Give a machine port only to a port a module's container publishes, which is the only one the mesh can move (hq ADR 0038)

internal/catalogue/adoption_test.go

@@ -397,3 +397,16 @@ func TestPublishedLeavesOutLoopbackInBothFamilies(t *testing.T) {
 		t.Fatalf("published is %v, want %v", got, want)
 	}
 }
+
+// novox/hq ADR 0038: only a published port is the mesh's to move. A module that binds the machine
+// itself listens where its software was told to, so giving it a machine port is refused.
+func TestAGivenPortIsRefusedForAPortNoContainerPublishes(t *testing.T) {
+	onTheMachine := Manifest{Module: "daemon",
+		Listens: []Listening{{Port: 9000, From: FromMesh}}, Guards: []int{9000}}
+	layers := []Layer{{From: "node anchor",
+		Values: map[string]any{PortsSetting: map[string]any{"9000": float64(9100)}}}}
+	_, err := GivenPorts(onTheMachine, layers)
+	if err == nil || !strings.Contains(err.Error(), "does not publish") {
+		t.Fatalf("a port no container publishes was given: %v", err)
+	}
+}

internal/catalogue/filtering.go

@@ -475,17 +475,16 @@ const MeshWideLayer = "the mesh"
 // GivenPorts reads a module's given machine ports from its settings: software port → machine port.
 //
 // Refused from a mesh-wide layer — a port is a fact about one machine, and one number for every
-// machine is the collision this exists to avoid — and for a port the module neither listens on,
-// publishes from a container, nor guards: a given port that reaches nothing is a setting somebody
-// believes changed something.
+// machine is the collision this exists to avoid — and for a port the module's containers do not
+// publish.
+//
+// **Only a published port is the mesh's to move** (novox/hq ADR 0038). A container's mapping is
+// what translates; a module binding the machine's network directly binds the number its software
+// was configured with, and moving that number would put it in the filter, in the openings and in
+// what consumers are told while the software still listens on the old one — a port that reads as
+// moved and is not.
 func GivenPorts(m Manifest, layers []Layer) (map[int]int, error) {
 	known := map[int]bool{}
-	for _, l := range m.Listens {
-		known[l.Port] = true
-	}
-	for _, p := range m.Guards {
-		known[p] = true
-	}
 	for _, p := range containerPorts(m) {
 		known[p] = true
 	}
@@ -510,8 +509,9 @@ func GivenPorts(m Manifest, layers []Layer) (map[int]int, error) {
 				return nil, fmt.Errorf("%s gives %q a port, which is not a port", m.Module, portText)
 			}
 			if !known[port] {
-				return nil, fmt.Errorf("%s gives port %d a machine port, and it neither listens "+
-					"on, publishes nor guards %d — the setting reaches nothing", m.Module, port, port)
+				return nil, fmt.Errorf("%s gives port %d a machine port, and no container of its "+
+					"publishes %d — the mesh cannot move a port the module does not publish; the "+
+					"software would go on listening where it was told to", m.Module, port, port)
 			}
 			at, ok := asPort(value)
 			if !ok || at < 1 || at > 65535 {