Wake: a target may list several broadcast addresses

Config keeps broadcast (one) and adds broadcasts (a list); exactly one must
be present. Wake.Addresses() returns Broadcast then Broadcasts; checkWake
errors on both-set, neither-or-empty, and non-host:port entries. Waker sends
to every address in order, logging/past a failure so one dead address does
not stop the others, and returns false only when none could be sent.

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

internal/wake/broadcasts_test.go

@@ -0,0 +1,73 @@
+package wake_test
+
+import (
+	"net"
+	"testing"
+	"time"
+
+	"git.wntrmute.dev/kyle/crossbar/internal/wake"
+)
+
+// listener returns a UDP socket on 127.0.0.1 and a channel that gets one value per datagram.
+func listener(t *testing.T) (string, <-chan []byte) {
+	t.Helper()
+	pc, err := net.ListenPacket("udp4", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { pc.Close() })
+	got := make(chan []byte, 4)
+	go func() {
+		buf := make([]byte, 256)
+		for {
+			n, _, err := pc.ReadFrom(buf)
+			if err != nil {
+				return
+			}
+			b := make([]byte, n)
+			copy(b, buf[:n])
+			got <- b
+		}
+	}()
+	return pc.LocalAddr().String(), got
+}
+
+func expectPacket(t *testing.T, name string, got <-chan []byte) {
+	t.Helper()
+	select {
+	case b := <-got:
+		if len(b) != 102 {
+			t.Errorf("%s: got %d bytes, want a 102-byte magic packet", name, len(b))
+		}
+	case <-time.After(2 * time.Second):
+		t.Errorf("%s: no packet within two seconds", name)
+	}
+}
+
+// A target may name several broadcast addresses (a host that roams between two networks): the
+// packet goes to every one of them, and one address that cannot be resolved does not stop the
+// others.
+func TestWakeSendsToEveryBroadcast(t *testing.T) {
+	a, gotA := listener(t)
+	b, gotB := listener(t)
+	h := &fakeHealth{after: 1 << 30} // never healthy
+	w := wake.New(map[string]wake.Target{"titan": {MAC: "aa:bb:cc:dd:ee:ff", Broadcasts: []string{a, "256.1.1.1:9", b}, Wait: 300 * time.Millisecond}}, h)
+	w.PollEvery(20 * time.Millisecond)
+	if w.Wake(t.Context(), "titan") {
+		t.Errorf("Wake must report false when the host never comes up")
+	}
+	expectPacket(t, "first address", gotA)
+	expectPacket(t, "third address, after an unresolvable second", gotB)
+}
+
+// The single-address form keeps working, alone or together with the list.
+func TestWakeBroadcastAndBroadcastsCombine(t *testing.T) {
+	a, gotA := listener(t)
+	b, gotB := listener(t)
+	h := &fakeHealth{after: 1 << 30} // never healthy
+	w := wake.New(map[string]wake.Target{"titan": {MAC: "aa:bb:cc:dd:ee:ff", Broadcast: a, Broadcasts: []string{b}, Wait: 300 * time.Millisecond}}, h)
+	w.PollEvery(20 * time.Millisecond)
+	w.Wake(t.Context(), "titan")
+	expectPacket(t, "Broadcast", gotA)
+	expectPacket(t, "Broadcasts[0]", gotB)
+}