cmd/tailscale/cli,ipn,all: make peer relay server port a *uint16

In preparation for exposing its configuration via ipn.ConfigVAlpha,
change {Masked}Prefs.RelayServerPort from *int to *uint16. This takes a
defensive stance against invalid inputs at JSON decode time.

'tailscale set --relay-server-port' is currently the only input to this
pref, and has always sanitized input to fit within a uint16.

Updates tailscale/corp#34591

Signed-off-by: Jordan Whited <jordan@tailscale.com>

ipn/ipn_clone.go

@@ -102,7 +102,7 @@ var _PrefsCloneNeedsRegeneration = Prefs(struct {
 	PostureChecking            bool
 	NetfilterKind              string
 	DriveShares                []*drive.Share
-	RelayServerPort            *int
+	RelayServerPort            *uint16
 	RelayServerStaticEndpoints []netip.AddrPort
 	AllowSingleHosts           marshalAsTrueInJSON
 	Persist                    *persist.Persist

ipn/ipn_view.go

@@ -441,10 +441,8 @@ func (v PrefsView) DriveShares() views.SliceView[*drive.Share, drive.ShareView]
 // RelayServerPort is the UDP port number for the relay server to bind to,
 // on all interfaces. A non-nil zero value signifies a random unused port
 // should be used. A nil value signifies relay server functionality
-// should be disabled. This field is currently experimental, and therefore
-// no guarantees are made about its current naming and functionality when
-// non-nil/enabled.
-func (v PrefsView) RelayServerPort() views.ValuePointer[int] {
+// should be disabled.
+func (v PrefsView) RelayServerPort() views.ValuePointer[uint16] {
 	return views.ValuePointerOf(v.ж.RelayServerPort)
 }
 
@@ -506,7 +504,7 @@ var _PrefsViewNeedsRegeneration = Prefs(struct {
 	PostureChecking            bool
 	NetfilterKind              string
 	DriveShares                []*drive.Share
-	RelayServerPort            *int
+	RelayServerPort            *uint16
 	RelayServerStaticEndpoints []netip.AddrPort
 	AllowSingleHosts           marshalAsTrueInJSON
 	Persist                    *persist.Persist

ipn/prefs.go

@@ -283,10 +283,8 @@ type Prefs struct {
 	// RelayServerPort is the UDP port number for the relay server to bind to,
 	// on all interfaces. A non-nil zero value signifies a random unused port
 	// should be used. A nil value signifies relay server functionality
-	// should be disabled. This field is currently experimental, and therefore
-	// no guarantees are made about its current naming and functionality when
-	// non-nil/enabled.
-	RelayServerPort *int `json:",omitempty"`
+	// should be disabled.
+	RelayServerPort *uint16 `json:",omitempty"`
 
 	// RelayServerStaticEndpoints are static IP:port endpoints to advertise as
 	// candidates for relay connections. Only relevant when RelayServerPort is
@@ -694,7 +692,7 @@ func (p *Prefs) Equals(p2 *Prefs) bool {
 		p.PostureChecking == p2.PostureChecking &&
 		slices.EqualFunc(p.DriveShares, p2.DriveShares, drive.SharesEqual) &&
 		p.NetfilterKind == p2.NetfilterKind &&
-		compareIntPtrs(p.RelayServerPort, p2.RelayServerPort) &&
+		compareUint16Ptrs(p.RelayServerPort, p2.RelayServerPort) &&
 		slices.Equal(p.RelayServerStaticEndpoints, p2.RelayServerStaticEndpoints)
 }
 
@@ -715,7 +713,7 @@ func (ap AppConnectorPrefs) Pretty() string {
 	return ""
 }
 
-func compareIntPtrs(a, b *int) bool {
+func compareUint16Ptrs(a, b *uint16) bool {
 	if (a == nil) != (b == nil) {
 		return false
 	}

ipn/prefs_test.go

@@ -78,7 +78,7 @@ func TestPrefsEqual(t *testing.T) {
 			have, prefsHandles)
 	}
 
-	relayServerPort := func(port int) *int {
+	relayServerPort := func(port uint16) *uint16 {
 		return &port
 	}
 	nets := func(strs ...string) (ns []netip.Prefix) {