cmd/viewer,types/views,various: avoid allocations in pointer field getters whenever possible

In this PR, we add a generic views.ValuePointer type that can be used as a view for pointers
to basic types and struct types that do not require deep cloning and do not have corresponding
view types. Its Get/GetOk methods return stack-allocated shallow copies of the underlying value.

We then update the cmd/viewer codegen to produce getters that return either concrete views
when available or ValuePointer views when not, for pointer fields in generated view types.
This allows us to avoid unnecessary allocations compared to returning pointers to newly
allocated shallow copies.

Updates #14570

Signed-off-by: Nick Khyl <[email protected]>

cmd/tsconnect/wasm/wasm_js.go

@@ -282,7 +282,7 @@ func (i *jsIPN) run(jsCallbacks js.Value) {
 							MachineKey: p.Machine().String(),
 							NodeKey:    p.Key().String(),
 						},
-						Online:              p.Online(),
+						Online:              p.Online().Clone(),
 						TailscaleSSHEnabled: p.Hostinfo().TailscaleSSHEnabled(),
 					}
 				}),

cmd/viewer/tests/tests.go

@@ -37,9 +37,14 @@ type Map struct {
 	StructWithPtrKey map[StructWithPtrs]int `json:"-"`
 }
 
+type StructWithNoView struct {
+	Value int
+}
+
 type StructWithPtrs struct {
-	Value *StructWithoutPtrs
-	Int   *int
+	Value  *StructWithoutPtrs
+	Int    *int
+	NoView *StructWithNoView
 
 	NoCloneValue *StructWithoutPtrs `codegen:"noclone"`
 }

cmd/viewer/tests/tests_clone.go

@@ -28,6 +28,9 @@ func (src *StructWithPtrs) Clone() *StructWithPtrs {
 	if dst.Int != nil {
 		dst.Int = ptr.To(*src.Int)
 	}
+	if dst.NoView != nil {
+		dst.NoView = ptr.To(*src.NoView)
+	}
 	return dst
 }
 
@@ -35,6 +38,7 @@ func (src *StructWithPtrs) Clone() *StructWithPtrs {
 var _StructWithPtrsCloneNeedsRegeneration = StructWithPtrs(struct {
 	Value        *StructWithoutPtrs
 	Int          *int
+	NoView       *StructWithNoView
 	NoCloneValue *StructWithoutPtrs
 }{})
 

cmd/viewer/tests/tests_view.go

@@ -61,20 +61,11 @@ func (v *StructWithPtrsView) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (v StructWithPtrsView) Value() *StructWithoutPtrs {
-	if v.ж.Value == nil {
-		return nil
-	}
-	x := *v.ж.Value
-	return &x
-}
+func (v StructWithPtrsView) Value() StructWithoutPtrsView { return v.ж.Value.View() }
+func (v StructWithPtrsView) Int() views.ValuePointer[int] { return views.ValuePointerOf(v.ж.Int) }
 
-func (v StructWithPtrsView) Int() *int {
-	if v.ж.Int == nil {
-		return nil
-	}
-	x := *v.ж.Int
-	return &x
+func (v StructWithPtrsView) NoView() views.ValuePointer[StructWithNoView] {
+	return views.ValuePointerOf(v.ж.NoView)
 }
 
 func (v StructWithPtrsView) NoCloneValue() *StructWithoutPtrs { return v.ж.NoCloneValue }
@@ -85,6 +76,7 @@ func (v StructWithPtrsView) Equal(v2 StructWithPtrsView) bool { return v.ж.Equa
 var _StructWithPtrsViewNeedsRegeneration = StructWithPtrs(struct {
 	Value        *StructWithoutPtrs
 	Int          *int
+	NoView       *StructWithNoView
 	NoCloneValue *StructWithoutPtrs
 }{})
 
