chore(cmd): clean up commands (#9705)

Move infrastructure related commands to under `cmd/infra` and
development stuff to `cmd/dev`. The default build command builds the
regular user facing binaries: syncthing, stdiscosrv, and strelaysrv.

cmd/dev/stdisco/main.go

@@ -0,0 +1,117 @@
+// Copyright (C) 2016 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/binary"
+	"flag"
+	"log"
+	"strings"
+	"time"
+
+	_ "github.com/syncthing/syncthing/lib/automaxprocs"
+	"github.com/syncthing/syncthing/lib/beacon"
+	"github.com/syncthing/syncthing/lib/discover"
+	"github.com/syncthing/syncthing/lib/protocol"
+)
+
+var (
+	all  = false // print all packets, not just first from each device/source
+	fake = false // send fake packets to lure out other devices faster
+	mc   = "[ff12::8384]:21027"
+	bc   = 21027
+)
+
+var (
+	// Static prefix that we use when generating fake device IDs, so that we
+	// can recognize them ourselves. Also makes the device ID start with
+	// "STPROBE-" which is humanly recognizable.
+	randomPrefix = []byte{148, 223, 23, 4, 148}
+
+	// Our random, fake, device ID that we use when sending announcements.
+	myID = randomDeviceID()
+)
+
+func main() {
+	flag.BoolVar(&all, "all", all, "Print all received announcements (not only first)")
+	flag.BoolVar(&fake, "fake", fake, "Send fake announcements")
+	flag.StringVar(&mc, "mc", mc, "IPv6 multicast address")
+	flag.IntVar(&bc, "bc", bc, "IPv4 broadcast port number")
+	flag.Parse()
+
+	if fake {
+		log.Println("My ID:", myID)
+	}
+
+	ctx := context.Background()
+
+	runbeacon(ctx, beacon.NewMulticast(mc), fake)
+	runbeacon(ctx, beacon.NewBroadcast(bc), fake)
+
+	select {}
+}
+
+func runbeacon(ctx context.Context, bc beacon.Interface, fake bool) {
+	go bc.Serve(ctx)
+	go recv(bc)
+	if fake {
+		go send(bc)
+	}
+}
+
+// receives and prints discovery announcements
+func recv(bc beacon.Interface) {
+	seen := make(map[string]bool)
+	for {
+		data, src := bc.Recv()
+		if m := binary.BigEndian.Uint32(data); m != discover.Magic {
+			log.Printf("Incorrect magic %x in announcement from %v", m, src)
+			continue
+		}
+
+		var ann discover.Announce
+		ann.Unmarshal(data[4:])
+
+		if ann.ID == myID {
+			// This is one of our own fake packets, don't print it.
+			continue
+		}
+
+		// Print announcement details for the first packet from a given
+		// device ID and source address, or if -all was given.
+		key := ann.ID.String() + src.String()
+		if all || !seen[key] {
+			log.Printf("Announcement from %v\n", src)
+			log.Printf(" %v at %s\n", ann.ID, strings.Join(ann.Addresses, ", "))
+			seen[key] = true
+		}
+	}
+}
+
+// sends fake discovery announcements once every second
+func send(bc beacon.Interface) {
+	ann := discover.Announce{
+		ID:        myID,
+		Addresses: []string{"tcp://fake.example.com:12345"},
+	}
+	bs, _ := ann.Marshal()
+
+	for {
+		bc.Send(bs)
+		time.Sleep(time.Second)
+	}
+}
+
+// returns a random but recognizable device ID
+func randomDeviceID() protocol.DeviceID {
+	var id protocol.DeviceID
+	copy(id[:], randomPrefix)
+	rand.Read(id[len(randomPrefix):])
+	return id
+}