client/local/local.go

@@ -607,6 +607,24 @@ func (lc *Client) DebugResultJSON(ctx context.Context, action string) (any, erro
 	return x, nil
 }
 
+// GetDebugResultJSON invokes a debug action and decodes the JSON response
+// into a value of type T. It avoids the marshal/unmarshal roundtrip that
+// callers of [Client.DebugResultJSON] otherwise need to do to get a typed
+// value.
+//
+// These are development tools and subject to change or removal over time.
+func GetDebugResultJSON[T any](ctx context.Context, lc *Client, action string) (T, error) {
+	var v T
+	body, err := lc.send(ctx, "POST", "/localapi/v0/debug?action="+url.QueryEscape(action), 200, nil)
+	if err != nil {
+		return v, fmt.Errorf("error %w: %s", err, body)
+	}
+	if err := json.Unmarshal(body, &v); err != nil {
+		return v, err
+	}
+	return v, nil
+}
+
 // QueryOptionalFeatures queries the optional features supported by the Tailscale daemon.
 func (lc *Client) QueryOptionalFeatures(ctx context.Context) (*apitype.OptionalFeatures, error) {
 	body, err := lc.send(ctx, "POST", "/localapi/v0/debug-optional-features", 200, nil)

feature/doctor/doctor.go

@@ -63,7 +63,7 @@ func visitDoctor(ctx context.Context, b *ipnlocal.LocalBackend, logf logger.Logf
 	// IPs; this can interfere with our ability to connect to the Tailscale
 	// controlplane.
 	checks = append(checks, doctor.CheckFunc("dns-resolvers", func(_ context.Context, logf logger.Logf) error {
-		nm := b.NetMap()
+		nm := b.NetMapNoPeers()
 		if nm == nil {
 			return nil
 		}

ipn/ipnlocal/cert.go

@@ -909,7 +909,7 @@ func (b *LocalBackend) resolveCertDomain(domain string) (string, error) {
 	}
 
 	// Read the netmap once to get both CertDomains and capabilities atomically.
-	nm := b.NetMap()
+	nm := b.NetMapNoPeers()
 	if nm == nil {
 		return "", errors.New("no netmap available")
 	}

ipn/ipnlocal/local.go

@@ -701,7 +701,9 @@ func (b *LocalBackend) onHomeDERPUpdateLocked(du magicsock.HomeDERPChanged) {
 		return
 	}
 
-	if err := b.writeNetmapToDiskLocked(b.NetMap()); err != nil {
+	// Persist the full netmap (including up-to-date Peers) to disk for
+	// fast restart.
+	if err := b.writeNetmapToDiskLocked(b.NetMapWithPeers()); err != nil {
 		b.logf("write netmap to cache: %v", err)
 	}
 }
@@ -1023,7 +1025,7 @@ func (b *LocalBackend) pauseOrResumeControlClientLocked() {
 		return
 	}
 	networkUp := b.interfaceState.AnyInterfaceUp()
-	pauseForNetwork := (b.state == ipn.Stopped && b.NetMap() != nil) || (!networkUp && !testenv.InTest() && !envknob.AssumeNetworkUp())
+	pauseForNetwork := (b.state == ipn.Stopped && b.NetMapNoPeers() != nil) || (!networkUp && !testenv.InTest() && !envknob.AssumeNetworkUp())
 
 	prefs := b.pm.CurrentPrefs()
 	pauseForSyncPref := prefs.Valid() && prefs.Sync().EqualBool(false)
@@ -4057,7 +4059,8 @@ func (b *LocalBackend) pingPeerAPI(ctx context.Context, ip netip.Addr) (peer tai
 	var zero tailcfg.NodeView
 	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
 	defer cancel()
-	nm := b.NetMap()
+	// PeerByTailscaleIP needs an up-to-date Peers slice.
+	nm := b.NetMapWithPeers()
 	if nm == nil {
 		return zero, "", errors.New("no netmap")
 	}
@@ -4967,7 +4970,7 @@ func (b *LocalBackend) handlePeerAPIConn(remote, local netip.AddrPort, c net.Con
 }
 
 func (b *LocalBackend) isLocalIP(ip netip.Addr) bool {
-	nm := b.NetMap()
+	nm := b.NetMapNoPeers()
 	return nm != nil && views.SliceContains(nm.GetAddresses(), netip.PrefixFrom(ip, ip.BitLen()))
 }
 