@@ -424,12 +416,8 @@ func (v *GenericIntStructView[T]) UnmarshalJSON(b []byte) error {
 }
 
 func (v GenericIntStructView[T]) Value() T { return v.ж.Value }
-func (v GenericIntStructView[T]) Pointer() *T {
-	if v.ж.Pointer == nil {
-		return nil
-	}
-	x := *v.ж.Pointer
-	return &x
+func (v GenericIntStructView[T]) Pointer() views.ValuePointer[T] {
+	return views.ValuePointerOf(v.ж.Pointer)
 }
 
 func (v GenericIntStructView[T]) Slice() views.Slice[T] { return views.SliceOf(v.ж.Slice) }
@@ -500,12 +488,8 @@ func (v *GenericNoPtrsStructView[T]) UnmarshalJSON(b []byte) error {
 }
 
 func (v GenericNoPtrsStructView[T]) Value() T { return v.ж.Value }
-func (v GenericNoPtrsStructView[T]) Pointer() *T {
-	if v.ж.Pointer == nil {
-		return nil
-	}
-	x := *v.ж.Pointer
-	return &x
+func (v GenericNoPtrsStructView[T]) Pointer() views.ValuePointer[T] {
+	return views.ValuePointerOf(v.ж.Pointer)
 }
 
 func (v GenericNoPtrsStructView[T]) Slice() views.Slice[T] { return views.SliceOf(v.ж.Slice) }
@@ -722,19 +706,14 @@ func (v *StructWithTypeAliasFieldsView) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (v StructWithTypeAliasFieldsView) WithPtr() StructWithPtrsView        { return v.ж.WithPtr.View() }
+func (v StructWithTypeAliasFieldsView) WithPtr() StructWithPtrsAliasView   { return v.ж.WithPtr.View() }
 func (v StructWithTypeAliasFieldsView) WithoutPtr() StructWithoutPtrsAlias { return v.ж.WithoutPtr }
 func (v StructWithTypeAliasFieldsView) WithPtrByPtr() StructWithPtrsAliasView {
 	return v.ж.WithPtrByPtr.View()
 }
-func (v StructWithTypeAliasFieldsView) WithoutPtrByPtr() *StructWithoutPtrsAlias {
-	if v.ж.WithoutPtrByPtr == nil {
-		return nil
-	}
-	x := *v.ж.WithoutPtrByPtr
-	return &x
+func (v StructWithTypeAliasFieldsView) WithoutPtrByPtr() StructWithoutPtrsAliasView {
+	return v.ж.WithoutPtrByPtr.View()
 }
-
 func (v StructWithTypeAliasFieldsView) SliceWithPtrs() views.SliceView[*StructWithPtrsAlias, StructWithPtrsAliasView] {
 	return views.SliceOfViews[*StructWithPtrsAlias, StructWithPtrsAliasView](v.ж.SliceWithPtrs)
 }

cmd/viewer/viewer.go

@@ -79,13 +79,7 @@ func (v *{{.ViewName}}{{.TypeParamNames}}) UnmarshalJSON(b []byte) error {
 {{end}}
 {{define "makeViewField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldViewName}} { return {{.MakeViewFnName}}(&v.ж.{{.FieldName}}) }
 {{end}}
-{{define "valuePointerField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() {{.FieldType}} {
-	if v.ж.{{.FieldName}} == nil {
-		return nil
-	}
-	x := *v.ж.{{.FieldName}}
-	return &x
-}
+{{define "valuePointerField"}}func (v {{.ViewName}}{{.TypeParamNames}}) {{.FieldName}}() views.ValuePointer[{{.FieldType}}] { return views.ValuePointerOf(v.ж.{{.FieldName}}) }
 
 {{end}}
 {{define "mapField"}}
@@ -126,7 +120,7 @@ func requiresCloning(t types.Type) (shallow, deep bool, base types.Type) {
 	return p, p, t
 }
 
