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>

1 files changed, 9 insertions, 16 deletions

diff --git a/control/controlknobs/controlknobs.go b/control/controlknobs/controlknobs.go
index 884c0f8dd..84d71fdf2 100644
--- a/control/controlknobs/controlknobs.go
+++ b/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)
 }