control/controlclient, types/netmap: start plumbing delta netmap updates

Currently only the top four most popular changes: endpoints, DERP
home, online, and LastSeen.

Updates #1909

Change-Id: I03152da176b2b95232b56acabfb55dcdfaa16b79
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/auto.go

@@ -432,6 +432,8 @@ type mapRoutineState struct {
 	bo *backoff.Backoff
 }
 
+var _ NetmapDeltaUpdater = mapRoutineState{}
+
 func (mrs mapRoutineState) UpdateFullNetmap(nm *netmap.NetworkMap) {
 	c := mrs.c
 
@@ -453,6 +455,28 @@ func (mrs mapRoutineState) UpdateFullNetmap(nm *netmap.NetworkMap) {
 	mrs.bo.BackOff(ctx, nil)
 }
 
+func (mrs mapRoutineState) UpdateNetmapDelta(muts []netmap.NodeMutation) bool {
+	c := mrs.c
+
+	c.mu.Lock()
+	goodState := c.loggedIn && c.inMapPoll
+	ndu, canDelta := c.observer.(NetmapDeltaUpdater)
+	c.mu.Unlock()
+
+	if !goodState || !canDelta {
+		return false
+	}
+
+	ctx, cancel := context.WithTimeout(c.mapCtx, 2*time.Second)
+	defer cancel()
+
+	var ok bool
+	err := c.observerQueue.RunSync(ctx, func() {
+		ok = ndu.UpdateNetmapDelta(muts)
+	})
+	return err == nil && ok
+}
+
 // mapRoutine is responsible for keeping a read-only streaming connection to the
 // control server, and keeping the netmap up to date.
 func (c *Auto) mapRoutine() {
@@ -752,6 +776,27 @@ func (q *execQueue) Add(f func()) {
 	}
 }
 
+// RunSync waits for the queue to be drained and then synchronously runs f.
+// It returns an error if the queue is closed before f is run or ctx expires.
+func (q *execQueue) RunSync(ctx context.Context, f func()) error {
+	for {
+		if err := q.wait(ctx); err != nil {
+			return err
+		}
+		q.mu.Lock()
+		if q.inFlight {
+			q.mu.Unlock()
+			continue
+		}
+		defer q.mu.Unlock()
+		if q.closed {
+			return errors.New("closed")
+		}
+		f()
+		return nil
+	}
+}
+
 func (q *execQueue) run(f func()) {
 	f()
 

control/controlclient/direct.go

@@ -194,6 +194,19 @@ type NetmapUpdater interface {
 	// the diff themselves between the previous full & next full network maps.
 }
 
+// NetmapDeltaUpdater is an optional interface that can be implemented by
+// NetmapUpdater implementations to receive delta updates from the controlclient
+// rather than just full updates.
+type NetmapDeltaUpdater interface {
+	// UpdateNetmapDelta is called with discrete changes to the network map.
+	//
+	// The ok result is whether the implementation was able to apply the
+	// mutations. It might return false if its internal state doesn't
+	// support applying them or a NetmapUpdater it's wrapping doesn't
+	// implement the NetmapDeltaUpdater optional method.
+	UpdateNetmapDelta([]netmap.NodeMutation) (ok bool)
+}
+
 // NewDirect returns a new Direct client.
 func NewDirect(opts Options) (*Direct, error) {
 	if opts.ServerURL == "" {
@@ -1301,6 +1314,7 @@ func (ms *mapSession) setControlKnobsFromNodeAttrs(selfNodeAttrs []string) {
 		disableDRPO         bool
 		disableUPnP         bool
 		randomizeClientPort bool
+		disableDeltaUpdates bool
 		oneCGNAT            opt.Bool
 		forceBackgroundSTUN bool
 	)
@@ -1320,6 +1334,8 @@ func (ms *mapSession) setControlKnobsFromNodeAttrs(selfNodeAttrs []string) {
 			oneCGNAT.Set(false)
 		case tailcfg.NodeAttrDebugForceBackgroundSTUN:
 			forceBackgroundSTUN = true
+		case tailcfg.NodeAttrDisableDeltaUpdates:
+			disableDeltaUpdates = true
 		}
 	}
 	k.KeepFullWGConfig.Store(keepFullWG)
@@ -1328,6 +1344,7 @@ func (ms *mapSession) setControlKnobsFromNodeAttrs(selfNodeAttrs []string) {
 	k.RandomizeClientPort.Store(randomizeClientPort)
 	k.OneCGNAT.Store(oneCGNAT)
 	k.ForceBackgroundSTUN.Store(forceBackgroundSTUN)
+	k.DisableDeltaUpdates.Store(disableDeltaUpdates)
 }
 