-func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, thisPkg *types.Package) {
+func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, _ *types.Package) {
 	t, ok := typ.Underlying().(*types.Struct)
 	if !ok || codegen.IsViewType(t) {
 		return
@@ -354,10 +348,32 @@ func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, thi
 				} else {
 					writeTemplate("unsupportedField")
 				}
-			} else {
-				args.FieldType = it.QualifiedName(ptr)
-				writeTemplate("valuePointerField")
+				continue
+			}
+
+			// If a view type is already defined for the base type, use it as the field's view type.
+			if viewType := viewTypeForValueType(base); viewType != nil {
+				args.FieldType = it.QualifiedName(base)
+				args.FieldViewName = it.QualifiedName(viewType)
+				writeTemplate("viewField")
+				continue
+			}
+
+			// Otherwise, if the unaliased base type is a named type whose view type will be generated by this viewer invocation,
+			// append the "View" suffix to the unaliased base type name and use it as the field's view type.
+			if base, ok := types.Unalias(base).(*types.Named); ok && slices.Contains(typeNames, it.QualifiedName(base)) {
+				baseTypeName := it.QualifiedName(base)
+				args.FieldType = baseTypeName
+				args.FieldViewName = appendNameSuffix(args.FieldType, "View")
+				writeTemplate("viewField")
+				continue
 			}
+
+			// Otherwise, if the base type does not require deep cloning, has no existing view type,
+			// and will not have a generated view type, use views.ValuePointer[T] as the field's view type.
+			// Its Get/GetOk methods return stack-allocated shallow copies of the field's value.
+			args.FieldType = it.QualifiedName(base)
+			writeTemplate("valuePointerField")
 			continue
 		case *types.Interface:
 			// If fieldType is an interface with a "View() {ViewType}" method, it can be used to clone the field.
@@ -405,6 +421,33 @@ func appendNameSuffix(name, suffix string) string {
 	return name + suffix
 }
 
+func typeNameOf(typ types.Type) (name *types.TypeName, ok bool) {
+	switch t := typ.(type) {
+	case *types.Alias:
+		return t.Obj(), true
+	case *types.Named:
+		return t.Obj(), true
+	default:
+		return nil, false
+	}
+}
+
+func lookupViewType(typ types.Type) types.Type {
+	for {
+		if typeName, ok := typeNameOf(typ); ok && typeName.Pkg() != nil {
+			if viewTypeObj := typeName.Pkg().Scope().Lookup(typeName.Name() + "View"); viewTypeObj != nil {
+				return viewTypeObj.Type()
+			}
+		}
+		switch alias := typ.(type) {
+		case *types.Alias:
+			typ = alias.Rhs()
+		default:
+			return nil
+		}
+	}
+}
+
 func viewTypeForValueType(typ types.Type) types.Type {
 	if ptr, ok := typ.(*types.Pointer); ok {
 		return viewTypeForValueType(ptr.Elem())
@@ -417,7 +460,12 @@ func viewTypeForValueType(typ types.Type) types.Type {
 	if !ok || sig.Results().Len() != 1 {
 		return nil
 	}
-	return sig.Results().At(0).Type()
+	viewType := sig.Results().At(0).Type()
+	// Check if the typ's package defines an alias for the view type, and use it if so.
+	if viewTypeAlias, ok := lookupViewType(typ).(*types.Alias); ok && types.AssignableTo(viewType, viewTypeAlias) {
+		viewType = viewTypeAlias
+	}
+	return viewType
 }
 
 func viewTypeForContainerType(typ types.Type) (*types.Named, *types.Func) {

control/controlclient/map.go

@@ -689,13 +689,11 @@ func peerChangeDiff(was tailcfg.NodeView, n *tailcfg.Node) (_ *tailcfg.PeerChang
 				return nil, false
 			}
 		case "Online":
-			wasOnline := was.Online()
-			if n.Online != nil && wasOnline != nil && *n.Online != *wasOnline {
+			if wasOnline, ok := was.Online().GetOk(); ok && n.Online != nil && *n.Online != wasOnline {
 				pc().Online = ptr.To(*n.Online)
 			}
 		case "LastSeen":
-			wasSeen := was.LastSeen()
-			if n.LastSeen != nil && wasSeen != nil && !wasSeen.Equal(*n.LastSeen) {
+			if wasSeen, ok := was.LastSeen().GetOk(); ok && n.LastSeen != nil && !wasSeen.Equal(*n.LastSeen) {
 				pc().LastSeen = ptr.To(*n.LastSeen)
 			}
 		case "MachineAuthorized":
@@ -720,18 +718,18 @@ func peerChangeDiff(was tailcfg.NodeView, n *tailcfg.Node) (_ *tailcfg.PeerChang
 			}
 		case "SelfNodeV4MasqAddrForThisPeer":
 			va, vb := was.SelfNodeV4MasqAddrForThisPeer(), n.SelfNodeV4MasqAddrForThisPeer
-			if va == nil && vb == nil {
+			if !va.Valid() && vb == nil {
 				continue
 			}
-			if va == nil || vb == nil || *va != *vb {
+			if va, ok := va.GetOk(); !ok || vb == nil || va != *vb {
 				return nil, false
 			}
 		case "SelfNodeV6MasqAddrForThisPeer":
 			va, vb := was.SelfNodeV6MasqAddrForThisPeer(), n.SelfNodeV6MasqAddrForThisPeer
-			if va == nil && vb == nil {
+			if !va.Valid() && vb == nil {
 				continue
 			}
-			if va == nil || vb == nil || *va != *vb {
+			if va, ok := va.GetOk(); !ok || vb == nil || va != *vb {
 				return nil, false
 			}
 		case "ExitNodeDNSResolvers":

