mapper: reconcile self on policy recomputes

Self renders from the same state as peers, so leaving it out of policy
responses hid an exit node's approved routes until it reconnected.

Fixes #3502

hscontrol/mapper/batcher.go

@@ -129,9 +129,7 @@ func generateMapResponse(
 		}
 
 		removed = nc.computePeerDiff(currentPeerIDs)
-		// Include self node when this is a self-update (e.g., node's own tags changed)
-		// so the node sees its updated self info along with new packet filters.
-		resp, err = mapper.policyChangeResponse(nodeID, version, currentPeers, isSelfUpdate)
+		resp, err = mapper.policyChangeResponse(nodeID, version, currentPeers)
 	} else if isSelfUpdate {
 		// Non-policy self-update: just send the self node info
 		resp, err = mapper.selfMapResponse(nodeID, version)
@@ -386,6 +384,9 @@ func (b *Batcher) AddNode(
 
 		nodeConn.workMu.Unlock()
 
+		// Still pendingInitial, so no broadcast can race this.
+		newEntry.lastSelf.Store(initialMap.Node)
+
 		// Open the connection for broadcast sends now that the initial
 		// map is the stream's first frame; send() requeued any changes
 		// that arrived in the meantime.

hscontrol/mapper/batcher_test.go

@@ -2715,3 +2715,61 @@ func TestDNSConfigOnlyWithSelfRefresh(t *testing.T) {
 	assert.Nil(t, sent[0].DNSConfig, "policy response must not carry DNSConfig")
 	assert.NotNil(t, sent[1].DNSConfig, "self refresh must carry DNSConfig")
 }
+
+// TestSelfSentOnlyWhenChanged pins that a policy recompute carries the
+// node's own self to each connection that does not hold it yet: self renders
+// from the same state as peers (issue #3502), and a Node forces a full client
+// netmap rebuild.
+func TestSelfSentOnlyWhenChanged(t *testing.T) {
+	testData, cleanup := setupBatcherWithTestData(t, NewBatcherAndMapper, 1, 2, normalBufferSize)
+	defer cleanup()
+
+	b := testData.Batcher.Batcher
+	self := &testData.Nodes[0]
+
+	rename := func(name string) {
+		_, _, err := testData.State.RenameNode(self.n.ID, name)
+		require.NoError(t, err)
+	}
+
+	require.NoError(t, b.AddNode(self.n.ID, self.ch, tailcfg.CapabilityVersion(100), nil))
+	require.NotNil(t, expectReceive(t, self.ch, "initial map").Node)
+
+	nc, ok := b.nodes.Load(self.n.ID)
+	require.True(t, ok)
+
+	policyFrame := func(chs ...chan *tailcfg.MapResponse) []*tailcfg.MapResponse {
+		nc.workMu.Lock()
+		defer nc.workMu.Unlock()
+
+		require.NoError(t, handleNodeChange(nc, b.mapper, change.PolicyChange()))
+
+		frames := make([]*tailcfg.MapResponse, 0, len(chs))
+		for _, ch := range chs {
+			frames = append(frames, expectReceive(t, ch, "policy frame"))
+		}
+
+		return frames
+	}
+
+	assert.Nil(t, policyFrame(self.ch)[0].Node, "unchanged self must be dropped")
+
+	rename("renamed")
+
+	frame := policyFrame(self.ch)[0]
+	require.NotNil(t, frame.Node, "moved self must be sent")
+	assert.Contains(t, frame.Node.Name, "renamed")
+
+	// A connection joining after self moved gets the new self in its
+	// initial map; the next recompute must still reach the older one.
+	rename("renamed-again")
+
+	ch2 := make(chan *tailcfg.MapResponse, normalBufferSize)
+	require.NoError(t, b.AddNode(self.n.ID, ch2, tailcfg.CapabilityVersion(100), nil))
+	require.NotNil(t, expectReceive(t, ch2, "second connection's initial map").Node)
+
+	frames := policyFrame(self.ch, ch2)
+	require.NotNil(t, frames[0].Node, "first connection still holds the old self")
+	assert.Contains(t, frames[0].Node.Name, "renamed-again")
+	assert.Nil(t, frames[1].Node, "second connection already holds the new self")
+}

