fix: stop spamming DERP map updates for equivalent maps (#11792)

Fixes 2 related issues:

1. wsconncache had incorrect logic to test whether to send DERPMap updates, sending if the maps were equivalent, instead of if they were _not equivalent_.
2. configmaps used a bugged check to test equality between DERPMaps, since it contains a map and the map entries are serialized in random order. Instead, we avoid comparing the protobufs and instead depend on the existing function that compares `tailcfg.DERPMap`. This also has the effect of reducing the number of times we convert to and from protobuf.

coderd/workspaceagents.go

@@ -904,7 +904,7 @@ func (api *API) _dialWorkspaceAgentTailnet(agentID uuid.UUID) (*codersdk.Workspa
 				}
 
 				derpMap := api.DERPMap()
-				if lastDERPMap == nil || tailnet.CompareDERPMaps(lastDERPMap, derpMap) {
+				if lastDERPMap == nil || !tailnet.CompareDERPMaps(lastDERPMap, derpMap) {
 					conn.SetDERPMap(derpMap)
 					lastDERPMap = derpMap
 				}

tailnet/configmaps.go

@@ -65,7 +65,7 @@ type configMaps struct {
 	static         netmap.NetworkMap
 	peers          map[uuid.UUID]*peerLifecycle
 	addresses      []netip.Prefix
-	derpMap        *proto.DERPMap
+	derpMap        *tailcfg.DERPMap
 	logger         slog.Logger
 	blockEndpoints bool
 
@@ -204,7 +204,7 @@ func (c *configMaps) netMapLocked() *netmap.NetworkMap {
 	nm.Addresses = make([]netip.Prefix, len(c.addresses))
 	copy(nm.Addresses, c.addresses)
 
-	nm.DERPMap = DERPMapFromProto(c.derpMap)
+	nm.DERPMap = c.derpMap.Clone()
 	nm.Peers = c.peerConfigLocked()
 	nm.SelfNode.Addresses = nm.Addresses
 	nm.SelfNode.AllowedIPs = nm.Addresses
@@ -255,15 +255,10 @@ func (c *configMaps) setBlockEndpoints(blockEndpoints bool) {
 
 // setDERPMap sets the DERP map, triggering a configuration of the engine if it has changed.
 // c.L MUST NOT be held.
-func (c *configMaps) setDERPMap(derpMap *proto.DERPMap) {
+func (c *configMaps) setDERPMap(derpMap *tailcfg.DERPMap) {
 	c.L.Lock()
 	defer c.L.Unlock()
-	eq, err := c.derpMap.Equal(derpMap)
-	if err != nil {
-		c.logger.Critical(context.Background(), "failed to compare DERP maps", slog.Error(err))
-		return
-	}
-	if eq {
+	if CompareDERPMaps(c.derpMap, derpMap) {
 		return
 	}
 	c.derpMap = derpMap
@@ -273,8 +268,7 @@ func (c *configMaps) setDERPMap(derpMap *proto.DERPMap) {
 
 // derMapLocked returns the current DERPMap.  c.L must be held
 func (c *configMaps) derpMapLocked() *tailcfg.DERPMap {
-	m := DERPMapFromProto(c.derpMap)
-	return m
+	return c.derpMap.Clone()
 }
 
 // reconfig computes the correct wireguard config and calls the engine.Reconfig

tailnet/configmaps_internal_test.go

@@ -674,12 +674,12 @@ func TestConfigMaps_setDERPMap_different(t *testing.T) {
 	uut := newConfigMaps(logger, fEng, nodeID, nodePrivateKey, discoKey.Public())
 	defer uut.close()
 