 // ipForwardingBroken reports whether the system's IP forwarding is disabled

control/controlclient/map.go

@@ -14,6 +14,7 @@
 	"sort"
 	"strconv"
 	"sync"
+	"time"
 
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/envknob"
@@ -39,7 +40,7 @@
 // one MapRequest).
 type mapSession struct {
 	// Immutable fields.
-	nu             NetmapUpdater       // called on changes (in addition to the optional hooks below)
+	netmapUpdater  NetmapUpdater       // called on changes (in addition to the optional hooks below)
 	controlKnobs   *controlknobs.Knobs // or nil
 	privateNodeKey key.NodePrivate
 	publicNodeKey  key.NodePublic
@@ -98,7 +99,7 @@ type mapSession struct {
 // It must have its Close method called to release resources.
 func newMapSession(privateNodeKey key.NodePrivate, nu NetmapUpdater, controlKnobs *controlknobs.Knobs) *mapSession {
 	ms := &mapSession{
-		nu:              nu,
+		netmapUpdater:   nu,
 		controlKnobs:    controlKnobs,
 		privateNodeKey:  privateNodeKey,
 		publicNodeKey:   privateNodeKey.Public(),
@@ -197,8 +198,16 @@ func (ms *mapSession) HandleNonKeepAliveMapResponse(ctx context.Context, resp *t
 
 	ms.updateStateFromResponse(resp)
 
-	nm := ms.netmap()
+	if ms.tryHandleIncrementally(resp) {
+		ms.onConciseNetMapSummary(ms.lastNetmapSummary) // every 5s log
+		return nil
+	}
 
+	// We have to rebuild the whole netmap (lots of garbage & work downstream of
+	// our UpdateFullNetmap call). This is the part we tried to avoid but
+	// some field mutations (especially rare ones) aren't yet handled.
+
+	nm := ms.netmap()
 	ms.lastNetmapSummary = nm.VeryConcise()
 	ms.onConciseNetMapSummary(ms.lastNetmapSummary)
 
@@ -207,10 +216,25 @@ func (ms *mapSession) HandleNonKeepAliveMapResponse(ctx context.Context, resp *t
 		ms.onSelfNodeChanged(nm)
 	}
 
-	ms.nu.UpdateFullNetmap(nm)
+	ms.netmapUpdater.UpdateFullNetmap(nm)
 	return nil
 }
 
+func (ms *mapSession) tryHandleIncrementally(res *tailcfg.MapResponse) bool {
+	if ms.controlKnobs != nil && ms.controlKnobs.DisableDeltaUpdates.Load() {
+		return false
+	}
+	nud, ok := ms.netmapUpdater.(NetmapDeltaUpdater)
+	if !ok {
+		return false
+	}
+	mutations, ok := netmap.MutationsFromMapResponse(res, time.Now())
+	if ok && len(mutations) > 0 {
+		return nud.UpdateNetmapDelta(mutations)
+	}
+	return ok
+}
+
 // updateStats are some stats from updateStateFromResponse, primarily for
 // testing. It's meant to be cheap enough to always compute, though. It doesn't
 // allocate.

control/controlknobs/controlknobs.go

@@ -38,6 +38,11 @@ type Knobs struct {
 	// ForceBackgroundSTUN forces netcheck STUN queries to keep
 	// running in magicsock, even when idle.
 	ForceBackgroundSTUN atomic.Bool
+
+	// DisableDeltaUpdates is whether the node should not process
+	// incremental (delta) netmap updates and should treat all netmap
+	// changes as "full" ones as tailscaled did in 1.48.x and earlier.
+	DisableDeltaUpdates atomic.Bool
 }
 