@@ -5119,10 +5122,46 @@ func extractPeerAPIPorts(services []tailcfg.Service) portPair {
 
 // NetMap returns the latest cached network map received from
 // controlclient, or nil if no network map was received yet.
+//
+// Deprecated: callers should declare their needs explicitly by calling
+// either [LocalBackend.NetMapNoPeers] (cheap; for code that reads
+// non-Peers fields like SelfNode, DNS, PacketFilter, capabilities) or
+// [LocalBackend.NetMapWithPeers] (currently the same; will be made to
+// return an up-to-date Peers slice in a follow-up change, at the cost of
+// O(N) work per call). NetMap will eventually be removed.
 func (b *LocalBackend) NetMap() *netmap.NetworkMap {
 	return b.currentNode().NetMap()
 }
 
+// NetMapNoPeers returns the latest cached network map received from
+// controlclient WITHOUT a freshly-built Peers slice.
+//
+// On a tailnet with frequent peer churn the cached netmap's Peers slice
+// can be stale relative to the live per-node-backend peers map; non-Peers
+// fields (SelfNode, DNS, PacketFilter, capabilities, ...) are always
+// current. Use this for any caller that does not need to iterate Peers,
+// since it's O(1) regardless of tailnet size.
+//
+// Returns nil if no network map has been received yet.
+func (b *LocalBackend) NetMapNoPeers() *netmap.NetworkMap {
+	return b.currentNode().NetMap()
+}
+
+// NetMapWithPeers returns the latest network map with the Peers slice
+// populated.
+//
+// Currently this is the same as [LocalBackend.NetMapNoPeers]: the cached
+// netmap's Peers slice may be stale relative to the live per-node-backend
+// peers map. A follow-up change will switch this method to return a
+// freshly-built netmap with up-to-date Peers, at O(N) cost per call.
+// Callers that genuinely need the up-to-date peer set should use this
+// method (and document why) so the upcoming change reaches them.
+//
+// Returns nil if no network map has been received yet.
+func (b *LocalBackend) NetMapWithPeers() *netmap.NetworkMap {
+	return b.currentNode().NetMap()
+}
+
 // lookupPeerByIP returns the node public key for the peer that owns the
 // given IP address. It is the fast path for [Engine.SetPeerByIPPacketFunc],
 // handling exact-IP matches against node addresses; subnet routes and exit
@@ -6978,7 +7017,7 @@ func (b *LocalBackend) AppConnector() *appc.AppConnector {
 func (b *LocalBackend) allowExitNodeDNSProxyToServeName(name string) bool {
 	b.mu.Lock()
 	defer b.mu.Unlock()
-	nm := b.NetMap()
+	nm := b.NetMapNoPeers()
 	if nm == nil {
 		return false
 	}

ipn/ipnlocal/peerapi.go

@@ -192,7 +192,7 @@ func (pln *peerAPIListener) ServeConn(src netip.AddrPort, c net.Conn) {
 		c.Close()
 		return
 	}
-	nm := pln.lb.NetMap()
+	nm := pln.lb.NetMapNoPeers()
 	if nm == nil || !nm.SelfNode.Valid() {
 		logf("peerapi: no netmap")
 		c.Close()

ipn/ipnlocal/serve.go

@@ -276,7 +276,7 @@ func (b *LocalBackend) updateServeTCPPortNetMapAddrListenersLocked(ports []uint1
 		}
 	}
 
-	nm := b.NetMap()
+	nm := b.NetMapNoPeers()
 	if nm == nil {
 		b.logf("netMap is nil")
 		return
@@ -333,7 +333,7 @@ func (b *LocalBackend) setServeConfigLocked(config *ipn.ServeConfig, etag string
 		return errors.New("can't reconfigure tailscaled when using a config file; config file is locked")
 	}
 