hscontrol/mapper/mapper.go

@@ -309,7 +309,8 @@ func (m *mapper) selfMapResponse(
 //   - PeersChanged for remaining peers (their AllowedIPs may have changed due to policy)
 //   - Updated PacketFilters
 //   - Updated SSHPolicy (SSH rules may reference users/groups that changed)
-//   - Optionally, the node's own self info (when includeSelf is true)
+//   - The node's own self info, which renders from the same state as peers;
+//     dropped per connection when unchanged, see [connectionEntry.withSelfDelta]
 //
 // DNSConfig is left out: it forces clients into a full netmap rebuild, and
 // the node's DNS config inputs arrive with its own [change.SelfUpdate], see
@@ -317,24 +318,17 @@ func (m *mapper) selfMapResponse(
 //
 // This avoids the issue where an empty Peers slice is interpreted by Tailscale
 // clients as "no change" rather than "no peers".
-// When includeSelf is true, the node's self info is included so that a node
-// whose own attributes changed (e.g., tags via admin API) sees its updated
-// self info along with the new packet filters.
 func (m *mapper) policyChangeResponse(
 	nodeID types.NodeID,
 	capVer tailcfg.CapabilityVersion,
 	currentPeers views.Slice[types.NodeView],
-	includeSelf bool,
 ) (*tailcfg.MapResponse, error) {
 	builder := m.NewMapResponseBuilder(nodeID).
 		WithDebugType(policyResponseDebug).
 		WithCapabilityVersion(capVer).
 		WithPacketFilters().
-		WithSSHPolicy()
-
-	if includeSelf {
-		builder = builder.WithSelfNode()
-	}
+		WithSSHPolicy().
+		WithSelfNode()
 
 	// Send remaining peers in PeersChanged - their AllowedIPs may have
 	// changed due to the policy update (e.g., different routes allowed).

hscontrol/mapper/node_conn.go

@@ -50,6 +50,25 @@ type connectionEntry struct {
 	// can never become the stream's first frame ahead of the initial
 	// map. The zero value means the connection is ready.
 	pendingInitial atomic.Bool
+
+	// lastSelf is the self node last delivered to this connection's
+	// client, which keeps it until sent another. Every send to an
+	// established connection must go through [multiChannelNodeConn.send]
+	// to keep it current.
+	lastSelf atomic.Pointer[tailcfg.Node]
+}
+
+// withSelfDelta returns data without its Node when this client already
+// holds an equal one: a Node forces a full client netmap rebuild.
+func (entry *connectionEntry) withSelfDelta(data *tailcfg.MapResponse) *tailcfg.MapResponse {
+	if data.Node == nil || !data.Node.Equal(entry.lastSelf.Load()) {
+		return data
+	}
+
+	stripped := *data
+	stripped.Node = nil
+
+	return &stripped
 }
 
 // multiChannelNodeConn manages multiple concurrent connections for a single node.
@@ -341,7 +360,7 @@ func (mc *multiChannelNodeConn) send(data *tailcfg.MapResponse) error {
 	)
 
 	for _, conn := range snapshot {
-		err := conn.send(data)
+		err := conn.send(conn.withSelfDelta(data))
 		if err != nil {
 			lastErr = err
 
@@ -352,6 +371,10 @@ func (mc *multiChannelNodeConn) send(data *tailcfg.MapResponse) error {
 				Msg("send: connection failed")
 		} else {
 			successCount++
+
+			if data.Node != nil {
+				conn.lastSelf.Store(data.Node)
+			}
 		}
 	}
 

hscontrol/servertest/issues_test.go

@@ -222,36 +222,128 @@ func TestIssuesRoutes(t *testing.T) {
 		}
 	})
 
-	// When the server approves routes for a node, that node
-	// should receive a self-update reflecting the change.
-	t.Run("self_update_after_route_approval", func(t *testing.T) {
+	// The client derives ExitNodeOption from its own SelfNode.AllowedIPs,
+	// and SelfNode only changes when a MapResponse carries Node. SaaS
+	// captures show approved exit routes on the exit node's own SelfNode
+	// (routes-ea*, routes-b17/b18). Peers are the control: they must see
+	// the routes, proving the change was dispatched.
+	// https://github.com/juanfont/headscale/issues/3502
+	t.Run("exit_route_approval_reaches_self", func(t *testing.T) {
 		t.Parallel()
 
 		srv := servertest.NewServer(t)
-		user := srv.CreateUser(t, "selfup-user")
+		user := srv.CreateUser(t, "selfexit-user")
 
