Give a machine port one holder: refuse ssh's, another module's and a doubled one, and release the assignment a given port replaces (hq ADR 0100)

internal/catalogue/adoption_test.go

@@ -317,6 +317,14 @@ func TestAGivenPortIsTheNodesAndReachesSomething(t *testing.T) {
 	if _, err := GivenPorts(store, node(map[string]any{"5432": float64(70000)})); err == nil {
 		t.Fatal("a machine port that is not a port was given")
 	}
+	if _, err := GivenPorts(store, node(map[string]any{"5432": float64(22)})); err == nil {
+		t.Fatal("ssh's port was given")
+	}
+	broker := anAdoptedAnchor().Modules[2]
+	if _, err := GivenPorts(broker, node(map[string]any{"5671": float64(5700),
+		"5672": float64(5700)})); err == nil {
+		t.Fatal("one machine port was given for two of the module's ports")
+	}
 	if stray := UnusedSettings(store, node(map[string]any{"5432": float64(5433)})); len(stray) != 0 {
 		t.Fatalf("a given port is called stray: %v", stray)
 	}

internal/catalogue/filtering.go

@@ -518,9 +518,22 @@ func GivenPorts(m Manifest, layers []Layer) (map[int]int, error) {
 				return nil, fmt.Errorf("%s gives port %d the machine port %v, which is not a port",
 					m.Module, port, value)
 			}
+			if at == SSHPort {
+				return nil, fmt.Errorf("%s gives port %d the machine port %d, which is ssh's — the "+
+					"one port a machine may never lose", m.Module, port, at)
+			}
 			out[port] = at
 		}
 	}
+	// One holder per machine port, within the module too.
+	holder := map[int]int{}
+	for port, at := range out {
+		if other, twice := holder[at]; twice {
+			return nil, fmt.Errorf("%s gives machine port %d to both its %d and its %d", m.Module,
+				at, min(port, other), max(port, other))
+		}
+		holder[at] = port
+	}
 	if len(out) == 0 {
 		return nil, nil
 	}