ipn/ipnlocal/drive.go

@@ -347,8 +347,7 @@ func (b *LocalBackend) driveRemotesFromPeers(nm *netmap.NetworkMap) []*drive.Rem
 				// TODO(oxtoacart): for some reason, this correctly
 				// catches when a node goes from offline to online,
 				// but not the other way around...
-				online := peer.Online()
-				if online == nil || !*online {
+				if !peer.Online().Get() {
 					return false
 				}
 

ipn/ipnlocal/expiry_test.go

@@ -283,11 +283,11 @@ func formatNodes(nodes []tailcfg.NodeView) string {
 		}
 		fmt.Fprintf(&sb, "(%d, %q", n.ID(), n.Name())
 
-		if n.Online() != nil {
-			fmt.Fprintf(&sb, ", online=%v", *n.Online())
+		if online, ok := n.Online().GetOk(); ok {
+			fmt.Fprintf(&sb, ", online=%v", online)
 		}
-		if n.LastSeen() != nil {
-			fmt.Fprintf(&sb, ", lastSeen=%v", n.LastSeen().Unix())
+		if lastSeen, ok := n.LastSeen().GetOk(); ok {
+			fmt.Fprintf(&sb, ", lastSeen=%v", lastSeen.Unix())
 		}
 		if n.Key() != (key.NodePublic{}) {
 			fmt.Fprintf(&sb, ", key=%v", n.Key().String())