 // AsDebugJSON returns k as something that can be marshalled with json.Marshal
@@ -53,5 +58,6 @@ func (k *Knobs) AsDebugJSON() map[string]any {
 		"RandomizeClientPort": k.RandomizeClientPort.Load(),
 		"OneCGNAT":            k.OneCGNAT.Load(),
 		"ForceBackgroundSTUN": k.ForceBackgroundSTUN.Load(),
+		"DisableDeltaUpdates": k.DisableDeltaUpdates.Load(),
 	}
 }

control/controlknobs/controlknobs_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package controlknobs
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestAsDebugJSON(t *testing.T) {
+	var nilPtr *Knobs
+	if got := nilPtr.AsDebugJSON(); got != nil {
+		t.Errorf("AsDebugJSON(nil) = %v; want nil", got)
+	}
+	k := new(Knobs)
+	got := k.AsDebugJSON()
+	if want := reflect.TypeOf(Knobs{}).NumField(); len(got) != want {
+		t.Errorf("AsDebugJSON map has %d fields; want %v", len(got), want)
+	}
+}

ipn/ipnlocal/local.go

@@ -203,9 +203,8 @@ type LocalBackend struct {
 	capFileSharing bool // whether netMap contains the file sharing capability
 	capTailnetLock bool // whether netMap contains the tailnet lock capability
 	// hostinfo is mutated in-place while mu is held.
-	hostinfo *tailcfg.Hostinfo
-	// netMap is not mutated in-place once set.
-	netMap           *netmap.NetworkMap
+	hostinfo         *tailcfg.Hostinfo
+	netMap           *netmap.NetworkMap     // not mutated in place once set (except for Peers slice)
 	nmExpiryTimer    tstime.TimerController // for updating netMap on node expiry; can be nil
 	nodeByAddr       map[netip.Addr]tailcfg.NodeView
 	activeLogin      string // last logged LoginName from netMap
@@ -1121,6 +1120,56 @@ func (b *LocalBackend) SetControlClientStatus(c controlclient.Client, st control
 	b.authReconfig()
 }
 
+var _ controlclient.NetmapDeltaUpdater = (*LocalBackend)(nil)
+
+// UpdateNetmapDelta implements controlclient.NetmapDeltaUpdater.
+func (b *LocalBackend) UpdateNetmapDelta(muts []netmap.NodeMutation) (handled bool) {
+	mc, err := b.magicConn()
+	if err != nil {
+		panic(err) // shouldn't happen
+	}
+	if !mc.UpdateNetmapDelta(muts) {
+		return false
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.updateNetmapDeltaLocked(muts)
+}
+
+func (b *LocalBackend) updateNetmapDeltaLocked(muts []netmap.NodeMutation) (handled bool) {
+	if b.netMap == nil {
+		return false
+	}
+	peers := b.netMap.Peers
+
+	for _, m := range muts {
+		// LocalBackend only cares about some types of mutations.
+		// (magicsock cares about different ones.)
+		switch m.(type) {
+		case netmap.NodeMutationOnline, netmap.NodeMutationLastSeen:
+		default:
+			continue
+		}
+
+		nodeID := m.NodeIDBeingMutated()
+		idx := b.netMap.PeerIndexByNodeID(nodeID)
+		if idx == -1 {
+			continue
+		}
+		mut := peers[idx].AsStruct()
+
+		switch m := m.(type) {
+		case netmap.NodeMutationOnline:
+			mut.Online = ptr.To(m.Online)
+		case netmap.NodeMutationLastSeen:
+			mut.LastSeen = ptr.To(m.LastSeen)
+		}
+		peers[idx] = mut.View()
+	}
+	return true
+}
+
 // setExitNodeID updates prefs to reference an exit node by ID, rather
 // than by IP. It returns whether prefs was mutated.
 func setExitNodeID(prefs *ipn.Prefs, nm *netmap.NetworkMap) (prefsChanged bool) {

