control/{controlknobs,controlclient}: simplify knobs API, fix controlclient crash

From integration tests elsewhere:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x70 pc=0x845c9b]

goroutine 226 [running]:
tailscale.com/control/controlclient.(*Direct).sendMapRequest(0xc00053e1e0, 0x16670f0, 0xc000353780, 0xffffffffffffffff, 0xc0003e5f10, 0x0, 0x0)
   /home/runner/go/pkg/mod/tailscale.com@v1.1.1-0.20210715222212-1bb6abc604c1/control/controlclient/direct.go:803 +0x19bb
tailscale.com/control/controlclient.(*Direct).PollNetMap(...)
   /home/runner/go/pkg/mod/tailscale.com@v1.1.1-0.20210715222212-1bb6abc604c1/control/controlclient/direct.go:574
tailscale.com/control/controlclient.(*Auto).mapRoutine(0xc00052a1e0)
   /home/runner/go/pkg/mod/tailscale.com@v1.1.1-0.20210715222212-1bb6abc604c1/control/controlclient/auto.go:464 +0x571
created by tailscale.com/control/controlclient.(*Auto).Start
   /home/runner/go/pkg/mod/tailscale.com@v1.1.1-0.20210715222212-1bb6abc604c1/control/controlclient/auto.go:151 +0x65
exit status 2

Also remove types/opt.Bool API addition which is now unnecessary.

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

control/controlclient/direct.go

@@ -800,7 +800,7 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 
 		hasDebug := resp.Debug != nil
 		// being conservative here, if Debug not present set to False
-		controlknobs.SetDisableUPnP(resp.Debug.DisableUPnP.And(hasDebug))
+		controlknobs.SetDisableUPnP(hasDebug && resp.Debug.DisableUPnP.EqualBool(true))
 		if hasDebug {
 			if resp.Debug.LogHeapPprof {
 				go logheap.LogHeap(resp.Debug.LogHeapURL)

control/controlknobs/controlknobs.go

@@ -9,33 +9,26 @@ package controlknobs
 import (
 	"os"
 	"strconv"
-	"sync/atomic"
 
-	"tailscale.com/types/opt"
+	"tailscale.com/syncs"
 )
 
 // disableUPnP indicates whether to attempt UPnP mapping.
-var disableUPnP atomic.Value
+var disableUPnP syncs.AtomicBool
 
 func init() {
 	v, _ := strconv.ParseBool(os.Getenv("TS_DISABLE_UPNP"))
-	var toStore opt.Bool
-	toStore.Set(v)
-	disableUPnP.Store(toStore)
+	SetDisableUPnP(v)
 }
 
 // DisableUPnP reports the last reported value from control
 // whether UPnP portmapping should be disabled.
-func DisableUPnP() opt.Bool {
-	v, _ := disableUPnP.Load().(opt.Bool)
-	return v
+func DisableUPnP() bool {
+	return disableUPnP.Get()
 }
 
-// SetDisableUPnP will set whether UPnP connections are permitted or not,
-// intended to be set from control.
-func SetDisableUPnP(v opt.Bool) {
-	old, ok := disableUPnP.Load().(opt.Bool)
-	if !ok || old != v {
-		disableUPnP.Store(v)
-	}
+// SetDisableUPnP sets whether control says that UPnP should be
+// disabled.
+func SetDisableUPnP(v bool) {
+	disableUPnP.Set(v)
 }

net/portmapper/upnp.go

@@ -125,7 +125,7 @@ func addAnyPortMapping(
 // now.
 // Adapted from https://github.com/huin/goupnp/blob/master/GUIDE.md.
 func getUPnPClient(ctx context.Context, gw netaddr.IP) (upnpClient, error) {
-	if dis, ok := controlknobs.DisableUPnP().Get(); ok && dis {
+	if controlknobs.DisableUPnP() {
 		return nil, nil
 	}
 	ctx, cancel := context.WithTimeout(ctx, 250*time.Millisecond)
@@ -177,7 +177,7 @@ func (c *Client) getUPnPPortMapping(
 	internal netaddr.IPPort,
 	prevPort uint16,
 ) (external netaddr.IPPort, ok bool) {
-	if dis, ok := controlknobs.DisableUPnP().Get(); ok && dis {
+	if controlknobs.DisableUPnP() {
 		return netaddr.IPPort{}, false
 	}
 	now := time.Now()

types/opt/bool.go

@@ -29,13 +29,6 @@ func (b Bool) Get() (v bool, ok bool) {
 	return v, err == nil
 }
 
-func (b Bool) And(v bool) Bool {
-	if v {
-		return b
-	}
-	return "false"
-}
-
 // EqualBool reports whether b is equal to v.
 // If b is empty or not a valid bool, it reports false.
 func (b Bool) EqualBool(v bool) bool {

types/opt/bool_test.go

@@ -87,26 +87,3 @@ func TestBoolEqualBool(t *testing.T) {
 	}
 
 }
-
-func TestBoolAnd(t *testing.T) {
-	tests := []struct {
-		lhs  Bool
-		rhs  bool
-		want Bool
-	}{
-		{"true", true, "true"},
-		{"true", false, "false"},
-
-		{"false", true, "false"},
-		{"false", false, "false"},
-
-		{"", true, ""},
-		{"", false, "false"},
-	}
-	for _, tt := range tests {
-		if got := tt.lhs.And(tt.rhs); got != tt.want {
-			t.Errorf("(%q).And(%v) = %v; want %v", string(tt.lhs), tt.rhs, got, tt.want)
-		}
-	}
-
-}