ipn/ipnlocal/local.go

@@ -1117,13 +1117,9 @@ func (b *LocalBackend) UpdateStatus(sb *ipnstate.StatusBuilder) {
 				}
 				if !prefs.ExitNodeID().IsZero() {
 					if exitPeer, ok := b.netMap.PeerWithStableID(prefs.ExitNodeID()); ok {
-						online := false
-						if v := exitPeer.Online(); v != nil {
-							online = *v
-						}
 						s.ExitNodeStatus = &ipnstate.ExitNodeStatus{
 							ID:           prefs.ExitNodeID(),
-							Online:       online,
+							Online:       exitPeer.Online().Get(),
 							TailscaleIPs: exitPeer.Addresses().AsSlice(),
 						}
 					}
@@ -1194,10 +1190,6 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 	}
 	exitNodeID := b.pm.CurrentPrefs().ExitNodeID()
 	for _, p := range b.peers {
-		var lastSeen time.Time
-		if p.LastSeen() != nil {
-			lastSeen = *p.LastSeen()
-		}
 		tailscaleIPs := make([]netip.Addr, 0, p.Addresses().Len())
 		for i := range p.Addresses().Len() {
 			addr := p.Addresses().At(i)
@@ -1205,7 +1197,6 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 				tailscaleIPs = append(tailscaleIPs, addr.Addr())
 			}
 		}
-		online := p.Online()
 		ps := &ipnstate.PeerStatus{
 			InNetworkMap:    true,
 			UserID:          p.User(),
@@ -1214,12 +1205,12 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 			HostName:        p.Hostinfo().Hostname(),
 			DNSName:         p.Name(),
 			OS:              p.Hostinfo().OS(),
-			LastSeen:        lastSeen,
-			Online:          online != nil && *online,
+			LastSeen:        p.LastSeen().Get(),
+			Online:          p.Online().Get(),
 			ShareeNode:      p.Hostinfo().ShareeNode(),
 			ExitNode:        p.StableID() != "" && p.StableID() == exitNodeID,
 			SSH_HostKeys:    p.Hostinfo().SSH_HostKeys().AsSlice(),
-			Location:        p.Hostinfo().Location(),
+			Location:        p.Hostinfo().Location().AsStruct(),
 			Capabilities:    p.Capabilities().AsSlice(),
 		}
 		if cm := p.CapMap(); cm.Len() > 0 {
@@ -7369,8 +7360,8 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, prevSug
 	if len(candidates) == 1 {
 		peer := candidates[0]
 		if hi := peer.Hostinfo(); hi.Valid() {
-			if loc := hi.Location(); loc != nil {
-				res.Location = loc.View()
+			if loc := hi.Location(); loc.Valid() {
+				res.Location = loc
 			}
 		}
 		res.ID = peer.StableID()
@@ -7414,10 +7405,10 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, prevSug
 			continue
 		}
 		loc := hi.Location()
-		if loc == nil {
+		if !loc.Valid() {
 			continue
 		}
-		distance := longLatDistance(preferredDERP.Latitude, preferredDERP.Longitude, loc.Latitude, loc.Longitude)
+		distance := longLatDistance(preferredDERP.Latitude, preferredDERP.Longitude, loc.Latitude(), loc.Longitude())
 		if distance < minDistance {
 			minDistance = distance
 		}
@@ -7438,8 +7429,8 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, prevSug
 		res.ID = chosen.StableID()
 		res.Name = chosen.Name()
 		if hi := chosen.Hostinfo(); hi.Valid() {
-			if loc := hi.Location(); loc != nil {
-				res.Location = loc.View()
+			if loc := hi.Location(); loc.Valid() {
+				res.Location = loc
 			}
 		}
 		return res, nil
@@ -7468,8 +7459,8 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, prevSug
 	res.ID = chosen.StableID()
 	res.Name = chosen.Name()
 	if hi := chosen.Hostinfo(); hi.Valid() {
-		if loc := hi.Location(); loc != nil {
-			res.Location = loc.View()
+		if loc := hi.Location(); loc.Valid() {
+			res.Location = loc
 		}
 	}
 	return res, nil
@@ -7485,13 +7476,13 @@ func pickWeighted(candidates []tailcfg.NodeView) []tailcfg.NodeView {
 			continue
 		}
 		loc := hi.Location()
-		if loc == nil || loc.Priority < maxWeight {
+		if !loc.Valid() || loc.Priority() < maxWeight {
 			continue
 		}
-		if maxWeight != loc.Priority {
+		if maxWeight != loc.Priority() {
 			best = best[:0]
 		}
-		maxWeight = loc.Priority
+		maxWeight = loc.Priority()
 		best = append(best, c)
 	}
 	return best

ipn/ipnlocal/peerapi.go

@@ -233,11 +233,11 @@ func (h *peerAPIHandler) logf(format string, a ...any) {
 // isAddressValid reports whether addr is a valid destination address for this
 // node originating from the peer.
 func (h *peerAPIHandler) isAddressValid(addr netip.Addr) bool {
-	if v := h.peerNode.SelfNodeV4MasqAddrForThisPeer(); v != nil {
-		return *v == addr
+	if v, ok := h.peerNode.SelfNodeV4MasqAddrForThisPeer().GetOk(); ok {
+		return v == addr
 	}
-	if v := h.peerNode.SelfNodeV6MasqAddrForThisPeer(); v != nil {
-		return *v == addr
+	if v, ok := h.peerNode.SelfNodeV6MasqAddrForThisPeer().GetOk(); ok {
+		return v == addr
 	}
 	pfx := netip.PrefixFrom(addr, addr.BitLen())
 	return views.SliceContains(h.selfNode.Addresses(), pfx)

