Reset static host list addresses on change

lighthouse.go

@@ -272,16 +272,18 @@ func (lh *LightHouse) reload(c *config.C, initial bool) error {
 	//NOTE: many things will get much simpler when we combine static_host_map and lighthouse.hosts in config
 	if initial || c.HasChanged("static_host_map") || c.HasChanged("static_map.cadence") || c.HasChanged("static_map.network") || c.HasChanged("static_map.lookup_timeout") {
 		// Clean up. Entries still in the static_host_map will be re-built.
-		// Entries no longer present must have their (possible) background DNS goroutines stopped.
-		if existingStaticList := lh.staticList.Load(); existingStaticList != nil {
+		ourselves := lh.myVpnNetworks[0].Addr()
+		oldStaticList := lh.staticList.Load()
+		if oldStaticList != nil {
 			lh.RLock()
-			for staticVpnAddr := range *existingStaticList {
+			for staticVpnAddr := range *oldStaticList {
 				if am, ok := lh.addrMap[staticVpnAddr]; ok && am != nil {
-					am.hr.Cancel()
+					am.ResetForOwner(ourselves)
 				}
 			}
 			lh.RUnlock()
 		}
+
 		// Build a new list based on current config.
 		staticList := make(map[netip.Addr]struct{})
 		err := lh.loadStaticMap(c, staticList)
@@ -289,6 +291,21 @@ func (lh *LightHouse) reload(c *config.C, initial bool) error {
 			return err
 		}
 
+		// For entries removed from static_host_map, stop the DNS goroutine and drop the cached addrs.
+		// All addrs must come from the lighthouses now that it's no longer a static host.
+		if oldStaticList != nil {
+			lh.RLock()
+			for staticVpnAddr := range *oldStaticList {
+				if _, stillStatic := staticList[staticVpnAddr]; stillStatic {
+					continue
+				}
+				if am, ok := lh.addrMap[staticVpnAddr]; ok && am != nil {
+					am.ClearHostnameResults()
+				}
+			}
+			lh.RUnlock()
+		}
+
 		lh.staticList.Store(&staticList)
 		if !initial {
 			if c.HasChanged("static_host_map") {

lighthouse_test.go

@@ -303,6 +303,132 @@ func TestLighthouse_reload(t *testing.T) {
 	require.NoError(t, err)
 }
 