-	nm := b.NetMap()
+	nm := b.NetMapNoPeers()
 	if nm == nil {
 		return errors.New("netMap is nil")
 	}

ipn/ipnlocal/web_client.go

@@ -173,7 +173,7 @@ func (b *LocalBackend) waitWebClientAuthURL(ctx context.Context, id string, src
 // one to be completed, based on the presence or absence of the
 // provided id value.
 func (b *LocalBackend) doWebClientNoiseRequest(ctx context.Context, id string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
-	nm := b.NetMap()
+	nm := b.NetMapNoPeers()
 	if nm == nil || !nm.SelfNode.Valid() {
 		return nil, errors.New("[unexpected] no self node")
 	}

ipn/localapi/debug.go

@@ -9,6 +9,7 @@ import (
 	"cmp"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -249,6 +250,22 @@ func (h *Handler) serveDebug(w http.ResponseWriter, r *http.Request) {
 		}
 	case "clear-netmap-cache":
 		h.b.ClearNetmapCache(r.Context())
+	case "current-netmap":
+		// Return the current netmap (with peers populated) as JSON. This
+		// is a debug-only path: the netmap.NetworkMap shape is an
+		// internal type and may change without notice. Production
+		// callers should fetch the narrower bits they need via their
+		// own LocalAPI methods instead.
+		nm := h.b.NetMapWithPeers()
+		if nm == nil {
+			err = errors.New("no netmap")
+			break
+		}
+		w.Header().Set("Content-Type", "application/json")
+		err = json.NewEncoder(w).Encode(nm)
+		if err == nil {
+			return
+		}
 	case "":
 		err = fmt.Errorf("missing parameter 'action'")
 	default:
@@ -284,7 +301,7 @@ func (h *Handler) serveDebugPacketFilterRules(w http.ResponseWriter, r *http.Req
 		http.Error(w, "debug access denied", http.StatusForbidden)
 		return
 	}
-	nm := h.b.NetMap()
+	nm := h.b.NetMapNoPeers()
 	if nm == nil {
 		http.Error(w, "no netmap", http.StatusNotFound)
 		return
@@ -301,7 +318,7 @@ func (h *Handler) serveDebugPacketFilterMatches(w http.ResponseWriter, r *http.R
 		http.Error(w, "debug access denied", http.StatusForbidden)
 		return
 	}
-	nm := h.b.NetMap()
+	nm := h.b.NetMapNoPeers()
 	if nm == nil {
 		http.Error(w, "no netmap", http.StatusNotFound)
 		return

ipn/localapi/localapi.go

@@ -347,7 +347,7 @@ func (h *Handler) serveIDToken(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "id-token access denied", http.StatusForbidden)
 		return
 	}
-	nm := h.b.NetMap()
+	nm := h.b.NetMapNoPeers()
 	if nm == nil {
 		http.Error(w, "no netmap", http.StatusServiceUnavailable)
 		return
@@ -417,7 +417,7 @@ func (h *Handler) serveBugReport(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Information about the current node from the netmap
-	if nm := h.b.NetMap(); nm != nil {
+	if nm := h.b.NetMapNoPeers(); nm != nil {
 		if self := nm.SelfNode; self.Valid() {
 			h.logf("user bugreport node info: nodeid=%q stableid=%q expiry=%q", self.ID(), self.StableID(), self.KeyExpiry().Format(time.RFC3339))
 		}
@@ -1476,7 +1476,7 @@ func (h *Handler) serveQueryFeature(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "missing feature", http.StatusInternalServerError)
 		return
 	}
-	nm := h.b.NetMap()
+	nm := h.b.NetMapNoPeers()
 	if nm == nil {
 		http.Error(w, "no netmap", http.StatusServiceUnavailable)
 		return
@@ -1731,7 +1731,7 @@ func (h *Handler) serveServices(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "only GET allowed", http.StatusMethodNotAllowed)
 		return
 	}
-	nm := h.b.NetMap()
+	nm := h.b.NetMapNoPeers()
 	if nm == nil {
 		http.Error(w, "no netmap", http.StatusServiceUnavailable)
 		return

ssh/tailssh/incubator.go

@@ -202,7 +202,7 @@ func (ss *sshSession) newIncubatorCommand(logf logger.Logf) (cmd *exec.Cmd, err
 		incubatorArgs = append(incubatorArgs, "--is-selinux-enforcing")
 	}
 