tailcfg/tailcfg_view.go

@@ -145,21 +145,11 @@ func (v NodeView) Created() time.Time                       { return v.ж.Create
 func (v NodeView) Cap() CapabilityVersion                   { return v.ж.Cap }
 func (v NodeView) Tags() views.Slice[string]                { return views.SliceOf(v.ж.Tags) }
 func (v NodeView) PrimaryRoutes() views.Slice[netip.Prefix] { return views.SliceOf(v.ж.PrimaryRoutes) }
-func (v NodeView) LastSeen() *time.Time {
-	if v.ж.LastSeen == nil {
-		return nil
-	}
-	x := *v.ж.LastSeen
-	return &x
+func (v NodeView) LastSeen() views.ValuePointer[time.Time] {
+	return views.ValuePointerOf(v.ж.LastSeen)
 }
 
-func (v NodeView) Online() *bool {
-	if v.ж.Online == nil {
-		return nil
-	}
-	x := *v.ж.Online
-	return &x
-}
+func (v NodeView) Online() views.ValuePointer[bool] { return views.ValuePointerOf(v.ж.Online) }
 
 func (v NodeView) MachineAuthorized() bool                   { return v.ж.MachineAuthorized }
 func (v NodeView) Capabilities() views.Slice[NodeCapability] { return views.SliceOf(v.ж.Capabilities) }
@@ -172,20 +162,12 @@ func (v NodeView) ComputedName() string         { return v.ж.ComputedName }
 func (v NodeView) ComputedNameWithHost() string { return v.ж.ComputedNameWithHost }
 func (v NodeView) DataPlaneAuditLogID() string  { return v.ж.DataPlaneAuditLogID }
 func (v NodeView) Expired() bool                { return v.ж.Expired }
-func (v NodeView) SelfNodeV4MasqAddrForThisPeer() *netip.Addr {
-	if v.ж.SelfNodeV4MasqAddrForThisPeer == nil {
-		return nil
-	}
-	x := *v.ж.SelfNodeV4MasqAddrForThisPeer
-	return &x
+func (v NodeView) SelfNodeV4MasqAddrForThisPeer() views.ValuePointer[netip.Addr] {
+	return views.ValuePointerOf(v.ж.SelfNodeV4MasqAddrForThisPeer)
 }
 
-func (v NodeView) SelfNodeV6MasqAddrForThisPeer() *netip.Addr {
-	if v.ж.SelfNodeV6MasqAddrForThisPeer == nil {
-		return nil
-	}
-	x := *v.ж.SelfNodeV6MasqAddrForThisPeer
-	return &x
+func (v NodeView) SelfNodeV6MasqAddrForThisPeer() views.ValuePointer[netip.Addr] {
+	return views.ValuePointerOf(v.ж.SelfNodeV6MasqAddrForThisPeer)
 }
 
 func (v NodeView) IsWireGuardOnly() bool { return v.ж.IsWireGuardOnly }
@@ -315,15 +297,8 @@ func (v HostinfoView) Userspace() opt.Bool                    { return v.ж.User
 func (v HostinfoView) UserspaceRouter() opt.Bool              { return v.ж.UserspaceRouter }
 func (v HostinfoView) AppConnector() opt.Bool                 { return v.ж.AppConnector }
 func (v HostinfoView) ServicesHash() string                   { return v.ж.ServicesHash }
-func (v HostinfoView) Location() *Location {
-	if v.ж.Location == nil {
-		return nil
-	}
-	x := *v.ж.Location
-	return &x
-}
-
-func (v HostinfoView) Equal(v2 HostinfoView) bool { return v.ж.Equal(v2.ж) }
+func (v HostinfoView) Location() LocationView                 { return v.ж.Location.View() }
+func (v HostinfoView) Equal(v2 HostinfoView) bool             { return v.ж.Equal(v2.ж) }
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.
 var _HostinfoViewNeedsRegeneration = Hostinfo(struct {
@@ -699,12 +674,8 @@ func (v *RegisterResponseAuthView) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (v RegisterResponseAuthView) Oauth2Token() *Oauth2Token {
-	if v.ж.Oauth2Token == nil {
-		return nil
-	}
-	x := *v.ж.Oauth2Token
-	return &x
+func (v RegisterResponseAuthView) Oauth2Token() views.ValuePointer[Oauth2Token] {
+	return views.ValuePointerOf(v.ж.Oauth2Token)
 }
 