ipn/ipnlocal/local_test.go

@@ -26,6 +26,7 @@
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
 	"tailscale.com/types/netmap"
+	"tailscale.com/types/ptr"
 	"tailscale.com/util/set"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/filter"
@@ -879,3 +880,75 @@ func TestWatchNotificationsCallbacks(t *testing.T) {
 		t.Fatalf("unexpected number of watchers in new LocalBackend, want: 0 got: %v", len(b.notifyWatchers))
 	}
 }
+
+// tests LocalBackend.updateNetmapDeltaLocked
+func TestUpdateNetmapDelta(t *testing.T) {
+	var b LocalBackend
+	if b.updateNetmapDeltaLocked(nil) {
+		t.Errorf("updateNetmapDeltaLocked() = true, want false with nil netmap")
+	}
+
+	b.netMap = &netmap.NetworkMap{}
+	for i := 0; i < 5; i++ {
+		b.netMap.Peers = append(b.netMap.Peers, (&tailcfg.Node{ID: (tailcfg.NodeID(i) + 1)}).View())
+	}
+
+	someTime := time.Unix(123, 0)
+	muts, ok := netmap.MutationsFromMapResponse(&tailcfg.MapResponse{
+		PeersChangedPatch: []*tailcfg.PeerChange{
+			{
+				NodeID:     1,
+				DERPRegion: 1,
+			},
+			{
+				NodeID: 2,
+				Online: ptr.To(true),
+			},
+			{
+				NodeID: 3,
+				Online: ptr.To(false),
+			},
+			{
+				NodeID:   4,
+				LastSeen: ptr.To(someTime),
+			},
+		},
+	}, someTime)
+	if !ok {
+		t.Fatal("netmap.MutationsFromMapResponse failed")
+	}
+
+	if !b.updateNetmapDeltaLocked(muts) {
+		t.Fatalf("updateNetmapDeltaLocked() = false, want true with new netmap")
+	}
+
+	wants := []*tailcfg.Node{
+		{
+			ID:   1,
+			DERP: "", // unmodified by the delta
+		},
+		{
+			ID:     2,
+			Online: ptr.To(true),
+		},
+		{
+			ID:     3,
+			Online: ptr.To(false),
+		},
+		{
+			ID:       4,
+			LastSeen: ptr.To(someTime),
+		},
+	}
+	for _, want := range wants {
+		idx := b.netMap.PeerIndexByNodeID(want.ID)
+		if idx == -1 {
+			t.Errorf("ID %v not found in netmap", want.ID)
+			continue
+		}
+		got := b.netMap.Peers[idx].AsStruct()
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("netmap.Peer %v wrong.\n got: %v\nwant: %v", want.ID, logger.AsJSON(got), logger.AsJSON(want))
+		}
+	}
+}

tailcfg/tailcfg.go

@@ -1995,6 +1995,11 @@ type Oauth2Token struct {
 	// new attempts at UPnP connections.
 	NodeAttrDisableUPnP = "debug-disable-upnp"
 
+	// NodeAttrDisableDeltaUpdates makes the client not process updates via the
+	// delta update mechanism and should instead treat all netmap changes as
+	// "full" ones as tailscaled did in 1.48.x and earlier.
+	NodeAttrDisableDeltaUpdates = "disable-delta-updates"
+
 	// NodeAttrRandomizeClientPort makes magicsock UDP bind to
 	// :0 to get a random local port, ignoring any configured
 	// fixed port.

types/netmap/netmap.go

@@ -8,6 +8,7 @@
 	"encoding/json"
 	"fmt"
 	"net/netip"
+	"sort"
 	"strings"
 	"time"
 
@@ -15,6 +16,7 @@
 	"tailscale.com/tka"
 	"tailscale.com/types/key"
 	"tailscale.com/types/views"
+	"tailscale.com/util/cmpx"
 	"tailscale.com/wgengine/filter"
 )
 
@@ -124,6 +126,23 @@ func (nm *NetworkMap) PeerByTailscaleIP(ip netip.Addr) (peer tailcfg.NodeView, o
 	return tailcfg.NodeView{}, false
 }
 
+// PeerIndexByNodeID returns the index of the peer with the given nodeID
+// in nm.Peers, or -1 if nm is nil or not found.
+//
+// It assumes nm.Peers is sorted by Node.ID.
+func (nm *NetworkMap) PeerIndexByNodeID(nodeID tailcfg.NodeID) int {
+	if nm == nil {
+		return -1
+	}
+	idx, ok := sort.Find(len(nm.Peers), func(i int) int {
+		return cmpx.Compare(nodeID, nm.Peers[i].ID())
+	})
+	if !ok {
+		return -1
+	}
+	return idx
+}
+
 // MagicDNSSuffix returns the domain's MagicDNS suffix (even if MagicDNS isn't
 // necessarily in use) of the provided Node.Name value.
 //