+// TestLighthouse_reloadStaticHostMap verifies that reloading static_host_map applies the new
+// config rather than appending to it. See issue #718.
+func TestLighthouse_reloadStaticHostMap(t *testing.T) {
+	l := test.NewLogger()
+	c := config.NewC(l)
+	c.Settings["lighthouse"] = map[string]any{"am_lighthouse": true}
+	c.Settings["listen"] = map[string]any{"port": 4242}
+	c.Settings["static_host_map"] = map[string]any{
+		"10.128.0.2": []any{"1.1.1.1:4242"},
+	}
+
+	myVpnNet := netip.MustParsePrefix("10.128.0.1/24")
+	nt := new(bart.Lite)
+	nt.Insert(myVpnNet)
+	cs := &CertState{
+		myVpnNetworks:      []netip.Prefix{myVpnNet},
+		myVpnNetworksTable: nt,
+	}
+
+	lh, err := NewLightHouseFromConfig(t.Context(), l, c, cs, nil, nil)
+	require.NoError(t, err)
+
+	staticHost := netip.MustParseAddr("10.128.0.2")
+	otherHost := netip.MustParseAddr("10.128.0.3")
+
+	// Capture the RemoteList pointer up front; an in-flight handshake would hold the same one
+	// on hostinfo.remotes, so it must reflect every reload below.
+	pinned := lh.Query(staticHost)
+	require.NotNil(t, pinned)
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("1.1.1.1:4242")}, pinned.CopyAddrs([]netip.Prefix{}))
+
+	// Replace the remote address. The new address should be the only entry.
+	nc := map[string]any{
+		"static_host_map": map[string]any{
+			"10.128.0.2": []any{"2.2.2.2:4242"},
+		},
+	}
+	rc, err := yaml.Marshal(nc)
+	require.NoError(t, err)
+	require.NoError(t, c.ReloadConfigString(string(rc)))
+
+	rl := lh.Query(staticHost)
+	require.NotNil(t, rl)
+	assert.Same(t, pinned, rl, "RemoteList pointer must stay stable so in-flight handshakes pick up the change")
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("2.2.2.2:4242")}, rl.CopyAddrs([]netip.Prefix{}))
+
+	// Reload back to the original IP. Mirrors the round-trip in issue #718 step 6-8 where
+	// the buggy reload produced [1.1.1.1, 2.2.2.2, 1.1.1.1] instead of [1.1.1.1].
+	nc = map[string]any{
+		"static_host_map": map[string]any{
+			"10.128.0.2": []any{"1.1.1.1:4242"},
+		},
+	}
+	rc, err = yaml.Marshal(nc)
+	require.NoError(t, err)
+	require.NoError(t, c.ReloadConfigString(string(rc)))
+
+	rl = lh.Query(staticHost)
+	require.NotNil(t, rl)
+	assert.Same(t, pinned, rl)
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("1.1.1.1:4242")}, rl.CopyAddrs([]netip.Prefix{}))
+
+	// Reload with the same config. An unchanged entry must not duplicate.
+	require.NoError(t, c.ReloadConfigString(string(rc)))
+
+	rl = lh.Query(staticHost)
+	require.NotNil(t, rl)
+	assert.Same(t, pinned, rl)
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("1.1.1.1:4242")}, rl.CopyAddrs([]netip.Prefix{}))
+
+	// Switch back to 2.2.2.2 so the rest of the test continues against a known address.
+	nc = map[string]any{
+		"static_host_map": map[string]any{
+			"10.128.0.2": []any{"2.2.2.2:4242"},
+		},
+	}
+	rc, err = yaml.Marshal(nc)
+	require.NoError(t, err)
+	require.NoError(t, c.ReloadConfigString(string(rc)))
+
+	// Add a second host alongside the first. Both should be present, neither duplicated.
+	nc = map[string]any{
+		"static_host_map": map[string]any{
+			"10.128.0.2": []any{"2.2.2.2:4242"},
+			"10.128.0.3": []any{"3.3.3.3:4242"},
+		},
+	}
+	rc, err = yaml.Marshal(nc)
+	require.NoError(t, err)
+	require.NoError(t, c.ReloadConfigString(string(rc)))
+
+	rl = lh.Query(staticHost)
+	require.NotNil(t, rl)
+	assert.Same(t, pinned, rl, "adding a sibling entry must not displace the existing RemoteList")
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("2.2.2.2:4242")}, rl.CopyAddrs([]netip.Prefix{}))
+
+	rl = lh.Query(otherHost)
+	require.NotNil(t, rl)
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("3.3.3.3:4242")}, rl.CopyAddrs([]netip.Prefix{}))
+
+	// Drop the first host entirely. The vpnAddr is no longer marked static, our owner
+	// contribution is cleared, but the addrMap entry stays in place so non-static cache
+	// data (from lighthouse queries) on the same RemoteList isn't lost. In-flight handshakes
+	// that already had the pointer see an empty address list rather than retrying stale ones.
+	nc = map[string]any{
+		"static_host_map": map[string]any{
+			"10.128.0.3": []any{"3.3.3.3:4242"},
+		},
+	}
+	rc, err = yaml.Marshal(nc)
+	require.NoError(t, err)
+	require.NoError(t, c.ReloadConfigString(string(rc)))
+
+	_, isStatic := lh.GetStaticHostList()[staticHost]
+	assert.False(t, isStatic)
+
+	rl = lh.Query(staticHost)
+	require.NotNil(t, rl)
+	assert.Same(t, pinned, rl)
+	assert.Empty(t, rl.CopyAddrs([]netip.Prefix{}))
+
+	rl = lh.Query(otherHost)
+	require.NotNil(t, rl)
+	assert.Equal(t, []netip.AddrPort{netip.MustParseAddrPort("3.3.3.3:4242")}, rl.CopyAddrs([]netip.Prefix{}))
+}
+
 func newLHHostRequest(fromAddr netip.AddrPort, myVpnIp, queryVpnIp netip.Addr, lhh *LightHouseHandler) testLhReply {
 	req := &NebulaMeta{
 		Type:    NebulaMeta_HostQuery,

remote_list.go

@@ -239,6 +239,31 @@ func (r *RemoteList) unlockedSetHostnamesResults(hr *hostnamesResults) {
 	r.hr = hr
 }
 
+// ResetForOwner zeros the reported address slices for the given owner and marks the addrs list dirty.
+// Any pending hostname resolution will be canceled.
+func (r *RemoteList) ResetForOwner(ownerVpnAddr netip.Addr) {
+	r.Lock()
+	defer r.Unlock()
+	r.hr.Cancel()
+	if c, ok := r.cache[ownerVpnAddr]; ok {
+		if c.v4 != nil {
+			c.v4.reported = c.v4.reported[:0]
+		}
+		if c.v6 != nil {
+			c.v6.reported = c.v6.reported[:0]
+		}
+	}
+	r.shouldRebuild = true
+}
+
+// ClearHostnameResults cancels the in-flight DNS resolver goroutine (if any) and drops the resolved IP cache.
+func (r *RemoteList) ClearHostnameResults() {
+	r.Lock()
+	defer r.Unlock()
+	r.unlockedSetHostnamesResults(nil)
+	r.shouldRebuild = true
+}
+
 // Len locks and reports the size of the deduplicated address list
 // The deduplication work may need to occur here, so you must pass preferredRanges
 func (r *RemoteList) Len(preferredRanges []netip.Prefix) int {

remote_list_test.go

@@ -6,8 +6,22 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
+// trackedHostnameResults builds a *hostnamesResults with a known cancel function and a
+// pre-populated ips map so tests can assert cancellation and verify previously-resolved
+// IPs survive a cancel without spinning up a real DNS resolver.
+func trackedHostnameResults(cancelFn func(), addrs ...string) *hostnamesResults {
+	hr := &hostnamesResults{cancelFn: cancelFn}
+	ips := map[netip.AddrPort]struct{}{}
+	for _, a := range addrs {
+		ips[netip.MustParseAddrPort(a)] = struct{}{}
+	}
+	hr.ips.Store(&ips)
+	return hr
+}
+
 func TestRemoteList_Rebuild(t *testing.T) {
 	rl := NewRemoteList([]netip.Addr{netip.MustParseAddr("0.0.0.0")}, nil)
 	rl.unlockedSetV4(
@@ -112,6 +126,81 @@ func TestRemoteList_Rebuild(t *testing.T) {
 	assert.Equal(t, "172.31.0.1:10101", rl.addrs[9].String())
 }
 