 func (v RegisterResponseAuthView) AuthKey() string { return v.ж.AuthKey }
@@ -774,12 +745,8 @@ func (v RegisterRequestView) NodeKeySignature() views.ByteSlice[tkatype.Marshale
 	return views.ByteSliceOf(v.ж.NodeKeySignature)
 }
 func (v RegisterRequestView) SignatureType() SignatureType { return v.ж.SignatureType }
-func (v RegisterRequestView) Timestamp() *time.Time {
-	if v.ж.Timestamp == nil {
-		return nil
-	}
-	x := *v.ж.Timestamp
-	return &x
+func (v RegisterRequestView) Timestamp() views.ValuePointer[time.Time] {
+	return views.ValuePointerOf(v.ж.Timestamp)
 }
 
 func (v RegisterRequestView) DeviceCert() views.ByteSlice[[]byte] {
@@ -1110,12 +1077,8 @@ func (v *SSHRuleView) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (v SSHRuleView) RuleExpires() *time.Time {
-	if v.ж.RuleExpires == nil {
-		return nil
-	}
-	x := *v.ж.RuleExpires
-	return &x
+func (v SSHRuleView) RuleExpires() views.ValuePointer[time.Time] {
+	return views.ValuePointerOf(v.ж.RuleExpires)
 }
 
 func (v SSHRuleView) Principals() views.SliceView[*SSHPrincipal, SSHPrincipalView] {
@@ -1189,12 +1152,8 @@ func (v SSHActionView) HoldAndDelegate() string                { return v.ж.Hol
 func (v SSHActionView) AllowLocalPortForwarding() bool         { return v.ж.AllowLocalPortForwarding }
 func (v SSHActionView) AllowRemotePortForwarding() bool        { return v.ж.AllowRemotePortForwarding }
 func (v SSHActionView) Recorders() views.Slice[netip.AddrPort] { return views.SliceOf(v.ж.Recorders) }
-func (v SSHActionView) OnRecordingFailure() *SSHRecorderFailureAction {
-	if v.ж.OnRecordingFailure == nil {
-		return nil
-	}
-	x := *v.ж.OnRecordingFailure
-	return &x
+func (v SSHActionView) OnRecordingFailure() views.ValuePointer[SSHRecorderFailureAction] {
+	return views.ValuePointerOf(v.ж.OnRecordingFailure)
 }
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.

types/prefs/prefs_view_test.go

@@ -162,15 +162,8 @@ func (v *TestBundleView) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (v TestBundleView) Name() string { return v.ж.Name }
-func (v TestBundleView) Nested() *TestValueStruct {
-	if v.ж.Nested == nil {
-		return nil
-	}
-	x := *v.ж.Nested
-	return &x
-}
-
+func (v TestBundleView) Name() string                 { return v.ж.Name }
+func (v TestBundleView) Nested() TestValueStructView  { return v.ж.Nested.View() }
 func (v TestBundleView) Equal(v2 TestBundleView) bool { return v.ж.Equal(v2.ж) }
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.

types/views/views.go

@@ -16,6 +16,7 @@ import (
 	"slices"
 
 	"go4.org/mem"
+	"tailscale.com/types/ptr"
 )
 
 func unmarshalSliceFromJSON[T any](b []byte, x *[]T) error {
@@ -690,6 +691,85 @@ func (m MapFn[K, T, V]) All() iter.Seq2[K, V] {
 	}
 }
 