types/netmap/netmap_test.go

@@ -280,3 +280,31 @@ func TestConciseDiffFrom(t *testing.T) {
 		})
 	}
 }
+
+func TestPeerIndexByNodeID(t *testing.T) {
+	var nilPtr *NetworkMap
+	if nilPtr.PeerIndexByNodeID(123) != -1 {
+		t.Errorf("nil PeerIndexByNodeID should return -1")
+	}
+	var nm NetworkMap
+	const min = 2
+	const max = 10000
+	const hole = max / 2
+	for nid := tailcfg.NodeID(2); nid <= max; nid++ {
+		if nid == hole {
+			continue
+		}
+		nm.Peers = append(nm.Peers, (&tailcfg.Node{ID: nid}).View())
+	}
+	for want, nv := range nm.Peers {
+		got := nm.PeerIndexByNodeID(nv.ID())
+		if got != want {
+			t.Errorf("PeerIndexByNodeID(%v) = %v; want %v", nv.ID(), got, want)
+		}
+	}
+	for _, miss := range []tailcfg.NodeID{min - 1, hole, max + 1} {
+		if got := nm.PeerIndexByNodeID(miss); got != -1 {
+			t.Errorf("PeerIndexByNodeID(%v) = %v; want -1", miss, got)
+		}
+	}
+}

types/netmap/nodemut.go

@@ -0,0 +1,168 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package netmap
+
+import (
+	"net/netip"
+	"reflect"
+	"slices"
+	"sync"
+	"time"
+
+	"tailscale.com/tailcfg"
+	"tailscale.com/util/cmpx"
+)
+
+// NodeMutation is the common interface for types that describe
+// the change of a node's state.
+type NodeMutation interface {
+	NodeIDBeingMutated() tailcfg.NodeID
+}
+
+type mutatingNodeID tailcfg.NodeID
+
+func (m mutatingNodeID) NodeIDBeingMutated() tailcfg.NodeID { return tailcfg.NodeID(m) }
+
+// NodeMutationDERPHome is a NodeMutation that says a node
+// has changed its DERP home region.
+type NodeMutationDERPHome struct {
+	mutatingNodeID
+	DERPRegion int
+}
+
+// NodeMutation is a NodeMutation that says a node's endpoints have changed.
+type NodeMutationEndpoints struct {
+	mutatingNodeID
+	Endpoints []netip.AddrPort
+}
+
+// NodeMutationOnline is a NodeMutation that says a node is now online or
+// offline.
+type NodeMutationOnline struct {
+	mutatingNodeID
+	Online bool
+}
+
+// NodeMutationLastSeen is a NodeMutation that says a node's LastSeen
+// value should be set to the current time.
+type NodeMutationLastSeen struct {
+	mutatingNodeID
+	LastSeen time.Time
+}
+
+var peerChangeFields = sync.OnceValue(func() []reflect.StructField {
+	var fields []reflect.StructField
+	rt := reflect.TypeOf((*tailcfg.PeerChange)(nil)).Elem()
+	for i := 0; i < rt.NumField(); i++ {
+		fields = append(fields, rt.Field(i))
+	}
+	return fields
+})
+
+// NodeMutationsFromPatch returns the NodeMutations that
+// p describes. If p describes something not yet supported
+// by a specific NodeMutation type, it returns (nil, false).
+func NodeMutationsFromPatch(p *tailcfg.PeerChange) (_ []NodeMutation, ok bool) {
+	if p == nil || p.NodeID == 0 {
+		return nil, false
+	}
+	var ret []NodeMutation
+	rv := reflect.ValueOf(p).Elem()
+	for i, sf := range peerChangeFields() {
+		if rv.Field(i).IsZero() {
+			continue
+		}
+		switch sf.Name {
+		default:
+			// Unhandled field.
+			return nil, false
+		case "NodeID":
+			continue
+		case "DERPRegion":
+			ret = append(ret, NodeMutationDERPHome{mutatingNodeID(p.NodeID), p.DERPRegion})
