forge","node":"anchor","values":{"name":"forge.example","path":"/api/internal","deny":true}}
+	]}`)
+
+	answer := ask(t, proxy, "forge.example", "/elsewhere", [2]string{})
+	if answer.StatusCode != http.StatusNotFound {
+		t.Fatalf("an uncovered path answered %d", answer.StatusCode)
+	}
+	body := make([]byte, 256)
+	n, _ := answer.Body.Read(body)
+	said := string(body[:n])
+	if !strings.Contains(said, "is served here") || !strings.Contains(said, "/elsewhere") {
+		t.Fatalf("the refusal does not distinguish an uncovered path from an unserved name: %q", said)
+	}
+}