-	derpMap := &proto.DERPMap{
-		HomeParams: &proto.DERPMap_HomeParams{RegionScore: map[int64]float64{1: 0.025}},
-		Regions: map[int64]*proto.DERPMap_Region{
+	derpMap := &tailcfg.DERPMap{
+		HomeParams: &tailcfg.DERPHomeParams{RegionScore: map[int]float64{1: 0.025}},
+		Regions: map[int]*tailcfg.DERPRegion{
 			1: {
 				RegionCode: "AUH",
-				Nodes: []*proto.DERPMap_Region_Node{
+				Nodes: []*tailcfg.DERPNode{
 					{Name: "AUH0"},
 				},
 			},
@@ -716,15 +716,24 @@ func TestConfigMaps_setDERPMap_same(t *testing.T) {
 	defer uut.close()
 
 	// Given: DERP Map already set
-	derpMap := &proto.DERPMap{
-		HomeParams: &proto.DERPMap_HomeParams{RegionScore: map[int64]float64{1: 0.025}},
-		Regions: map[int64]*proto.DERPMap_Region{
+	derpMap := &tailcfg.DERPMap{
+		HomeParams: &tailcfg.DERPHomeParams{RegionScore: map[int]float64{
+			1:    0.025,
+			1001: 0.111,
+		}},
+		Regions: map[int]*tailcfg.DERPRegion{
 			1: {
 				RegionCode: "AUH",
-				Nodes: []*proto.DERPMap_Region_Node{
+				Nodes: []*tailcfg.DERPNode{
 					{Name: "AUH0"},
 				},
 			},
+			1001: {
+				RegionCode: "DXB",
+				Nodes: []*tailcfg.DERPNode{
+					{Name: "DXB0"},
+				},
+			},
 		},
 	}
 	uut.L.Lock()
@@ -734,8 +743,27 @@ func TestConfigMaps_setDERPMap_same(t *testing.T) {
 	// Then: we don't configure
 	requireNeverConfigures(ctx, t, &uut.phased)
 
-	// When we set the same DERP map
-	uut.setDERPMap(derpMap)
+	// When we set the equivalent DERP map, with different ordering
+	uut.setDERPMap(&tailcfg.DERPMap{
+		HomeParams: &tailcfg.DERPHomeParams{RegionScore: map[int]float64{
+			1001: 0.111,
+			1:    0.025,
+		}},
+		Regions: map[int]*tailcfg.DERPRegion{
+			1001: {
+				RegionCode: "DXB",
+				Nodes: []*tailcfg.DERPNode{
+					{Name: "DXB0"},
+				},
+			},
+			1: {
+				RegionCode: "AUH",
+				Nodes: []*tailcfg.DERPNode{
+					{Name: "AUH0"},
+				},
+			},
+		},
+	})
 
 	done := make(chan struct{})
 	go func() {

tailnet/conn.go

@@ -218,7 +218,7 @@ func NewConn(options *Options) (conn *Conn, err error) {
 		magicConn.DiscoPublicKey(),
 	)
 	cfgMaps.setAddresses(options.Addresses)
-	cfgMaps.setDERPMap(DERPMapToProto(options.DERPMap))
+	cfgMaps.setDERPMap(options.DERPMap)
 	cfgMaps.setBlockEndpoints(options.BlockEndpoints)
 
 	nodeUp := newNodeUpdater(
@@ -326,7 +326,7 @@ func (c *Conn) SetNodeCallback(callback func(node *Node)) {
 
 // SetDERPMap updates the DERPMap of a connection.
 func (c *Conn) SetDERPMap(derpMap *tailcfg.DERPMap) {
-	c.configMaps.setDERPMap(DERPMapToProto(derpMap))
+	c.configMaps.setDERPMap(derpMap)
 }
 
 func (c *Conn) SetDERPForceWebSockets(v bool) {

tailnet/proto/compare.go

@@ -18,15 +18,3 @@ func (s *Node) Equal(o *Node) (bool, error) {
 	}
 	return bytes.Equal(sBytes, oBytes), nil
 }
-
-func (s *DERPMap) Equal(o *DERPMap) (bool, error) {
-	sBytes, err := gProto.Marshal(s)
-	if err != nil {
-		return false, err
-	}
-	oBytes, err := gProto.Marshal(o)
-	if err != nil {
-		return false, err
-	}
-	return bytes.Equal(sBytes, oBytes), nil
-}