+		case "Endpoints":
+			eps := make([]netip.AddrPort, len(p.Endpoints))
+			for i, epStr := range p.Endpoints {
+				var err error
+				eps[i], err = netip.ParseAddrPort(epStr)
+				if err != nil {
+					return nil, false
+				}
+			}
+			ret = append(ret, NodeMutationEndpoints{mutatingNodeID(p.NodeID), eps})
+		case "Online":
+			ret = append(ret, NodeMutationOnline{mutatingNodeID(p.NodeID), *p.Online})
+		case "LastSeen":
+			ret = append(ret, NodeMutationLastSeen{mutatingNodeID(p.NodeID), *p.LastSeen})
+		}
+	}
+	return ret, true
+}
+
+// MutationsFromMapResponse returns all the discrete node mutations described
+// by res. It returns ok=false if res contains any non-patch field as defined
+// by mapResponseContainsNonPatchFields.
+func MutationsFromMapResponse(res *tailcfg.MapResponse, now time.Time) (ret []NodeMutation, ok bool) {
+	if now.IsZero() {
+		now = time.Now()
+	}
+	if mapResponseContainsNonPatchFields(res) {
+		return nil, false
+	}
+	// All that remains is PeersChangedPatch, OnlineChange, and LastSeenChange.
+
+	for _, p := range res.PeersChangedPatch {
+		deltas, ok := NodeMutationsFromPatch(p)
+		if !ok {
+			return nil, false
+		}
+		ret = append(ret, deltas...)
+	}
+	for nid, v := range res.OnlineChange {
+		ret = append(ret, NodeMutationOnline{mutatingNodeID(nid), v})
+	}
+	for nid, v := range res.PeerSeenChange {
+		if v {
+			ret = append(ret, NodeMutationLastSeen{mutatingNodeID(nid), now})
+		}
+	}
+	slices.SortStableFunc(ret, func(a, b NodeMutation) int {
+		return cmpx.Compare(a.NodeIDBeingMutated(), b.NodeIDBeingMutated())
+	})
+	return ret, true
+}
+
+// mapResponseContainsNonPatchFields reports whether res contains only "patch"
+// fields set (PeersChangedPatch primarily, but also including the legacy
+// PeerSeenChange and OnlineChange fields).
+//
+// It ignores any of the meta fields that are handled by PollNetMap before the
+// peer change handling gets involved.
+//
+// The purpose of this function is to ask whether this is a tricky enough
+// MapResponse to warrant a full netmap update. When this returns false, it
+// means the response can be handled incrementally, patching up the local state.
+func mapResponseContainsNonPatchFields(res *tailcfg.MapResponse) bool {
+	return res.Node != nil ||
+		res.DERPMap != nil ||
+		res.DNSConfig != nil ||
+		res.Domain != "" ||
+		res.CollectServices != "" ||
+		res.PacketFilter != nil ||
+		res.UserProfiles != nil ||
+		res.Health != nil ||
+		res.SSHPolicy != nil ||
+		res.TKAInfo != nil ||
+		res.DomainDataPlaneAuditLogID != "" ||
+		res.Debug != nil ||
+		res.ControlDialPlan != nil ||
+		res.ClientVersion != nil ||
+		res.Peers != nil ||
+		res.PeersRemoved != nil ||
+		// PeersChanged is too coarse to be considered a patch. Also, we convert
+		// PeersChanged to PeersChangedPatch in patchifyPeersChanged before this
+		// function is called, so it should never be set anyway. But for
+		// completedness, and for tests, check it too:
+		res.PeersChanged != nil
+}

