tsd: add package with System type to unify subsystem init, discovery

This is part of an effort to clean up tailscaled initialization between
tailscaled, tailscaled Windows service, tsnet, and the mac GUI.

Updates #8036

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/netstack/netstack_test.go

@@ -16,6 +16,7 @@ import (
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/net/tstun"
+	"tailscale.com/tsd"
 	"tailscale.com/tstest"
 	"tailscale.com/types/ipproto"
 	"tailscale.com/types/logid"
@@ -33,29 +34,26 @@ func TestInjectInboundLeak(t *testing.T) {
 			t.Logf(format, args...)
 		}
 	}
+	sys := new(tsd.System)
 	eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
-		Tun:    tunDev,
-		Dialer: dialer,
+		Tun:          tunDev,
+		Dialer:       dialer,
+		SetSubsystem: sys.Set,
 	})
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer eng.Close()
-	ig, ok := eng.(wgengine.InternalsGetter)
-	if !ok {
-		t.Fatal("not an InternalsGetter")
-	}
-	tunWrap, magicSock, dns, ok := ig.GetInternals()
-	if !ok {
-		t.Fatal("failed to get internals")
-	}
+	sys.Set(eng)
+	sys.Set(new(mem.Store))
 
-	lb, err := ipnlocal.NewLocalBackend(logf, logid.PublicID{}, new(mem.Store), dialer, eng, 0)
+	tunWrap := sys.Tun.Get()
+	lb, err := ipnlocal.NewLocalBackend(logf, logid.PublicID{}, sys, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	ns, err := Create(logf, tunWrap, eng, magicSock, dialer, dns)
+	ns, err := Create(logf, tunWrap, eng, sys.MagicSock.Get(), dialer, sys.DNSManager.Get())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -89,32 +87,28 @@ func getMemStats() (ms runtime.MemStats) {
 
 func makeNetstack(t *testing.T, config func(*Impl)) *Impl {
 	tunDev := tstun.NewFake()
+	sys := &tsd.System{}
+	sys.Set(new(mem.Store))
 	dialer := new(tsdial.Dialer)
 	logf := tstest.WhileTestRunningLogger(t)
 	eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
-		Tun:    tunDev,
-		Dialer: dialer,
+		Tun:          tunDev,
+		Dialer:       dialer,
+		SetSubsystem: sys.Set,
 	})
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { eng.Close() })
-	ig, ok := eng.(wgengine.InternalsGetter)
-	if !ok {
-		t.Fatal("not an InternalsGetter")
-	}
-	tunWrap, magicSock, dns, ok := ig.GetInternals()
-	if !ok {
-		t.Fatal("failed to get internals")
-	}
+	sys.Set(eng)
 
-	ns, err := Create(logf, tunWrap, eng, magicSock, dialer, dns)
+	ns, err := Create(logf, sys.Tun.Get(), eng, sys.MagicSock.Get(), dialer, sys.DNSManager.Get())
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { ns.Close() })
 
-	lb, err := ipnlocal.NewLocalBackend(logf, logid.PublicID{}, new(mem.Store), dialer, eng, 0)
+	lb, err := ipnlocal.NewLocalBackend(logf, logid.PublicID{}, sys, 0)
 	if err != nil {
 		t.Fatalf("NewLocalBackend: %v", err)
 	}

wgengine/netstack/subnet_router_wrapper.go

@@ -4,16 +4,9 @@
 package netstack
 
 import (
-	"reflect"
-
-	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/router"
 )
 
-func init() {
-	wgengine.NetstackRouterType = reflect.TypeOf(&subnetRouter{})
-}
-
 type subnetRouter struct {
 	router.Router
 }