Wire wake and identity into crossbar; v2 smoke and README

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

cmd/fakeupstream/main.go

@@ -7,7 +7,9 @@
 // SSE chunks 200 ms apart when the body has "stream": true, then a final chunk carrying
 // "usage" and llama-server style "timings", then [DONE]; one JSON answer with usage and
 // timings otherwise. -slow adds that many milliseconds before answering (for queue tests).
-// Every response carries X-Upstream: <name>.
+// Every response carries X-Upstream: <name>. /props reports -n-ctx and -slots. With -wol-listen,
+// a valid wake-on-LAN magic packet for -wol-mac received on that UDP address removes the down
+// file, so the fake "boots" when woken.
 package main
 
 import (
@@ -16,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"strings"
@@ -28,7 +31,14 @@ func main() {
 	models := flag.String("models", "m", "comma-separated model ids for /v1/models")
 	downFile := flag.String("down-file", "", "while this file exists, /health answers 503")
 	slow := flag.Int("slow", 0, "milliseconds to wait before answering a completion")
+	nCtx := flag.Int("n-ctx", 8192, "n_ctx reported by /props")
+	slots := flag.Int("slots", 2, "total_slots reported by /props")
+	wolListen := flag.String("wol-listen", "", "UDP address to listen on for a wake-on-LAN magic packet")
+	wolMAC := flag.String("wol-mac", "aa:bb:cc:dd:ee:01", "MAC the magic packet must carry")
 	flag.Parse()
+	if *wolListen != "" && *downFile != "" {
+		go wakeOnPacket(*wolListen, *wolMAC, *downFile)
+	}
 
 	ids := strings.Split(*models, ",")
 	mux := http.NewServeMux()
@@ -56,7 +66,7 @@ func main() {
 	})
 	mux.HandleFunc("/props", func(w http.ResponseWriter, r *http.Request) {
 		stamp(w)
-		writeJSON(w, map[string]any{"default_generation_settings": map[string]any{"n_ctx": 8192}, "total_slots": 2, "model_path": *name})
+		writeJSON(w, map[string]any{"default_generation_settings": map[string]any{"n_ctx": *nCtx}, "total_slots": *slots, "model_path": *name})
 	})
 	mux.HandleFunc("/v1/chat/completions", func(w http.ResponseWriter, r *http.Request) {
 		stamp(w)
@@ -113,3 +123,39 @@ func writeJSON(w http.ResponseWriter, v any) {
 	w.Header().Set("Content-Type", "application/json")
 	_ = json.NewEncoder(w).Encode(v)
 }
+
+// wakeOnPacket removes downFile when a magic packet for mac arrives: 6×0xff then the MAC 16 times.
+func wakeOnPacket(addr, mac, downFile string) {
+	hw, err := net.ParseMAC(mac)
+	if err != nil {
+		log.Fatalf("wol-mac: %v", err)
+	}
+	pc, err := net.ListenPacket("udp4", addr)
+	if err != nil {
+		log.Fatalf("wol-listen: %v", err)
+	}
+	log.Printf("fakeupstream listening for wake-on-LAN on %s (mac %s)", addr, hw)
+	buf := make([]byte, 256)
+	for {
+		n, _, err := pc.ReadFrom(buf)
+		if err != nil {
+			return
+		}
+		if n != 102 {
+			continue
+		}
+		ok := true
+		for i := 0; i < 6; i++ {
+			ok = ok && buf[i] == 0xff
+		}
+		for i := 0; i < 16 && ok; i++ {
+			for j := 0; j < 6; j++ {
+				ok = ok && buf[6+6*i+j] == hw[j]
+			}
+		}
+		if ok {
+			log.Printf("magic packet received: waking (removing %s)", downFile)
+			_ = os.Remove(downFile)
+		}
+	}
+}