types/netmap/nodemut_test.go

@@ -0,0 +1,199 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package netmap
+
+import (
+	"fmt"
+	"net/netip"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"tailscale.com/tailcfg"
+	"tailscale.com/types/logger"
+	"tailscale.com/types/ptr"
+)
+
+// tests mapResponseContainsNonPatchFields
+func TestMapResponseContainsNonPatchFields(t *testing.T) {
+
+	// reflectNonzero returns a non-zero value of the given type.
+	reflectNonzero := func(t reflect.Type) reflect.Value {
+
+		switch t.Kind() {
+		case reflect.Bool:
+			return reflect.ValueOf(true)
+		case reflect.String:
+			return reflect.ValueOf("foo").Convert(t)
+		case reflect.Int64:
+			return reflect.ValueOf(int64(1))
+		case reflect.Slice:
+			return reflect.MakeSlice(t, 1, 1)
+		case reflect.Ptr:
+			return reflect.New(t.Elem())
+		case reflect.Map:
+			return reflect.MakeMap(t)
+		}
+		panic(fmt.Sprintf("unhandled %v", t))
+	}
+
+	rt := reflect.TypeOf(tailcfg.MapResponse{})
+	for i := 0; i < rt.NumField(); i++ {
+		f := rt.Field(i)
+
+		var want bool
+		switch f.Name {
+		case "MapSessionHandle", "Seq", "KeepAlive", "PingRequest", "PopBrowserURL", "ControlTime":
+			// There are meta fields that apply to all MapResponse values.
+			// They should be ignored.
+			want = false
+		case "PeersChangedPatch", "PeerSeenChange", "OnlineChange":
+			// The actual three delta fields we care about handling.
+			want = false
+		default:
+			// Everything else should be conseratively handled as a
+			// non-delta field. We want it to return true so if
+			// the field is not listed in the function being tested,
+			// it'll return false and we'll fail this test.
+			// This makes sure any new fields added to MapResponse
+			// are accounted for here.
+			want = true
+		}
+
+		var v tailcfg.MapResponse
+		rv := reflect.ValueOf(&v).Elem()
+		rv.FieldByName(f.Name).Set(reflectNonzero(f.Type))
+
+		got := mapResponseContainsNonPatchFields(&v)
+		if got != want {
+			t.Errorf("field %q: got %v; want %v\nJSON: %v", f.Name, got, want, logger.AsJSON(v))
+		}
+	}
+}
+
+// tests MutationsFromMapResponse
+func TestMutationsFromMapResponse(t *testing.T) {
+	someTime := time.Unix(123, 0)
+	fromChanges := func(changes ...*tailcfg.PeerChange) *tailcfg.MapResponse {
+		return &tailcfg.MapResponse{
+			PeersChangedPatch: changes,
+		}
+	}
+	muts := func(muts ...NodeMutation) []NodeMutation { return muts }
+	tests := []struct {
+		name string
+		mr   *tailcfg.MapResponse
+		want []NodeMutation // nil means !ok, zero-length means none
+	}{
+		{
+			name: "patch-ep",
+			mr: fromChanges(&tailcfg.PeerChange{
+				NodeID:    1,
+				Endpoints: []string{"1.2.3.4:567"},
+			}, &tailcfg.PeerChange{
+				NodeID:    2,
+				Endpoints: []string{"8.9.10.11:1234"},
+			}),
+			want: muts(
+				NodeMutationEndpoints{1, []netip.AddrPort{netip.MustParseAddrPort("1.2.3.4:567")}},
+				NodeMutationEndpoints{2, []netip.AddrPort{netip.MustParseAddrPort("8.9.10.11:1234")}},
+			),
+		},
+		{
+			name: "patch-derp",
+			mr: fromChanges(&tailcfg.PeerChange{
+				NodeID:     1,
+				DERPRegion: 2,
+			}),
+			want: muts(NodeMutationDERPHome{1, 2}),
+		},
+		{
+			name: "patch-online",
+			mr: fromChanges(&tailcfg.PeerChange{
+				NodeID: 1,
+				Online: ptr.To(true),
+			}),
+			want: muts(NodeMutationOnline{1, true}),
+		},
+		{
+			name: "patch-online-false",
+			mr: fromChanges(&tailcfg.PeerChange{
+				NodeID: 1,
+				Online: ptr.To(false),
+			}),
+			want: muts(NodeMutationOnline{1, false}),
+		},
+		{
+			name: "patch-lastseen",
+			mr: fromChanges(&tailcfg.PeerChange{
+				NodeID:   1,
+				LastSeen: ptr.To(time.Unix(12345, 0)),
+			}),
+			want: muts(NodeMutationLastSeen{1, time.Unix(12345, 0)}),
+		},
+		{
+			name: "legacy-online-change", // the old pre-Patch style
+			mr: &tailcfg.MapResponse{
+				OnlineChange: map[tailcfg.NodeID]bool{
+					1: true,
+					2: false,
+				},
+			},
+			want: muts(
+				NodeMutationOnline{1, true},
+				NodeMutationOnline{2, false},
+			),
+		},
+		{
+			name: "legacy-lastseen-change", // the old pre-Patch style
+			mr: &tailcfg.MapResponse{
+				PeerSeenChange: map[tailcfg.NodeID]bool{
+					1: true,
+				},
+			},
+			want: muts(
+				NodeMutationLastSeen{1, someTime},
+			),
+		},
+		{
+			name: "no-changes",
+			mr:   fromChanges(),
+			want: make([]NodeMutation, 0), // non-nil to mean want ok but no changes
+		},
+		{
+			name: "not-okay-patch-node-change",
+			mr: &tailcfg.MapResponse{
+				Node: &tailcfg.Node{}, // non-nil
+				PeersChangedPatch: []*tailcfg.PeerChange{{
+					NodeID:     1,
+					DERPRegion: 2,
+				}},
+			},
+			want: nil,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, gotOK := MutationsFromMapResponse(tt.mr, someTime)
+			wantOK := tt.want != nil
+			if gotOK != wantOK {
+				t.Errorf("got ok=%v; want %v", gotOK, wantOK)
+			} else if got == nil && gotOK {
+				got = make([]NodeMutation, 0) // for cmd.Diff
+			}
+			if diff := cmp.Diff(tt.want, got,
+				cmp.Comparer(func(a, b netip.Addr) bool { return a == b }),
+				cmp.Comparer(func(a, b netip.AddrPort) bool { return a == b }),
+				cmp.AllowUnexported(
+					NodeMutationEndpoints{},
+					NodeMutationDERPHome{},
+					NodeMutationOnline{},
+					NodeMutationLastSeen{},
+				)); diff != "" {
+				t.Errorf("wrong result (-want +got):\n%s", diff)
+			}
+		})
+	}
+}