-		c1 := servertest.NewClient(t, srv, "selfup-node1",
+		exit := servertest.NewClient(t, srv, "selfexit-node",
 			servertest.WithUser(user))
-		servertest.NewClient(t, srv, "selfup-node2",
+		obs := servertest.NewClient(t, srv, "selfexit-obs",
 			servertest.WithUser(user))
 
-		c1.WaitForPeers(t, 1, 10*time.Second)
+		exit.WaitForPeers(t, 1, 10*time.Second)
+		advertiseRoutes(t, exit, obs, tsaddr.ExitRoutes())
 
-		nodeID := findNodeID(t, srv, "selfup-node1")
-		route := netip.MustParsePrefix("10.77.0.0/24")
-
-		countBefore := c1.UpdateCount()
-
-		_, routeChange, err := srv.State().SetApprovedRoutes(
-			nodeID, []netip.Prefix{route})
+		_, c, err := srv.State().SetApprovedRoutes(
+			findNodeID(t, srv, "selfexit-node"), tsaddr.ExitRoutes())
 		require.NoError(t, err)
-		srv.App.Change(routeChange)
+		srv.App.Change(c)
 
-		c1.WaitForCondition(t, "self-update after route approval",
-			10*time.Second,
-			func(nm *netmap.NetworkMap) bool {
-				return c1.UpdateCount() > countBefore
-			})
+		obs.WaitForCondition(t, "peer offers exit node", 10*time.Second,
+			peerOffersExit("selfexit-node"))
+		exit.WaitForCondition(t, "self offers exit node", 10*time.Second,
+			selfOffersExit)
+	})
+
+	// Advertising an already-approved exit route goes through
+	// UpdateNodeFromMapRequest instead of SetApprovedRoutes. This is the
+	// re-advertise workaround from the issue that 0.29.4 broke.
+	t.Run("exit_route_advertised_after_approval_reaches_self", func(t *testing.T) {
+		t.Parallel()
+
+		srv := servertest.NewServer(t)
+		user := srv.CreateUser(t, "preexit-user")
+
+		exit := servertest.NewClient(t, srv, "preexit-node",
+			servertest.WithUser(user))
+		obs := servertest.NewClient(t, srv, "preexit-obs",
+			servertest.WithUser(user))
+
+		exit.WaitForPeers(t, 1, 10*time.Second)
+
+		_, c, err := srv.State().SetApprovedRoutes(
+			findNodeID(t, srv, "preexit-node"), tsaddr.ExitRoutes())
+		require.NoError(t, err)
+		srv.App.Change(c)
+
+		advertiseRoutes(t, exit, obs, tsaddr.ExitRoutes())
+
+		obs.WaitForCondition(t, "peer offers exit node", 10*time.Second,
+			peerOffersExit("preexit-node"))
+		exit.WaitForCondition(t, "self offers exit node", 10*time.Second,
+			selfOffersExit)
+	})
+
+	// A policy reload that auto-approves an advertised exit route goes
+	// through autoApproveNodes, a third producer of the same change.
+	t.Run("exit_route_auto_approved_on_reload_reaches_self", func(t *testing.T) {
+		t.Parallel()
+
+		srv := servertest.NewServer(t)
+		user := srv.CreateUser(t, "reloadexit-user")
+
+		exit := servertest.NewClient(t, srv, "reloadexit-node",
+			servertest.WithUser(user))
+		obs := servertest.NewClient(t, srv, "reloadexit-obs",
+			servertest.WithUser(user))
+
+		exit.WaitForPeers(t, 1, 10*time.Second)
+		advertiseRoutes(t, exit, obs, tsaddr.ExitRoutes())
+
+		_, err := srv.State().SetPolicyInDB(`{
+			"acls": [{"action": "accept", "src": ["*"], "dst": ["*:*"]}],
+			"autoApprovers": {"exitNode": ["reloadexit-user@"]}
+		}`)
+		require.NoError(t, err)
+
+		changes, err := srv.State().ReloadPolicy()
+		require.NoError(t, err)
+		srv.App.Change(changes...)
+
+		obs.WaitForCondition(t, "peer offers exit node", 10*time.Second,
+			peerOffersExit("reloadexit-node"))
+		exit.WaitForCondition(t, "self offers exit node", 10*time.Second,
+			selfOffersExit)
+	})
+
+	// An auto-approver approves the route inside the advertising map
+	// request, a fourth producer of the same change.
+	t.Run("exit_route_auto_approved_on_advertise_reaches_self", func(t *testing.T) {
+		t.Parallel()
+
+		srv := servertest.NewServer(t)
+		user := srv.CreateUser(t, "advexit-user")
+
+		_, err := srv.State().SetPolicyInDB(`{
+			"acls": [{"action": "accept", "src": ["*"], "dst": ["*:*"]}],
+			"autoApprovers": {"exitNode": ["advexit-user@"]}
+		}`)
+		require.NoError(t, err)
+
+		changes, err := srv.State().ReloadPolicy()
+		require.NoError(t, err)
+		srv.App.Change(changes...)
+
+		exit := servertest.NewClient(t, srv, "advexit-node",
+			servertest.WithUser(user))
+		obs := servertest.NewClient(t, srv, "advexit-obs",
+			servertest.WithUser(user))
+
+		exit.WaitForPeers(t, 1, 10*time.Second)
+		advertiseRoutes(t, exit, obs, tsaddr.ExitRoutes())
+
+		obs.WaitForCondition(t, "peer offers exit node", 10*time.Second,
+			peerOffersExit("advexit-node"))
+		exit.WaitForCondition(t, "self offers exit node", 10*time.Second,
+			selfOffersExit)
 	})
 