-	nm := ss.conn.srv.lb.NetMap()
+	nm := ss.conn.srv.lb.NetMapNoPeers()
 	forceV1Behavior := nm.HasCap(tailcfg.NodeAttrSSHBehaviorV1) && !nm.HasCap(tailcfg.NodeAttrSSHBehaviorV2)
 	if forceV1Behavior {
 		incubatorArgs = append(incubatorArgs, "--force-v1-behavior")

ssh/tailssh/incubator_plan9.go

@@ -92,7 +92,7 @@ func (ss *sshSession) newIncubatorCommand(logf logger.Logf) (cmd *exec.Cmd, err
 		"--tty-name=",     // updated in-place by startWithPTY
 	}
 
-	nm := ss.conn.srv.lb.NetMap()
+	nm := ss.conn.srv.lb.NetMapNoPeers()
 	forceV1Behavior := nm.HasCap(tailcfg.NodeAttrSSHBehaviorV1) && !nm.HasCap(tailcfg.NodeAttrSSHBehaviorV2)
 	if forceV1Behavior {
 		incubatorArgs = append(incubatorArgs, "--force-v1-behavior")

ssh/tailssh/tailssh.go

@@ -76,6 +76,7 @@ const (
 type ipnLocalBackend interface {
 	ShouldRunSSH() bool
 	NetMap() *netmap.NetworkMap
+	NetMapNoPeers() *netmap.NetworkMap
 	WhoIs(proto string, ipp netip.AddrPort) (n tailcfg.NodeView, u tailcfg.UserProfile, ok bool)
 	DoNoiseRequest(req *http.Request) (*http.Response, error)
 	Dialer() *tsdial.Dialer
@@ -598,7 +599,7 @@ func (c *conn) sshPolicy() (_ *tailcfg.SSHPolicy, ok bool) {
 	if !lb.ShouldRunSSH() {
 		return nil, false
 	}
-	nm := lb.NetMap()
+	nm := lb.NetMapNoPeers()
 	if nm == nil {
 		return nil, false
 	}
@@ -717,7 +718,7 @@ func (c *conn) handleSessionPostSSHAuth(s gliderssh.Session) {
 }
 
 func (c *conn) expandDelegateURLLocked(actionURL string) string {
-	nm := c.srv.lb.NetMap()
+	nm := c.srv.lb.NetMapNoPeers()
 	ci := c.info
 	lu := c.localUser
 	var dstNodeID string

ssh/tailssh/tailssh_integration_test.go

@@ -910,6 +910,8 @@ func (tb *testBackend) NetMap() *netmap.NetworkMap {
 	}
 }
 
+func (tb *testBackend) NetMapNoPeers() *netmap.NetworkMap { return tb.NetMap() }
+
 func (tb *testBackend) WhoIs(_ string, ipp netip.AddrPort) (n tailcfg.NodeView, u tailcfg.UserProfile, ok bool) {
 	return (&tailcfg.Node{}).View(), tailcfg.UserProfile{
 		LoginName: tb.localUser + "@example.com",

ssh/tailssh/tailssh_test.go

@@ -422,6 +422,8 @@ func (ts *localState) NetMap() *netmap.NetworkMap {
 	}
 }
 
+func (ts *localState) NetMapNoPeers() *netmap.NetworkMap { return ts.NetMap() }
+
 func (ts *localState) WhoIs(proto string, ipp netip.AddrPort) (n tailcfg.NodeView, u tailcfg.UserProfile, ok bool) {
 	if proto != "tcp" {
 		return tailcfg.NodeView{}, tailcfg.UserProfile{}, false

tsnet/tsnet.go

@@ -668,7 +668,7 @@ func (s *Server) doInit() {
 // Server.
 // If the server is not running, it returns nil.
 func (s *Server) CertDomains() []string {
-	nm := s.lb.NetMap()
+	nm := s.lb.NetMapNoPeers()
 	if nm == nil {
 		return nil
 	}
@@ -679,7 +679,7 @@ func (s *Server) CertDomains() []string {
 // has not yet joined a tailnet or is otherwise unaware of its own IP addresses,
 // the returned ip4, ip6 will be !netip.IsValid().
 func (s *Server) TailscaleIPs() (ip4, ip6 netip.Addr) {
-	nm := s.lb.NetMap()
+	nm := s.lb.NetMapNoPeers()
 	if nm == nil {
 		return
 	}