cmd/testcontrol: add test control server

This is useful for manual performance testing
of networks with many nodes.
I imagine it'll grow more knobs over time.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

cmd/testcontrol/testcontrol.go

@@ -0,0 +1,98 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Program testcontrol runs a simple test control server.
+package main
+
+import (
+	"flag"
+	"log"
+	"net/http"
+	"testing"
+
+	"tailscale.com/tstest/integration"
+	"tailscale.com/tstest/integration/testcontrol"
+	"tailscale.com/types/logger"
+)
+
+var (
+	flagNFake = flag.Int("nfake", 0, "number of fake nodes to add to network")
+)
+
+func main() {
+	flag.Parse()
+
+	var t fakeTB
+	derpMap := integration.RunDERPAndSTUN(t, logger.Discard, "127.0.0.1")
+
+	control := &testcontrol.Server{
+		DERPMap:         derpMap,
+		ExplicitBaseURL: "http://127.0.0.1:9911",
+	}
+	for i := 0; i < *flagNFake; i++ {
+		control.AddFakeNode()
+	}
+	mux := http.NewServeMux()
+	mux.Handle("/", control)
+	addr := "127.0.0.1:9911"
+	log.Printf("listening on %s", addr)
+	err := http.ListenAndServe(addr, mux)
+	log.Fatal(err)
+}
+
+type fakeTB struct {
+	*testing.T
+}
+
+func (t fakeTB) Cleanup(_ func()) {}
+func (t fakeTB) Error(args ...interface{}) {
+	t.Fatal(args...)
+}
+func (t fakeTB) Errorf(format string, args ...interface{}) {
+	t.Fatalf(format, args...)
+}
+func (t fakeTB) Fail() {
+	t.Fatal("failed")
+}
+func (t fakeTB) FailNow() {
+	t.Fatal("failed")
+}
+func (t fakeTB) Failed() bool {
+	return false
+}
+func (t fakeTB) Fatal(args ...interface{}) {
+	log.Fatal(args...)
+}
+func (t fakeTB) Fatalf(format string, args ...interface{}) {
+	log.Fatalf(format, args...)
+}
+func (t fakeTB) Helper() {}
+func (t fakeTB) Log(args ...interface{}) {
+	log.Print(args...)
+}
+func (t fakeTB) Logf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+}
+func (t fakeTB) Name() string {
+	return "faketest"
+}
+func (t fakeTB) Setenv(key string, value string) {
+	panic("not implemented")
+}
+func (t fakeTB) Skip(args ...interface{}) {
+	t.Fatal("skipped")
+}
+func (t fakeTB) SkipNow() {
+	t.Fatal("skipnow")
+}
+func (t fakeTB) Skipf(format string, args ...interface{}) {
+	t.Logf(format, args...)
+	t.Fatal("skipped")
+}
+func (t fakeTB) Skipped() bool {
+	return false
+}
+func (t fakeTB) TempDir() string {
+	panic("not implemented")
+}

tstest/integration/testcontrol/testcontrol.go

@@ -31,6 +31,7 @@ import (
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/smallzstd"
 	"tailscale.com/tailcfg"
+	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/wgkey"
 )
@@ -269,6 +270,33 @@ func (s *Server) nodeLocked(nodeKey tailcfg.NodeKey) *tailcfg.Node {
 	return s.nodes[nodeKey].Clone()
 }
 
+// AddFakeNode injects a fake node into the server.
+func (s *Server) AddFakeNode() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.nodes == nil {
+		s.nodes = make(map[tailcfg.NodeKey]*tailcfg.Node)
+	}
+	nk := tailcfg.NodeKey(key.NewPrivate().Public())
+	mk := tailcfg.MachineKey(key.NewPrivate().Public())
+	dk := tailcfg.DiscoKey(key.NewPrivate().Public())
+	id := int64(binary.LittleEndian.Uint64(nk[:]))
+	ip := netaddr.IPv4(nk[0], nk[1], nk[2], nk[3])
+	addr := netaddr.IPPrefixFrom(ip, 32)
+	s.nodes[nk] = &tailcfg.Node{
+		ID:                tailcfg.NodeID(id),
+		StableID:          tailcfg.StableNodeID(fmt.Sprintf("TESTCTRL%08x", id)),
+		User:              tailcfg.UserID(id),
+		Machine:           mk,
+		Key:               nk,
+		MachineAuthorized: true,
+		DiscoKey:          dk,
+		Addresses:         []netaddr.IPPrefix{addr},
+		AllowedIPs:        []netaddr.IPPrefix{addr},
+	}
+	// TODO: send updates to other (non-fake?) nodes
+}
+
 func (s *Server) AllNodes() (nodes []*tailcfg.Node) {
 	s.mu.Lock()
 	defer s.mu.Unlock()