ipn/ipnlocal: clear magicsock's netmap on logout

magicsock was hanging onto its netmap on logout,
which caused tailscale status to display partial
information about a bunch of zombie peers.
After logout, there should be no peers.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

ipn/ipnlocal/local.go

@@ -536,6 +536,7 @@ func (b *LocalBackend) setClientStatus(st controlclient.Status) {
 		// Since st.NetMap==nil means "netmap is unchanged", there is
 		// no other way to represent this change.
 		b.setNetMapLocked(nil)
+		b.e.SetNetworkMap(new(netmap.NetworkMap))
 	}
 
 	prefs := b.prefs

tstest/integration/integration_test.go

@@ -409,6 +409,56 @@ func TestOneNodeUpWindowsStyle(t *testing.T) {
 	d1.MustCleanShutdown(t)
 }
 
+func TestLogoutRemovesAllPeers(t *testing.T) {
+	t.Parallel()
+	env := newTestEnv(t)
+	// Spin up some nodes.
+	nodes := make([]*testNode, 2)
+	for i := range nodes {
+		nodes[i] = newTestNode(t, env)
+		nodes[i].StartDaemon(t)
+		nodes[i].AwaitResponding(t)
+		nodes[i].MustUp()
+		nodes[i].AwaitIP(t)
+		nodes[i].AwaitRunning(t)
+	}
+
+	// Make every node ping every other node.
+	// This makes sure magicsock is fully populated.
+	for i := range nodes {
+		for j := range nodes {
+			if i <= j {
+				continue
+			}
+			if err := tstest.WaitFor(20*time.Second, func() error {
+				return nodes[i].Ping(nodes[j])
+			}); err != nil {
+				t.Fatalf("ping %v -> %v: %v", nodes[i].AwaitIP(t), nodes[j].AwaitIP(t), err)
+			}
+		}
+	}
+
+	// wantNode0PeerCount waits until node[0] status includes exactly want peers.
+	wantNode0PeerCount := func(want int) {
+		if err := tstest.WaitFor(20*time.Second, func() error {
+			s := nodes[0].MustStatus(t)
+			if peers := s.Peers(); len(peers) != want {
+				return fmt.Errorf("want %d peer(s) in status, got %v", want, peers)
+			}
+			return nil
+		}); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	wantNode0PeerCount(len(nodes) - 1) // all other nodes are peers
+	nodes[0].MustLogOut()
+	wantNode0PeerCount(0) // node[0] is logged out, so it should not have any peers
+	nodes[0].MustUp()
+	nodes[0].AwaitIP(t)
+	wantNode0PeerCount(len(nodes) - 1) // all other nodes are peers again
+}
+
 // testEnv contains the test environment (set of servers) used by one
 // or more nodes.
 type testEnv struct {
@@ -703,6 +753,21 @@ func (n *testNode) MustDown() {
 	}
 }
 
+func (n *testNode) MustLogOut() {
+	t := n.env.t
+	t.Logf("Running logout ...")
+	if err := n.Tailscale("logout").Run(); err != nil {
+		t.Fatalf("logout: %v", err)
+	}
+}
+
+func (n *testNode) Ping(otherNode *testNode) error {
+	t := n.env.t
+	ip := otherNode.AwaitIP(t).String()
+	t.Logf("Running ping %v (from %v)...", ip, n.AwaitIP(t))
+	return n.Tailscale("ping", ip).Run()
+}
+
 // AwaitListening waits for the tailscaled to be serving local clients
 // over its localhost IPC mechanism. (Unix socket, etc)
 func (n *testNode) AwaitListening(t testing.TB) {

wgengine/netstack/netstack.go

@@ -239,6 +239,7 @@ func (ns *Impl) updateIPs(nm *netmap.NetworkMap) {
 	newIPs := make(map[tcpip.AddressWithPrefix]bool)
 
 	isAddr := map[netaddr.IPPrefix]bool{}
+	if nm.SelfNode != nil {
 		for _, ipp := range nm.SelfNode.Addresses {
 			isAddr[ipp] = true
 		}
@@ -248,6 +249,7 @@ func (ns *Impl) updateIPs(nm *netmap.NetworkMap) {
 				newIPs[ipPrefixToAddressWithPrefix(ipp)] = true
 			}
 		}
+	}
 
 	ipsToBeAdded := make(map[tcpip.AddressWithPrefix]bool)
 	for ipp := range newIPs {