 	// [tailcfg.Hostinfo] route advertisement should be stored on server.
@@ -1104,3 +1196,50 @@ func findNodeID(tb testing.TB, srv *servertest.TestServer, hostname string) type
 
 	return 0
 }
+
+// advertiseRoutes pushes routes in c's Hostinfo and waits until obs sees
+// them, so the server has stored the announcement.
+func advertiseRoutes(tb testing.TB, c, obs *servertest.TestClient, routes []netip.Prefix) {
+	tb.Helper()
+
+	c.Direct().SetHostinfo(&tailcfg.Hostinfo{
+		BackendLogID: "servertest-" + c.Name,
+		Hostname:     c.Name,
+		RoutableIPs:  routes,
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	_ = c.Direct().SendUpdate(ctx)
+
+	obs.WaitForCondition(tb, "routes in peer hostinfo", 10*time.Second,
+		func(nm *netmap.NetworkMap) bool {
+			p, ok := peerByHostname(nm, c.Name)
+
+			return ok && p.Hostinfo().RoutableIPs().Len() == len(routes)
+		})
+}
+
+// selfOffersExit mirrors how tailscaled computes Self.ExitNodeOption.
+func selfOffersExit(nm *netmap.NetworkMap) bool {
+	return nm.SelfNode.Valid() && tsaddr.ContainsExitRoutes(nm.SelfNode.AllowedIPs())
+}
+
+func peerOffersExit(hostname string) func(*netmap.NetworkMap) bool {
+	return func(nm *netmap.NetworkMap) bool {
+		p, ok := peerByHostname(nm, hostname)
+
+		return ok && tsaddr.ContainsExitRoutes(p.AllowedIPs())
+	}
+}
+
+func peerByHostname(nm *netmap.NetworkMap, hostname string) (tailcfg.NodeView, bool) {
+	for _, p := range nm.Peers {
+		if hi := p.Hostinfo(); hi.Valid() && hi.Hostname() == hostname {
+			return p, true
+		}
+	}
+
+	return tailcfg.NodeView{}, false
+}

hscontrol/servertest/via_compat_test.go

@@ -255,6 +255,11 @@ func runViaMapCompat(t *testing.T, c *testcapture.Capture) {
 				nm := cl.Netmap()
 				require.NotNil(tt, nm, "netmap is nil")
 
+				// Routes were approved on live sessions: verify that approval
+				// reached SelfNode throughout the stable comparison window.
+				require.Equal(tt, selfOffersExit(capture.Netmap), selfOffersExit(nm),
+					"SelfNode exit routes should match SaaS")
+
 				compareNetmap(tt, nm, capture, clients, saasAddrs)
 			})
 		})

integration/route_test.go

@@ -1693,6 +1693,11 @@ func TestEnablingExitRoutes(t *testing.T) {
 					assert.Contains(c, peerStatus.AllowedIPs.AsSlice(), tsaddr.AllIPv6())
 				}
 			}
+
+			// The approved node must learn its own routes on its live
+			// session, not only after reconnecting (issue #3502).
+			assert.True(c, status.Self.ExitNodeOption,
+				"%s should offer itself as exit node", client.Hostname())
 		}
 	}, integrationutil.ScaledTimeout(10*time.Second), integrationutil.SlowPoll, "clients should see new routes")
 }