+// ValuePointer provides a read-only view of a pointer to a value type,
+// such as a primitive type or an immutable struct. Its Value and ValueOk
+// methods return a stack-allocated shallow copy of the underlying value.
+// It is the caller's responsibility to ensure that T
+// is free from memory aliasing/mutation concerns.
+type ValuePointer[T any] struct {
+	// ж is the underlying value, named with a hard-to-type
+	// character that looks pointy like a pointer.
+	// It is named distinctively to make you think of how dangerous it is to escape
+	// to callers. You must not let callers be able to mutate it.
+	ж *T
+}
+
+// Valid reports whether the underlying pointer is non-nil.
+func (p ValuePointer[T]) Valid() bool {
+	return p.ж != nil
+}
+
+// Get returns a shallow copy of the value if the underlying pointer is non-nil.
+// Otherwise, it returns a zero value.
+func (p ValuePointer[T]) Get() T {
+	v, _ := p.GetOk()
+	return v
+}
+
+// GetOk returns a shallow copy of the underlying value and true if the underlying
+// pointer is non-nil. Otherwise, it returns a zero value and false.
+func (p ValuePointer[T]) GetOk() (value T, ok bool) {
+	if p.ж == nil {
+		return value, false // value holds a zero value
+	}
+	return *p.ж, true
+}
+
+// GetOr returns a shallow copy of the underlying value if it is non-nil.
+// Otherwise, it returns the provided default value.
+func (p ValuePointer[T]) GetOr(def T) T {
+	if p.ж == nil {
+		return def
+	}
+	return *p.ж
+}
+
+// Clone returns a shallow copy of the underlying value.
+func (p ValuePointer[T]) Clone() *T {
+	if p.ж == nil {
+		return nil
+	}
+	return ptr.To(*p.ж)
+}
+
+// String implements [fmt.Stringer].
+func (p ValuePointer[T]) String() string {
+	if p.ж == nil {
+		return "nil"
+	}
+	return fmt.Sprint(p.ж)
+}
+
+// ValuePointerOf returns an immutable view of a pointer to an immutable value.
+// It is the caller's responsibility to ensure that T
+// is free from memory aliasing/mutation concerns.
+func ValuePointerOf[T any](v *T) ValuePointer[T] {
+	return ValuePointer[T]{v}
+}
+
+// MarshalJSON implements [json.Marshaler].
+func (p ValuePointer[T]) MarshalJSON() ([]byte, error) {
+	return json.Marshal(p.ж)
+}
+
+// UnmarshalJSON implements [json.Unmarshaler].
+func (p *ValuePointer[T]) UnmarshalJSON(b []byte) error {
+	if p.ж != nil {
+		return errors.New("already initialized")
+	}
+	return json.Unmarshal(b, &p.ж)
+}
+
 // ContainsPointers reports whether T contains any pointers,
 // either explicitly or implicitly.
 // It has special handling for some types that contain pointers

wgengine/pendopen.go

@@ -239,15 +239,15 @@ func (e *userspaceEngine) onOpenTimeout(flow flowtrack.Tuple) {
 	if n.IsWireGuardOnly() {
 		online = "wg"
 	} else {
-		if v := n.Online(); v != nil {
-			if *v {
+		if v, ok := n.Online().GetOk(); ok {
+			if v {
 				online = "yes"
 			} else {
 				online = "no"
 			}
 		}
-		if n.LastSeen() != nil && online != "yes" {
-			online += fmt.Sprintf(", lastseen=%v", durFmt(*n.LastSeen()))
+		if lastSeen, ok := n.LastSeen().GetOk(); ok && online != "yes" {
+			online += fmt.Sprintf(", lastseen=%v", durFmt(lastSeen))
 		}
 	}
 	e.logf("open-conn-track: timeout opening %v to node %v; online=%v, lastRecv=%v",

wgengine/wgcfg/nmcfg/nmcfg.go

@@ -106,8 +106,8 @@ func WGCfg(nm *netmap.NetworkMap, logf logger.Logf, flags netmap.WGConfigFlags,
 		cpeer := &cfg.Peers[len(cfg.Peers)-1]
 
 		didExitNodeWarn := false
-		cpeer.V4MasqAddr = peer.SelfNodeV4MasqAddrForThisPeer()
-		cpeer.V6MasqAddr = peer.SelfNodeV6MasqAddrForThisPeer()
+		cpeer.V4MasqAddr = peer.SelfNodeV4MasqAddrForThisPeer().Clone()
+		cpeer.V6MasqAddr = peer.SelfNodeV6MasqAddrForThisPeer().Clone()
 		cpeer.IsJailed = peer.IsJailed()
 		for _, allowedIP := range peer.AllowedIPs().All() {
 			if allowedIP.Bits() == 0 && peer.StableID() != exitNode {