wgengine/magicsock/endpoint.go

@@ -29,6 +29,7 @@
 	"tailscale.com/tstime/mono"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
+	"tailscale.com/types/views"
 	"tailscale.com/util/mak"
 	"tailscale.com/util/ringbuffer"
 )
@@ -805,20 +806,38 @@ func (de *endpoint) updateFromNode(n tailcfg.NodeView, heartbeatDisabled bool) {
 		de.derpAddr = newDerp
 	}
 
+	de.setEndpointsLocked(addrPortsFromStringsView{n.Endpoints()})
+}
+
+// addrPortsFromStringsView converts a view of AddrPort strings
+// to a view-like thing of netip.AddrPort.
+// TODO(bradfitz): change the type of tailcfg.Node.Endpoint.
+type addrPortsFromStringsView struct {
+	views.Slice[string]
+}
+
+func (a addrPortsFromStringsView) At(i int) netip.AddrPort {
+	ap, _ := netip.ParseAddrPort(a.Slice.At(i))
+	return ap // or the zero value on error
+}
+
+func (de *endpoint) setEndpointsLocked(eps interface {
+	LenIter() []struct{}
+	At(i int) netip.AddrPort
+}) {
 	for _, st := range de.endpointState {
 		st.index = indexSentinelDeleted // assume deleted until updated in next loop
 	}
 
 	var newIpps []netip.AddrPort
-	for i := range n.Endpoints().LenIter() {
-		epStr := n.Endpoints().At(i)
+	for i := range eps.LenIter() {
 		if i > math.MaxInt16 {
 			// Seems unlikely.
-			continue
+			break
 		}
-		ipp, err := netip.ParseAddrPort(epStr)
-		if err != nil {
-			de.c.logf("magicsock: bogus netmap endpoint %q", epStr)
+		ipp := eps.At(i)
+		if !ipp.IsValid() {
+			de.c.logf("magicsock: bogus netmap endpoint from %v", eps)
 			continue
 		}
 		if st, ok := de.endpointState[ipp]; ok {
@@ -1214,3 +1233,9 @@ func (de *endpoint) resetLocked() {
 func (de *endpoint) numStopAndReset() int64 {
 	return atomic.LoadInt64(&de.numStopAndResetAtomic)
 }
+
+func (de *endpoint) setDERPHome(regionID uint16) {
+	de.mu.Lock()
+	defer de.mu.Unlock()
+	de.derpAddr = netip.AddrPortFrom(tailcfg.DerpMagicIPAddr, uint16(regionID))
+}

wgengine/magicsock/magicsock.go

@@ -2588,6 +2588,29 @@ func simpleDur(d time.Duration) time.Duration {
 	return d.Round(time.Minute)
 }
 
+// UpdateNetmapDelta implements controlclient.NetmapDeltaUpdater.
+func (c *Conn) UpdateNetmapDelta(muts []netmap.NodeMutation) (handled bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	for _, m := range muts {
+		nodeID := m.NodeIDBeingMutated()
+		ep, ok := c.peerMap.endpointForNodeID(nodeID)
+		if !ok {
+			continue
+		}
+		switch m := m.(type) {
+		case netmap.NodeMutationDERPHome:
+			ep.setDERPHome(uint16(m.DERPRegion))
+		case netmap.NodeMutationEndpoints:
+			ep.mu.Lock()
+			ep.setEndpointsLocked(views.SliceOf(m.Endpoints))
+			ep.mu.Unlock()
+		}
+	}
+	return true
+}
+
 // UpdateStatus implements the interface nede by ipnstate.StatusBuilder.
 //
 // This method adds in the magicsock-specific information only. Most