+func TestRemoteList_ResetForOwner(t *testing.T) {
+	ourselves := netip.MustParseAddr("10.0.0.1")
+	otherOwner := netip.MustParseAddr("10.0.0.2")
+	vpnAddr := netip.MustParseAddr("10.0.0.99")
+
+	rl := NewRemoteList([]netip.Addr{vpnAddr}, nil)
+	rl.unlockedSetV4(ourselves, vpnAddr,
+		[]*V4AddrPort{newIp4AndPortFromString("1.1.1.1:4242")},
+		func(netip.Addr, *V4AddrPort) bool { return true },
+	)
+	rl.unlockedSetV6(ourselves, vpnAddr,
+		[]*V6AddrPort{newIp6AndPortFromString("[1::1]:4242")},
+		func(netip.Addr, *V6AddrPort) bool { return true },
+	)
+	rl.unlockedSetV4(otherOwner, vpnAddr,
+		[]*V4AddrPort{newIp4AndPortFromString("2.2.2.2:4242")},
+		func(netip.Addr, *V4AddrPort) bool { return true },
+	)
+
+	canceled := 0
+	hr := trackedHostnameResults(func() { canceled++ }, "3.3.3.3:4242")
+	rl.Lock()
+	rl.unlockedSetHostnamesResults(hr)
+	rl.Unlock()
+
+	rl.ResetForOwner(ourselves)
+
+	rl.RLock()
+	defer rl.RUnlock()
+	assert.Empty(t, rl.cache[ourselves].v4.reported, "our v4 reported should be cleared")
+	assert.Empty(t, rl.cache[ourselves].v6.reported, "our v6 reported should be cleared")
+	assert.Len(t, rl.cache[otherOwner].v4.reported, 1, "other owner's contribution must be preserved")
+	assert.Equal(t, "2.2.2.2:4242", protoV4AddrPortToNetAddrPort(rl.cache[otherOwner].v4.reported[0]).String())
+	assert.Equal(t, 1, canceled, "DNS resolution goroutine should be canceled")
+	assert.Same(t, hr, rl.hr, "hostnamesResults must be preserved so DNS-resolved IPs keep feeding addrs until replaced")
+	assert.NotEmpty(t, rl.hr.GetAddrs(), "previously-resolved IPs should still be readable after cancel")
+	assert.True(t, rl.shouldRebuild, "shouldRebuild must be set so the next Rebuild recomputes addrs")
+}
+
+func TestRemoteList_ResetForOwner_NoEntry(t *testing.T) {
+	// An owner with no cache entry must not panic; shouldRebuild is still set and any
+	// existing hostnamesResults is canceled.
+	rl := NewRemoteList([]netip.Addr{netip.MustParseAddr("10.0.0.99")}, nil)
+	canceled := 0
+	rl.Lock()
+	rl.unlockedSetHostnamesResults(trackedHostnameResults(func() { canceled++ }, "3.3.3.3:4242"))
+	rl.Unlock()
+
+	rl.ResetForOwner(netip.MustParseAddr("10.0.0.1"))
+
+	rl.RLock()
+	defer rl.RUnlock()
+	assert.Equal(t, 1, canceled)
+	assert.True(t, rl.shouldRebuild)
+}
+
+func TestRemoteList_ClearHostnameResults(t *testing.T) {
+	rl := NewRemoteList([]netip.Addr{netip.MustParseAddr("10.0.0.99")}, nil)
+
+	canceled := 0
+	hr := trackedHostnameResults(func() { canceled++ }, "3.3.3.3:4242")
+	rl.Lock()
+	rl.unlockedSetHostnamesResults(hr)
+	rl.Unlock()
+	require.NotEmpty(t, hr.GetAddrs(), "hostnamesResults should have its fastrack IPs populated")
+
+	rl.ClearHostnameResults()
+
+	rl.RLock()
+	defer rl.RUnlock()
+	assert.Equal(t, 1, canceled, "DNS resolution goroutine should be canceled")
+	assert.Nil(t, rl.hr, "hostnamesResults should be dropped")
+	assert.True(t, rl.shouldRebuild)
+}
+
 func BenchmarkFullRebuild(b *testing.B) {
 	rl := NewRemoteList([]netip.Addr{netip.MustParseAddr("0.0.0.0")}, nil)
 	rl.unlockedSetV4(